ObjectivesThis study sought to assess the comparative effectiveness of cardiac resynchronization therapy with defibrillator (CRT-D) over implantable cardioverter-defibrillator (ICD) alone in older Medicare patients with heart failure with reduced ejection fraction (HFrEF). BackgroundDespite growing numbers of older patients with HFrEF, the benefits of cardiac resynchronization therapy (CRT) in this group are largely unknown. MethodsA cohort of fee-for-service Medicare beneficiaries ≥65 years of age with HFrEF and enrolled in Medicare Part D who underwent CRT-D or ICD implantation from January 2008 to August 2015 was identified. Beneficiaries were divided by age (65-74, 75-84, and 85+ years), and outcomes were compared between the CRT-D and ICD groups after inverse probability weighting. ResultsCompared with the ICD group, the CRT-D group was older and more likely to be White, be female, and have left bundle branch block. After weighting, overall complications were high across age and device groups (14%-20%). The 1-year mortality was high across all groups. In the 2 oldest age strata, the hazard of death was lower in the CRT-D group (HR: 0.90; 95% CI: 0.86-0.95 and HR: 0.81; 95% CI: 0.72-0.90, respectively; P < 0.001); the hazard of heart failure hospitalization was lower for CRT-D vs ICD in the 85+ years age group (HR: 0.82; 95% CI: 0.74-0.92; P < 0.001). ConclusionsIn older Medicare beneficiaries undergoing ICD with or without CRT, complications and 1-year mortality were high. Compared with ICD alone, CRT-D was associated with a lower hazard of mortality in patients ≥74 years of age and lower hazard of HF hospitalization in those ≥85 years of age. These findings support the use of CRT in eligible older patients undergoing ICD implantation.