The echocardiographic determinants of functional mitral regurgitation differ in ischemic and non-ischemic cardiomyopathy

Background Functional mitral regurgitation (MR) is one of the common and severe complications in patients with dilated cardiomyopathy. The detailed mechanisms that cause functional MR remain to be elucidated. Using two-dimensional transthoracic echocardiography, we investigated the differences in major determinants of MR severity between ischemic cardiomyopathy (ICM) and non-ICM patients. Methods We enrolled 103 patients (91 males; age 64 ± 12 years) with significant left ventricular (LV) dilatation. They were divided into ICM group (n = 69) with significant coronary disease, and non-ICM (n = 34) group without coronary disease. We devised a novel and simple parameter; the short-axis sphericity index (SI), to evaluate global LV remodeling, and used coaptation depth (CD) and tenting area (TA) to evaluate mitral deformity. Results In all cases, CD, TA and left atrium diameter (LAD) correlated positively with maximum regurgitation area (MRA) (r = 0.54, 0.57, 0.57; P < 0.0001). A negative correlation was observed between MRA and SI (r = −0.33, P = 0.0008). There was no significant relationship between MRA and LV ejection fraction (EF). In non-ICM cases, SI tended to be lower with reduced EF. Multivariate stepwise linear regression analysis showed the following equations; ICM: MRA = −9.4 +0.81CD + 0.21LAD (r2 = 0.47, P < 0.0001), non-ICM: MRA = −7.2 + 0.17LVDs (LV end systolic diameter) −8.7SI + 0.27LAD (r2 = 0.63, P < 0.0001). Conclusions The strongest determinants of functional MR severity differ in ICM and non-ICM. While LV diameter and SI (global LV remodeling index) mainly determine the severity in non-ICM, CD that reflects mitral deformity is the major determinant in ICM.