New-onset left bundle branch block independently predicts long-term mortality in patients with idiopathic dilated cardiomyopathy: data from the Trieste Heart Muscle Disease Registry.

Left bundle branch block (LBBB) is commonly associated with heart failure. We evaluated the prevalence, incidence, and impact of LBBB on long-term outcome in young patients with heart failure affected by idiopathic dilated cardiomyopathy (DCM).METHODS AND RESULTS: We included 608 patients with DCM from the Heart Muscle Disease Registry of Trieste in this retrospective analysis. At baseline electrocardiogram (ECG), 189 patients (31.1\%) had LBBB. The patients with baseline LBBB had a significantly higher mortality rate than the patients without LBBB (38.6 vs. 27.9\%, P = 0.002) at the univariate analysis. After a multiple covariate adjustment, the baseline LBBB was not associated with a significantly increased risk of death [hazard ratio (HR) 1.27, 95\% confidence interval (CI): 0.88-1.81, P = 0.2]. Forty-seven (11.2\%) patients without LBBB at baseline ECG developed LBBB during follow-up. Among these, the mortality rate was 49 vs. 25\% in patients without new-onset LBBB (P = 0.001). New-onset LBBB was a strong and independent predictor of all-cause mortality (HR 3.18, 95\% CI: 1.90-5.31, P < 0.001) at multivariate analysis.CONCLUSION: After correcting for potential confounders, new-onset LBBB was found to be associated with an increased risk of all-cause mortality. The management of patients with new-onset LBBB may need to be more aggressive, possibly including early cardiac resynchronization therapy/implantable cardioverter-defibrillator therapy.