COMPARISON BETWEEN BANDS ANNULOPLASTY AND DEVEGA ANNULOPLASTY IN TRICUSPID VALVE

Similar documents
human anatomy 2016 lecture thirteen Dr meethak ali ahmed neurosurgeon

Two semilunar valves. Two atrioventricular valves. Valves of the heart. Left atrioventricular or bicuspid valve Mitral valve

Anatomy of left ventricular outflow tract'

JOINT MEETING 2 Tricuspid club Chairpersons: G. Athanassopoulos, A. Avgeropoulou, M. Khoury, G. Stavridis

Outcomes of Mitral Valve Repair for Mitral Regurgitation Due to Degenerative Disease

the Cardiovascular System I

Chapter 20 (1) The Heart

LECTURE 5. Anatomy of the heart

Introduction. Aortic Valve. Outflow Tract and Aortic Valve Annulus

LAB 12-1 HEART DISSECTION GROSS ANATOMY OF THE HEART

Valve Analysis and Pathoanatomy: THE MITRAL VALVE

Anatomy lab -1- Imp note: papillary muscle Trabeculae Carneae chordae tendineae

The Edge-to-Edge Technique f For Barlow's Disease

Tricuspid Valve Repair for Ebstein's Anomaly

Middle mediastinum---- heart & pericardium. Dep. of Human Anatomy Zhou Hongying

THE CARDIOVASCULAR SYSTEM. Part 1

THE HEART. A. The Pericardium - a double sac of serous membrane surrounding the heart

Chapter 14. Circulatory System Images. VT-122 Anatomy & Physiology II

2. right heart = pulmonary pump takes blood to lungs to pick up oxygen and get rid of carbon dioxide

Introduction to Anatomy. Dr. Maher Hadidi. Bayan Yanes. April/9 th /2013

14 Valvular Stenosis

Lab Activity 23. Cardiac Anatomy. Portland Community College BI 232

Despite advances in our understanding of the pathophysiology

The Management of the Cleft Mitral

THE HEART OBJECTIVES: LOCATION OF THE HEART IN THE THORACIC CAVITY CARDIOVASCULAR SYSTEM

CV Anatomy Quiz. Dr Ella Kim Dr Pip Green

Anatomy of the Heart. Figure 20 2c

Anatomy of the Heart

Surgical Repair of the Mitral Valve Presenter: Graham McCrystal Cardiothoracic Surgeon Christchurch Public Hospital

Human Anatomy, First Edition

The Heart. Happy Friday! #takeoutyournotes #testnotgradedyet

Eva Maria Delmo Walter Takeshi Komoda Roland Hetzer

The radial procedure was developed as an outgrowth

Ch 19: Cardiovascular System - The Heart -

HISTORY. Question: What category of heart disease is suggested by this history? CHIEF COMPLAINT: Heart murmur present since early infancy.

CJ Shuster A&P2 Lab Addenum Beef Heart Dissection 1. Heart Dissection. (taken from Johnson, Weipz and Savage Lab Book)

Heart Anatomy. 7/5/02 Stephen G Davenport 1

Posterior leaflet prolapse is the most common lesion seen

Ebstein s anomaly is defined by a downward displacement

Repair of Congenital Mitral Valve Insufficiency

Chapter 4: The thoracic cavity and heart. The Heart

The Heart. The Heart A muscular double pump. The Pulmonary and Systemic Circuits

DEVELOPMENT OF THE CIRCULATORY SYSTEM L E C T U R E 5

PROSTHETIC VALVE BOARD REVIEW

Chapter 20: Cardiovascular System: The Heart

Surgery For Ebstein Anomaly

Mitral incompetence after repair of ostium

FURTHER STUDIES OF THE CONDUCTING SYSTEM OF THE BIRD'S HEART

Heart Dissection. 5. Locate the tip of the heart or the apex. Only the left ventricle extends all the way to the apex.

The stentless bioprosthesis has many salient features that

Cardiovascular Anatomy Dr. Gary Mumaugh

The anatomy of the mitral valve and its associated structures

ANATOMY. lecture#: Date : Lecturer : Maher Hadidi

Danil Hammoudi.MD 1/12/2009

The Heart. Size, Form, and Location of the Heart. 1. Blunt, rounded point; most inferior part of the heart.

