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.