Variations in Mitral Valve Leaflet and Scallop Anatomy on Three-Dimensional Transesophageal Echocardiography

Abstract

Textbook depictions of the mitral valve (MV) often illustrate it as composed of a single nonscalloped anterior leaflet, with the posterior leaflet having three symmetric and evenly spaced scallops. However, common variations in this anatomy have been noted in autopsy series for decades. Improved cardiac imaging with three-dimensional transesophageal echocardiography (TEE) now affords the ability to detect variations in scallop anatomy invivo. The aims of this study were to catalog variations in mitral anatomy and to examine for association with mitral regurgitation in patients referred for clinical three-dimensional TEE. Three-dimensional transesophageal echocardiographic images of the MV from 107 subjects were reviewed for MV variations. Three-dimensional analysis software was used to characterize mitral leaflet anatomy and assess the relative sizes of posterior leaflet scallops. Variations from the classic MV configuration were seen in 58.9%. Symmetric variations in the posterior leaflet (dominant P2 scallop, accessory P2 scallop, absent P2 scallop, and dichotomous P2 scallop) were seen in 33.6% of the study group. Asymmetric variants in the posterior leaflet (fused P1 and P2, fused P2 and P3, commissural scallop, accessory scallops, dichotomous P1 or P3, and dominant P2 or P3) were seen in 24.3%. Indentations or folds in the anterior leaflet were noted in 5.6%. Leaflet variations were not associated with patient demographics, indication for TEE, mitral regurgitation, mitral annular dimensions, or Carpentier class. Mitral leaflet morphologic variants were well characterized using three-dimensional TEE. Variants are common and were present with a frequency consistent with autopsy series. Mitral scallop variations were not associated with mitral regurgitation.