A Study of Normal Anatomy and Variations of the Human Mitral Valve Apparatus in Autopsy Speciments

Ponnusami, T M (2006) A Study of Normal Anatomy and Variations of the Human Mitral Valve Apparatus in Autopsy Speciments. Masters thesis, Madras Medical College, Chennai.


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INTRODUCTION One hundred human hearts from autopsies are studied to clarify controversies in the literature about commissures, slits, chordae and leaflets of the mitral valve. This study revealed that no 2 hearts are alike in the morphology of commissures, slits and scallops. We have designed perpendiculars drawn from the annulus to the free edge at the shortest height of the mitral valve on either side of the aortic leaflet as the anterolateral (AL) and posteromedial (PM) commissural lines. These lines divide the mitral valve precisely into aortic and mural leaflets. Slits in the leaflets are easily identified by the dipping in of the free edge into the cusp tissue. There are no slits in the aortic leaflet. Ninety-eight hearts has slits in mural leaflet varied from one to five. Unlike the relatively static and straight annulus of the aortic leaflet. The curved annulus of the mural leaflet contracts and changes in contour during systole. Hence slits are necessary in the mural leaflet to help it fold and adapt to the reduced orifice during systole and unfold during diastole. In addition to this coarse adjustment of the mural leaflet, both leaflets are pleated due to "hooding up" of the leaflet tissue between chordal attachments during systole, providing the fine tunning to enable the leaflets to adapt themselves to the reduce systolic orifice. The nodular appearance (rather than a straight ridge) of the line of apposition of the leaflet is evidence of this pleating mechanism during valve closure. Slit lines, designed as perpendiculars drawn from the summit of the slits to the annulus, are used arbitrarily to divide the mural leaflet into 2 to 6 scallops. When slits are absent there are no scallops. The slits and scallops are best serially numbered counterclockwise from the surgeon's view through the atrium. The scallops immediately behind the commissural lines, customarily labeled as the commissural scallops, are best defined as mural leaflet tissue between the AL or PM commissural line and the closet AL or PM slit line. All commissural scallops are seen in 81 hearts and PM commissural scallops in 76 hearts. There is no consistent fan-shaped chordal pattern at the commissural lines or at the slits. However the chordae arising from each papillary muscle group, in total, from a fan, reaching out to the corresponding adjacent halves of the 2 leaflets, restraining their splaying out in diastole and upward bulge during systole. These findings are relevant to the pathogenesis of mitral valvular disease and reparative procedures. AIM OF STUDY : Study of anatomy and Anatomical variations of mitral valve and nature of sub valvular apparatus helps to preserve anatomical position of mitral valve in its natural position by preserving all relations of mitral valve in repair of mitral valve instead of replacing with mechanical valve. The mechanical valve replacement is a long procedure with life long anticoagulant like warfarin. In view of, life long management of mechanical valve with anticoagulants it is cumbersome for Indian Poor People. So, it is well advised to preserve mitral valve with repair instead of replacement with mechanical valve. So by studying the normal anatomy of mitral valve apparatus we can preserve the natural parts of mitral valve in its normal anatomical position. MATERIAL AND METHODS : One hundred normal human autopsy hearts collected at random are studied. The age and sex of persons are not known. Looking through the left atrium, the mural leaflet is divided between its anterolateral and posteromedial chordopapillary support. A few false chordae connecting the two groups of papillary muscles are divided to splay the valve open with the aortic leaflet in the middle, the anterolateral half of the mural leaflet with anterolateral group of papillary muscles on the left, and the posteromedial half of mural leaflet with posteromedial group of papillary muscles on the right. The number of papillary muscle bellies in each varied from 1 to 5. When single, the shape and size of the muscle belly varied. When there are 2 to 5 muscle bellies they form various configurations. The papillary muscles varied in the extent of protrusion into the ventricular cavity and adherence to the ventricular wall. When mostly intraluminal, the tip of the muscle may be anchored to the ventricular wall by a small mjuscle band. Commonly, papillary muscle are related to the middle third of the ventricle. The variations in number of chordae arising from each group of papillary muscle is studied. The number of chordae inserting into the free edge of the leaflets in the corresponding half of the valve is also noted. In two hearts, the anterolateral papillary muscle remained muscular upto the annulus also, the strut chordae to the aortic leaflet in two hearts had separate muscular bellies. DISCUSSION & INTERPRETATION : The mitral valve apparatus, including the papillary muscles, is as unique to each individual as one's own finger prints. The papillary muscles occupy either side of the mid-mitral line, passing through the middle of the aortic and mural leaflects. The anterolateral papillary muscle group provides chordal supports for the anterolateral halves of the aortic and mural leaflets separated by the anterolateral commissural line. The posteromedial halves of the two leaflets separted by the posteromedial commissural line. The adjacent chordae from either group "shake hands" across the mid-mitral line, two with a flimsy narrow band of leaflet tissue uniting the chordae across the line on either side. It is of interest that a midtricuspid line passing through the middle of the septal and "anterior" component of the mural leaflet of the tricuspid valve also divides the chordopapillary support into two (superior and inferior) groups. The direction of chordae in the groups is different as in the mitral valve. The direction of chordae in the two groups is different as in the mitral valve. The chordae band of leaflet tissue at the free edge, as in the mitral valve. Similarity in divisibility of mitral and tricuspid valves in this fashion is in consonance with the similarity of the basic bicuspid design of these valves. CONCLUSION : Detailed knowledge of the anatomy of slits and scallops of the mitral valve provides improved understanding of mitral valve function, which aids the surgeon in understanding valve pathophysiology and in designing reconstructive procedures.

Item Type: Thesis (Masters)
Uncontrolled Keywords: Normal Anatomy ; Variations ; Human Mitral Valve Apparatus ; Autopsy Speciments.
Subjects: MEDICAL > Cardio Vascular and Thoracic Surgery
Depositing User: Kambaraman B
Date Deposited: 10 Nov 2017 16:52
Last Modified: 10 Nov 2017 16:56
URI: http://repository-tnmgrmu.ac.in/id/eprint/3869

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