A STUDY OF COMPARATIVE ANATOMY OF THE PAPILLARY MUSCLES IN THE VENTRICLES OF THE HEART OF HUMAN, SHEEP, GOAT, COW AND PIG by Dr. KOMALA. N Dissertation submitted to the Rajiv Gandhi University of Health Sciences, Karnataka, Bangalore. In partial fulfillment of the requirements for the degree of DOCTOR OF MEDICINE In ANATOMY Under the guidance of Dr. K.S. JAYANTHI DEPARTMENT OF ANATOMY KEMPEGOWDA INSTITUTE OF MEDICAL SCIENCES BANGALORE 2006

Rajiv Gandhi University Of Health Sciences, Karnataka, Bangalore

DECLARATION BY THE CANDIDATE I hereby declare that this dissertation entitled

A study of Comparative

Anatomy of Papillary muscles in the ventricles of the heart of Human, Sheep, Goat, Cow and Pig is a bonafide and genuine research work carried out by me under the guidance of Dr. K.S. Jayanthi, Professor and Head, Department of Anatomy, Kempegowda Institute of Medical Sciences, Bangalore.

Date: 3rd April 2006 Place: Bangalore

Dr. Komala. N

i

CERTIFICATE BY THE GUIDE

This is to certify that the dissertation entitled

A study of Comparative

Anatomy of Papillary muscles in the ventricles of the heart of Human, Sheep, Goat, Cow and Pig is a bonafide research work done by Dr. Komala. N in partial fulfillment of the requirement for the degree of Doctor of Medicine in Anatomy.

Date: 3rd April 2006

Dr.K.S. Jayanthi

Place: Bangalore

Professor and head, Department of Anatomy, Kempegowda Institute of Medical Sciences, Bangalore.

ii

ENDORSEMENT BY THE HOD, PRINICIPAL/HEAD OF THE INSTITUTION

This is to certify that the dissertation entitled

A study of Comparative

Anatomy of Papillary muscles in the ventricles of the heart of Human, Sheep, Goat, Cow and Pig is a bonafide research work done by Dr. Komala. N under the guidance of Dr. K.S. Jayanthi, Professor and Head, Department of Anatomy, Kempegowda Institute of Medical Sciences, Bangalore.

Seal and Signature of the HOD

Seal and Signature of the Principal

Dr. K.S. Jayanthi

Dr. M.K. Sudarshan

Date: 3rd April 2006

Date: 3rd April 2006

Place: Bangalore

Place: Bangalore

iii

COPYRIGHT Declaration by the candidate

I hereby declare that Rajiv Gandhi University of Health Sciences, Karnataka shall have the rights to preserve, use and disseminate this dissertation in print or electronic format for academic/research purpose.

Date: 3rd April 2006

Dr. Komala. N

Place: Bangalore

© Rajiv Gandhi University of Health Sciences, Karnataka

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ACKNOWLEDGEMENT

I am grateful to Dr. K.S. Jayanthi, Professor and Head, Department of Anatomy, K.I.M.S, Bangalore for the encouragement, constant supervision and guidance throughout the research work without which this work would not have been possible.

I express my gratitude to Dr. M.K. Sudarshan, Principal, K.I.M.S, Bangalore for providing the permission to carry out the research work.

I thank Dr. R. Shubha, Dr. Lalitha, Dr. K. Jeyanthi, Dr. M. Rajeshwari, Dr. M. Pushpalatha, Dr. T.K. Jyothilakshmi for their advice and encouragement. I also thank my colleagues and other non-teaching staff for their timely support.

I also convey my thanks to Dr. H.R. Krishna Rao, Professor and former Head, Department of Anatomy, K.I.M.S, Bangalore and presently Principal, P.E.S. Institute of Medical Sciences and Research, Kuppam, Chittor, Andhra Pradesh and Dr. S.V. Chinnappa, Professor and Head, Department of Anatomy, P.E.S. Institute of Medical Sciences and Research, Kuppam, Chittor, Andhra Pradesh, for the inspiration and encouragement.

I am thankful to Dr. H.P. Pundarikaksha, Professor and Head, Department of Pharmacology, K.I.M.S, Bangalore for giving me permission to utilize the necessary instruments.

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I also thank my husband, Mr. M.C. Srinivas, and all my family members for their encouragement and constant support without which this work would not have been possible.

I remember all of them with gratitude in this regard.

Date: 3rd April 2006 Place: Bangalore

Dr. Komala. N

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LIST OF ABBREVIATIONS USED AL

Anterior Leaflet

ALC

Antero-lateral Commissure

APC

Antero-posterior Commissure

APM

Anterior Papillary Muscle

ASC

Antero-septal Commissure

AZ

Appositional Zone

AZC

Appositional Zone Chordae

B

Breadth

BC

Basal Chordae

CC

Cleft Chordae

CTN

Chordae Tendineae Number

DC

Deep Chordae

FC

Fan-shaped Chordae

FEC

Free Edge Chordae

FZ

Free Zone

FZC

Free Zone Chordae

L

Length

PL

Posterior Leaflet

PMC

Postero-medial Commissure

PPM

Posterior Papillary Muscle

PSC

Postero-septal Commissure

RZC

Rough Zone Chordae

SL

Septal Leaflet

SPM

Septal Papillary Muscle

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ABSTRACT

Background and Objectives In today s world, a large population of human beings suffer from valvular incompetence of heart leading to death because of congestive cardiac failure. Dysfunction of the papillary muscles and their chordae leads to the incompetence. A comparative study of papillary muscles of ventricles of human, sheep, goat, cow and pig is done. By adopting this comparative anatomic approach, the complete significance of the human atrioventricular valve complexes, become more apparent. The ratio of the heart weight to the body weight, the diameters of the mitral and the tri-cuspid valve, the position, number, length and thickness of papillary muscles and the number of chordae tendineae attached to each papillary muscle, cusp and the zones to which they were attached were studied for comparison.

Methods Size of the heart was measured by noting down the maximum length and breadth of each of the specimen using slide calipers. The hearts were opened to view the interior of the ventricles. Diameter of the valve from antero-lateral to postero-lateral commissure was measured by using a pair of dividers with fine points and ordinary ruler. The number of papillary muscles and their positions were noted. The length of the papillary muscles was also measured using a pair of dividers and ruler. Thickness of the papillary muscles was measured at their origin using slide calipers. The number of chordae tendineae

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attached to each papillary muscle and the cusps along with their attachment to different zones of the cusps were observed and counted using a hand lens.

Results The ratio of heart weight to the body weight was more in human. The number and position of the papillary muscle was similar in all the specimens but the number of bellies of each papillary muscle varied. Length and thickness of the papillary muscles were more in cow and least in pig. Chordae tendineae number to the papillary muscle and the cusp was more in pig and man. It was least in sheep and goat.

Interpretation and Conclusion The internal structure of the heart differs from species to species. Even in the same species, no one heart is exactly the same as another. The complicated embryology involved in the formation of the components of the valve may be responsible for this. The ratio of the weight of the heart to the weight of the human body being the highest among the mammals (compared in this study) implies that human heart is well developed. Although differences exist, the pig s heart appears very similar to that of man. The heart of sheep and goat are similar.

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TABLE OF CONTENTS

1. Introduction

Page No. 1

2. Objectives

Page No. 4

3. Review of Literature

Page No. 6

4. Methodology

Page No. 45

5. Results

Page No. 50

6. Discussion

Page No. 82

7. Conclusion

Page No. 106

8. Summary

Page No. 111

9. Bibliography

Page No. 115

10. Annexures

Page No. 120

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LIST OF TABLES

Sl. No

Tables

Pages

1

Comparison of size and weight of human heart with other mammals in ratio of their body weight

51

2

Comparison of the diameters of valvular complexes in various mammals

52

3

Comparison of the average length and thickness of the papillary muscles in the ventricles of different mammals

57

4

Comparison of the average number of chordae tendineae attached to each papillary muscle in the ventricles of different mammals

74

5

Comparison of the average number of chordae attached to each leaflets of left and right ventricles in different species

75

6

Table showing average number of different types of chordae inserted into the leaflets in human hearts

76

7

Table showing average number of different types of chordae inserted into the leaflets and commissures in hearts of various animals

77

8

Comparison of the mean heart weight / body weight ratio of different animals of the present study with previous work done

84

9

Comparison of the measurements of diameters of the valves of human obtained in the present study with those of the measurements obtained in the literature

86

10

Comparison of percentage of papillary muscles of left ventricle containing two or more bellies in the present study with those figures obtained by earlier authors

94

11

Comparison of the figures of average length and thickness of the papillary muscles of left ventricles of different mammals obtained in the present study to those figures given by an other author

95

12

Comparison of figures of the average number of chordae tendineae attached to both papillary muscles of the left ventricle obtained in the present study with the previous work done

100

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Sl. No

Tables

Pages

13

Comparison of the number of chordae tendineae attached to different zones of cusps of the valves of left ventricles in human obtained in the present study with that of earlier works

101

14

Comparison of the number of chordae tendineae attached to different zones of cusps of the valves of left ventricles in human obtained in the present study with that of earlier works

102

15

Comparison of the percentage of hearts with various types of chordae tendineae of human right ventricle obtained in the present study with that of the percentage obtained by earlier works

103

16

Comparison of the total number of chordae attached to each leaflet of human left ventricle in the present study with those of earlier works

104

17

Comparison of the total number of chordae attached to each leaflet of human right ventricle in the present study with those of earlier works

104

18

Master Chart showing various parameters in specimens of human 128 hearts studied

130

19

Master Chart showing various parameters in specimens of sheep 131 hearts studied

132

20

Master Chart showing various parameters in specimens of goat 133 hearts studied

134

21

Master Chart showing various parameters in specimens of cow 135 hearts studied

136

22

Master Chart showing various parameters in specimens of pig 137 hearts studied

138

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LIST OF FIGURES

Sl. No

Figures

Pages

1

Interior of ventricles in human heart

11

2

Interior of ventricles in the heart of the sheep

16

3

Interior of ventricles in the heart of the goat

16

4

Interior of ventricles in the heart of the cow

17

5

Interior of ventricles in the heart of the pig

17

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LIST OF PHOTOGRAPHS

Sl. No.

Photographs

Pages

1

Photograph showing the instruments used for the study

48

2

Photograph of cusp of Human ventricle showing rough zone and basal zone

53

3

Photograph of cusp of Cow s ventricle showing rough zone and basal zone

54

4

Photograph of the closer view of the interior of the Human right ventricle

58

5

Photograph of Human Left ventricle showing two papillary muscles

59

6

Photograph of Human Left ventricle showing two bellies each of anterior and posterior papillary muscles

60

7

Photograph of Human Left ventricle showing single belly of anterior papillary muscle with three heads and two bellies of posterior papillary muscle

61

8

Photograph of Human Right ventricle showing two bellies of anterior papillary muscle, groups of bellies of posterior papillary muscle and septal papillary muscle

62

9

Photograph of right ventricle of sheep showing single bellies each of anterior, posterior and septal papillary muscles

63

10

Photograph of left ventricle of sheep with two papillary muscles

64

11

Photograph of right ventricle of Goat with three papillary muscles

65

12

Photograph of left ventricle of Goat showing two papillary muscles

66

13

Photograph of interior of right ventricle of Cow showing single bellies each of anterior and posterior papillary muscle

67

14

Photograph of closer view of right ventricle of Cow showing the tips of anterior and posterior papillary muscle and septal muscle

68

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Sl. No.

Photographs

Pages

15

Photograph of left ventricle of Cow showing single bellies each of anterior and posterior papillary muscles

69

16

Photograph of right ventricle of Cow showing single belly of anterior papillary muscle and two bellies of posterior papillary muscle

70

17

Photograph of right ventricle of Pig showing the three papillary muscles

71

18

Photograph of closer view of right ventricle of Pig showing single belly of anterior papillary muscle, groups of bellies of posterior papillary muscle and septal papillary muscles

72

19

Photograph of left ventricle of Pig showing single belly of anterior papillary muscle and dual bellies of posterior papillary muscle

73

20

Photograph of human right ventricle showing attachment of chordae tendineae to the rough zone and basal zone

79

21

Photograph of human left ventricle showing attachment of fan shaped chordae to the commissures

80

22

Photograph of right ventricle of Goat showing attachment of chordae tendineae to the appositional zone

81

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LIST OF REPRESENTATIONS Sl. No.

Representations

Pages

1

Bar Diagram representing the Ratio of average weight of heart to the average total body weight of various Animals

121

2

Bar Diagram showing the average diameters of Mitral and Tricuspid valvular complexes

121

3

Bar Diagram depicting the length and thickness of APM in Left Ventricle in different animals

122

4

Bar Diagram depicting the length and thickness of PPM in Left Ventricle in different animals

122

5

Bar Diagram depicting the length and thickness of APM in Right Ventricle in different animals

123

6

Bar Diagram depicting the length and thickness of PPM in Right Ventricle in different animals

123

7

Bar Diagram depicting the length and thickness of SPM in Right Ventricle in different animals

124

8

Bar Diagram representing the number of Chordae Tendineae attached to each papillary muscle of Left Ventricle in various animals

124

9

Bar Diagram representing the number of Chordae Tendineae attached to each papillary muscle of Right Ventricle in various animals

125

10

Bar Diagram representing the number of Chordae Tendineae attached to the leaflets of Left Ventricle in various animals

125

11

Bar Diagram representing the number of Chordae Tendineae attached to the leaflets of Right Ventricle in various animals

126

12

Pie Chart showing the percentage of hearts with single belly / dual belly of APM

126

13

Pie Chart showing the percentage of hearts with single belly / multiple belly of PPM

127

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INTRODUCTION

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1. Introduction

The heart s interior resembled an accurate and effective apparatus, like ship s rigging, to assist the heart on all sides to produce a fuller, stronger contraction to expel blood from the ventricles . (William Harvey (1628), who dissected numerous hearts, commented in his celebrated Exercitatio anatomica de motu cordis et sanguinis in animalibus ). 1 This early account forms an accurate description of cardiac morphology. The papillary muscles of the heart are conical muscular projections into the respective ventricles from their walls.

They are attached to the cusp of the

atrioventricular valves through the chordae tendineae.

Functionally, the papillary

muscles are important part of the respective valve complex. They play an important role in perfect closure of the atrioventricular orifices and prevent the cusps of the valve from being everted during ventricular systole. Hypoxia, necrosis, or fibrosis of the papillary muscles may be associated with varying degrees of valvular regurgitation. It is also observed in case of human beings, a large population suffer from valvular incompetence of the heart leading to death because of congestive cardiac failure. Papillary muscle dysfunction causes valvular insufficiency. This is a well-known entity in patients with chronic ischemic heart disease and is a common complication of myocardial infarction. Papillary muscle rupture almost always leads to cardiogenic shock and carries mortality in the range of 80% to 90%. A total rupture of the entire papillary muscle trunk is generally viewed to be incompatible with life.2

Also, primary prolapse of the valve

results from congenital structural defects of papillary muscles, trabeculae and chordae tendineae.3 2

For the normal function of the valve apparatus, it is necessary that proper spatial relationship has to be maintained between its components, i.e. the annulus, valve leaflets, chordae tendineae and the papillary muscles.4 Inspite of our increased awareness of the disorders of each of the components our anatomical knowledge about these structures is incomplete.5 Understanding of cardiac anatomy is a pre-requisite for cardiac surgery. Almost all surgeons have stressed upon the importance of avoiding incisions or tears at any region other than at the commissures.6

Thus the papillary muscle, being an excellent

guide to its corresponding commissure, is of practical importance to the surgeon. In order to appreciate the structure of the atrioventricular valvular complexes in the human heart, it has been of considerable value to examine the valve and its components in other mammals. By adopting this comparative anatomic approach, the complete significance of the human atrioventricular valve complexes, become more apparent.7 Hence the comparative study of papillary muscles and other components of the atrioventricular valvular complexes of the hearts of human, sheep, goat, cow and pig are undertaken.

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OBJECTIVES

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2. Objectives 1. Comparison of the size and weight of human heart with other mammals in ratio of their body weight.

2. Comparison of diameters of mitral and tricuspid valvular complexes along with number of cusps and to find any differences.

3. Study of papillary muscles, their number, positions, length and thickness.

4. Study of attachment of chordae tendineae a. their number attached to each papillary muscle and cusp. b. their attachment to different zones of cusps.

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REVIEW OF LITERATURE

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3. Review of literature Normal anatomy: (a) Human The heart is a hollow, muscular organ enclosed in a fibro-serous sac called pericardium, and is situated in the middle mediastinum.

The cavity of the fully

developed heart is separated into right and left halves by an obliquely placed longitudinal septum and each half consists of atrium and ventricle. The interventricular septum is placed obliquely with one surface facing forwards and to the right and the other backwards and to the left.

