Relation Between Left Ventricular Morphology and Reduction in Functional Mitral Regurgitation by Cardiac Resynchronization Therapy in Patients With Idiopathic Dilated Cardiomyopathy

The presence of functional mitral regurgitation (MR) is considered a significant risk factor for poor clinical prognosis in patients with idiopathic dilated cardiomyopathy (IDC). The objectives of this study were to test the hypothesis that not only global but also local left ventricular (LV) remodeling, including the position of the papillary muscles, may contribute to the development of MR in patients with IDC and wide QRS durations and can be reversed with cardiac resynchronization therapy (CRT). Eighty-four subjects were studied, 44 patients with IDC who underwent CRT and 40 age- and gender-matched controls. The position of the posteromedial papillary muscle was similar in the 2 groups, whereas the position of the anterolateral papillary muscle in patients with IDC was displaced more posteriorly than in controls. Multivariate analysis revealed that reduction in coaptation height (β = 0.44, p <0.001) and LV dyssynchrony by speckle-tracking radial strain (β = 0.303, p <0.01) were independent determinants of reduction in MR 5 ± 2 days after CRT; in contrast, restoration of the position of the posteriorly displaced anterolateral papillary muscle (β = 0.50, p <0.001) and the increase in sphericity index (β = 0.440, p <0.001) were identified as independent determinants of reduction in MR 6 ± 1 months after CRT. In conclusion, asymmetric local LV remodeling was observed at baseline, and asymmetric local LV reverse remodeling was observed at long-term follow-up after CRT in patients with IDC. Furthermore, different parameters contribute to the reduction in MR observed at short- and long-term follow-up after CRT.