Adult Congenital Heart Disease: What All Echocardiographers Should Know Sharon L. Roble, MD, FACC Echo Hawaii 2016

THE VESSELS OF THE HEART

Blood supply of the Heart & Conduction System. Dr. Nabil Khouri

This lab activity is aligned with Visible Body s A&P app. Learn more at visiblebody.com/professors

Giovanni Di Salvo MD, PhD, FESC Second University of Naples Monaldi Hospital

Circulation. Circulation = is a process used for the transport of oxygen, carbon! dioxide, nutrients and wastes through-out the body

The Heart & Pericardium Dr. Rakesh Kumar Verma Assistant Professor Department of Anatomy KGMU UP Lucknow

Kent Bundles in the Anterior Septal Space Will C. Sealy, M.D.

Chapter 18 - Heart. I. Heart Anatomy: size of your fist; located in mediastinum (medial cavity)

The Cardiovascular System. Chapter 15. Cardiovascular System FYI. Cardiology Closed systemof the heart & blood vessels. Functions

Read Me. covering the Heart Anatomy. Labs. textbook. use. car: you

Atrioventricular valve repair: The limits of operability

Replacement of the mitral valve in the presence of

Cardiac ultrasound protocols

Ebstein s anomaly is a congenital malformation of the right

The HEART. What is it???? Pericardium. Heart Facts. This muscle never stops working It works when you are asleep

Results of Mitral Valve Replacement, with Special Reference to the Functional Tricuspid Insufficiency

CARDIAC ANATOMY. David McGiffin Director of Cardiothoracic Surgery and Transplantation Alfred Health, Melbourne

Tetralogy of Fallot (TOF) with atrioventricular (AV)

CIRCULATORY SYSTEM BLOOD VESSELS

8/31/2016. Mitraclip in Matthew Johnson, MD

Embryology of the Heart

Atrial Septal Defects

ECHOCARDIOGRAPHIC APPROACH TO CONGENITAL HEART DISEASE: THE UNOPERATED ADULT

Sarah J. Miller, DVM, Diplomate ACVIM (Cardiology) Degenerative Valvular Disease What s New?

Technical aspects of robotic posterior mitral valve leaflet repair

Read Chapters 21 & 22, McKinley et al

Large Arteries of Heart

Anatomical Problems with Identification and Interruption of Posterior Septa1 Kent Bundles

I have nothing to disclose.

Anatomy of the coronary arteries in transposition

Section 5.1 The heart and heart disease

How to Perform a Valve Sparing Root Replacement Joseph S. Coselli, M.D.

The Tricuspid Valve: The Not So Forgotten Valve. Manuel J Antunes Cardiothoracic Surgery Coimbra, Portugal

When should we intervene surgically in pediatric patient with MR?

The Heart and Heart Disease

Aortic valve repair is a technique that is gaining popularity

University of Zurich. Normal valves. Zurich Open Repository and Archive. Bettex, D; Chassot, P G. Year: 2010

PATIENT BOOKLET MEDTRONIC MITRAL AND TRICUSPID HEART VALVE REPAIR

Ο ΡΟΛΟΣ ΤΩΝ ΚΟΛΠΩΝ ΣΤΗ ΛΕΙΤΟΥΡΓΙΚΗ ΑΝΕΠΑΡΚΕΙΑ ΤΩΝ ΚΟΛΠΟΚΟΙΛΙΑΚΩΝ ΒΑΛΒΙΔΩΝ

A new era in cardiac valve surgery has begun...

Anatomy of Atrioventricular Septal Defect (AVSD)

The Heart and Cardiovascular System

Development of the Heart

Transcription:

COMPARISON BETWEEN BANDS ANNULOPLASTY AND DEVEGA ANNULOPLASTY IN TRICUSPID VALVE Thesis Submitted in Partial Fulfillment of The Doctorate Degree (M.D) in Cardiothoracic Surgery By Aly Mohamed Kamel Ghoneim (M.B.; B.Ch., M.Sc., Cairo University) Under supervision of PROF. DR. AMR BASTAWISY AHMED Professor of Cardiothoracic Surgery, Faculty of Medicine, Cairo University PROF. DR. MAGUED ABDEL MESSIH ZIKRI Professor of Cardiothoracic Surgery, Faculty of Medicine, Cairo University DR. WALEED GAMAL EL-DIN ABOU SENNA Assistant Professor of Cardiothoracic Surgery, Faculty of Medicine, Cairo University Faculty of Medicine, Cairo University 2012