Its margins are indicated by the anterior and posterior

interventricular grooves. Atrium communicates with the corresponding ventricle through the atrioventricular orifices guarded by atrioventricular valves. Atrioventricular valve is defined as a complex consisting of a fibrous ring or annulus, cusps, chordae tendineae and papillary muscles. Right atrium communicates with the right ventricle through the right atrioventricular orifice guarded on the ventricular side by a tricuspid valve and so is known as tricuspid orifice. Left atrium communicates with the left ventricle through the left atrioventricular orifice.

Left atrioventricular orifice or mitral orifice opens forwards and slightly

downwards and to the left.

It admits the tips of 2 fingers and is guarded on the

ventricular side by a valve formed of two cusps arranged like a Bishop s mitre, known as left atrioventricular or mitral valve.

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(i) The right ventricle: This chamber forms the greater part of the sternocostal surface of the heart and of its lower border, but the smaller part of the diaphragmatic surface. Right atrioventricular orifice is guarded by right atrioventricular valve. This orifice is situated in the anteroinferior part of the left wall of the atrium, and admits the tips of three fingers. It measures 10.8 cm to 11.4 cm in circumference. Roughly triangular in shape, its margins are described as anterosuperior, inferior and septal.

This orifice is guarded by the

tricuspid valve. It is possible to distinguish three cusps in the tricuspid valve, which project into the ventricle. They are located anterosuperiorly, septally and inferiorly. Small accessory cusps are frequently present in the angles between the named cusps and like them consist of a fold of endocardium strengthened by fibrous tissue. All cusps of the atrioventricular valves display, passing from the free margin to the inserted margin, rough, clear and basal zones. Rough zone provides attachment to most of the chordae tendineae. The clear zone is smooth and translucent, receives few chordae tendineae. The basal zone is thicker, and it contains the insertions of atrial myocardium. The ventricular surfaces of the cusps, which are roughened give insertion to the chordae tendineae. The chordae tendineae are fine tendinous cords supporting the cusps of the atrioventricular valves. False chordae connect papillary muscles to each other or to the ventricular wall or pass directly between points on the wall.

The true chordae

usually arise from small projections on the tips or margins of the apical onethirds of papillary muscles, but sometimes arise from the bases of papillary muscles or directly from the ventricular walls and the septum.

They are attached to

various parts of the ventricular aspects or the free margin of the cusps. They

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have been classified into first, second and third order chordae according to the distance of the attachment from the margins of the cusps. Fan shaped chordae have a short stem from which branches radiate to attach to the margins of the zones of apposition between cusps and to the ends of adjacent cusps. Rough zone chordae arise from a single stem which usually splits into three components that attach to the free margin, the ventricular aspect of the rough zone and to some intermediate point on the cusp respectively. Free edge chordae are single, thread like and often long, passing from either the apex or the base of a papillary muscle into a marginal attachment usually near the mid point of a cusp or one of its scallops. Deep chordae, also long, pass beyond the margins and branching to various extents, reach the more peripheral rough zone or even the clear zone. Basal chordae are round chordae or flat ribbons, long and slender, or short and muscular. The two major papillary muscles in the right ventricle are located in anterior and posterior positions. A third, smaller muscle has a medial position together with several smaller, and variable, muscles attached to the ventricular septum. The anterior papillary muscle is largest. Its base arises from the right anterolateral ventricular wall below the anteroinferior commissure of the inferior cusp.

The posterior or inferior, papillary

muscle arises from the myocardium below the inferoseptal commissure. It is frequently bifid or trifid. The septal or medial papillary muscle is small but typical, and arises from the posterior septal limb of septomarginal trabecula. All the major papillary muscles supply chordae to adjacent components of the cusps they support. A feature of right ventricle is that the septal cusp is tethered by individual chordae tendineae directly to the ventricular septum; such septal insertions are never seen in left

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ventricle. When closed, the three cusps fit snugly together, the pattern of the zones of apposition confirming the trifoliate arrangement of the tricuspid valve.

(ii) Left ventricle This ventricle is conical and its apex forms the apex of the heart. At its base, the cavity communicates posteroinferiorly, with the left atrium through the mitral valve. The left atrioventricular (mitral) orifice is oval, with its long axis running downwards, backwards and to the right. It is smaller than the tricuspid orifice, the circumference ranging from 7.2 cm to 9 cm. It is guarded by the left atrioventricular or mitral valve, a bicuspid valve with triangular unequal cusps. The smaller posterior cusp is posteroinferior and to the left of the orifice; the larger anterior cusp is anterosuperior and to the right, between the mitral and aortic orifices. The bases of the cusps are attached to the fibrous ring, round the mitral orifice where they are either continuous with one another or separated by accessory cusps. It is described as consisting of a continuous veil attached around the entire circumference of the mitral orifice.

Its free edge bears several

indentations, two are sufficiently deep and regular to be nominated as commissure. They are known as anterior and posterior commissures. When the valve is laid open, the anterior cusp is seen to be semicircular or triangular, with few or no marginal indentations. The cusp has a deep cresentric rough zone, which receives various chordae tendineae. A clear zone is seen between the rough zone and the valvular annulus, which is devoid of attachments of chordae. The anterior cusp has no basal zone, continuing instead into the valvular curtain. The posterior cusp usually has two or more minor indentations. These indentations divide the cusp into a relatively large middle scallop and

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Figure No. 1: Interior of ventricles in human heart

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smaller anterolateral and posteromedial commissural scallops.

Each scallop has a

cresentric, opaque rough zone, receiving on its ventricular aspect the attachments of chordae tendineae. From the rough zone to within 2-3 mm of its annular attachment, there is a membranous clear zone devoid of chordae. The basal 2-3 mm is thick and vascular, and receives basal chordae. The margins of the cusps receive insertions of chordae tendineae. They resemble those supporting the tricuspid valve. False chordae are irregularly distributed. True chordae of the mitral valve may be divided into intercusp or commissural chordae, rough zone chordae, including the special srut chordae, so called cleft chordae and basal chordae. Most true chordae divide into several branches near their attachment. There are two papillary muscles supporting the cusps of the mitral valve. They vary in length and breadth and may be bifid. The anterolateral muscle arises from the sternocostal mural myocardium, the posteromedial from diaphragmatic region. Chordae tendineae arise mostly from the tip and apical one third of each muscle, but sometimes take origin near their base. The chordae from each papillary muscle diverge and are attached to corresponding areas of closure on both valvular cusps.8

(b) Mammals The heart is the muscular central organ of the blood vascular system which, by its rhythmic contraction, act like a double suction and pressure pump and thus suction and pressure pump and thus maintains the motion of the blood through the closed system of tubes, the blood vessels. Although somewhat variable from species to species, its shape resembles that of a more or less pointed and bilaterally flattened cone.

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The heart is differentiated into a right venous and a left arterial part. Each of these two parts consists of an atrium (atrium cordis dext et sin) and a ventricle (ventriculus cordis dext et sin).

Atrium communicates with the ventricles through

atrioventricular orifices guarded by atrioventricular valves. The atrioventricular valve complex is described as consisting have a fibrous ring or annulus, cusps, chordae tendineae and papillary muscles. Right atrium communicates with the right ventricle (ventriculus dexter) through the ostium atrioventriculare dext. The ventricular wall carries the trabeculae carnae, which are well developed in the area near the interventricular grooves. Apart from trabeculae carnae, there are a variable number of rounded muscular beams, which form cross, connections between the septum and the outer wall of the ventricle. One of these is especially powerful and runs from the septum below the subarterial m. papillaris to the base of m. papillaris magnus. It represents the trabecula septomarginalis, and integral part of the conduction system of the heart. Three papillary muscles project into the right ventricle. They have a special function and show species and individual variations in shape. One of these papillary muscles of the septum of the right ventricle is termed m.papillaris subarteriosus (septal papillary muscle), because of its proximity to the pulmonary trunk. The second comprises a group of muscles also situated on the septum, which forms a functional unit known collectively as mm.papillares parvi (posterior papillary muscle), the third and largest papillary muscle is the m.papillaris magnus (anterior papillary muscle) which is generally located on the outer wall.

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The papillary muscles give rise to groups of chordae tendineae, which fan out and radiate into the free borders and onto the luminal surface of the tricuspid valve (valva atrioventricularis dextra, s.tricuspidalis). The latter originates at the annulus fibrosus, surrounds the ostium atrioventriuclare dext, and divides into three cusps viz. cuspis septalis (posterior cusp), cuspis parietalis (anterior cusp) and cuspis angularis (septal cusp), which projects into the lumen of the ventricle and can give rise to secondary cusps. Each of the main cusp is fixed by means of chordae to two papillary muscles. The valva atrioventriculare dext acts a non-return valve. The papillary muscles have the function of maintaining the tendinous chords under tension when the valve plane is displaced during the phases of heart action with the commencement of systole and onset of the phase of increased pressure the atrioventricular valve closes.

This is

achieved by contraction of the papillary muscles, which, through the tendinous chords, exert pull on the cusps, which are then unfolded and apposed at their broad rims. Left ventricle (ventriculus cordis sin.) receives its blood from the left atrium through the ostium atrioventriculare sin. The muscular wall of the left ventricle is very thick, being two or three times thicker than the outer wall of the right ventricle. The same is true of the septum interventriculare, that forms a functional unit with the outer wall of the left ventricle. The trabeculae carnae are less numerous than in the right ventricle but are concentrated in the apical region and shallow recesses are formed between them. The two papillary muscles of the left ventricle are situated on the outer wall and are termed, according to their location, m.papillaris subauricularis (anterior papillary muscle) and subatrialis (posterior papillary muscle). Their chordae tendineae go to the bicuspid valva atrioventricualris sin.s.valva bicuspidalis.s.valva mitralis. The

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valve originates at the fibrous ring, which surrounds the left atrioventricular orifice. Because of their location the two cusps are termed cuspis septalis (posterior cusp) and cuspis parietalis (anterior cusp) respectively. (i) Heart of sheep and goat The heart of the sheep is in the form of a blunt cone. The goat s heart has the form of a pointed cone. In the sheep both papillary muscles of the outer wall of the left ventricle are stout. The subauricular papillary muscle has a cylindrical shape and two apices. The subarterial papillary muscle is better developed than the preceding and invariable has a doublepointed cupola. Two of the papillary muscles of the right ventricle are situated on the septum and the third is placed on the outer wall. The latter is the m.papillaris magnus and usually has three-pointed apex. The m.papillaris subarteriosus is the smallest and appears as a protrusion the size of a pea on the septum. The mm.papillares parvi vary in shape. They consist of a united group, which usually carries two distinctly separated papillae. The papillary muscles of the goat are similar.

(ii) Heart of the cow Both ventricles have certain distinctive features. The outer wall of the right ventricle carries numerous stout trabeculae carneae in the inflow region, i.e. below the right atrioventricular orifice. In the region of the outflow tract, which extends into the conus arteriosus, the outer wall is smooth. The septum and almost the entire left ventricle are also smooth walled. The two papillary muscles of the left ventricle are considerable

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Figure No. 2: Interior of ventricles in the heart of sheep

Figure No. 3: Interior of ventricles in the heart of goat

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Figure No. 4: Interior of ventricles in the heart of cow

Figure No. 5: Interior of ventricles in the heart of pig

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thicker than those of the right ventricle. The m.papillaris subauricularis appears as a column on the outer wall of the left ventricle. The presence of a deep longitudinal groove clearly divides it into two parts each of which terminates at the ostial end in a prominent papilla from which chordae tendineae extend to the membranous valves.

The

m.papillaris subatrialis, which is more distally situated, also presents as a muscular column, which is fused to the outer wall. The thin mm.transversi form a wide-meshed network between the septum and the base of the papillary muscle. Further more there are other, irregularly arranged but also thin, transverse muscles, which connect the septum with the outer wall.

Of the three papillary muscles of the right ventricle, the m.papillaris magnus is situated on the outer wall while the mm.papillares parvi and m.papillaris subarteriosus arise from the septum.

The base of the great papillary muscle consists of several

trabeculae carneae and this muscle also bears multinodular cupola. Its tendinous chords go to the cuspis parietalis and angularis. The small papillary muscles are situated on the septum where the latter meets the subsinuous part of the outer wall of the right ventricle in an acute angle. They each have a uniform base, which carries two or three

18

free standing wart-like processes and give rise to chordae tendineae stretching to the septal and parietal cusps.

The subarterial papillary muscle arises from the septum

supraventricularis where it gives rise to double rows of tendinous chords running to the septal and angular cusps.

(iii) Heart of the pig

The interior of the pig s ventricle exhibits some species peculiarities, especially in its papillary muscles. Both papillary muscles of the left ventricle arise form the outer wall but m.papillaris subatrialis, which borders on the interventricular septum, is broad and low. Its base is formed by several muscular columns, which unite into a single structure. Its cupola, which rises towards the cuspis septalis, usually carries two or less commonly, three projections. The system of muscular bands running from the papillary muscle to the septum consists of a rounded muscle column, which divides repeatedly after its origin from the septum.

The m.papillaris subauricularis can be clearly

distinguished against the ventricular wall by its rounded, beam-like shape. Its cupola is either uniformly rounded or bears several small wart-like processes. In addition to these two papillary muscles there are usually several small accessory papillary muscles on the outer wall of the left ventricle.

19

Two of the three papillary muscles of the right ventricle are situated on the septum, whereas the third is on the outer wall. The m.papillaris subarteriosus is a small cupola like eminence on the septum while the plinth of m.papillaris magnus is formed by a number of muscular beams, which unite into a single complex. The body of the latter extends prominently from the outer wall and unite into a single complex. Always present between the base of the great papillary muscle and the septum is the trabecula septomarginalis. The mm.papillaris parvi form a pleomorphic muscle group consisting of several components. The right ventricle may also contain accessory papillary muscles.9

20

Embryology of atrioventricular valve complexes During the early stages of development, the heart tube with its arterial and venous ends shows dilatations, namely truncus arteriosus, bulbus cordis, the ventricle, common atria and sinous venosus. The straight tube forms a loop due to paucity of space. The primitive atrial chamber communicates ventrally with the bulbo-ventricular cavity through the atrioventricular canal.

From the ventral and dorsal walls of the atrio-

ventricular canal the mesenchymal cells proliferate and form the ventral and dorsal endocardial cushions which fuse to form the septum intermedium. This septum divides the atrio-ventricular canal into the right and left atrio-ventricular orifices.

These

endocardial cushions contribute to the formation of the atrioventricular valves, and also the membranous part of the ventricular septum. By the seventh week, the endocardial cushions fuse together uniting with the interventricular and interatrial septum to divide the heart into four chambers, communicating only through the foramen ovale. By the eighth week, thick, blunt tabs of valvular tissue arise from these fused cushions and from its lateral aspect to provide a ring of tissue projecting into the left atrioventricular orifice. This tissue is anchored on its undersurface by considerable trabecular muscle to the ventricular wall. The valvular tissue then becomes more defined by absorption and undermining. In this manner three leaflets are developed around the right atrio-ventricular canal, and two leaflets around the corresponding left canal. These leaflets form respectively the cusps of the tricuspid and mitral valves.

The muscular trabecular connections to the apex of the valve are

transformed into fibrous tissue, the chordae tendineae. The muscular connections from the chordae tendineae to the ventricular wall remain as the papillary muscles. The

21

chordae tendineae and the papillary muscles undergo considerable thinning and undercutting eventually retaining the contact only at or near the edge of the valve. The valve leaflets, which were almost completely muscular tissue earlier, are invaded and replaced almost entirely by collagen.10

Comparative study of the morphology of papillary muscles of left ventricle in 135 normal adult hearts of different species (20 human, 25 dogs, 60 sheep and 30 goats) showed that the anterior and posterior papillary muscles were present in 100 % of cases of both human and animal hearts. To view the interior of the hearts, their left margin was opened, and a digital meter was used to measure the length and width of the papillary muscles. The shapes of papillary muscles were similar in animal hearts while variations of shapes were more common in human hearts. The papillary muscles support had one belly in many hearts, and two or three bellies in some hearts of human. In hearts of all animals, generally the papillary muscles support had generally one belly. The single muscle was conical or mammilated. The peak values of length of APM were 3.94 cm in sheep, width of APM in dog was 1.55 belly in hearts of all animals. Head number of APM in human was 1.9 and 11.5 was the CTN in human. The peak values of length of PPM in sheep were 3.95 cm, width of PPM in human is 1.55 cm, and the CTN was 11.8. The values of both anterior and posterior papillary were not statistically significant (p<0.05) in measurements of length, width and head number. But those of CTN were significant (p<0.05) between sheep and goat hearts.3

22

In human hearts, papillary muscles were classified into four types.

The

classification was based on how the papillary muscle was related to the leaflets through the chordae. The four types were as follows

In type 1, the papillary muscle was single.

