Papillary Muscle Viability Correlates with Changes of Functional Mitral Regurgitation in Patients with Non-Ischemic Dilated Cardiomyopathy

Abstract

Functional mitral regurgitation (FMR) in non-ischemic cardiomyopathy (NICM) may be partly related to the dysfunction of subvalvular apparatus. Thus, we sought to investigate the correlation between papillary muscle viability and FMR changes in NICM. Of 35 patients with NICM (LVEF<40%, NHYA III) undergoing repeated CD34+ cell transplantation we enrolled 30 patients (86%) who presented with ≥1+ grade FMR. At baseline, all patients underwent electroanatomical mapping, and papillary muscle viability was defined by local unipolar voltage measurement. All patients received granulocyte-colony stimulating factor; CD34+ cells were collected by apheresis and delivered by transendocardial injections. At 6 months, electroanatomical mapping was repeated. Echocardiography was performed at baseline and 6 months, and severity of FMR was graded by multi-parametric approach. FMR improvement was defined as a reduction in FMR by ≥1 grade when compared to baseline. At baseline, FMR grade was mild (1+) in 19 patients (63%), moderate (2+) in 8 patients (27%), and severe (3-4+) in 3 patients (10%). During follow-up, we found improvement of FMR in 15/30 patients (Group A), and in 15 FMR did not improve (Group B). At baseline, Groups A and B did not differ in age (55±9 years in Group A vs. 54±11 years in Group B, P=0.42), sex (male: 94% vs. 87%, P=0.54), creatinine (0.84±0.22 mg/dL vs. 0.89±0.29 mg/dL, P=0.66), bilirubin (0.87±0.35 mg/dL vs. 0.90±0.45 mg/dL, P=0.41), LVEF (33.8±10.0% vs. 33.6±9.3%, P=0.26), NTproBNP levels (1441±1257 pg/mL vs. 1321±1175 pg/mL, P=0.78), or the degree of FMR (1.27±0.79 vs. 1.32±0.82, P=0.27). However, on baseline electroanatomical mapping we found significantly higher papillary muscle viability in Group A than in Group B (9.6±3.8 mV vs. 7.5±2.5 mV, P=0.01). At 6 months, there was a significant increase in papillary muscle viability in Group A (+3.1±1.3 mV, P=0.02), but not in Group B (+0.2±0.4 mV, P=0.89). On multivariate analysis, baseline papillary muscle viability >8 mV was an independent correlate of FMR improvement (P=0.01). Papillary muscle viability appears to correlate with changes in FMR in patients with NICM. Further studies are warranted to investigate whether measurement of papillary muscle viability may improve patient selection for mitral valve repair in NICM.