Challenges in Comparing Effectiveness of Angiotensin Receptor Blockers vs. Angiotensin-Converting Enzyme Inhibitors for Hypertension in Medicare Data

An evidence gap exists in comparing the effectiveness of angiotensin receptor II blockers (ARBs) vs. angiotensin-converting enzyme inhibitors (ACEIs). We identified elderly hypertensive patients who initiated ACEI/ARBs after a hospitalization for coronary artery disease, heart failure, or stroke eligible for Medicare and state pharmacy assistance programs. Among 18,801 initiators of ACEIs and 2,641 initiators of ARBs, 2,535 deaths were identified. We observed substantial differences in characteristics between ARB and ACEI initiators, suggesting that ARB users were more health-seeking. The incidence of death and sudden cardiac death (SCD) in ACEI initiators was 77 and 22 per 1000 person-years, respectively. The relative risk for SCD was 0.69 (95% CI 0.50–0.96) in ARB initiators, which was 1.1 after restricting to low ejection fraction (EF) patients. The reduced risk of SCD is explained, at least partly, by 1) residual confounding by ARB users being healthier on unobserved domains and 2) lack of data on EF.