In type 2, the papillary muscle had two heads, one of which sent chordae exclusively to the posterior leaflet.

In type 3, the papillary muscles were also divided, one head

supported the commissural area exclusively. Type 4, papillary muscles resembled type 3, but were distinguished from it in the way that the head supporting the commissure was very short. In this type, the different heads also originated at different levels on the ventricular wall from the apex to base.11

The anatomy of porcine hearts studied in detail, was compared with that of normal adult and neonatal human hearts. All hearts studied were normal, obtained from healthy animals. This comparison would be relevant if transgenic pig hearts can be used in cardiac transplantation. The basic components of both ventricles of pig were very similar to that of man with some notable differences. These differences were considered as the arguments continue concerning the use of transgenic pig hearts for xenotransplantation. The three leaflets of the tricuspid valve are located septally, anterosuperiorly and inferiorly or murally and their attachments were as found in the human right ventricle. As in man, the anterior papillary muscle, was the largest. A notable difference was seen, in the prominence of the muscular moderator band. This was situated in a much higher position within the ventricle compared with man. The apical component of the pig right ventricle possessed very coarse trabeculation, much broader

23

than those observed in the human right ventricle. In the left ventricle a pair of papillary muscles were located within the cavity. As in man the mitral valve had 2 leaflets, mural and aortic, with the mural (posterior) leaflet guarding two-thirds of the circumference of the valve, and with the aortic (anterior) leaflet in the fibrous continuity with the leaflets of the aortic valve. Both in pig and man, the paired papillary muscles were attached to the mitral leaflets.

They were located anterolaterally and posteromedially within the

ventricular mass. As in right ventricle, these muscles were coarser in the pig. The apical trabeculations of the left ventricle were also coarse.12

A comparative anatomical study of mitral ring and 2 major mitral cusps of 12 adult mammals, including man, horse, ox, sheep, pig, dog, rabbit, cat, guinea pig, hedgehog showed great variation in the structure, attachments, relative size, and mobility of the 2 major mitral cusps. The two major cusps were called aortic (anterior) and mural (posterior) and these terms were equally applicable to man and quadruped mammals. The basic pattern of each major mitral cusp had two zones; an appositional zone and a free basal non- appositional zone. The structure of each zone was an expression of its function.

During valve closure the appositional zone comes into contact with a

corresponding zone on the opposing cusp. A ridge of demarcation was present between the appositional and free zones; this when present represented the line of closure of the valve. In man the mitral orifice was irregular in contour and was oriented vertically, commissural areas being one above the other. The mural cusp was rectangular and had a wider basal attachment than that of aortic cusp. Its free border showed 2 or more indentations. The mitral aortic cusp in human heart was larger. The line of demarcation

24

between the free and appositional zones was very apparent to the naked eye when the whole cusp was inspected. There was absence of this line in few mitral aortic cusps. Also in quadruped mammals, the aortic and mural cusps usually had two zones, a proximal free zone and a distal appositional zone. In the mitral aortic cusp of some animals, particularly sheep and ox, the appositional and free zones were sharply demarcated from each other. The mural cusp in sheep and ox was entirely appositional in type.7

The left ventricle of human heart consisted of 2 papillary muscles. In most individuals the papillary muscles were attached to the left ventricular walls over a large base. The muscles received chordae tendineae from each mitral leaflet. Each papillary muscle had an average of six heads, and an average of 12 chordae tendineae per head. Each primary or first order chordae tendineae was divided into an average of three secondary or second-order chordae tendineae. Each second-order chorda was again divided into two or three tertiary or third order chordae tendineae, which were attached to the mitral leaflet. Thus each primary chorda had an average of five tertiary chordae. So each papillary muscle supported an average of 62 chordae attached to the mitral leaflets. Hence both papillary muscles supported 24 first order chordae and 124 third order chordae. Variations in the number of chordae tendineae attached to either papillary muscle or to either mitral leaflet were also noted. The thickness of either papillary muscle was about the same as that of the left ventricular free wall or ventricular septum. The antero-lateral papillary muscle was slightly larger than the postero-medial one. 75 %

25

of antero-lateral papillary muscle consisted of a single muscle group whereas 65 % of the postero-medial papillary muscle consisted of 2 or 3 major muscle groups.5

Studies regarding anatomic features of normal mitral valve and associated structures in fifty normal human hearts revealed that the intercommissural diameter varied from 2.5 to 3.5 cm. The valve less than two finger breadths from commissure to commissure may not be considered as stenotic, while one that admitted two fingers may be mildly stenotic. 100 hearts were examined for the accessory cusps. Only 5% of specimens had tiny projections, which could be called as accessory cusps. Folding and pleating of the posterior cusp was common and 14% of the cases showed 2 projections of the posterior cusp adjacent to the commissures, and 28% showed one projection of the posterior cusp adjacent to a commissure. These findings led to the conclusion that the normal valve had 2 cusps, the posterior cusp commonly showed some irregularity. In the anterior cusp, most of the chordae tendineae were attached near the free edge of the valve. They appeared to be inserted into the fibrous band within the endocardial layers of the valve running along its line of closure. In the posterior cusp, the chordae traversed most of the distance through the cusp towards its base. In both leaflets majority of chordae tendineae were inserted into the free edge and have been called chordae of first order. The chordae those inserted into the endocardial folds on the ventricular aspect of the leaflets, 0.3 to 0.6 cm from the free edge were known as chordae of the second order. The origins of these second order chordae were independent from the papillary muscles.

26

The papillary muscles were named as anterior or antero-lateral and posterior or postero-medial based on their relationship to the valve commissures.

The anterior

papillary muscle was usually single. In 60% of cases, the posterior papillary muscle had 2 or 3 muscles or one muscle with 2 or 3 heads. Multiple muscles at the postero-medial location caused gaps between the groups of chordae arising from them.6

The mitral valve consisted of 2 leaflets anchored at their bases to the annulus. Antero-medial leaflet was larger than the postero-lateral leaflet.

Occasionally an

accessory or commissural leaflet was present, rarely supplied by a separate papillary muscle with chordae tendineae. The chordae tendineae were inserted near the edges of the leaflets. 3 varieties of chordae tendineae were described. The first variety arising from the nearby stronger threads were inserted along and close to the leaflet margins, and were most abundant in the peripheral part of each leaflet. The second type were stronger structures that arose from the papillary muscles and were inserted on the ventricular surface of the leaflet margin. The third type was short and broad, which arose from the summit of the papillary muscles and they passed directly in a straight line to be inserted on the ventricular surface of the leaflets near their base. The antero-lateral papillary muscle was single in 75 % of cases, double of a single muscle with a bifid head in 10%. The postero-medial papillary muscle arose between the junction of ventricular septum and the posterior wall, and had multiple heads in two thirds of the cases. The position of the papillary muscles prevented herniation of the valve flaps towards the atrium during systole and excessive traction in diastole. The papillary muscles were important guides to its corresponding commissures.13

27

The shortage of organs for xenotransplantation led to the exploitation of donor sources. The possible solution for this was the use of animals as a source of organs. Use of non-human primates as an organ source was of limited value as they were scarce. Those that were in plenty such as baboons also cannot be used because of their maximum size. Usage of porcine organs solved these difficulties. Pigs were domesticated, and were easy to breed them. They also had large litters and these grew rapidly to a size of the very largest human being. Pig and man having many anatomical similarities favoured the use of pig organs but there were immunological difficulties. There was occurrence of the antipig antibodies in the recipient, which rejected the grafts. Even after overcoming the immunological difficulties, several other barriers still prevented the pig organs to support life in a human being.14

Mitral valves from 50 hearts were studied and four types of chordae tendineae were described based on their insertion. The four types were commissural chorda rough zone chorda, cleft chorda and basal chorda. 1. Commissural chorda were those inserted into the commissures between anterior and posterior leaflet. 2. Rough zone chorda were the chorda inserted into the ventricular aspect of the distal rough portion of both leaflets. They were split into three cords before they were inserted into the leaflet. 3. Cleft chorda were those, which were inserted into the clefts between the scallops of the posterior leaflet.

28

4. Basal chorda were single strands, which originated from the posterior ventricular mass and were inserted into the basal zone of the posterior leaflet. Commissural chorda originated as a main stem and branched radially to be inserted into the free margin of the commissural regions. The branches of the posteromedial commissural chordae were longer, thicker, and had a wider spread than those of the anterolateral commissural chordae. In the anterior leaflet, chorda tendineae were inserted exclusively into the rough zone i.e. into the distal part of the leaflet. At the apex of the leaflet the rough zone extended about 0.8 to 1 cm from the free margin to the line of closure. Two of the rough zone chordae of the anterior leaflet were very thick and were named strut chordae. These were observed in 90% of the hearts examined. Chordae tendineae those inserted into the posterior leaflet were as follows

the

first type i.e the basal chorda were unique to the posterior leaflet. They were inserted into the basal portion of the leaflet. These were found in 31 of the 50 hearts. The second type was similar to the rough zone chorda of the anterior leaflet, but there was absence of strut chordae. The third type was cleft chordae, which inserted into the indentations or clefts between the scallops of the posterior leaflet. Out of 50, 37 hearts had atypical rough zone chordae. Among the rough zone chordae of the anterior leaflet, 17% were atypical. 16% among those of posterior leaflet were atypical. The various orders of chordae tendineae described were old terminologies. According to this, the first order included commissural chorda, rough zone chorda that insert into the free margin of the leaflets and branches of cleft chorda of the posterior

29

leaflet. Second order chorda included rough zone chordae of the leaflets, which were inserted beyond the free margin. Strut chordae of the anterior leaflet, and the main stem of the cleft chordae of the posterior leaflet. Third order chordae included the basal chordae of the posterior leaflet. On an average, 25 chordae insert into the mitral valve. Of the 25 chordae, 9 pass to the anterior leaflet, 14 to the posterior leaflet.15

The mitral valve consisted of two cusps, the antero-medial and postero-lateral leaflets, of which the antero-medial leaflet is the largest. One or two accessory leaflets named anterior and posterior were present. The papillary muscles (antero-lateral and postero-medial) arose between the intervals of the two valve leaflets.

The chordae

tendineae extended from the papillary muscles or directly from the ventricular myocardium, to be inserted on the corresponding halves of the ventricular surface of the mitral leaflets.

First order chordae tendineae were those that originated from the

papillary muscles and got inserted onto the free edge of the mitral leaflets. Thicker chordae tendineae that arose from the papillary muscles and were inserted at a short distance from the free edge of the cusp were known as chordae tendineae of the second order. Chordae tendineae of the second order also insert on the central portion of the antero-medial (aortic) cusp in 71 % of hearts. Chordae tendineae of the third order arose directly from the ventricular musculature and were inserted onto the postero-lateral leaflet of the mitral valve. Proper spatial relationship should be maintained between the components of the valve for proper functioning. The antero-lateral papillary muscle was commonly infarcted. Failure of the infarcted papillary muscle to contract during systole

30

resulted in mitral regurgitation. Mitral regurgitation due to infarction of a papillary muscle was described as a differential diagnosis of precordial systolic murmur, which developed suddenly after myocardial infarction.4

The importance of the continuity between the mitral annulus and the papillary muscle for left ventricular performance was stressed. In case of mitral valve replacement for patients who required total excision of the leaflets and the chordae tendineae, mitral allograft have been used to restore the annulo-papillary muscle continuity.

It was

difficult to determine the proper length of this allograft chordae for the re-suspension. Hence the human hearts at autopsy were studied to provide an anatomic reference for the re-suspension procedure. The weight of the hearts studied ranged from 150 to 490 grams. In the study, the mitral annular circumference was calculated with the sum of the all attachments of the valves. Then it was divided by 3.142 to yield the mitral annular diameter. The mitral annular circumference was 93.2 mm. The mitral annular diameter ranged from 22.3 to 40.1 mm.16

Pathological study of mitral valvular lesions in 55 infant hearts revealed that these hearts had primary congenital malformation of the mitral valve, or an acquired infarction of papillary muscles secondary to some other malformation. Some of the anomalies noted were as follows: 1. Mild fusion of the commissures of the mitral valve. 2. Accessory tissue of the mitral valve: in this case large accessory papillary mass was attached to the atrial aspect of the posterior leaflet.

31

3. Parachute deformity of the mitral valve: In this deformity there was a single left ventricular papillary muscle into which the chordae tendineae from both mitral leaflets inserted. Chordae tendineae were usually short and thickened. 4. Anomalous attachment of chordae tendineae to the rim of the ventricular septal defect. 5. Accessory orifice of mitral valve:

This was a circular deficiency in the

substance of a valve leaflet, which varied in size. From the circumference of the accessory orifice, chordae tendineae were inserted into an independent papillary muscle. 6. Ebstein s malformation of inverted tricuspid valve: atrio-ventricular valves were inverted, so that left atrio-ventricular valve had the structure of a tricuspid valve. 7. Anomalies involving chordae tendineae were abnormal insertion or abnormal length. They may be short or long. 8. Anomalies involving the papillary muscles may be: a. Anomalous mitral arcade:

The anterolateral and posteromedial papillary

muscles of the left ventricle and anterior mitral leaflet together formed an arcade. A bridge of fibrous tissue arched between the two papillary muscles. Chordae tendineae were thickened and short so that papillary muscles were in direct continuity with the anterior mitral leaflet. b. Abnormal position of papillary muscles: In normal heart, papillary muscles arose at the junction of middle and lower thirds of the left ventricle. Their origins at abnormal sites like upper one third of the left ventricular wall were also seen.

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c. Large papillary muscles may obstruct the mitral valve.17

10 hearts obtained from routine autopsies were studied for morphological characteristics, vascular anatomy of papillary muscles and the relation between them, based on detailed postmortem angiographic investigations. The papillary muscles of the left ventricle were grouped into three broad categories depending on the nature of attachment to the ventricular wall and the relative length of the body of papillary muscle that protruded freely into the ventricular cavity. The groups were: 1. Completely tethered papillary muscle: In this type papillary muscle was fully adherent to the subjacent ventricular myocardium and protruded very little into the ventricular cavity with few trabecular attachments. 2. Finger like papillary muscle: in this type one third or more of the body of the papillary muscle protruded freely into the ventricular cavity with very few or no trabecular attachments. 3. Mixed type papillary muscle: This papillary muscle had part of the body protruding freely into the ventricular cavity but also with considerable trabecular attachments and tethering. Both the antero-lateral and the postero-medial papillary muscles usually had one or two distinct bellies of muscle. In the same heart, the antero-lateral papillary muscle and the postero-medial muscle varied morphologically.

When two or more bellies

existed for any one of the papillary muscles, those bellies also showed morphological differences. In four hearts, the bases of papillary muscles had moved upwards towards the atrio-ventricular valves.18

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The functional anatomy of the components of the mitral apparatus was studied. The acquired and congenital disorders of each of the components that disturbed the harmony of the finely coordinated valve mechanism, which rendered it incompetent, were studied. The annulus served as a fulcrum for the leaflets and exhibited spincteric contraction in systole.

The two leaflets differed in shape, but the areas identical.

Anterior leaflet was more mobile.

Several different orders of chorda were noted.

Papillary muscles emerged as single bodies from the left ventricular wall and divided into a variable number of heads, each of which served as an anchor for chordae tendineae. Papillary muscle, as a functional unit included its muscular foundation in the contiguous left ventricular wall. The loss of sphincteric action of the basal attachments of the mitral cusps, leaflet abnormalities which may be due to excessive or deficient leaflet tissue or restricted leaflet mobility, abnormally long and short chordae, ectopically inserted, or ruptured chordae, dysfunction of the papillary muscle due to its rupture led to mitral regurgitation.19

3000 animal hearts varying in weight from 50 mg in a shrew to 15 kg in a female Indian elephant were studied. All mammalian hearts had four chambers. The mean heart weight / body weight ratio of some of the animals were as follows: (a) The mean heart weight / body weight ratio of a cow was 0.48, the range being 0.30

0.87.

(b) The mean heart weight / body weight ratio of a pig was 0.40, the range being 0.23

0.48.

34

(c) The mean heart weight / body weight ratio of a goat was 0.46, the range being 0.26

0.66.

