Dobutamine-induced improvement in inferior myocardial contractile function predicts reduction in functional mitral regurgitation

Background - Left ventricular (LV) remodeling can increase tethering force to mitral valve and functional mitral regurgitation (FMR). Because the relationship between FMR and regional myocardial function has not been quantitatively evaluated, we conducted a quantitative investigation of this association. Methods and Results-The effective regurgitant orifice (ERO) of FMR in 51 patients with depressed LV ejection fraction (32±9%) secondary to ischemic or nonischemic cardiomyopathy was compared with mitral deformation (valve and annulus), global LV remodeling (volume indices, function, and sphericity), and regional myocardial contractile function, as assessed by longitudinal peak systolic strain rate (Ssr) in LV anterior, anteroseptal, inferoseptal, inferior, inferolateral, and anterolateral segments at rest. Low-dose dobutamine (10 μg/kg per minute)-induced changes in ERO were compared with changes in the variables. Multivariable analysis identified the predictors of ERO at rest as mitral valvular tenting (β=0.062; P<0.001), Ssr in the inferior segment (inferior Ssr) (β=-0.178; P<';.001), and LV sphericity (β=0.414; P=0.001) and the predictors of valvular tenting at rest as inferior Ssr (β=1.680; P<;0.001), LV end-systolic volume index (β=0.022; P=0.001), and LV sphericity (β=3.886; P=0.012). Furthermore, dobutamineinduced reduction in ERO was predicted by reduction in valvular tenting (β=-0.087; P<;0.001) and increase in inferior Ssr (β=-0.082; P<;0.001), and dobutamine-induced reduction in valvular tenting was predicted by increase in inferior Ssr (β=-0.860; P<;0.001).Conclusions-Inferior regional myocardial dysfunction was quantitatively associated with mitral valvular tenting and FMR. Moreover, improvement with dobutamine of inferior myocardial contractile function attenuated valvular tenting and FMR. Inferior myocardial contractile function can affect the configuration of the mitral apparatus and predict FMR severity.