ii بسم االله الرحمن الرحيم

ACKNOWLEDGEMENT I would like to start this humble work by expressing my deepest gratitude to all the team that helped me in achieving it. I wish to thank our Professor Dr. Amr Bastawisy,Professor of Cardiothoracic Surgery, Faculty of Medicine, Cairo University; who honored me by carrying out the burden of meticulously revising my script and guiding my thoughts. I am also profoundly grateful to Prof. Dr. Magued Zikri, Professor of Cardiothoracic Surgery, Faculty of Medicine, Cairo University, for his brotherly guidance and enormous support that was a great help to me. I am deeply indebted to Dr. Waleed Abou Senna, Assistant Professor of Cardiothoracic Surgery, Faculty of Medicine, Cairo University, whose kindness was more than encouraging. iii

TO MY FAMILY iv

Contents CONTENTS Page INTRODUCTION... 1 AIM OF THE WORK.. 3 REVIEW OF LITERATURE.. 4 o Embryology of the tricuspid valve.. 4 o Anatomy and histology of the tricuspid valve 7 o Physiology of the tricuspid valve 21 o Historical background. 27 o Definition and etiology of functional tricuspid insufficiency... 29 o Pathology and pathophysiology of functional tricuspid insufficiency. 32 o Clinical picture of tricuspid insufficiency age and sex. 36 o Investigations of tricuspid regurgitation 43 o Treatment of tricuspid insufficiency.. 60 PATIENTS AND METHODS 98 RESULTS.. 125 DISCUSSION.... 159 CONCLUSION. 169 SUMMARY. 170 REFERENCES.. 172 ARABIC SUMMARY 187 v

List of Figures LIST OF FIGURES No. Title Page 1 Formation of endocardial cushions and mitral and 5 tricuspid valve 2 Schematic anterosuperior view of the heart with the atria 9 removed 3 The tricuspid valve viewed from the right atrium (The 10 tricuspid veil) 4 Diagrammatic representation of the tricuspid valve opened 14 through the acute (lateral) margin of the right ventricle 5 a.schematic representation of a frontal view of the heart b.surgical anatomy of the tricuspid valve 19 20 6 Schematic frontal view of the right atrium and right 23 ventricle 7 Dilatation of the tricuspid ring does not affect all its parts 35 equally. 8 Tricuspid Annular Dilation 35 9 Signs of tricuspid insufficiency 38 10 Normal jugular venous pulse: the jugular v wave is built 40 up during systole, and its height reflects the rate of filling and the elasticity of the right atrium` 11 As the degree of tricuspid regurgitation (TR) increases, the 40 x descent is increasingly encroached upon 12 Diagram of pulsed Doppler echocardiographic technique, shown from the apical 4-chamber view 50 13 Hemodynamic changes in tricuspid incompetence 55 recorded by cardiac catheterization 14 Prosthetic cardiac valves. A, Starr-Edwards caged-ball 66 valve with cloth sewing ring and bare struts 15 Technique of bioprosthetic Tr.V. replacement 67 16 Tricuspid valve bicuspidization 73 17 Technique of tricuspid annuloplasty described by Boyd 74 18 Technique of measured annuloplasty 75 19 Technique of Danielson annuloplasty 76 20 Circumferential annuloplasty 77 21 Modification described by Nakano by placing interrupted 77 sutures on the leaflets adjacent to commissural zone 22 Selective annuloplasty. 78 vi

List of Figures No. Title Page 23 a.tricuspid annuloplasty with rigid prosthetic ring b. Technique of tricuspid ring valvuloplasty 80 81 24 Annular sutures extend from the posteroseptal to the 83 anteroseptal commissure and are placed through the polyester velour band of the annuloplasty system 25 The annuloplasty system is slid into position and the 83 handle is removed from the frame 26 The frame is released from the band 84 27 A measured plication of the annulus adjacent to the 84 anterior and posterior leaflets is achieved and the conduction system is not jeopardized 28 Repair of severe functional tricuspid insufficiency 86 29 a.de Vega tricuspid annuloplasty b. De Vega repair: 88 89 30 Antunes modification of De Vega tricuspid annuloplasty 91 31 Failure of the DeVega technique 92 32 Tricuspid repair with Band 94 33 The 3/0 ethibond sutures passed in the annulus and 105 correspondingly in the Cortex Band 34 Band to annulus approximation while observing the 105 geometrical alteration in the Tricuspid annulus 35 Coaptation enhancement while the Band is being applied 106 to the annulus 36 The final appearance of the downsized Tricuspid valve 106 after tying the stitches 37 Gross testing with saline reveals good leaflets coaptation 107 vii