(d) The mean heart weight / body weight ratio of a man was 0.55.20

Papillary muscle rupture led to cardiogenic shock and carried mortality in the range of 80 to 90%. 260 hearts at autopsy of patients who died of acute myocardial infarction showed 13 were found to have a frank rupture of the papillary muscle of which eleven of the ruptures involved the posterior papillary muscle and two involved the anterior papillary muscle. Papillary muscle rupture usually occurred at one of the muscle heads, which supported two or three chordae tendineae, and sometimes at the muscle trunk, which supported one half of all chordae distributed to both mitral valve leaflets.2

In a review of the mitral complex, the mitral valve was described to be suspended between the mitral annulus above and the two papillary muscles below. The annulus fibrosus of the mitral orifice measured 8 to 12 cm in circumference. The anteromedial leaflet was triangular in shape with the base of the triangle attached to the annulus fibrosus and its apex extended into the left ventricular cavity. The posterolateral leaflet is quadrangular and encircles about two-thirds of the mitral orifice. The chordae that were attached into the fibrous band running along the entire free edge of both the leaflets sparing only the tip of the apex were the first order chordae. Those, which were attached to valvular tissue a few millimeters deep to the free edge, were known as second order chordae. The posterolateral leaflet differed from the anteromedial leaflet as it also had third order chordae crossing from the ventricular wall to the undersurface of the body of

35

the leaflet.

The body of the anteromedial leaflet was free of third order chordal

attachments and therefore was more mobile than the posterolateral leaflet. There were two papillary muscles in the left ventricle, which were bifid, trifid, or a row of muscles. The papillary muscles originated at the junction of the middle and apical thirds of the left ventricular wall as a component of the interlacing trabeculae carneae. They were located at the anterolateral free wall and diagonally across the ventricular cavity at the junction of the posterior free wall and the muscular ventricular septum.10

91 specimens with atrio-ventricular septal defect that had a common atrioventricular valve or bi-ventricular atrio-ventricular connections were studied. Anatomic measurements were made of the number of major papillary muscles, the diameter and length of the papillary muscles.

Their location within the ventricle was examined.

Presence of a solitary papillary muscle, or deviation of the attachments of the papillary muscles, was more frequent in hearts with isomeric right appendages.

Among 91

specimens, a solitary papillary muscle was found in 13 hearts. In two hearts with right isomerism, the solitary structure was suspected to be a result of fusion of dual papillary muscles located adjacent to one another. The anterior or posterior papillary muscle was found to be lacking in the other 11 cases. 78 hearts had paired papillary muscles, the ventricular mural origins were deviated anteriorly in 9 and posteriorly in 3. The diameter of the papillary muscles, standardized by the ventricular inlet length, was smaller in hearts with either right or left isomerism than in those with usual atrial arrangement. The proportional length of the papillary muscles was significantly shorter in those with right isomerism than in those with either left isomerism or usual atrial arrangement.21

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Evaluation of the prognosis and functional outcome of mitral regurgitation caused by ischemic papillary muscle dysfunction with respect to treatment was done in 30 patients. Severe ischemic mitral regurgitation caused by papillary muscle dysfunction was regarded as a serious complication of coronary artery disease. The mechanisms involved in papillary muscle dysfunction were abnormalities of ventricular wall motion at the site of insertion of posterior papillary muscle, with either ballooning of posterior mitral leaflet and an elongated posterior papillary muscle or a pseudo-prolapse of the anterior mitral leaflet by shortening of the posterior papillary muscle and retraction of the posterior mitral leaflet towards the apex.22

Development of papillary muscles were studied to understand papillary muscle malformations such as in parachute mitral valves or parachute like asymmetric mitral valves.

Normal human hearts at between 5 and 19 weeks of development and rat

embryos from 12 to 18 days were used for the study. There was a horseshoe shaped ridge in the left ventricle which when traced in consecutive stages of development, appeared to be transformed into the papillary muscles of the mitral valve.

This transformation

implied gradual loosening of the muscular ridge from the left ventricular wall, starting in the atrioventricular region. In parachute mitral valves, there was one single papillary muscle to which all chordae were attached. In parachute-like asymmetric mitral valves, two papillary muscles could be recognized, one of which had abnormal morphologic characteristics. In the most severe cases, i.e grade 3, the abnormally long papillary muscle was attached over its entire length to the ventricular wall, with its tip located close

37

to the atrioventricular annulus. The valve leaflets were directly attached to the papillary muscle because chordae were not present. In grade 2, a few short chordae were attached to an abnormal long papillary muscle. In grade 1, abnormally long papillary muscle was present, but chordal morphologic characteristics were close to normal. A variation was found where adult mitral valve had three papillary muscles. The additional papillary muscle was attached to the parietal wall in the left ventricle at the location where the myocardial connections between cushion tissue and ventricular wall normally disappeared.23

Study of 78 mitral valves excised from patients with hypertrophied cardiomyopathy showed anomalous insertion of papillary muscle directly into anterior mitral leaflet in 13%. This abnormality identified by echocardiography demonstrated direct continuity between the hypertrophied papillary muscle and mitral leaflet and this appeared to be responsible for outflow obstruction.

Out of them 10 (13 %) were

identified as having distinctive morphological appearance in which one or both left ventricular papillary muscles were inserted directly into the anterior mitral leaflet. Anomalous papillary muscle insertion involved the commissural region in each valve. It also extended to contiguous portions of the anterior and posterior mitral leaflets. Chordae tendineae were absent in the area of direct anomalous muscle insertion. Among the ten valves with anomalous insertion, eight valves had a single papillary muscle, inserted into the mitral leaflet either near the antero-lateral (6 patients) or postero-medial commissure (2 patients). In the other two valves, both papillary muscles were inserted into the anterior mitral leaflet, each near its respective commissure. Only one (1 %) of the 100

38

valves from control had direct insertion of a papillary muscle into the ventricular surface of the anterior mitral leaflet.24

Mitral insufficiency represented the major cardiovascular manifestation in a case study of a patient 2 year and 10 month old girl with external features of Marfan s syndrome. The mitral valve showed abnormalities. The mitral orifice was wide, leaflets were large, especially the posterior one, the chordae tendineae were long and thin. The valve leaflets showed spongy thickening at the region of chordal insertions. Mucoid cysts were found in the leaflets of the mitral valve. Mitral insufficiency appeared to have been resulted from elongation of the chordae tendineae of the mitral valve.25

The hearts of three infants in whom mitral insufficiency resulted from an abnormal relationship of the papillary muscles, chordae tendineae and valvular leaflets were studied and the condition named as anomalous mitral chordal arcade was described. There was a bridge of fibrous tissue arched between the two papillary muscles which in some areas was directly attached to the free edge of the anterior leaflet and while in others, by chordae tendineae which were short, and poorly differentiated. The malformation reported was perhaps a result of a developmental arrest at a stage after loss of muscle in chordae and leaflets but before final attenuation and elongation of chordae have occurred.26

The papillary muscles described, as specialized form of the trabeculae carneae often resembled an exaggerated portion of the trabeculae with a free extremity, to which

39

the chordae tendineae were attached. In the left ventricle there were two groups of papillary muscles.

One group was situated posteriorly near the attachment of the

posterior free wall of the left ventricle to the interventricular septum. The other group was on the anterolateral free wall. These consisted of a set of two or even three well defined structures, each with chordae tendineae attached at the tip. The axis of the papillary muscles was oriented in a direction parallel to the axis of the left ventricular cavity. Left ventricular papillary muscle truly free from the adjacent ventricular wall was rarely seen.27

The mitral valve complex of the human heart consisted of functional units, which included the valve leaflets, chordae tendineae and the papillary muscles. The function of these units depended to a large extent on the link between the muscle and the valve. These links were the chordae tendineae, which transmitted contractions of the papillary muscle to the leaflets. Human bicuspid atrioventricular valve consisted of 8

12 chordae

tendineae, which on approaching the valve leaflet divided into thinner secondary branches.1

The chordae tendineae were described as follows

the chordae tendineae arising

from the papillary muscle and attached to the free edge of the mitral leaflet were primary or first order. Those that arose from the papillary muscle and were incorporated into the ventricular surface of the leaflet a few millimeters away from the free edge were secondary or second order. Tertiary or third order chordae, did not have any connection

40

to the papillary muscles but they coursed from the ventricular wall to the undersurface of the posterolateral mitral leaflet.28

Morphology of 50 normal tricuspid valves was examined. The valve leaflets and the number of chordae attached to each leaflet, and their morphology at the site of their insertion were studied. The chordae may arise from a papillary muscle either directly from the apex of the muscle or from small nipples which are usually on its upper third. Also the chordae may arise directly from the muscle of the posterior or septal walls of the right ventricle. Each chorda took origin as a single cord, often subsequently dividing. Its point of insertion was defined as the point at which it begins its attachment to the leaflet, irrespective of the extent of that attachment. The two types of fan shaped chorda were present in the tricuspid valve but they were not inserting into a particular region consistently. This was in contradistinction to the mitral valve. Attachments of rough zone and basal chordae were similar to that of the mitral valve. In addition to these the tricuspid valve had two more types of chordae, which were not present in the mitral valve. They were free edge chordae and deep chordae. Thus five types of chordae were attached to the tricuspid valve. Fan shaped chordae were present at the anteroposterior commissure in 47 hearts, at the posteroseptal commissure in 50 and at the anteroseptal in 41 hearts. Rough zone chordae were attached to the anterior leaflet in all 50 hearts, to the posterior leaflet in 41 and to the septal leaflet in 49. The free edge chordae branch before insertion, and their fine subdivisions form a delta-shaped insertion at the free edge. One or more were found attached to 32 anterior, 24 posterior, and 25 septal leaflets. Basal chordae were found attached to 23 anterior, 23 posterior, and 45 septal leaflets.

41

On the average 25 chordae were inserted into the tricuspid valve. Of the 25 chordae 7, were inserted to the anterior leaflet, 6 to the posterior leaflet, 9 to the septal leaflet and 3 were inserted into the commissural areas.29

The projections of the trabeculae carneae, into the lumen from the ventricular walls formed the papillary muscles, which were connected to the cusps of the tricuspid valve. The tricuspid valve guarded the right atrioventricular orifice. It had three cusps and admitted the tips of three fingers. The three cusps, called anterior, posterior, and septal, were attached by their bases to the fibrous atrioventricular ring. The edges and ventricular surfaces of the cusps received the attachments of the chordae tendineae, which diverged from the papillary muscles and prevented the cusps from being everted when the ventricle contracts. The main papillary muscles were anterior, inferior and septal in location and each was connected to more than one cusp. The walls of left ventricular cavity were thrice as thicker as those of the right ventricle. There were two papillary muscles, anterior and posterior, the anterior being the larger.

Both were

connected by chordae tendineae to each valve cusp. The posterior cusp received the chordae on both its margins and its ventricular surface, but the chordae of the anterior cusp were attached to it only along its margins.30

The right ventricle communicated posteriorly with the right atrium through the right ventricular orifice, guarded by the tricuspid valve. The valve consisted of three cusps, anterior, posterior and septal. On the inner surface of the ventricular wall, a number of irregular projections, the trabeculae carneae, formed by raised bundles of

42

muscle fibres were present. Other muscle bundles were the papillary muscles, which projected into the ventricular cavity to become continuous with the chordae tendineae. Chordae tendineae were attached chiefly to the free border of the cusps of the valve and to a lesser extent they were attached to their ventricular surface. The left ventricle communicated with left atrium through the left atrioventricular orifice whose valve, the mitral, consisted of two cusps, anterior and posterior. Anterior was also referred to as the aortic cusp of the mitral valve. From two large papillary muscles, chordae tendineae proceeded to both cusps of the mitral valve, but those, which proceeded to the anterior cusp, were attached to its free edge, and the ventricular surface of the cusp was therefore smooth.31

The right atrioventricular orifice was guarded by right atrioventricular valve whose three cusps were named posterior, septal and anterior. Small accessory cusps were frequently present in the angles between the named cusps. The cusps project into the ventricle. The cusp margins are irregularly notched and thinner than the central portions. The ventricular surfaces of these cusps are roughened and give insertion to the chordae tendineae. The left atrioventricular orifice is guarded by mitral valve with two cusps, anterior and posterior. The chordae do not extend far beyond the margin of the anterior cusp on its ventricular surface. The cusp is therefore smooth on both its surfaces.32

The walls of the right ventricle had prominent fleshy ridges, the trabecular carneae and it also gave rise to column like or nipple-like projections called papillary muscles. 3 sets of papillary muscles, anterior, posterior and septal named according to

43

the location of their base were described. From each papillary muscle several tendon like fibrous cords known as chordae tendineae extended to the cusps of the atrioventricular valve. The largest and most constant was the anterior papillary muscle, the septal muscle was tiny or which was even absent and the chordae tendineae spring directly from the septum. There may be one to three posterior muscles. The right atrioventricular valve known as tricuspid valve, consisted of three cusps. More often there were only two cusps, which made the use of the term tricuspid not always apt. The left atrioventricular ostium was protected by left atrioventricular valve, which had two cusps. The two cusps were reminiscent of a Bishop s mitre, hence the valve got its name, i.e mitral valve. The cusps were anterior and posterior. Chordae tendineae, which originated in papillary muscles were attached to the free edges of the cusps. There were two papillary muscles, an anterior and posterior.33

The pig heart was small in relation to the size of its body, especially in fat animals. The relatively low heart weight of only 0.3% of the body weight seemed that the size of the heart has not kept pace with the increase in body weight. Pigs reached an average of 100 kg in five to six months.34

The heart was small in proportion to the body weight (0.23 to 0.28%) especially in fat animals.35

44

METHODOLOGY

45

4. Methodology The present study was done by dissecting 10 hearts each of human, sheep, goat, cow and pig. The sex of human or animal was not considered. The materials used for the study are: 1. 10 hearts each of human, sheep, goat, cow and pig 2. Acetone - dehydrant agent. 3. Enamel paint. 4. Amyl acetate

thinner and solvent for the above.

5. Whatman s filter paper. 6. Colour brushes no 00, 0, 1. 7. Preservative solution for the specimen

5% formalin.

The human hearts were obtained from formalin fixed cadavers of department of Anatomy, Kempegowda Institute of Medical Sciences (KIMS), Bangalore. Hearts of cow, pig, sheep and goat were collected from local slaughterhouses after they were killed and were brought in jars containing 10% formalin solution to KIMS, Bangalore. 10% formalin solution was injected into the chambers of the hearts and the specimens were kept immersed in the preservative. Few animal hearts, used earlier by Dr. Seema, a senior postgraduate student of KIMS, for her dissertation work on coronary arteries were also utilized for the present study. The hearts were weighed using standardized weighing machine available in the department of pharmacology, KIMS, Bangalore. Size of the heart was measured by noting down the maximum length and breadth of each of the specimen using slide calipers.

46

The hearts were dissected using the classical approach of opening each of the four chambers according to the flow of blood. In this dissection, the right atrium was opened from the inferior venacava to the tip of the right atrial appendage. The right ventricle was opened along its attachment to the ventricular septum from the tricuspid orifice to the pulmonary outflow tract. An incision was then made along the acute (right) margin of the heart and was extended from the initial cut to the right ventricular apex. Another incision was made from the apex to the anterior papillary muscle creating a triangular flap, which remained attached to the septum by the moderator band. The left atrium was opened by an incision across its roof between the left and right pulmonary veins. The left ventricle was then opened laterally between the anterior and posterior papillary muscles, along the obtuse margin to the apex. Another incision was then made along the anterior wall adjacent to the ventricular septum through the aortic outflow tract. Blood clots if present were washed out from all chambers. Diameter of the valve from anterolateral to posterolateral commissure, that is the greatest diameter of the orifice was done by using a pair of dividers with fine points and ordinary ruler with subdivisions of 0.1 cm. The number of papillary muscles, and their positions were noted. The length of the papillary muscles were also measured using a pair of dividers with fine points and ordinary ruler with sub-divisions of 0.1 cm. Thickness of the papillary muscles was measured at their origin using slide calipers. The number of chordae tendineae attached to each papillary muscle and the cusps along with their attachment to different zones of the cusps were observed and counted using a hand lens.

47

Photograph No. 1: Photograph showing the instruments used for the study 1. Slide Calipers 2. Pair of dividers 3. Ordinary Ruler

48

After observations, the moisture over the papillary muscles, valve leaflets, and chordae tendineae has been removed with Whatman s filter paper. It is then dehydrated with acetone and then painted with enamel paint, using amyl acetate, thinner and solvent. The specimens were allowed to dry. The papillary muscles were painted in brown and Chordae tendineae in white. The photographs of the painted specimens were taken.

49

RESULTS

50

5. Results 1. Comparison of size and weight of human heart with other mammals in ratio of their body weight (Table No. 1): The results are tabulated as follows: Table No. 1: Comparison of average weight and size of various hearts Specimen

Average weight of the heart

Average total body weight

Average size (L x B in cms.)

Ratio of weight of the heart to total body weight

(in kgs.)

(in gms.) Human

339.6

60

9.40 x 11.50

0.0057

Sheep

82.3

18

8.32 x 8.49

0.0046

Goat

64.2

18

7.57 x 8.09

0.0036

Cow

1684.0

400

18.31 x 18.58

0.0042

Pig

217.0

100

7.56 x 7.78

0.0022

51

2. Comparison of diameters of the mitral and tricuspid valvular complexes along with number of cusps: (a) Diameters: Table No. 2: Comparison of the diameters of valvular complexes in mammals (All figures in cms.)

