A Study of Structure of the Human Tricupsid Valve Apparatus in 50 Autopsy Specimens

INTRODUCTION: The tricuspid valve complex consists of functional units, which include the valve leaflets, chordae tendineae and papillary muscles. The mechanical properties of these functional units depend on the large extent of the link between the muscle and the valve. This link is usually arranged in a branching network of avascular chordae tendineae composed of collagen and elastic fibers, which transmit contractions of the papillary muscle to the valve leaflets. Although it has been known for many years that the tricuspid valve has 3 leaflets, almost always smaller or larger accessory cusps are to be found at one or all of the angles between the principal cusps. Based on morphological and morphometric criteria, tricuspid valve can be formed by 2 - 6 habitual/supernumerary leaflets besides commissural leaflets. The chordae tendineae, associated with the tricuspid valve, originated from a major anterior papillary muscle, a minor posterior papillary muscle and the septal wall. The anterior and posterior leaflets were the major components of this valve and received their major support from chordae tendineae originating from the anterior papillary muscle and the posterior wall. Morphometric criteria such as area of leaflet, the basal width and the ratio of commissure depth to leaflet depth can be utilized for characterization of the tricuspid valve leaflets. The great variation in leaflet appearances is probably due to embryological development. Division of the common atrioventricular canal into the right and left channels starts in the embryo of 40 days. These channels, which are surrounded by mesenchymal subendothelial tissue called endocardial cushions that contribute to the future atrioventricular valve, grow and straighten to approximate the margins of these endocardial cushions. The inferior leaflet is formed from the lateral and inferior wall of the myocardial gully and the anterosuperior leaflet from the supraventricular crest, which develops from the intraventricular part of the muscular outlet septum. This difference could explain the anatomical differences between the anterior and posterior leaflets. In particular, minor anatomical differences in tricuspid valve anatomy are frequent. The tricuspid valve is not always in the same shape and configuration. Controversies still exist on the importance of these variations and put the human beings at risk of unexpected deaths. The left atrioventricular valve and its papillary muscle and chordae tendineae have been largely studied. Victor and Nayak pointed out that the internal morphology of the two cardiac chambers was extremely complicated and remarkably variable. In particular, the observation of chordae tendineae of the right ventricle showed endless variability in their number, shape and location. The number, size, location and morphology of the right papillary muscle and their correlation to age and race were studied in an attempt to provide a classification. A normal right ventricular cavity has coarse trabeculations, with diffuse and variable chordal attachment to papillary muscles within the body of the ventricle and to the interventricular septum. The cavity of the right ventricle is triangular in shape and contains an identifiable muscular moderator band. It is guarded at its inflow by a tricuspid valve of variable anatomy and is separated from the outflow tract by an infundibular muscular band. With aging, the tricuspid valve, like other tissues, changes; this changes consist mainly of local fibrous thickening of both the papillary muscle and chordae. AIM OF THE STUDY: The aim of this study is to investigate the relationship of valvochordal anatomy of tricuspid valve in autopsy specimen and its surgical application. MATERIALS AND METHODS: The 50 human hearts were collected between 2003 and 2006 from 50 autopsy cases during a medicolegal autopsy with permission from the Forensic Medicine, MMC. Morphometric and morphological data were obtained from each valve namely area, basal width, depth of leaflets, depth of commissure, number of chordae tendinease and their relation to the leaflets. These data were correlated for various anatomical variants. The materials were collected from 50 AUTOPSY cases (25 male and 25 female) during a medicolegal autopsy with permission from the Forensic Medicine, MMC. We studied hearts with macroscopic evidence of normal hearts. There were 2 groups, females 25 and from males 25. The age of the individuals, whose autopsies were performed between 2003 and 2006 in MMC, varied from 25-60 years. OBSERVATION: Our findings indicated that the average area of the septal leaflet (212.7mm2) was smaller than the anterior leaflet (221.3 mm2) and posterior leaflet (220.2mm2) in all specimen studied. Comparing the data of male and female, anterior leaflets would be considered to be the largest. The sum of average areas of the anterior leaflets would be considered to be the largest. The sum of average areas of the anterior leaflet (221.3mm2) and posterior leaflet (220.2mm2) happened to be higher than those of the septal leaflet (212.7mm2) in all specimen studied. The results of this anatomical study may explain the increased incidence in wide variations of chordae tendineae. Higher ratio of the abnormal chordae that were too short and too thick is also significant. Short, thick or differing from normal can be easily ruptured. This may exhibit individual differences. CONCLUSION: The valvochordal anatomy is found to correlate with literature findings in terms of morphologic data