Right Bundle Branch Block Predicts Appropriate Implantable Cardioverter Defibrillator Therapies in Patients with Non-Ischemic Dilated Cardiomyopathy and a Prophylactic Implantable Cardioverter Defibrillator.

Background: The benefit of prophylactic implantable cardioverter defibrillators (ICDs) in patients with severe systolic dysfunction of non-ischemic origin is still unclear, and the identification of patients at risk for sudden cardiac death remains a major challenge. Aims/Methods: We retrospectively reviewed all consecutive patients with non-ischemic dilated cardiomyopathy (NICM) who underwent prophylactic ICD implantation between 2008 and 2020 in two tertiary centers. Our main goal was to identify the predictors of appropriate ICD therapies (anti-tachycardia pacing [ATP] and/or shocks) in this cohort of patients. Results: A total of 224 patients were included. After a median follow-up of 51 months, 61 patients (27.2%) required appropriate ICD therapies. Patients with appropriate ICD therapies were more frequently men (87% vs. 69%, p = 0.006), of younger age (59 years, (53-65) vs. 64 years, (57-70); p = 0.02), showed more right bundle branch blocks (RBBBs) (15% vs. 4%, p = 0.007) and less left bundle branch blocks (LBBBs) (26% vs. 47%, p = 0.005) in the ECG, and had higher left ventricular end-diastolic (100 mL/m 2 , (90-117) vs. 86, (71-110); p = 0.011) and systolic volumes (72 mL/m 2 , (59-87) vs. 61, (47-81), p = 0.05). In a multivariate competing-risks regression analysis, RBBB (HR 2.26, CI 95% 1.02-4.98, p = 0.043) was identified as an independent predictor of appropriate ICD therapies. Conclusion: RBBBs may help to identify patients with NICM at high risk of ventricular arrhythmias and requiring ICD intervention.