Role of severe functional mitral regurgitation in predicting electrical remodeling in idiopathic dilated cardiomyopathy.

OBJECTIVE: To investigate incidence and predictors of clinically relevant QRS widening (predefined as >/= 10% with respect to baseline) in idiopathic dilated cardiomyopathy (IDC) and particularly the prognostic role of functional mitral regurgitation (MR). Although QRS widening in left ventricular systolic dysfunction carries relevant prognostic and therapeutic implications, its incidence and predictors in patients with IDC remain unknown. METHODS: We analyzed 114 patients with IDC receiving optimized medical treatment (age 52 +/- 10 years; 44% males; 36% New York Heart Association class III-IV) who underwent clinical, echocardiographic, hemodynamic, and laboratory evaluations and at least two electrocardiograms >/= 6 months after the index evaluation. RESULTS: During follow-up (median 20 months), 19 (17%) patients developed clinically relevant QRS widening, corresponding to an incidence of 8% per year. At multivariable analysis, the presence of echocardiographically detected severe MR (P = 0.029) and mean right atrial pressure (RAP) by right heart catheterization (P = 0.021) independently predicted clinically relevant QRS widening. CONCLUSIONS: Clinically relevant QRS widening is relatively frequent in IDC despite optimized medical treatment, and is independently predicted by MR severity and high RAP. IDC patients presenting either of these risk-factors might benefit from strict follow-up, which could also allow timely detection of the onset of indications for cardiac resynchronization therapy.