Effect of mitral annular dilation in the mechanism of functional mitral regurgitation

Objective To investigate the effect of mitral annular (MA) dilation in the mechanism of functional mitral regurgitation (FMR). Methods Jet/left atrial area, mid-systolic MA area, left ventricular (LV) volumes, systolic L/D, ejection fraction (EF) and leaflet tethering length between the posterior papillary muscle tips and contralateral anterior MA (PPM-AMA) were compared by echocardiography among 20 control subjects, 20 patients with lone atrial fibrillation (AF group) and 30 patients with coronary artery disease or dilated cardiomyopathy (FMR group). Results LV size, EF, systolic L/D and PPM-AMA in AF group were similar to those in normal group, but MA dilated significantly in AF group and which was comparable to that of FMR group (MA area: [5.3±1.1] cm2, [7.4±1.5] cm2, [8.0±2.0] cm2). However, AF group only had modest MR, which was smaller than FMR group (MR fraction: [12±7]%, [30±14]%). Conclusion Isolated annular dilation does not seem to cause moderate or severe MR.