Specimen

Mitral Valve

Tricuspid Valve

Human

2.55

2.85

Sheep

1.84

2.02

Goat

1.31

1.76

Cow

4.22

4.42

Pig

1.38

1.55

It was observed that the diameter of tricuspid valve was more than the corresponding mitral valve in all mammals. The highest values were found in hearts of cow followed by that of human, sheep, goat and pig.

(b) Comparison of the number of cusps in different ventricles of human and mammals. Human mitral valve: It consisted of 2 cusps, anteromedial and posterolateral, of which the anteromedial leaflet was larger. The leaflets consisted of rough, clear and basal zones. Human tricuspid valve: It had three cusps, anterior, posterior and septal. The cusps showed rough, clear and basal zones.

Rough zone of both anterior and posterior cusps 52

Photograph No. 2: Cusp of Human ventricle showing rough zone and basal zone 1. Rough zone 2. Basal zone

53

Photograph No. 3: Cusp of Cow s ventricle showing rough zone and basal zone 1. Appositional zone 2. Free zone

54

provided attachment to most of the chordae tendineae. The clear zone was smooth and provided attachment to few chordae. Mitral valve of animals It consisted of two cusps anterior and posterior.

Each cusp showed

appositional and free zones, with a clear ridge demarcating them. Tricuspid valve of animals In all hearts of sheep, goat, cow and pig it had three cusps as in man. In animals each major cusp had 2 zones, the appositional zone and free zone. There was a clear ridge demarcating them in most of the leaflets.

Accessory cusps were not noted in any of the hearts of human or animals.

3. Study of papillary muscles: (a) Their number and position The papillary muscles, the anterior and posterior of left ventricle and the anterior, posterior and septal of right ventricle were found in 100 % cases of both human and animal hearts. Human: Left ventricle: The anterior papillary muscles with single belly arose from the sternocostal wall and posterior arose from diaphragmatic region. In one heart anterior papillary muscle had two bellies. In another it was a single belly with three heads. Posterior papillary muscle had groups of bellies in many hearts examined.

55

Right ventricle: Anterior papillary muscle was noted to be the largest of the three. The anterior papillary muscle arose from the right anterolateral ventricular wall. It was a single belly in eight hearts. In two, the muscle had two bellies. Posterior papillary muscle arose from the septal wall. It frequently had two or three bellies. Septal muscle was small and arose from the septal wall.

Animals:

Left ventricle: In the hearts of all animals examined, the left ventricular papillary muscles were situated on the outer wall. Both muscles had a single belly except in pig where the posterior papillary muscle had two to three bellies. Right ventricle: In the right ventricle of all animals, the anterior papillary muscle had a single belly and was located on the outer wall. The posterior papillary muscle in sheep, goat and cow had single belly in all hearts examined except in one of the specimen of right ventricle of cow, where the posterior papillary muscle had two bellies (Photograph No. 16 Specimen C-4). The posterior papillary muscles of right ventricles of pig, had two to three bellies. The septal muscles were located on the septum.

56

(b) Their length and thickness Table No. 3: Comparison of the average length and thickness of the papillary muscles in the ventricles of different mammals (All figures in cms.)

Specimen

Left Ventricle Length

Right Ventricle

Thickness

Length

Thickness

APM PPM APM PPM APM PPM SPM

APM

PPM

SPM

Human

2.99

2.54

1.20

1.19

2.72

2.57

0.34

0.58

0.48

0.17

Sheep

3.26

3.20

1.21

1.11

2.72

2.56

0.40

0.53

0.41

0.13

Goat

3.00

2.87

1.14

0.93

2.68

2.66

0.39

0.38

0.35

0.14

Cow

7.34

7.28

2.57

2.45

6.08

5.75

2.05

1.35

1.27

1.06

Pig

2.74

2.69

1.02

0.90

2.60

2.22

0.45

0.27

0.26

0.07

The average length and thickness of papillary muscles were highest in cow. No

much

difference

was

found

in

57

the

values

among

other

mammals.

Photograph No. 4: Specimen H

3

Closer view of the interior of the Human right ventricle 1. Anterior papillary muscle 2. Groups of bellies of posterior papillary muscle 3. Septal papillary muscle

58

Photograph No. 5: Specimen H

3

Human Left ventricle showing two papillary muscles 1. Single belly of anterior papillary muscle 2. Single belly of posterior papillary muscle with two heads

59

Photograph No. 6: Specimen H

9

Human Left ventricle showing 1. Two bellies of anterior papillary muscle 2. Two bellies of posterior papillary muscle

60

Photograph No. 7: Specimen H

5

Human Left ventricle showing 1. Single belly of anterior papillary muscle with three heads 2. Two bellies of posterior papillary muscle

61

Photograph No. 8: Specimen H 10 Human Right ventricle showing 1. Two bellies of anterior papillary muscle 2. Groups of bellies of posterior papillary muscle 3. Septal papillary muscle

62

Photograph No. 9: Specimen S

8

Right ventricle of sheep showing 1. Single belly of anterior papillary muscle 2. Single belly of posterior papillary muscle 3. Single belly of septal papillary muscle

63

Photograph No. 10: Specimen S

8

Left ventricle of sheep with two papillary muscles showing 1. Single belly of anterior papillary muscle 2. Single belly of posterior papillary muscle

64

Photograph No. 11: Specimen G 6 Right ventricle of Goat with three papillary muscles showing 1. Single belly of anterior papillary muscle 2. Single belly of posterior papillary muscle 3. Single belly of septal papillary muscle

65

Photograph No. 12: Specimen G 6 Left ventricle of Goat showing 1. Single belly of anterior papillary muscle 2. Single belly of posterior papillary muscle

66

Photograph No. 13: Specimen C 6 Interior of right ventricle of Cow showing 1. Single belly of anterior papillary muscle 2. Single belly of posterior papillary muscle

67

Photograph No. 14: Specimen C 6 Closer view of right ventricle of Cow showing 1. Tip of anterior papillary muscle 2. Tip of posterior papillary muscle 3. Septal muscle

68

Photograph No. 15: Specimen C 6 Left ventricle of Cow showing 1. Single belly of anterior papillary muscle 2. Single belly of posterior papillary muscle

69

Photograph No. 16: Specimen C 4 Right ventricle of Cow 1. Single belly of anterior papillary muscle 2. Two bellies of posterior papillary muscle

70

Photograph No. 17: Specimen P 5 Right ventricle of Pig 1. Single belly of anterior papillary muscle 2. Groups of bellies of posterior papillary muscle 3. Septal papillary muscle

71

Photograph No. 18: Specimen P 5 Closer view of right ventricle of Pig 1. Single belly of anterior papillary muscle 2. Groups of bellies of posterior papillary muscle 3. Septal papillary muscle

72

Photograph No. 19: Specimen P 7 Left ventricle of Pig showing 1. Single belly of anterior papillary muscle 2. Dual bellies of posterior papillary muscle

73

4. Study of attachment of chordae tendineae (a) Number attached to each papillary muscle and cusp: Table No. 4: Comparison of the average number of chordae tendineae attached to each papillary muscle in the ventricles of different mammals

Specimen

Left Ventricle

Right Ventricle

APM

PPM

APM

PPM

SPM

Human

9.4

10.6

8.5

7.7

3.9

Sheep

4.5

5.5

4.8

3.4

2.6

Goat

5.6

6.1

5.9

4.8

2.8

Cow

6.4

6.5

5.5

6.7

3.6

Pig

8.0

7.2

5.0

5.2

3.3

It was noted that the number of chordae tendineae attached to papillary muscle were significantly less in ventricles of sheep and goat when compared with those of human and pig.

74

Table No. 5: Comparison of the average number of chordae attached to each leaflets of left and right ventricles in different species Specimen

Left ventricle

Right ventricle

AL

ALC

PL

PMC

AL

APC

PL

PSC

SL

ASC

Human

7.7

0.5

11.1

0.6

7.2

0.8

5.7

0.4

8.7

0.7

Sheep

3.8

0.8

6.0

0.7

3.0

0.4

4.0

0.6

3.9

0.6

Goat

5.0

0.6

5.1

0.8

4.5

0.6

3.3

0.6

6.2

0.6

Cow

5.3

0.8

6.1

0.6

5.1

0.6

6.0

0.6

5.0

0.7

Pig

6.2

0.8

7.5

0.8

4.4

0.5

4.3

0.3

3.5

0.6

The number of chorda tendineae attached to the cusps was highest in human, followed by pig, and cow. It was observed that the number of chorda tendineae was less in sheep and goat.

(b) the attachment of chordae tendineae to different zones of cusps: Human: The observation of the number of chorda tendineae inserted to the different zones of the cusps of left ventricle was done based on the classification given by Lam.15 The observation of the insertion of chorda tendineae to different zones of the cusps of right ventricle was done based on the classification given by Silver. 29

75

The results are as follows: Table No. 6: Table showing average number of different types of chordae inserted into the leaflets in human hearts Site of insertion

Type of chorda

Avg. number of chordae inserted

Left Ventricle Anterior leaflet

Posterior leaflet

Rough zone chorda

7.7

Rough zone chorda

8.6

Cleft chorda

1.4

Basal chorda

1.1

Rough zone chorda

4.7

Free edge chorda

0.8

Deep chorda

1.1

Basal zone chorda

0.6

Fan shaped chorda

0.4

Rough zone chorda

2.4

Free edge chorda

0.9

Deep chorda

1.1

Basal chorda

0.9

Rough zone chorda

3.8

Free edge chorda

1.1

Deep chorda

1.1

Basal chorda

2.7

Right Ventricle

Anterior leaflet

Posterior leaflet

Septal leaflet

76

Animals: The attachment of chorda tendineae to different zones of the cusps was followed according to the description of the zones, i.e. appositional and free zone as given by Walmsley. 7 The results are tabulated as given below: Table No. 7: Table showing average number of different types of chordae inserted into the leaflets and commissures in hearts of various animals

Specimen

Left Ventricle AL

ALC

AZ

FZ

Sheep

3.8

0.0

Goat

5.0

Cow Pig

Right Ventricle

PL

PMC

AZ

FZ

0.8

4.3

1.7

0.0

0.6

3.6

5.3

0.0

0.8

6.2

0.0

0.8

AL

APC

AZ

FZ

0.7

2.6

0.4

1.5

0.8

4.0

4.3

1.8

0.6

5.8

1.7

0.8

PL

PSC

AZ

FZ

0.4

2.3

1.7

0.5

0.6

2.4

4.4

0.7

0.6

3.9

0.5

0.5

77

SL

ASC

AZ

FZ

0.6

2.4

1.5

0.6

0.9

0.6

3.8

2.4

0.6

4.0

2.0

0.6

3.8

1.2

0.7

3.0

1.3

0.3

2.6

0.9

0.6

The average number of chordae tendineae attached to each leaflets was more in human and porcine hearts.

They were less in the hearts of sheep and goat.

78

Photograph No. 20: Specimen H 3 Human right ventricle showing 1. Attachment of chordae tendineae to the rough zone 2. Attachment of chordae tendineae to the basal zone

79

Photograph No. 21: Specimen H 1 Human left ventricle showing 1. Attachment of fan shaped chordae to the commissures

80

Photograph No. 22: Specimen G 6 Right ventricle of Goat showing 1. Attachment of chordae tendineae to the appositional zone

81

DISCUSSION

82

6. Discussion

Discussion is based on the observations made in the present study and also comparison with studies done earlier wherever available.

1. Comparison of the size and weight of human heart with other mammals in ratio of their body weight: a. Human Human heart weight ranged between 150 gms. and 490 gms.16 The mean heart weight / body weight ratio of a man was 0.55.20 b. Animals The mean heart weight / body weight ratio of cow was 0.37 pig was 0.23

0.65 and that of

0.27.9

The mean heart weight / body weight ratio of a goat was 0.46, the range being 0.26 0.66. The mean heart weight / body weight ratio of a cow was 0.48, the range being 0.30

0.87. The mean heart weight / body weight ratio of a pig

was 0.40, the range being 0.23

0.48.20

The pig heart weight was only 0.3% of the body weight.34 The porcine heart is small in proportion to its body weight, the ratio being in the range of 0.23 and 0.28.35

83

Table No. 8: Comparison of the mean heart weight / body weight ratio of different animals of the present study with previous work done

Author

Human

Sheep

Goat

-

-

-

0.55

-

0.46

0.48

0.40

Essentials of Pig Anatomy 34

-

-

-

-

0.30

Getty 35

-

-

-

-

0.57

0.46

0.36

0.42

Nickel 9 IntroductionNormal hearts a comparison 20.

Present study.

Cow 0.37

0.65

Pig 0.23

0.23

0.27

0.28

0.22

To calculate the ratio, standard body weight was taken from a veterinary text book.9 Human heart weighs the highest in comparison with the total body weight. This has been noted when a similar comparison is done in animals. Weight and size of the heart was more in cow, but the ratio of its weight to the body weight was less than that of human beings. The ratio was least in pigs. The ratio of the mean heart weight to body weight of different animals obtained in the present study correlates with those obtained by other authors as tabulated.

84

2. Comparison of diameters of mitral and tricuspid valvular complexes along with number of cusps and to find any differences: a. Comparison of diameters Human mitral valve The inter-commissural diameter of the mitral valve, was roughly 2.5 cm to 3.5 cm.6 Left atrioventricular orifice or mitral orifice opens forwards and slightly downwards and to the left. It admits the tips of 2 fingers. It is smaller than the tricuspid orifice, the circumference ranging from 7.2 cm to 9 cm.8 The annulus fibrosus of the mitral orifice measured 8 cm to 12 cm in circumference.10 The mitral annular circumference was 93.2 mm. Mitral annular diameter ranged from 22.3 mm to 40.1mm.16 Human tricuspid valve It measures 10.8 cm to 11.4 cm in circumference.8 Some authors have given the circumference of the annulus. In order to compare, those values are converted into the diameters by dividing the circumference by 3.142.

85

Table No. 9: Comparison of the measurements of diameters of the valves of human obtained in the present study with those of the measurements obtained in the literature

Author

Mitral valve

Tricuspid valve

(cms.)

(cms.)

Rusted 6

2.50

3.50

Gray s Anatomy 8

2.29

2.86

Silverman 10

2.54

3.82

-

Sakai 16

2.23

4.01

-

Present study

2.55

3.43

3.63

2.85

In the present study, the diameter of the valve from anterolateral to posteromedial commissure was done. It is observed that in man as well as in other mammals under study, the diameter of the tricuspid valve is more than that of mitral valve. The above tabulation shows that the values of the diameters of the valves obtained in the present study is in accordance with the values obtained by the other authors. When comparison of the diameters of mitral and tricuspid valves among different mammals is done, it is observed that it is highest in cow, followed by man, sheep, goat and pig. It seems that the diameter of the valve is in direct proportion with the weight and size of the heart.

86

b. Comparison of the number of cusps Human Mitral valve The mitral valve consisted of two cusps, the antero-medial and postero-lateral leaflets, of which the antero-medial leaflet is the largest. One or two accessory leaflets named anterior and posterior was present. 4 The normal valve had 2 cusps, the posterior of which showed some irregularity. The accessory cusps between the two major cusps were seldom seen.6 The bicuspid valve is guarded on the ventricular side by a valve formed of two cusps. Small accessory cusps are frequently present in the angles between the cusps.8 The mitral valve consisted of 2 leaflets anchored at their bases to the annulus. Antero-medial leaflet was larger than the postero-lateral leaflet. Occasionally an accessory or commissural leaflet was present, rarely supplied by a separate papillary muscle with chordae tendineae.13 In the mitral valve, the anterior leaflet was large, semicircular or triangular has a free margin with few or no indentations. This leaflet has in its atrial surface, a distinct ridge that followed the rim of the leaflet but is 0.8 to 1 cm from its free margin. The ridge defines the line of leaflet closure. Distal to the ridge, is a rough zone of the leaflet tissue, which comes into apposition with its counterpart on the posterior leaflet during valve closure. It has abundant chordal insertions in the ventricular surface in this area. Between the rough

87

zone and the valve annulus, the anterior leaflet is clear on trans-illumination and is devoid of chordal insertions, but may show prolongations of chordal fibers passing from their insertions in the rough zone toward the base of the leaflet. The posterior leaflet has three zones; rough, clear and basal zones.15 The annulus served as a fulcrum for the leaflets and exhibited spincteric contraction in systole. The two leaflets differed in shape, but the areas were identical. Anterior leaflet was more mobile.19

Tricuspid valve It is possible to distinguish three cusps in the tricuspid valve. They are located anterosuperiorly, septally and inferiorly. A feature of right ventricle is that the septal cusp is tethered by individual chordae tendineae directly to the ventricular septum; such septal insertions are never seen in left ventricle. Small accessory cusps are frequently present in the angles between the cusps.8 In the tricuspid valve, the basal zone is present in all the three leaflets. It also extends into commissural areas.29 The right valve had three cusps, which were named posterior, septal and anterior. Small accessory cusps were frequently present in the angles between the named cusps.32

88

Animals Mitral Valve The two major cusps were called aortic (anterior) and mural (posterior) and these terms were equally applicable to man and quadruped mammals. The basic pattern of each major mitral cusp had two zones; a distal appositional zone and a proximal free basal non-appositional zone. The structure of each zone was an expression of its function. During valve closure the appositional zone comes into contact with a corresponding zone on the opposing cusp. A ridge of demarcation was present between the appositional and free zones; this when present represented the line of closure of the valve.7 The bicuspid valve had two cusps.9 Tricuspid Valve The tricuspid valve which originated at the annulus fibrosus, surrounded the right atrioventricular orifice and divided into three cusps which projected into the lumen of the ventricle.9 The three leaflets of the tricuspid valve were located septally, anterosuperiorly and inferiorly. Their attachments were as found in human right ventricle. The mitral valve of the pig had 2 leaflets i.e mural (posterior) and aortic (anterior).12

Based on Lam15 and Walmsely7, the appositional zone of the cusps of animals is comparable to the rough zone of the leaflets in human, the remaining part of the human cusps resembles the free zone of other mammals.

