Functional mitral regurgitation (FMR) is a frequent condition in the setting of dilated cardiomyopathy (DCM) and its physiopathological mechanisms are complex. The aim of this study was to determine the influence of left ventricular remodeling and mechanical dyssynchrony on the occurrence of FMR in non-ischemic DCM.

Prospective study involving 52 patients (mean age=57±10 years, sex ratio=1.8) with non ischemic dilated cardiomyopathy. Two groups were compared: the group with FMR (group MR+=31 patients) and that without FMR (group MR−=21 patients).

Mean QRS duration was 141±29ms and 63% of patients had complete left bundle branch block (LBBB), with no significant difference between the 2 groups. The echocardiographic parameters representing left ventricular systolic function were similar in the 2 groups except for cardiac output which was lower in the group MR+ (3.3±1L/min vs 4±1.3L/min; P=0.02). For mitral deformation indices, tenting area (3.6±1cm² vs 2.5±0.8cm²; P=0.005) and tenting height (1.5±0.3cm vs 1±0.2cm; P<0.001) were significantly larger in group MR+. For dyssynchrony indices, only temporal longitudinal dyssynchrony was associated to FMR (P=0.04). In the group MR+, more criteria of intraventricular dyssynchrony were noted (3.4±1.4) than in group MR− (2.4±1.4; P=0.01). FMR severity was well correlated to tenting area (r=0.66; P<0.001) and tenting height (r=0.67; P<0.01). However, parameters representing left ventricular systolic and diastolic function were not good determinants of FMR severity and dyssynchrony indices were not at all associated to FMR severity.

This study showed that only the mitral deformation indices were well correlated to both the presence and the severity of FMR. Left ventricular remodeling indices were not good determinants of FMT. However, the intra ventricular dyssynchrony indices were associated to the presence of FMR and not to its severity.