List of Tables LIST OF TABLES No. Title Page 1 Analysis of patients age and sex 125 2 Analysis of preoperative patients symptoms 127 3 Analysis of preoperative patients signs 129 4 Analysis of preoperative patients laboratory data 131 5 Analysis of preoperative patients ECG 132 6 Analysis of preoperative patients x-ray 133 7 Analysis of preoperative patients echocardiography 134 8 Analysis of intraoperative pre-repair patient data 135 9 Left side operative procedure 136 10 Analysis of intraoperative post-repair patient data 137 11 Analysis of postoperative patients symptoms in 1 st group 139 12 Changes in functional class of dyspnea in 1 st group 140 13 Analysis of postoperative patients signs in 1st group 141 14 Analysis of postoperative patients laboratory data in 1 st 142 group 15 Analysis of postoperative patients ECG in 1 st group 143 16 Analysis of postoperative patients x-ray in 1 st group 144 17 Analysis of postoperative patients echocardiography in 145 1 st group 18 Changes in echocardiographic tricuspid regurge in 1 st 147 group 19 Analysis of postoperative patients symptoms in 2 nd group 149 20 Changes in Functional class of dyspnea and group 150 21 Analysis of postoperative patients signs in 2 nd group 151 22 Analysis of postoperative patients laboratory data in 2 nd 152 group 23 Analysis of postoperative patients ECG in 2 nd group 153 24 Analysis of postoperative patients x-ray in 2 nd group 154 25 Analysis of postoperative patients echocardiography in 155 2 nd group 26 Changes in echocardiographic tricuspid regurge in 2 nd group 157 viii

Abstract ABSTRACT The treatment of functional tricuspid insufficiency associated with rheumatic left sided valvular lesions continues to challenge surgeons throughout the world. Opinions vary as to how tricuspid insufficiency should be treated. The present choices are: 1. To expect spontaneous regression after correction of left sided valvular lesions. 2. To replace tricuspid valve. Mechanical prosthesis is associated with high incidence of thromboembolism in tricuspid position while biological prosthesis is associated with rapid structural valve degeneration especially in young patients. 3. To repair tricuspid valve. Three methods are described for tricuspid valve repair. a. Bicuspidization annuloplasty: Changing tricuspid valve from trileaflet valve to bileaflet one. Bicuspidization annuloplasty has yielded rather unsatisfactory results especially long term due to interruption of tricuspid valve physiology. b. Ring annuloplasty: Is a good alternative but is associated with economic burden as these rings are very expensive & whether they have any advantages over semicircular annuloplasty is doubtful. c. Semicircular annuloplasty: The most commonly used semicircular annuloplasty techniques are the DeVega annuloplasty and bands annuloplasty. Both are simple, rapid, provide pliable annulus, eliminates the insertion of foreign material and free from the risk of producing atrioventricular block. This study compares the results of DeVega and bands annuloplasty in the management of functional tricuspid insufficiency. The operations were done in 50 patients and included simultaneous correction of rheumatic left sided valvular lesions. Each operation was performed in 25 patients. Re-evaluation of these patients showed that both annuloplasty techniques gave comparable and good results in early postoperative period. After 6 month, follow-up revealed maintenance of good results in bands annuloplasty group with deterioration of some patients in DeVega annuloplasty group. KEYWORDS: Tricuspid valve Tricuspid valve insufficiency Tricuspid valve surgery Tricuspid valve repair DeVega annuloplasty Bands annuloplasty ix

Introduction INTRODUCTION Tricuspid valve remains a challenge in terms of its precise diagnosis, indications and appropriate surgical treatment. This is due to: 1. Its relatively low incidence in relation to other valve pathology. 2. Its function in a low pressure system and therefore it can tolerate imperfect surgical results. 3. Its close relation to right ventricle functions. 4. It follows the dictates of the left side lesion (Duran, 2004). Significant acquired tricuspid insufficiency is a rather rare phenomenon. If diagnosed, it is in the majority of patients associated with chronic rheumatic mitral with or without aortic lesions indicating advanced disease and is thus part of a high risk condition (Holper et al., 2003). Tricuspid insufficiency associated with left sided valve disease is a manifestation of already significant advanced haemodynamic changes thereby constituting an adverse prognostic marker (Hejnal et al., 2002). The management of the tricuspid valve disease remains controversial. While some advocate repair or replacement, others ignore the tricuspid valve (Kulshrestha et al., 1999). Attention has been centered on left sided valve repair or replacement in hope that once its normal function has been restored, tricuspid regurgitation would disappear or at least diminish considerably. However, long term follow up showed this is not the case in most patients and particularly so in subjects with increased pulmonary vascular resistance (Hejnal et al., 2002). 1

