Intraventricular and Papillary Muscle Dyssynchrony is Related to the Diastolic Phase of Functional Mitral Regurgitation in Patients with Non-Ischemic Dilated Cardiomyopathy

Background and aim of the study: Functional mitral regurgitation (FMR) is commonly encountered in patients with heart failure, and is associated with an adverse prognosis. It is hypothesized that left ventricular (LV) and papillary muscle systolic dyssynchrony causes diastolic mitral regurgitation (DMR) in non-ischemic dilated cardiomyopathy (DC) patients. Methods: A total of 77 patients with non-ischemic DC was enrolled, of whom 25 were without DMR (group I) and 52 with DMR (group II). Mitral valve apparatus measurements were calculated using two-dimensional echocardiography, while LV/papillary muscle (Pap-index) systolic dyssynchrony parameters were calculated using tissue Doppler echocardiography. Results: The FMR volumes were similar between the two groups (19.4 +/- 10.6 and 22.4 +/- 11.1 ml/beat in groups I and II, respectively). Both groups had similar mitral valves, as assessed by the geometry of the mitral valve apparatus parameters, including tent area, mitral annulus diameter, and tethering distance. However, the maximal intraventricular mechanical delay (MIMD; p <0.001), peak (+/- SD) myocardial sustained systolic velocity (Ts-SD; p <0.001) and Pap-index (p <0.001) were each significantly increased in group II. Strong correlations were apparent between DMR and dyssynchrony parameters [(Ts-SD; r = 0.74, p <0.001), MIMD (r = 0.78, p <0.001) and Pap-index (r = 0.78, p <0.001)]. Linear regression analysis revealed the MIMD (OR 2.94, 95% CI 2.7-6.6, p <0.001), Ts-SD (OR 3.6, 95% CI 1.2-3.5, p <0.001) and Pap-index (OR 2.2, 95% CI 1.27-1.35, p = 0.001) to be independent predictors of DMR. Conclusion: In patients with non-ischemic DC, DMR may serve as a useful indicator of mechanical LV/papillary muscle dyssynchrony, especially when used in combination with the other echocardiographic parameters.