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In the present study, the mitral valves of all hearts of human and other mammals studied had 2 cusps, anterior and posterior. The tricuspid valve of human and that of animals had three cusps, anterior, posterior and septal. Accessory cusps were not seen in any of the hearts examined. In human the anterior cusp of left ventricle showed rough and clear zones. Its posterior leaflet showed rough, clear and basal zones. The cusps of animals resembled those of man but showed free and appositional zones.

3. Study of papillary muscles, their number, position, length and thickness: a. Papillary muscles, their number and position Human Left Ventricle The papillary muscles support had one belly in many hearts and two or three bellies in some hearts of human. Width of posterior papillary muscle in human was 1.55 cm.3 The anterolateral and posteromedial papillary muscle arises between the intervals of the 2 valve leaflets.4 There were 2 left ventricular papillary muscles. Thickness of the papillary muscle is the same as that of the left ventricular free wall or ventricular septum.

Anterolateral papillary muscle was slightly larger than the

posteromedial one.

75% of the anterolateral muscle consisted of single

muscle group whereas 65% of the posteromedial papillary muscle consisted of 2 or 3 major muscle groups. Papillary muscles were attached to the left

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ventricular walls over a large base.5 In the left ventricle anterior papillary muscle was usually single in more than 70% of cases.

At the posteromedial location 2 or 3 muscles or one muscle

with 2 or 3 heads were present in 60% of the cases.6 The anterolateral muscle arises from the sternocostal mural myocardium, the posteromedial from diaphragmatic region.8 The papillary muscles originated at the junction of middle and apical thirds of the left ventricular wall. They were located at the anterolateral free wall.10 In human the paired papillary muscles were located anterolaterally and posteromedially.12 Antero-lateral papillary muscle was a single structure in 75% of the cases. In another 10% it was a double muscle or a single muscle with bifid head. Posteromedial muscle arose between the junction of ventricular septum and posterior wall. It had multiple heads in two thirds of the cases.13 In normal heart, papillary muscles arise at the junction of middle and lower thirds of the left ventricle.17 Both anterolateral and posteromedial papillary muscles usually had one or 2 distinct bellies.18 The papillary muscle included a portion of the adjacent left ventricular wall. Papillary muscles emerged as single bodies from the left ventricular wall and divided into a number of heads.19

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Right ventricle The two major papillary muscles in the right ventricle are located in anterior and posterior positions. A third, smaller muscle has a medial position together with several smaller, and variable, muscles attached to the ventricular septum. The anterior papillary muscle was the largest. Its base arises from the right anterolateral ventricular wall below the anteroinferior commissure of the inferior cusp. The posterior or inferior, papillary muscle arises from the myocardium below the inferoseptal commissure. It is frequently bifid or trifid. The septal or medial papillary muscle is small but typical, and arises from the posterior septal limb of septomarginal trabecula. All the major papillary muscles supply chordae to adjacent components of the cusps they support.8

Animals Left ventricle The papillary muscle's support had generally one belly in all hearts of animals. The muscle was conical and mammilated.

Average length of anterior

papillary muscle in sheep was 3.94 cm. Average length of posterior papillary muscle in sheep was 3.95 cm.3 The two papillary muscles of the left ventricle are situated on the outer wall and are termed, according to their location, m.papillaris subauricularis and subatrialis.8 In left ventricle of pig there were two papillary muscles, which arose from the

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outer wall. There were several small accessory papillary muscles on the outer wall of left ventricle.9 In pig the paired papillary muscles were located anterolaterally and posteromedially.12

Right ventricle Two of the three papillary muscles of right ventricle termed m.papillaris subarteriosus, and mm.papillares parvi, were situated on septum. The third and largest papillary muscle is the m.papillaris magnus was generally located on the outer wall. This may also contain accessory papillary muscles.9

In the present study, two papillary muscles, anterior and posterior of the left ventricle and three muscles, anterior, posterior and septal of the right ventricle were present in 100 % of the hearts of man and other mammals examined. Accessory papillary muscles were not noted in any of the hearts of human or animals. It was noted that in human left ventricle the anterior papillary muscles had single belly in eight hearts. In one of heart, it had two bellies (Photograph No. 6 Specimen H-9 Left Ventricle). In another, it was a single belly with three heads (Photograph No. 7 Specimen H-5 Left Ventricle).

The muscles arose from the sternocostal wall and

posterior arose from diaphragmatic region. Posterior papillary muscles were in groups in many of the hearts examined. In the right ventricle, anterior papillary muscle arose from the right anterolateral ventricular wall. It was a single belly in eight hearts. In the other two, it consisted of two

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bellies (Photograph No. 8 Specimen H-10 / H-4 Right Ventricle). Posterior papillary muscle arose from the septal wall. It frequently had two or three bellies. Septal muscle was small and arose from the septal wall. In the hearts of all animals examined, the left ventricular papillary muscles were situated on the outer wall. Both muscles had a single belly except in pig where the posterior papillary muscle had two to three bellies. In the right ventricle of all animals, the anterior papillary muscle had a single belly and was located on the outer wall. The posterior papillary muscle in sheep, goat and cow had single belly in all hearts examined except in one of the specimen of right ventricle of cow, where the posterior papillary muscle had two bellies (Photograph No. 16 Specimen C-4 Right Ventricle). The posterior papillary muscles of right ventricles of pig had two to three bellies (Photograph No. 18 Specimen P-5 Right Ventricle). The septal muscles were located on the septum. Table No. 10: Comparison of percentage of papillary muscles of left ventricle containing two or more bellies in the present study with those figures obtained by earlier authors Author

Single belly

Multiple belly

of APM

of PPM

Robert 5

75%

65%

Rusted 6

70%

60%

Davila 13

75%

66%

Present study

80%

70%

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The number and position of the papillary muscles in man and other animals were similar. The papillary muscles of pig and man appeared to be similar with regard to the number of bellies in both ventricles. The number of bellies of different papillary muscles was similar in sheep, goat and cow.

b. Papillary muscles, their length and thickness: Table No. 11: Comparison of the figures of average length and thickness of the papillary muscles of left ventricles of different mammals obtained in the present study to those figures given by an other author

Specimen

Length of APM

Width of APM

Length of PPM

Width of PPM

Ozbag 3

3.36

1.52

3.30

1.55

Present study

2.99

1.20

2.54

1.19

Ozbag 3

3.94

1.43

3.95

1.55

Present study

3.26

1.21

3.20

1.11

Ozbag 3

3.47

1.26

3.47

1.26

Present study

3.00

1.14

2.87

0.93

Cow

Present study

7.34

2.57

7.28

2.45

Pig

Present study

2.74

1.02

2.69

0.90

Human

Sheep

Goat

Author

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The values of the length and thickness of each papillary muscle of human, sheep, and goat are compared. But those of cow and pig are not compared due to lack of literature. The comparison of the length and thickness of each papillary muscle in the ventricles shows that anterior papillary muscle is the largest of all. When the length and thickness of the papillary muscles in different mammals under study are compared, they are longer in animals (except cow) than in human. The values are highest in cow, which may be due to its large body and large size of the heart. Next highest values are found in sheep followed by that of goat, man and pig. However the difference among the values in sheep, goat, man and pig was less than those of cow.

4. Study of attachment of chordae tendineae: a. their numbers attached to each papillary muscle and cusp b. their attachment to different zones of the cusps. Human Mitral valve The link between papillary muscle and valve leaflet in the human bicuspid atrioventricular valve consisted of 8-12 chorda tendineae.1 Average no of chordae tendineae attached to anterior papillary muscle of left ventricle in human was 11.5, range being 9

15, Average number of chordae

tendineae attached to posterior papillary muscle in man was 11.8, range being 8 15.3 Most of the chordae tendineae, which reached the anterior cusp, were attached

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near the free edge. In the posterior cusp, the chordae traversed most of the distance through the cusp towards the base. In both leaflets two orders of chordae tendineae were described. The first.order were those, which were inserted into the free edge. Those that arose independently from papillary muscles and inserted into endocardial folds on the ventricular aspect of the leaflets 0.3 to 0.6 cm from the free edge were second order.6 The chordae tendineae attached to the fibrous band running along the entire free edge of both the leaflets except the tip of the apex were the first order chordae. Those that were attached to valvular tissue deep to the free edge were known as second order chordae. Posterolateral leaflet differed from the anterolateral leaflet as it also had third order chordae crossing form the ventricular wall to the undersurface of the body of the leaflet. The body of anteromedial leaflet which was free of third order chordal attachments was more mobile than posterolateral leaflet.10 Those chordae, which arose from nearby stronger threads and were inserted along and close to the leaflet margins were of the first variety. Second variety was the one, which arose from the papillary muscles and were inserted on the ventricular surface of the leaflet margin. Third variety was short and broad, which arose from the summit of the papillary muscles and passed directly in a straight line to be inserted on the ventricular surface of the leaflets near the base.13 The chordae tendineae were classified into four types based on their insertion. They were commissural chordae, rough zone chordae, cleft chordae and basal chordae. In the anterior zone, chorda tendineae were inserted exclusively in the

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rough zone. Chordae tendineae into the posterior leaflet were basal chordae, which were unique to it. The other types were rough zone chordae, and cleft chordae.

The various orders of the chordae tendineae described were old

terminologies. According to this the first order included commissural chorda, rough zone chorda that insert into the free margin of the leaflets and branches of cleft chorda of the posterior leaflet. Second order chorda included rough zone chordae of the leaflets, which were inserted beyond the free margin.

Strut

chordae of the anterior leaflet, and the main stem of the cleft chordae of the posterior leaflet. On an average 25 chordae were inserted into the mitral valve. Of them 9 were inserted to the anterior leaflet, 14 to the posterior leaflet.15 Chordae tendineae arising from the papillary muscles and inserting on the free edge of the mitral leaflets were chordae tendineae of the first order. Thicker chordae tendineae that arose from the papillary muscles and inserted to a short distance from the free edge of the cusp were chordae of second order. Chordae tendineae of the third order arose directly from the ventricular musculature to be inserted on to the posterolateral leaflet of the mitral valve.18

Tricuspid valve. The chorda tendineae were classified into first, second and third order chordae according to the distance of the attachment from the margins of the cusps. This scheme has little functional or morphological merits. Fan shaped chordae have a short stem from which branches radiate to attach to the margins of the zones of apposition between cusps and to the ends of adjacent cusps. Rough zone chordae

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arise from a single stem, which usually splits, into three components that attach to the free margin, the ventricular aspect of the rough zone and to some intermediate point on the cusp respectively. Free edge chordae are single, thread like and often long, passing from either the apex or the base of a papillary muscle into a marginal attachment usually near the midpoint of a cusp or one of its scallops. Deep chordae, also long, pass beyond the margins and, branching to various extents, reach the more peripheral rough zone or even the clear zone. Basal chordae are round chordae or flat ribbons, long and slender, or short and muscular.8 Rough zone and basal chordae of the tricuspid valve were similar to that of mitral valve. But unlike mitral valve basal chordae of the tricuspid valve were inserted into all the three leaflets. Five types of chordae tendineae were described. It had 2 additional types, which were not present in the mitral valve. These were the free edge chordae and deep chordae. Rough zone chordae were attached to the anterior leaflet in all 50 heats and to the posterior leaflet in 41 and the septal in 49. On an average 25 chordae were inserted into the tricuspid valve. Of them 7 were inserted to the anterior leaflet, 6 to the posterior leaflet, and 9 to the septal and 3 to the commissural areas.29

Animals Left ventricle Average number of chordae tendineae attached to anterior papillary muscle of left ventricle in sheep was 5.6, range being 3

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8, in goat it was 6.1, range being 4

10. Average number of chordae tendineae attached to posterior papillary muscle in sheep was 5.45, range being 3 - 8 and in goat it was 6.5, range being 3 11.3 Right ventricle The papillary muscles give rise to groups of chordae tendineae, which fan out and radiate into the free borders and onto the luminal surface of the tricuspid valve.9

Table No. 12: Comparison of figures of the average number of chordae tendineae attached to both papillary muscles of the left ventricle obtained in the present study with the previous work done Specimen

APM

PPM

Ozbag 3

11.5

11.8

Present study

9.4

10.6

Ozbag 3

5.6

5.45

Present study

4.5

5.5

Ozbag 3

6.1

6.5

Present study

5.6

6.1

Cow

Present study

6.4

6.5

Pig

Present study

8.0

7.2

Human

Sheep

Goat

Author

The values of the chorda tendineae number in cow and pig cannot be compared because of the non-availability of adequate literature.

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It was noted that the number of chordae tendineae attached to each papillary muscle was highest in man followed by pig and it was significantly less in sheep and goat when compared with that of human and pig.

Table No. 13: Comparison of the number of chordae tendineae attached to different zones of cusps of the valves of left ventricles in human obtained in the present study with that of earlier works15 Site of insertion

Types of chorda

Average number of chorda attached in the present study.

Lam15

Anterior leaflet

Rough zone chorda

7.7

9

Rough zone chorda

8.6

10

Basal chorda

1.1

2

Cleft chorda

1.4

2

Anterolateral commissure

Commissural chorda

0.5

1

Posteromedial commissure.

Commissural chorda.

0.6

1

Posterior leaflet

This comparison shows that the values obtained in the present study correlates with that of earlier works.

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Table No. 14: Comparison of the number of chordae tendineae attached to different zones of cusps of the valves of left ventricles in human obtained in the present study with that of earlier works29 Types of chorda

Average number of chorda attached in the present study.

Silver29

Rough zone chorda

4.7

4

Free edge chorda

0.8

1

Deep chorda

1.1

2

Basal chorda

0.6

1

Fan shaped chorda

0.4

1

Rough zone chorda

2.4

2

Free edge chorda

0.9

1

Deep chorda

1.1

1

Basal chorda

0.9

1

Rough zone chorda

3.8

4

Free edge chorda

1.1

1

Deep chorda

1.1

1

Basal chorda

2.7

3

APC

Fan shaped chorda

0.8

1

PSC

Fan shaped chorda

0.4

1

ASC

Fan shaped chorda

0.7

1

Site of insertion

Anterior leaflet

Posterior leaflet

Septal leaflet

This comparison shows that the values obtained in the present study correlates with that of earlier works.

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Table No. 15: Comparison of the percentage of hearts with various types of chorda tendineae of human right ventricle obtained in the present study with that of the percentage obtained by earlier works Leaflets

Type of chorda

Percentage in present study

Percentage as obtained by Silver29

Rough zone chorda

100

100

Free edge chorda

60

64

Deep chorda

70

76

Basal chorda

50

46

Fan shaped chorda

40

10

Rough zone chorda

80

84

Free edge chorda

50

48

Deep chorda

60

58

Basal chorda

50

46

Rough zone chorda

100

98

Free edge chorda

50

50

Deep chorda

70

66

Basal chorda

90

90

Anterior leaflet

Posterior leaflet

Septal leaflet

The table depicts that the percentage obtained in the present study is in accordance with earlier works.