Introduction Difficult weaning from cardiopulmonary bypass, a stormy postoperative course and late recurrence of symptoms in patients undergoing left sided valve correction with an uncorrected tricuspid valve disease, emphasize the need for elective repair of the tricuspid valve when significant disease is encountered (Kulshrestha et al., 1999). It is for many reasons that most cardiac surgeons today tend to believe that simultaneous management of the condition should be attempted in cases of significant tricuspid insufficiency associated with left sided valve disease (Hejnal et al., 2002). The options given are tricuspid valve repair or replacement. Since prosthetic tricuspid valve replacement by itself may induce considerable morbidity and mortality, there is at least wide agreement on trying to reconstruct tricuspid valvular competence by plastic repair whenever possible (Abe et al., 1999). Choosing the appropriate surgical technique is often associated with a variety of uncertainties (Holper et al., 2003). A number of techniques have been developed for tricuspid valve repair which can be divided into two groups: The first group includes the so called bicuspidization annuloplasty methods reshaping tricuspid valve into a bicuspid one. The second group includes the annuloplasty methods designed to manage the condition by reducing the area of the dilated tricuspid valve orifice. This is accomplished either by semicircular suture annuloplasty which when tightened decrease the tricuspid valve orifice area or by implanting rings of different designs and sizes. (Holper et al., 2003) DeVega, Bands and Segmental semicircular annuloplasties are simple and theoretically also effective. Economic considerations played a role, while rings of various sizes must be imported and paid for in hard currency, DeVega, Bands and Segmental annuloplasties requires only suture threads (Hejnal et al., 2002). 2

Aim of the Work AIM OF WORK The objective of this study is to evaluate DeVega Annuloplasty Vs Bands in repair of functional tricuspid insufficiency and to assess the performance of tricuspid valve following these techniques in the early postoperative period. 3

Review of Literature CHAPTER ONE EMBRYOLOGY OF THE TRICUSPID VALVE The superior (anterior, ventral) and inferior (posterior, dorsal) endocardial cushions develop in the atrial canal at about 6mm. of fetal length. Approximately about 9 to 10-mm of fetal length, these cushions fuse to produce the mitral and tricuspid orifices. At about 11- mm. of fetal length, two small lateral cushions develop. While cushions are developing, the atrial canal and its accompanying portions of the preampulla are gradually moving toward the right, so that the tricuspid orifice first straddles the developing ventricular septum and then opens completely into the right ventricle (Bharati and Lev, 2006). At the completion of septation of the atria and ventricles, the greater part of the atrioventricular valve leaflet tissue has not begun to develop (Van Mierop and Gessner, 1982 and Van Gils, 1989). At about the time of formation of the septum primum, the primitive canal is fashioned into mitral and tricuspid orifices, with responding valves, by the fusion of the endocardial cushions. The dorsal bar, thus leaving mitral and tricuspid orifices (Van Mierop, 1989). In an embryo of about 10 to 12 mm crown-rump length, both atrioventricular orifices are surrounded by mesenchymal endocardial cushion-type tissue which has a provisional valve function. The definitive isoventricular valves, however are derived only (muscular) ventricular wall, the internal layer of which is liberated by a process of diverticulation and undermining (Van Mierop, 1989). 4

Review of Literature Fig (1): Formation of endocardial cushions and mitral and tricuspid valve (Bharati and Lev, 2006). Most of the valve tissue is produced by in-growth of the fibrofatty tissue of the atrioventricular groove, together with delamination from the subendocardial layers of the developing myocardium. The latter process also produces the tensor apparatus of the valves (Van Mierop and Gessner, 1982 and Van Gils, 1989). The endocardial cushions, the dextrodorsal bulbar cushion and the connections of the endocardial cushions with the muscular trabeculae of the ventricular myocardium fashion the formation of the atrioventriculovalvular apparatus. This process occurs in three periods. In the first period, the various leaflets are fashioned (11 to 23- mm). The inferior (posterior) leaflets of the mitral and tricuspid valves are formed from the lateral endocardial cushions. The aortic leaflet of mitral valve is formed from the fused anterior and posterior endocardial cushions. The anterior leaflet of the tricuspid valve is fashioned from the fused anterior and posterior endocardial cushions and the dextrodorsal bulbar swelling. The septal leaflet of the tricuspid valve is formed from the posterior endocardial cushion and perhaps a small part of the anterior endocardial cushion. At this stage of the development, the leaflets consist of cushion material and muscular 5

