Ischemia-induced malcoaptation of scallops within the posterior mitral leaflet

The posterior mitral leaflet is divided into a variable number of scallops, and little is known about the role of scallopmalcoaptation in ischemic mitral regurgitation. The study aim was to assess whether acute ischemia in the posterolateral wall of the left ventricle would induce scallop separation that would contribute to mitral regurgitation.

Radio-opaque markers were surgically placed in the left ventricle, around the mitral annulus, and at three sites along the posterior mitral leaflet edge in eight sheep. Three-dimensional marker coordinates were obtained by biplane videofluoroscopy at 60 Hz and 0.1 mm resolution before and during echocardiographically verified acute ischemic mitral regurgitation produced by balloon occlusion of the circumflex coronary artery.

During systole, the mean (+/-SD) distance between the central and anterolateral markers, both placed on the central scallop of the posterior mitral leaflet, was unaffected by ischemia (7.4+/-2.4 versus 7.4+/-2.5 mm; n = 8; p = NS). In contrast, the systolic distance between the central scallop marker and the posteromedial marker increased by 2.3+/-0.2 mm (p = 0.008) in three hearts with the posteromedial marker on the posteromedial scallop, compared with no separation (0.2+/-0.5 mm; p = NS) in five hearts with both the central and posteromedial markers on the central scallop itself. This result shows systolic separation of the central and posteromedial scallops during acute ischemic mitral regurgitation.

During acute left ventricular ischemia, the central and posteromedial scallops of the posterior mitral leaflet can fail to coapt during systole, potentially contributing to the mitral regurgitation observed.