The mechanisms of functional mitral regurgitation in patients with dilated cardiomyopathy: a real-time 3D echocardiographic study.

Functional mitral regurgitation (FMR) conveys an adverse prognosis in dilated cardiomyopathy (DCM). Although incomplete closure of the normal leaflet is the immediate cause of FMR, the link between left ventricular (LV) geometry and the degree of mitral regurgitation (MR) is not well defined. The purpose of this study was to evaluate the mitral complex and the LV geometry, and to clarify the mechanisms of FMR in patients with DCM by using real-time 3D echocardiography. In this study we examined 36 DCM patients. These patients were divided into two groups according to MR volume (group 1: mild (<30ml), group 2: moderate to severe (≥30ml)). By using a novel valve software system (REALVIEW Ⓡ ), mitral apparatus geometry including annular size, tenting length and volume, coaptation index, tethering length, interpapillary distance and angle were quantitatively analyzed. The LV geometry was evaluated by measuring the following diameters from 3D volumetric data (QLAB TM ): LV longitudinal diameter, LV anterior-posterior (AP) diameter, LV medial-lateral (ML) diameter and ML/AP ratio. Patients in group 2 had a larger annular size, apparent leaflet tenting and longer distance from papillary muscle to mitral annulus (tethering length) compared to the patients in group 1. In DCM patients with moderate to severe MR, the LV ML diameter and the ML/AP ratio is higher compared to patients with mild MR due to a LV deformity. This laterally dilated LV results in the loss of coaptation, aggravating FMR in patients with DCM.