Morphometry and aberrant morphology of the adult human tricuspid valve leaflets.

The tricuspid valve complex has been studied since the beginning of the twentieth century, and variations in the structural orientation of the tricuspid leaflets has been reported before, as the occurrence of accessory leaflets poses a major problem during surgeries related to the tricuspid valve. In this study, 36 adult formalin-fixed human hearts were analyzed to compare the number, form and size of the tricuspid leaflets. The result shows that in right ventricles, the number of leaflets can vary from the routine three to as many as seven, and the localization of such accessory leaflets of the tricuspid valve differs between specimens. Five leaflet forms were the most common, and the 'typical' form of tricuspid valves with no accessory leaflets was only present in a small percentage of the cases studied. Measurements of the main and accessory leaflets showed that the anterior leaflets were the largest, followed by the inferior leaflets, while the septal and the accessory leaflets were the smallest in size. On the basis of these results, it is suggested that three leaflets of the tricuspid valve are relatively uncommon, with frequent occurrences of accessory leaflets. The multicuspidal form of the tricuspid valve therefore raises concern about understanding the functional and physiological significance of the accessory leaflets.