Abstract Background: Cardiac resynchronization therapy (CRT) is beneficial for patients with heart failure (HF) who have left bundle branch block. However, the benefits of CRT in patients with prior cardiac stimulation remain uncertain. Objective: Compare short-term mortality between upgrade and de novo CRT implantation. Methods: This prospective cohort study included patients with HF indicated for CRT with left ventricular ejection fraction (LVEF) below 35%. Overall survival was assessed using the Kaplan–Meier method, and multivariate analysis was performed using a Cox […]