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Table No. 16: Comparison of the total number of chordae attached to each leaflet of human left ventricle in the present study with those of earlier works

Site of insertion

CTN to each cusp as described by Lam15 (average)

CTN to each cusp as in the present study (average)

Anterior leaflet

9.0

7.7

Posterior leaflet

14.0

11.1

Each Commissure

1.0

1.0

Table No. 17: Comparison of the total number of chordae attached to each leaflet of human right ventricle in the present study with those of earlier works

Site of insertion

CTN to each cusp as described Silver29

CTN to each cusp as in the present study

Anterior leaflet

8

7.2

Posterior leaflet

7

5.7

Septal leaflet

9

8.7

Each commissure

1

1.0

The tables above shows that the number of chordae attached to each cusps of left and right ventricles obtained in the present study, correlates with that of earlier works.

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The following anomalies of the mitral valve components have been described in human hearts by earlier authors:13 1. Fusion of the commissures, 2. Accessory tissue of the mitral valve, 3. Short, long or thick chordae tendineae, single left ventricular papillary muscle into which chordae tendineae from both mitral leaflets were inserted (parachute deformity of the mitral valve) 4. Single left ventricular papillary muscle into which chordae tendineae from both mitral leaflets were inserted (parachute deformity of the mitral valve) 5. Papillary muscles were in direct continuity with the anterior mitral leaflet because of thick and short chordae tendineae. (Anomalous mitral arcade)

These anomalies were not seen in any of the hearts of human examined.

105

CONCLUSION

106

7. Conclusion The knowledge of the integrity and proper spatial relationship of the papillary muscles, the chordal apparatus and the leaflets of the atrioventricular valvular complexes is extremely important to understand the functions of the valves. Improper functioning of the components produces obstruction or regurgitation at the orifices. The comparative study of the papillary muscles will influence the understanding of functional anatomy of sub-valvular apparatus, which can be applied for reconstructive sub-valvular surgery. The animal hearts of sheep, goat, and pig can be used for xenotransplantation and also as models for human heart. So it becomes necessary to know to what extent the morphological shape of these animal hearts resembles to that of human. In this study, the components of the mitral and the tricuspid valves of human, sheep, goat cow and pig were studied under the following headings: 1. Comparison of the size and weight of human heart with other mammals in ratio of their body weight. 2. Comparison of diameters of mitral and tricuspid valvular complexes along with number of cusps and to find any differences. 3. Study of papillary muscles, their number, positions, length and thickness. 4. Study of attachment of chordae tendineae a. their number attached to each papillary muscle and cusp. b. their attachment to different zones of cusps.

107

The comparison of results of various parameters in human and animals reveals the following: Size and weight of heart of human and animals in ratio of their body weight: It is observed that human heart weight to its body weight ratio is the highest. Man has an orthograde posture due to which the heart lies at a lower level as compared to the head, neck and brain. It has to push blood against gravity to these regions. This may be the reason for its well development. It is found that weight and size of the heart is more in cow, but the ratio of its weight to the body weight is less than that of human beings. The ratio is least in pigs. It seems that the increase in the size of pig s heart has not kept pace with the increase of its body weight. Diameters of mitral and tricuspid valvular complexes: The diameters of mitral and tricuspid valves among different mammals, seems to be in direct proportion with the weight and size of the heart, in all animals except in pig. It is observed that the diameters are highest in cow, followed by man, sheep, goat and pig. The diameter of the tricuspid valve is more than that of mitral valve in all human and animal hearts. Leaflets of the valvular complexes: The mitral valves of all hearts of human and other mammals studied have 2 cusps, anterior and posterior. The tricuspid valve of human and that of animals has three cusps, anterior, posterior and septal.

Accessory cusps are not seen in any of the hearts

examined. In human the anterior cusp of left ventricle shows rough and clear zones. Its posterior leaflet shows rough, clear and basal zones. The cusps of animals consist of free and appositional zones.

108

Papillary muscles: Two papillary muscles in the left ventricle and three muscles in the right ventricle were present in 100 % of the hearts examined. Their positions are similar in all hearts of human and animals. But the number of bellies of the papillary muscles varies. It is noted that in human left ventricle the anterior papillary muscle that arises from the sternocostal wall has a single belly in most of the hearts (80%). Occasionally, it has two bellies or a single belly with two or three heads (20%). Posterior papillary muscle in majority of the hearts has groups of bellies that arise from diaphragmatic region. In the right ventricle, anterior papillary muscle has single belly in eight hearts and in two, the muscle has two bellies (Specimen H-4 and H-10).

These bellies arise from the right anterolateral

ventricular wall. Posterior papillary muscle with multiple bellies, and a small septal muscle arise from the septal wall. The left ventricular papillary muscles (anterior and posterior), of sheep, goat and cow usually has single belly and is situated on the outer wall. In pig, the posterior papillary muscle has two to three bellies as in man. In the right ventricle of all animals, the anterior papillary muscle has a single belly, located on the outer wall. The posterior papillary muscle in sheep, goat and cow has single belly in all hearts except in one of the specimen of the right ventricle of cow where it is found to have two bellies (Specimen C-4). The posterior papillary muscle in right ventricles of pig has multiple bellies similar to that of man. The septal muscle is located on the septum in all hearts of animals. When the length and thickness of the papillary muscles are studied in different mammals, it seems to be proportional to the size and weight of the heart. It is observed that among animals, the values are highest in cow followed by that of sheep and goat. It

109

is least in pigs. When compared to animals, in man the values are less and are closer to those of pig. Chordae tendineae: It is noted that the number of chordae tendineae attached to each papillary muscle is significantly less in sheep and goat when compared to those of human and pig. Also, the number of chordae tendineae attached to the cusps is more in pig, as in man. They are less in sheep, goat and cow. Anomalies of the valvular components are not found in any of the hearts (man and other animals) examined in the study.

110

SUMMARY

111

8. Summary The comparative anatomy of the papillary muscles in the ventricles of human, sheep, goat, cow and pig presents a very interesting study as understanding cardiac anatomy is a pre-requisite for cardiac surgery. The atrioventricular complexes consist of the annulus, valve leaflets, chordae tendineae and the papillary muscles.

These

components regulate perfect closure of the valve during systole by approximation the atrial surface of the rough zone of the leaflets. The papillary muscles, being an excellent guide to its corresponding commissure is of practical importance to the surgeon. Papillary muscle rupture leads to cardiogenic shock which results in mortality in 80% to 90% of the cases

2

Pig and man having many anatomical similarities favoured the use of pig organs for xenotransplantation

14

The animal hearts can be used as models for human heart. To do so, it becomes necessary to know the similarities and differences that exist among the hearts of man and other mammals. Hence the comparative study is done. All the hearts were opened as per the dissection methods described to view the interior of the heart.

The various

parameters used for the study are the ratio of the heart weight to body weight, the diameters of both the valvular complexes, the number, position, length and thickness of the papillary muscles, the number of chordae tendineae attached to the papillary muscles and the cusps, their attachment to different zones of the cusps. The measurements are done using a pair of dividers, ruler, and slide calipers. Hand lens is used wherever

112

necessary. After observations, the structures are painted with appropriate colours and photographs are taken. Similar to the human brain, the human heart is large and well formed. Due to orthograde posture of human beings, heart lies at a lower level below the head, neck and brain. It is observed that the ratio of the heart weight to the body weight is highest in human beings. This may be due to its increased workload involved to push blood to these areas against gravity. The diameter of the tricuspid valvular complex is more than the corresponding bicuspid valve in man and also in the animal hearts. Among different mammals, the diameter of the valvular complexes is highest in cow, followed by man, sheep, goat and pig. The position of the papillary muscles is similar in all animals but the number of bellies of each muscle differed. The anterior papillary muscle in both ventricles of man has single bellies in 80% of the hearts examined, while in another 20% it consists of dual bellies or single belly with dual heads. The posterior papillary muscle of both ventricles has groups of bellies in 70% of the hearts. All papillary muscles in both ventricles of sheep, goat and cow consist of single belly except in one heart of cow, where the right ventricle has the posterior papillary muscle with two bellies. The anterior papillary muscle of both ventricles of pig has a single belly. The posterior papillary muscles of both ventricles have groups of bellies as in man. The length and thickness of the papillary muscles are more in cow, which is proportional to its body size. The number of chordae tendineae attached to each papillary muscle and the cusps are more in human and pig but is significantly less in sheep and goat.

113

From the study it can be concluded that the internal structure of the heart differs from species to species. Also even in one and the same species, no one heart is exactly the same as another. The complicated embryology involved in the formation of the components of the valve may be responsible for this. Although differences exist, the heart of pig has many features resembling those of man. The heart of sheep and goat are similar. The detailed knowledge of the morphology of the atrioventricular valvular complexes in man and its comparison with other mammals is of practical importance to a surgeon for correction of valvular dysfunction and also for xenotransplantation.

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115

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Xenografting: probability, possibility or pipedream?

Lancet 1993; 342 : 879 880. 15. Lam. JHC, Ranganathan N, Wigle ED and Silver MD. Morphology of Human Mitral Valve I Chordae Tendineae 449

A new classification. Circulation 1970; 41 :

457.

16. Sakai T, Okita Y, Ueda Y, Tahata T, Ogino H, Matsuyama K. et al. Distance between mitral annulus and papillary muscles: Anatomic study in normal human hearts. The Journal of Thoracic and Cardiovascular Surgery; 1999 118, No. 4 : 636

640.

117

17. Davachi F, Moller JH and Edwards JE. Diseases of Mitral Valve in Infancy Anatomic analysis of 55 cases. Circulation 1971; XLIII : 565

An

579.

18. Ranganathan N, Burch GE. Gross morphology and arterial supply of the papillary muscles of the left ventricle of man. American Heart Journal 1969; 77, No. 4 : 506

516.

19. Perloff JK and Robert WC. The Mitral Apparatus Mitral Regurgitation. Circulation 1972; XLVI : 227

Functional Anatomy of 237.

20. http://www.worldscibooks.com/medsci/etextbook/p136/P136_Chap1.pdf

(24th

Mar. 2006) 21. Uemura H, Anderson RH, Ho SY, Devine WA, Neches WH, Smith A. et al. Left Ventricular Structures in Atrioventricular septal defect associated with isomerism of atrial appendages compared with similar features with usual atrial arrangement. The Journal of Thoracic and Cardiovascular Surgery 1995; 110, No. 2 : 445 452. 22. Feure CL, Metzger JP, Lachurie ML, Georges JL, Baubion N and Vacheron A. Treatment of severe mitral regurgitation caused by ischemic papillary dysfunction: Indications for coronary angioplasty. American Heart Journal 1992; 123 : 860

865.

23. Oosthoek PW, Wenink ACG, Wisse LJ. and Groot ACG. Development of the papillary muscles of the mitral valve: Morphogenetic background of parachutelike asymmetric mitral valves and other mitral valve anomalies. The Journal of Thoracic and Cardiovascular Surgery 1998; 116, No.1 : 36

118

46.

24. Klues HG, Roberts WC and Maron BJ. Anomalous insertion of papillary muscles directly into anterior mitral leaflet in hypertrophic cardiomyopathy. Circulation 1991; 84, No.3 : 1188

1197.

25. Raghib G, Jue KL, Anderson RC, Edwards JE. Marfan s Syndrome with Mitral Insufficiency. The American Journal of Cardiology 1965; 16 : 127 26. Layman TE and Edwards JE. Anomalous mitral arcade mitral insufficiency. Circulation 1967; XXXV : 389

132.

A type of congenital

395.

27. Estes EH, Dalton FM, Entman ML, Dixon HB, Hackel DB. The anatomy and blood supply of the papillary muscles of the left ventricle. American Heart Journal 1966; 71, No.3 : 356

362.

28. Towne WD. Classification of Chordae Tendineae. Circulation 1973; XLVII : 209 29. Silver MD, Lam JHC, Ranganathan N and Wigle ED. Morphology of the human tricuspid valve. Circulation 1971; XLIII : 333

348.

30. Sinnatamby CS. Last s Anatomy-Regional and Applied 10th edition Churchill Livingstone: Timothy Horne; 1999. 31. Hamilton WJ. Text book of Human Anatomy 2nd edition London Basingstoke: ELBS and Macmillan; 1978. 32. Romanes GJ. Cunningham s Text book of Anatomy 12th edition Oxford, New York and Toronto: Oxford University Press; 1981. 33. Hollinshead WH, Rossse C. Text book of Anatomy 4th edition Philadelphia: Harper and Row; 1985. 34. Sack WO. Essentials of Pig Anatomy 1982; 21

22.

35. Getty R. Sisson and Grossman s The Anatomy of the Domestic Animals 5th Edition; 1975.

119

ANNEXURES

120

10. Annexures (A) Graphs

Ratio of the average weight of heart to the average total body weight

Graph No. 1: Bar Diagram representing the Ratio of average weight of heart to the average total body weight of various Animals

Human

Sheep

Cow

Goat

Pig

Species

Graph No. 2: Bar Diagram showing the average diameters of Mitral and Tricuspid valvular complexes

Mitral Valve

Diameter (in cms.)

Tricuspid Valve

Cow

Human

Sheep Species

121

Goat

Pig

Graph No. 3: Bar Diagram depicting the length and thickness of APM in Left Ventricle in different animals

Length / Thickness of APM (in cms.)

Length Thickness

Cow

Sheep

Goat

Human

Pig

Species

Graph No. 4: Bar Diagram depicting the length and thickness of PPM in Left Ventricle in different animals

Length / Thickness of PPM (in cms.)

Length Thickness

Cow

Sheep

Goat Species

122

Human

Pig

Graph No. 5: Bar Diagram depicting the length and thickness of APM in Right Ventricle in different animals

Length / Thickness of APM (in cms.)

Length Thickness

Cow

Human

Sheep

Goat

Pig

Species

Length / Thickness of PPM (in cms.)

Graph No. 6: Bar Diagram depicting the length and thickness of PPM in Right Ventricle in different animals Length Thickness

Cow

Human

Sheep Species

123

Goat

Pig

Graph No. 7: Bar Diagram depicting the length and thickness of SPM in Right Ventricle in different animals

Length / Thickness of SPM (in cms.)

Length Thickness

Cow

Human

Sheep

Goat

Pig

Species

No. of Chordae Tendineae attached to APM and PPM

Graph No. 8: Bar Diagram representing the number of Chordae Tendineae attached to each papillary muscle of Left Ventricle in various animals

APM PPM

Human

Pig

Cow Species

124

Goat

Sheep

No. of Chordae Tendineae attached to APM, PPM and SPM

Graph No. 9: Bar Diagram representing the number of Chordae Tendineae attached to each papillary muscle of Right Ventricle in various animals

APM PPM SPM

Human

Pig

Cow

Goat

Sheep

Species

No. of Chordae Tendineae attached to AL and PL

Graph No. 10: Bar Diagram representing the number of Chordae Tendineae attached to the leaflets of Left Ventricle in various animals

AL

Human

Pig

Cow Species

125

Goat

PL

Sheep

No. of Chordae Tendineae attached to AL, PL and SL

Graph No. 11: Bar Diagram representing the number of Chordae Tendineae attached to the leaflets of Right Ventricle in various animals

AL

Human

Pig

Cow

Goat

Species

Graph No. 12: Pie Chart showing the percentage of hearts with single belly / dual belly of APM

Single Belly of APM

20%

Dual Belly of APM or Single Belly with two heads 80%

126

PL

Sheep

SL

Graph No. 13: Pie Chart showing the percentage of hearts with single belly / multiple belly of PPM

30% Multiple belly of PPM Single belly of PPM 70%

127

(B) Master Charts Table No. 18: Master chart showing various parameters in specimens of Human hearts studied

Specimen

Absolute weight of the heart

Size of the heart

Diameter (in cms.)

Length of Papillary Muscles (in cms.)

(L x B in cms.)

(in gms.)

Mitral Valve

Tri-cuspid Valve

Left Ventricle

Right Ventricle

APM

PPM

APM

PPM

SPM

H1

300

8x8

2.6

2.8

2.8

2.1

2.8

2.5

0.5

H2

380

8.5 x 12

2.5

2.6

2.9

2.3

3.0

2.6

0.4

H3

258

9x9

2.6

2.9

2.2

2.1

2.8

2.7

0.3

H4

230

7x9

2.5

2.9

2.8

2.4

2.7

2.8

0.4

H5

288

9 x 11

2.2

2.8

4.1

3.2

2.6

2.7

0.3

H6

360

8.5 x 12

3.1

3.5

2.8

2.2

2.5

2.4

0.3

H7

400

12 x 15

2.6

2.9

3.6

3.0

2.7

2.3

0.4

H8

420

14 x 17

2.3

2.4

2.7

2.6

2.6

2.4

0.3

H9

380

9 x 12

2.5

2.9

2.8

2.7

2.7

2.6

0.2

H 10

380

9 x 10

2.6

2.8

3.2

2.8

2.8

2.7

0.3

128

Table No. 18 (Continued): Master chart showing various parameters in specimens of Human hearts studied

Specimen

Thickness of Papillary Muscles (in cms.)