Review of Literature trabeculae. During the second period (23 to 61mm), muscle gradually invades and replaces the maternal. Also, during this period with developing the development of the tricuspid leaflets migrate to become more distal than the mitral leaflets. During the third period (85 mm), collagenous tissue invades and replaces muscle tissue (Bharati and Lev, 2006). The atrioventricular groove tissue also separates the atrial from ventricular myocardium and produces the fibrous annulus (Anderson, 2001). The conus septum forms the medial (conus) papillary muscle, its chordae tendinae and the medial portion of the anterior cusp. The primorduim of the lateral (posterior) and large portion of the anterior cusp is formed very early, long before the other cusps have begun to make their appearance. The small portion of the medial cusp, which in the adult, overlies the membranous septum, is formed last (Van Mierop et al., 1972). An extension towards the right of the endocardial cushions forms the septal leaflet of the tricuspid valve (Samuel, 1981). All the valve cusps are therefore initially thick and fleshy and only later in development are they transformed into thin and fibrous cusps (Van Mierop et al., 1972). 6

Review of Literature CHAPTER TWO ANATOMY AND HISTOLOGY OF THE TRICUSPID VALVE The tricuspid (right atrioventricular) orifice is oriented with its plane in a semivertical axis and directs the right atrial blood anteriorly, inferiorly and to the left. The tricuspid valve lies vertically behind the left sternal border but at an angle of 45 degree to the median plane (Walmsley and Hamish, 1988). The main axis of the tricuspid valve is transversal and the sharpest extremity corresponds to the anteroseptal commissure (Carpentier et al., 1984). The normal area of the tricuspid valve is 7 cm 2 (Rackley et al., 2000). The main components of each valvular apparatus are the leaflets, three for the tricuspid valve. The leaflets are attached by their base to the annulus, which forms part of the skeleton of the heart, and by their free edge, through the chordae tendineae, to the papillary muscles, which form a part of the myocardial structure of the ventricles (Antunes, 2005). The three tricuspid leaflets are supported by a tensor apparatus composed of chordae tendinae and papillary muscles. There is no definite tricuspid annulus but the bases of the three leaflets are attached to heart at the atrioventricular junction. In normal situs and connection, this annulus is related to the base of the aortic valve, the membranous septum, central fibrous body, the right coronary artery, the lateral atrioventricular junction, the coronary sinus and the bundle of His, clockwise from medially. With its tensor apparatus, the tricuspid valve in part defines the morphologic right ventricle (Karp, 2000). 7

Review of Literature The leaflets are separated by the commissures. Usually these deep indentations do not reach the annulus and a narrow band of leaflet tissue completes the veil around the valve orifice. Each leaflet of either atrioventricular valve has a different shape and size. In each case, the ventricular surface of the larger leaflet (anterior) is related to the outflow tract of the corresponding ventricle, hence separating the respective inflow and outflow chambers (Antunes, 2005). Cardiac Skeleton The central fibrous body Right fibrous trigone [Trigonum fibrosum dextrum], fuses at the center of the heart with the medial aspect of the mitral and tricuspid valves and the aortic root. The left fibrous trigone [Trigonum fibrosum sinistrusm], is formed by compact bundles of connective tissue that course from the central fibrous body to the left, posteroinferiorly and then anteriorly (Schlant et al., 2000). Continuations of fibroelastic tissue from the central fibrous body and the left fibrous trigone partially encircle the mitral and tricuspid valves. These rings of tissue are the mitral and tricuspid annuli. In general, the fibrous skeleton is less well developed around the tricuspid valve. The bundle of His penetrates the central fibrous body and travels along the inferior margin of the membranous portion of the ventricular septum (Schlant et al., 2000). This cardiac skeleton gives attachment to both myocardial musculature and valvular tissue, however, it is neither rigid nor static (Walmsley and Hamish, 1988). 8

