This prospective, multicenter, open-label, randomized comparative effectiveness trial, titled CARVTOP-ICD, evaluates the impact of carvedilol versus metoprolol succinate in patients with heart failure with reduced ejection fraction (HFrEF) and an implantable cardioverter defibrillator (ICD). The study will enroll 2,000 participants across 100 U.S. sites and includes an 18-month feasibility phase with 100 participants from 15 sites. Eligible participants must be currently treated with metoprolol succinate and willing to switch to carvedilol, with randomization in a 1:1 ratio. Participants will be followed for up to 3 years, with regular assessments including ICD interrogations, medication adherence, healthcare utilization, and quality of life surveys. The primary endpoint is the first occurrence of any ICD therapy (appropriate or inappropriate), cardiovascular (CV) hospitalization, or CV death. Secondary endpoints include ICD shock burden, healthcare utilization, and patient-reported quality of life. The trial aims to provide high-quality comparative data to address clinical equipoise surrounding the two commonly used beta-blockers in HFrEF management.