Left Ventricle

CTN to each Papillary muscle

Right Ventricle

Left Ventricle

Right Ventricle

APM

PPM

APM

PPM

SPM

APM

PPM

APM

PPM

SPM

H1

1.0

0.9

0.4

0.4

0.2

8

9

8

8

7

H2

1.2

1.0

0.6

0.5

0.1

10

10

9

6

3

H3

1.1

1.0

0.7

0.6

0.3

7

6

10

8

4

H4

1.3

1.2

0.5

0.4

0.2

9

14

8

7

4

H5

1.6

1.5

0.7

0.6

0.1

15

18

9

8

3

H6

0.9

1.0

0.8

0.5

0.1

12

10

8

7

4

H7

1.7

1.6

0.7

0.6

0.3

10

13

9

7

3

H8

1.2

1.5

0.3

0.4

0.1

8

10

8

8

3

H9

0.9

1.0

0.6

0.5

0.2

7

8

7

9

4

H 10

1.1

1.2

0.5

0.3

0.1

8

8

9

9

4

129

Table No. 18 (Continued): Master chart showing various parameters in specimens of Human hearts studied

Specimen

Number of Chordae Tendineae attached to the Cusps Left Ventricle AL

AL C

RZC

Right Ventricle

PL

PM C

RZC

CC

BC

AL

AP C

RZC

FEC

DC

BC

PL

PS C

FC

RZC

FEC

DC

BC

SL RZC

FEC

DC

BC

A S C

H1

7

0

7

2

2

1

6

0

0

2

1

0

4

0

2

1

1

4

0

2

4

1

H2

6

1

10

1

0

0

4

1

2

1

1

0

2

2

0

0

1

4

3

0

4

1

H3

5

0

7

1

0

0

6

0

1

0

1

1

4

0

0

0

0

3

2

1

3

0

H4

8

1

10

2

2

1

5

0

2

0

0

1

3

1

1

2

0

4

0

2

2

0

H5

9

0

10

2

3

1

4

2

0

1

1

0

4

1

2

0

0

3

0

0

3

0

H6

10

1

10

2

2

1

4

1

2

0

1

0

2

0

0

3

0

4

2

1

2

1

H7

9

1

10

1

1

0

4

2

0

1

1

0

0

2

3

1

1

4

2

0

3

1

H8

8

0

8

1

0

1

5

0

2

0

1

1

3

0

1

0

0

4

0

3

0

1

H9

7

1

7

1

0

1

4

1

1

1

1

0

2

0

2

0

0

4

2

1

3

1

H 10

8

0

7

1

1

0

5

1

1

0

0

1

0

3

0

2

1

4

0

1

3

1

130

Table No. 19: Master chart showing various parameters in specimens of Sheep hearts studied

Specimen

Absolute weight of the heart (in gms.)

Size of the heart (L x B in cms.)

Diameter (in cms.)

Mitral Valve

Length of Papillary Muscles (in cms.)

Left Ventricle

Right Ventricle

Thickness of Papillary Muscles (in cms.)

Tricuspid Valve

Left Ventricle

Right Ventricle

APM

PPM

APM

PPM

SPM

APM

PPM

APM

PPM

SPM

S1

80

8.2 x 8.1

2.0

2.2

2.9

3.1

2.2

2.1

0.5

0.9

1.1

0.5

0.4

0.16

S2

75

8.6 x 8.4

1.9

2.1

3.0

3.5

2.6

2.5

0.4

1.2

1.8

0.4

0.5

0.08

S3

85

8.8 x 8.9

2.1

2.2

2.8

2.2

3.1

2.4

0.2

1.3

0.8

0.6

0.5

0.19

S4

70

7.9 x 8.3

1.8

1.8

2.9

3.4

3.0

2.9

0.6

1.1

1.2

0.6

0.3

0.10

S5

90

8.2 x 9

1.7

1.9

3.0

2.8

3.1

3.0

0.2

1.0

0.8

0.7

0.5

0.17

S6

98

8.2 x 9.1

2.2

2.4

2.6

2.7

2.8

2.9

0.6

1.1

0.9

0.6

0.4

0.10

S7

90

8.6 x 8.7

2.0

2.3

3.4

2.8

2.2

1.7

0.4

0.9

0.7

0.6

0.4

0.12

S8

80

8.7 x 8.3

1.5

1.7

4.0

4.1

2.9

2.6

0.4

1.2

0.9

0.5

0.6

0.11

S9

85

8 x 8.1

1.9

2.1

3.8

3.5

2.8

2.8

0.3

1.5

1.3

0.6

0.3

0.20

S 10

70

8x8

1.3

1.5

4.2

3.9

2.5

2.7

0.4

1.9

1.6

0.2

0.2

0.09

131

Table No. 19 (Continued): Master chart showing various parameters in specimens of Sheep hearts studied

Specimen

CTN to each Papillary muscle

Left Ventricle APM

PPM

CTN attached to each cusp

Right Ventricle APM

PPM

Left Ventricle

SPM

AL

ALC

AZC

FZC

Right Ventricle PL

PM C

AZC

FZC

AL AZC

FZC

A P C

PL

PSC

AZC

FZC

SL

ASC

AZC

FZC

S1

5

5

5

3

2

5

0

1

6

1

0

3

0

0

2

2

0

3

1

0

S2

4

6

4

3

2

4

0

0

5

1

1

2

0

1

2

2

0

2

2

1

S3

5

4

5

2

4

3

0

1

5

2

0

2

1

0

2

2

1

2

2

1

S4

4

6

6

3

2

4

0

1

5

0

0

2

0

1

3

1

1

3

1

0

S5

3

5

5

4

3

3

0

1

3

2

1

3

1

0

3

1

0

2

2

1

S6

6

6

4

3

3

4

0

1

4

3

1

3

0

0

2

2

1

3

1

1

S7

5

6

5

4

3

4

0

1

3

3

1

2

0

1

3

2

0

2

2

1

S8

5

5

5

5

2

3

0

1

4

2

1

3

1

0

2

2

1

3

2

0

S9

4

6

4

4

2

4

0

0

4

2

1

3

1

0

2

1

1

2

1

1

S 10

4

6

5

3

3

4

0

1

4

1

1

3

0

1

2

2

1

2

1

0

132

Table No. 20: Master chart showing various parameters in specimens of Goat hearts studied

Specimen

Absolute weight of the heart (in gms.)

Size of the heart (L x B in cms.)

Diameter (in cms.)

Mitral Valve

Length of Papillary Muscles (in cms.)

Left Ventricle

Right Ventricle

Thickness of Papillary Muscles (in cms.)

Tricuspid Valve

Left Ventricle

Right Ventricle

APM

PPM

APM

PPM

SPM

APM

PPM

APM

PPM

SPM

G1

64

8.6 x 9.4

1.4

1.6

2.2

2.0

2.6

2.0

0.5

0.8

0.7

0.4

0.5

0.17

G2

70

8.9 x 9.6

1.3

1.6

3.1

3.3

2.7

2.6

0.4

1.0

0.9

0.6

0.3

0.08

G3

58

6.6 x 6.9

1.2

1.6

2.8

2.8

2.8

2.5

0.4

1.0

0.8

0.5

0.4

0.16

G4

76

7.1 x 8.6

1.5

1.8

2.9

2.8

2.5

2.9

0.3

0.9

0.8

0.4

0.4

0.08

G5

68

6.7 x 7.2

1.8

2.3

2.5

2.4

2.6

2.7

0.5

0.9

0.7

0.5

0.5

0.16

G6

74

8.1 x 8.1

1.2

1.6

3.4

3.2

3.0

2.9

0.4

1.3

1.1

0.3

0.4

0.13

G7

62

7.9 x 8.1

1.1

1.5

3.1

3.0

2.0

2.1

0.2

1.0

0.7

0.2

0.2

0.20

G8

48

6.1 x 6.2

1.3

1.6

3.2

3.0

2.9

3.0

0.3

1.5

1.0

0.4

0.3

0.19

G9

60

7.9 x 8.8

1.2

1.6

3.0

2.6

2.8

2.9

0.4

1.4

1.1

0.2

0.2

0.17

G 10

62

7.8 x 8.0

1.1

2.4

3.8

3.6

2.9

3.0

0.5

1.6

1.5

0.3

0.3

0.09

133

Table No. 20 (Continued): Master chart showing various parameters in specimens of Goat hearts studied

Specimen

CTN to each Papillary muscle

Left Ventricle APM

PPM

CTN attached to each cusp

Right Ventricle APM

PPM

Left Ventricle

SPM

AL

ALC

AZC

FZC

Right Ventricle

PL

PM C

AZC

FZC

AL

APC

AZC

FZC

PL

PSC

AZC

FZC

SL

ASC

AZC

FZC

G1

3

6

6

5

3

4

0

1

3

1

1

4

0

1

2

0

0

4

2

1

G2

6

6

8

7

2

5

0

1

3

2

1

3

0

0

2

2

1

5

3

1

G3

7

7

6

5

3

5

0

1

4

2

1

4

1

1

2

2

0

3

3

0

G4

8

6

5

6

2

6

0

0

5

1

1

4

0

1

2

0

1

3

3

1

G5

6

7

6

5

3

5

0

1

4

2

1

5

1

1

2

1

1

4

2

0

G6

6

5

5

3

3

6

0

1

3

1

1

4

1

0

4

2

1

5

2

1

G7

8

7

6

3

2

7

0

1

4

2

0

4

0

1

3

0

0

2

2

0

G8

5

7

6

5

3

5

0

0

4

2

0

3

1

0

3

1

1

3

2

1

G9

4

5

5

4

3

4

0

0

3

1

1

4

1

0

2

1

0

4

2

0

G 10

3

5

6

5

4

3

0

0

3

1

1

5

0

1

2

0

1

5

3

1

134

Table No. 21: Master chart showing various parameters in specimens of Cow hearts studied

Specimen

Absolute weight of the heart (in gms.)

Size of the heart (L x B in cms.)

Diameter (in cms.)

Mitral Valve

Length of Papillary Muscles (in cms.)

Left Ventricle

Right Ventricle

Thickness of Papillary Muscles (in cms.)

Tricuspid Valve

Left Ventricle

Right Ventricle

APM

PPM

APM

PPM

SPM

APM

PPM

APM

PPM

SPM

C1

1520

17 x 17.2

4.8

4.9

7.4

6.9

6.0

5.9

2.0

2.5

2.4

0.9

0.8

0.7

C2

1580

18 x 19.1

5.2

5.4

7.2

6.8

6.1

5.8

1.8

2.4

2.8

0.8

0.9

0.8

C3

1720

20.1 x 20.4

4.0

4.2

7.8

7.7

5.9

5.8

1.9

2.1

2.3

1.1

1.2

0.9

C4

1620

16 x 16.4

5.0

5.5

7.0

7.9

5.8

5.6

3.0

2.6

2.4

1.0

1.2

0.8

C5

1760

17 x 17.6

3.8

3.8

6.2

6.8

6.0

4.0

2.0

2.8

2.3

1.3

1.4

0.7

C6

1740

17 x 17.2

3.2

3.4

7.6

6.8

6.2

6.1

2.1

3.0

2.8

1.9

1.8

1.7

C7

1800

21.2 x 21

3.6

3.8

7.1

7.1

6.3

6.3

1.7

3.1

2.3

1.8

1.7

1.6

C8

1820

21.8 x 21.6

4.4

4.6

7.8

7.9

6.3

5.9

2.3

2.5

2.0

1.4

1.2

1.7

C9

1650

19 x 19.2

4.2

4.4

8.0

7.8

6.2

6.0

1.9

2.4

2.5

1.6

1.3

0.8

C 10

1630

16 x 16.1

4.0

4.2

7.3

7.1

6.0

6.1

1.8

2.3

2.7

1.7

1.2

0.9

135

Table No. 21 (Continued): Master chart showing various parameters in specimens of Cow hearts studied

Specimen

CTN to each Papillary muscle

Left Ventricle APM

PPM

CTN attached to each cusp

Right Ventricle APM

PPM

Left Ventricle

SPM

AL

ALC

AZC

FZC

Right Ventricle

PL

PM C

AZC

FZC

AL

APC

AZC

FZC

PL

PSC

AZC

FZC

SL

ASC

AZC

FZC

C1

8

11

6

10

7

7

0

1

7

3

1

6

0

1

4

3

0

6

2

1

C2

5

4

4

4

3

4

0

0

3

2

0

4

1

0

4

0

0

3

1

1

C3

6

5

4

5

2

4

0

1

4

2

0

4

1

1

4

2

0

3

1

0

C4

7

6

6

9

6

5

0

1

4

2

1

6

0

1

4

3

1

7

1

1

C5

6

6

5

7

4

6

0

1

3

2

0

4

1

1

5

3

1

3

0

1

C6

5

6

4

6

3

5

0

0

5

1

0

5

1

1

4

2

1

3

1

0

C7

6

6

6

7

3

6

0

1

3

1

1

4

1

0

5

2

0

4

2

1

C8

6

7

8

6

2

5

0

1

4

2

1

4

0

0

3

2

1

3

1

0

C9

7

8

5

7

3

6

0

1

5

2

1

4

1

1

4

1

1

3

2

1

C 10

8

6

7

6

3

5

0

1

5

1

1

3

1

0

3

2

1

3

1

1

136

Table No. 22: Master chart showing various parameters in specimens of Pig hearts studied

Specimen

Absolute weight of the heart (in gms.)

Size of the heart (L x B in cms.)

Diameter (in cms.)

Mitral Valve

Length of Papillary Muscles (in cms.)

Left Ventricle

Right Ventricle

Thickness of Papillary Muscles (in cms.)

Tricuspid Valve

Left Ventricle

Right Ventricle

APM

PPM

APM

PPM

SPM

APM

PPM

APM

PPM

SPM

P1

220

7.4 x 6.8

1.2

1.5

2.8

2.3

2.3

2.0

0.2

0.8

1.0

0.3

0.3

0.10

P2

200

7.2 x 7.3

1.4

1.6

2.7

2.7

2.5

2.4

1.0

0.7

0.9

0.2

0.3

0.05

P3

220

7.5 x 7.4

1.3

1.4

2.6

2.5

2.6

2.3

0.4

1.6

0.6

0.3

0.3

0.08

P4

200

7.4 x 6.7

1.7

1.8

2.9

2.8

2.5

2.3

0.3

0.8

0.8

0.6

0.2

0.07

P5

260

8.7 x 8.2

1.3

1.4

2.3

2.4

2.6

2.2

0.6

1.5

0.6

0.2

0.3

0.09

P6

190

6.9 x 6.9

1.2

1.5

2.2

2.3

2.5

2.2

0.3

1.0

1.3

0.4

0.3

0.05

P7

240

8.1 x 8.6

1.6

1.7

3.5

3.0

2.7

2.4

1.0

1.4

1.2

0.2

0.2

0.06

P8

200

7.2 x 7.9

1.4

1.6

2.8

3.1

2.8

2.2

0.2

0.9

0.6

0.2

0.4

0.09

P9

180

7x8

1.2

1.3

2.9

3.0

2.9

1.9

0.3

0.9

0.7

0.2

0.2

0.04

P 10

260

8.2 x 10

1.5

1.7

2.7

2.8

2.6

2.3

0.2

0.6

1.3

0.1

0.1

0.10

137

Table No. 22 (Continued): Master chart showing various parameters in specimens of Pig hearts studied

Specimen

CTN to each Papillary muscle

Left Ventricle APM

PPM

CTN attached to each cusp

Right Ventricle APM

PPM

Left Ventricle

SPM

AL

ALC

AZC

FZC

Right Ventricle

PL

PM C

AZC

FZC

AL

APC

AZC

FZC

PL

PSC

AZC

FZC

SL

ASC

AZC

FZC

P1

10

7

4

5

5

6

0

1

7

2

1

4

2

1

4

2

0

5

1

0

P2

8

8

3

6

3

6

0

1

6

2

1

3

0

1

3

1

1

2

1

1

P3

6

7

6

6

5

6

0

1

4

2

1

5

0

1

4

1

0

3

2

1

P4

7

8

5

7

3

6

0

1

5

2

1

4

1

0

4

2

0

3

1

1

P5

8

7

6

6

2

7

0

0

6

2

1

5

0

0

2

1

1

3

1

0

P6

7

6

6

5

3

6

0

1

6

1

1

4

0

1

3

1

0

2

1

0

P7

9

8

5

5

4

6

0

0

7

1

0

4

1

0

2

1

0

3

1

1

P8

10

6

5

4

3

7

0

1

6

2

0

3

0

1

2

1

1

2

0

0

P9

8

7

4

3

2

6

0

1

6

2

1

4

0

0

3

2

0

1

1

1

P 10

7

8

6

5

3

6

0

1

5

1

1

3

1

0

3

1

0

2

0

1

138

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