Introduction: Wide QRS with left bundle branch block (LBBB) morphology is a good predictor for positive clinical and echographic outcome in cardiac resynchronization therapy (CRT) patients. We sought to assess the effect of LBBB on long term mortality in a real-life cohort of CRT patients.
Methods: We included all patients with implanted CRT device between 2007 and 2010. Clinical and echocardiographic outcome was assessed during the first year post CRT. Clinical response at one year was defined in patients without death during this period by using a composite score based on NYHA class, 6-minute walk test and Quality of Life. Patients with LBBB at baseline were compared to all other patients. Survival data were obtained up to 6 years after implant.
Results: From the 179 included patients 73 died during a follow-up of 4.0 ± 1.6 years. Non-LBBB patients had a higher rate of atrial fibrillation (60.7% vs. 39.3%; p=0.002) and atrio-ventricular node ablation (6.8% vs. 1.0%; p=0.05). Mortality in LBBB patients was lower at two years (6.5% vs. 24.1%; Log Rank =0.001), but not at 4 years (47.9% vs. 52.1%; Log Rank = 0.157). LBBB predicted one year clinical response (OR 2.423; p=0.009) and was associated with lower 2-year mortality (HR 3.749; p=0.005). No significant difference was found between QRS 120-150 ms vs. >150 ms. Multivariate analysis demonstrated that clinical response to CRT at one year was associated with 55% reduction in the 4-year all-cause mortality (HR 0.431; p=0.023).
Conclusions: LBBB is associated with improved 2-year all-cause mortality but the effect tapers off at 4 years.
