Real-time 3-dimensional dynamics of functional mitral regurgitation: a prospective quantitative and mechanistic study.

Background: Three-dimensional transthoracic echocardiography (3D-TTE) with dedicated software permits quantification of mitral annulus dynamics and papillary muscle motion throughout the cardiac cycle.

Methods And Results: Mitral apparatus 3D-TTE was acquired in controls (n=42), patients with left ventricle dysfunction and functional mitral regurgitation (LVD-FMR; n=43) or without FMR (LVD-noMR, n=35). Annulus in both normal and LVD-noMR subjects displayed saddle shape accentuation in early-systole (ratio of height to intercommissural diameter, 10.6 ± 3.7 to 13.5 ± 4.0 in normal and 9.1 ± 4.3 to 12.6 ± 3.6 in LVD-noMR; P<0.001 for diastole to early-systole motion, P=NS between those groups). In contrast, saddle shape was unchanged from diastole in FMR patients (10.0 ± 6.4 to 8.0 ± 5.2; P=NS, P<0.05 compared to both other groups). Papillary tips moved symmetrically towards to the midanterior annulus in control and LVD-noMR subjects, maintaining constant ratio of the distances between both tips to midannulus (PtAR) throughout systole. In LVD-FMR patients midsystolic posterior papillary tip to anterior annulus distance was increased, resulting in higher PtAR (P=0.05 compared to both other groups). Mechanisms of early- and midsystolic FMR differed between different etiologies of LV dysfunction. In patients with anterior MI and global dysfunction annular function and dilatation were the dominant parameters, while papillary muscle motion was the predominant determinant of FMR in patients with inferior MI.

Conclusions: Inadequate early-systolic annular contraction and saddle-shape accentuation in patients with impaired LV contribute to early-mitral incompetency. Asymmetric papillary tip movement towards the midanterior annulus is a major determinant of mid- and late-systolic functional mitral regurgitation.