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

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.
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