Quantitation of the Mitral Tetrahedron in Patients With Ischemic Heart Disease Using Real-Time Three-Dimensional Echocardiography to Evaluate the Geometric Determinants of Ischemic Mitral Regurgitation

Abstract

Background: Ischemic mitral regurgitation (IMR) is common in ischemic heart disease and results in poor prognosis. However, the exact mechanism of IMR has not been fully elucidated. Hypothesis: Quantitation of the mitral tetrahedron using three-dimentianl (3D) echocardiography is capable of evaluating the geometric determinants and mechanisms of IMR. Methods: Forty patients with a history of ST-elevation myocardial infarction at least 6 months earlier were studied. Parameters of mitral deformation and global left ventricular (LV) function and shape were evaluated by 2-dimensional echocardiography. The effective regurgitant orifice (ERO) of IMR was obtained by the quantitative continuous-wave Doppler technique. Three-dimensional (3D) echocardiography was applied to assess the mitral tetrahedron. Results: Mitral valvular tenting area (P<0.001), mitral annular area (P=0.032), dilation of the LV in diastole, impairment of the LV ejection fraction, and volume of the spherically shaped LV in systole were greater in patients with an ERO >= 20 mm(2) than in those with an ERO <20 mm(2). In the mitral tetrahedron, only the interpapillary muscle roots distance showed a significant difference (P=0.004). Multivariate analysis with the logistic regression model showed the systolic mitral tenting area (odds ratio [OR]: 280.49, 95% confidence interval [CI]: 4.59-1.72 x 10(4), P=0.007) and interpapillary muscle distance (OR: 1.50, 95% CI: 1.03-2.19, P=0.036) to be independent factors in predicting significant IMR (ERO >= 20 mm(2)). Conclusions: 3D echocardiography can be effectively applied in measuring the mitral tetrahedron and evaluating the mechanism of IMR. Mitral valvular tenting and interpapillary muscle distance are 2 independent factors of significant IMR