Review of Literature Fig (2): Schematic anterosuperior view of the heart with the atria removed. The components of the fibrous skeleton and the orientation of the leaflets of each valve are shown (Schiant et al., 2000). 1. Annulus Fibrosus The tricuspid annulus is located at the junction between the right atrium and right ventricle. The tricuspid annulus is attached only to the right fibrous trigone where the septal leaflet and the anteroseptal commissure insert. Elsewhere, the connective tissue in the leaflets joins the subendocardial tissue and the anterior and posterior leaflets insert directly into the myocardium (Tei et al., 1982). It is at this specific site that dialation of the annulus occurs in functional tricuspid insufficiency (Carpentier et al., 1991 and Deloche et al., 1993). The attachments of the valve leaflets to the tricuspid annulus are at different levels (Silver et al., 1981). Progressing from left to right, the basal attachment of both posterior leaflet and postero-septal half of the septal leaflet are roughly horizontal and about 15 mm lower than the highest point of valve attachment. From about midpoint of the septal leaflet, the basal attachment angles upwards at 30 degree from the horizontal plane to reach the highest point of the basal attachment at the anteroseptal commissure. At this point, the annulus is reinforced 9

Review of Literature by connective tissue fibres of the right fibrous trigone. The anterior leaflet attachment then gradually slopes down to join the horizontally attached posterior leaflet at the anteroposterior commissure (Silver et al., 1981 and Carpentier et al., 1984). A fibrous tissue framework affords a firm anchor for the attachments of the atrial, ventricular musculature as well as the valvular tissue. The central fibrous body (right fibrous trigone) (trigonum fibrosum dextrum) fuses at the center of the heart with the medial aspect of the mitral and tricuspid annuli and the aortic root (Le Guerrier and Nasr, 1992). Fig (3): The tricuspid valve viewed from the right atrium (The tricuspid veil). A: Anterior leaflet. P: Posterior leaflet. S: Septal leaflet. The bundle of His (b) courses along a line from the coronary sinus (Cs) to the anteroseptal commissure passing beneath the base of the septal leaflet just posterior to the anteroseptal commisssure. The A.V. node (AVN) lies between this area and the coronary sinus (Carpentier et al., 1984). The Tricuspid Veil When viewed from its atrial aspect, the tricuspid valve orifice is roughly triangular with anterior, posterior and septal sides, with a circumference about 11 to 12 cm. The leaflets of the tricuspid valve fall into the right ventricle like a curtain. Many indentations of variable length are observed in their free edge. Some of these have fan-shaped chordae inserting into them and may be distinguished as commissures (Silver et al., 1981). 10

Review of Literature The valvular apparatus can be simply regarded originally as a single continuous diaphragm of fibrous tissue slit centrally to form the valve leaflets that open freely into the right ventricular cavity (Silver et al., 1981). 2. Valvular Tissue (A) Leaflets: The tricuspid leaflets differ from the mitral leaflets in being thinner, more translucent and less easily separated into well-defined leaflets. There are usually three major leaflets of unequal size. 1. Anterior Leaflet: It is also called the infundibular, lateral, superior, anterosuperior or the greater leaflet. Usually it is semicircular but it may be quadrangular. It is the largest leaflet and stretches from the infundibular area downward into the inferolateral wall of the right ventricle. Its basal attachment is at the atrioventricular junction anteriorly, to the fibrous annulus, at the stemocostal segment of the annulus. This part is reinforced inferiorly by the parietal band of erista supraventricularis (Silver et al., 1981). Its free edge is smooth or slightly serrated. On its free edge, close to the anteroseptal commissure, a notch can be observed. Sometimes, it is large enough to suggest a commissure. However, the chordae that insert into the notch arise from the septal band of the crista supraventricularis and are almost invariably rough-zone chordae. Another notch may be seen at the apex of the leaflet s free edge. The anterior leaflet partially partitions the right ventricular cavity into an inflow tract and an outflow tract. The chordae tendineae anchoring its free edge originate from the anterior papillary muscle (Silver et al., 1981). 2. Posterior Leaflet: Also called the marginal, dorsal or inferior leaflet. The posterior leaflet, which is usually the smallest, is attached to the tricuspid ring along its posteroinferior border. The posterior leaflet lies between the anteroposterior and the posteroseptal commissures. The leaflet has several indentations in its free edge that give it a scalloped appearance. Fan-shaped chordae insert into these clefts forming 11