Is tricuspid valve really tricuspid?

Abstract

Advancement in imaging techniques and interventional cardiology procedures have generated renewed interest in anatomy of tricuspid valve complex. The purpose of the present study was to characterize the morphology of tricuspid valve leaflets using objective criteria. Thirty-six embalmed cadaveric hearts were utilized for the present study. Leaflet morphology was studied using newly defined criteria. Commissural zones were identified and leaflets were delineated. Presence of scallops was also recorded. Single leaflet was observed in six cases, double in 26 cases, and triple in four cases. The anterior leaflet is large with multiple scallops and frequently accrues portion of inferior leaflet. The septal leaflet is in the form of a plateau and also frequently accrues parts of inferior leaflet. The inferior leaflet rarely occurs as independent leaflet. A wide un-indented basal zone exists across the valve leaflets. The study found that the tricuspid valve is rarely tricuspid. It also generated the hypotheses that the tricuspid valve does not open completely due to presence of a wide basal zone and the valve does not close completely owing to incongruence and lack of coaptation of leaflets. The findings provide clear understanding of leaflet morphology of tricuspid valve. This will help imaging specialists for interpretation of images and cardiologists for interventional procedures. The findings also enhance our understanding of pathophysiology of conditions like functional tricuspid regurgitation.

Keywords: Annulus; Commissure; Leaflet; Scallop.

Fig. 1. Schematic diagram showing position of major commissural zone along with their frequency along the annular circumference. Gaps represent the site of commissural zone and thickened continuous areas denote the leaflets. Black dots represent conventional positions (at the junction of different surfaces of the ventricular wall) of commissures.

Fig. 2. Supraventricular leaflet (SVL) overlying the supraventricular crest between the two major commissures (asterisks).

Fig. 3. Single (with wide unindented basal zone) (A), double (B), and three (C) leaflets. The valve has been cut open at the constant major commissure. MC, major commissure; A, anterior leaflet; I, inferior leaflet; S, septal leaflet; A+I, anterior has completely accrued the inferior leaflet.

Fig. 4. Schematic diagram depicting the pattern, characterization and number of leaflets and major commissures in the hearts studied. Gaps represent the site of major commissural zone and thickened continuous areas denote the leaflets. A, anterior leaflet; I, inferior leaflet; S, septal leaflet; SVL, supraventricular leaflet.

Fig. 5. Difference in coaptation of leaflets between tricuspid and mitral valve. (A) Poorly congruent tricuspid with minimum coaptation. (B) Perfectly congruent and coapted mitral valve.