Left bundle branch block in dilated cardiomyopathy with intermediate left ventricular dysfunction: Clinical phenotyping and outcome correlates.

Abstract Background Left bundle branch block (LBBB) negatively affects prognosis in heart failure patients with a reduced left ventricular ejection fraction (LVEF). Less is known about the prognostic role of LBBB in dilated cardiomyopathy (DCM) with intermediate LVEF (between 36% and 50%). We sought to assess the role of LBBB in optimally treated DCM patients with mildly to moderately reduced LVEF and to determine the possible variables associated with subsequent LVEF reduction. Methods We retrospectively analyzed DCM patients with LVEF >35% after 3-to-9 months of optimal medical treatment (OMT) consecutively evaluated from 1990 to 2010. All-cause mortality or heart transplantation (D/HTx) and sudden cardiac death (SCD) or major ventricular arrhythmias (MVA) were considered as outcome measures. LVEF deterioration during follow-up was also considered. Results Among 280 (49%) patients that met the study criteria, 76 had LBBB (27%). During a mean follow-up of 151 months, the rates of D/HTx and SCD/MVA were similar between LBBB and not LBBB patients (p value = 0.52 and p = 0.39, respectively). Twenty-six out of 76 (34%) patients with LBBB experienced LVEF deterioration below 36%. The persistence of moderate-severe mitral regurgitation (MR), left atrial end-systolic area index and LV end-diastolic volume index emerged as independent predictors of LVEF deterioration and were associated with an increased risk of D/HTx during follow-up. Conclusions LBBB does not affect mortality in DCM patients with intermediate LVEF after OMT. However, among these patients those with persistent significant MR, left atrial and LV remodeling carries a higher risk of LVEF deterioration during follow-up.