Comparative Effectiveness of β-Blocker Use Beyond 3 Years After Myocardial Infarction and Long-Term Outcomes Among Elderly Patients

Abstract

The benefit of β-blocker use beyond 3 years after a myocardial infarction (MI) has not been clearly determined. Using data from the CRUSADE Registry (Can Rapid Risk Stratification of Unstable Angina Patients Suppress Adverse Outcomes With Early Implementation of the American College of Cardiology/American Heart Association Guidelines) linked with Medicare claims, we studied patients ≥65 years of age with MI, discharged on β-blocker therapy and alive 3 years later without a recurrent MI to evaluate β-blocker use and dose (none, <50%, and ≥50% of the recommended target) at 3 years. Using inverse probability of treatment weighting, we then examined the adjusted association between β-blocker use (and dose) at 3 years and the cardiovascular composite of all-cause mortality, hospitalization for recurrent MI, ischemic stroke, or heart failure over the subsequent 5 years. Of the 6893 patients ≥65 years age, β-blocker use at 3 years was 72.2% (n=4980); 43% (n=2162) of these were treated with ≥50% of the target β-blocker dose. β-blocker use was not associated with a significant difference on the composite outcome (52.4% versus 55.4%, adjusted hazard ratio, 0.95; 95% CI, 0.88-1.03; P=0.23). Neither low dose (<50% target dose) nor high dose (≥50% target dose) β-blocker use was associated with a significant difference in risk when compared with no β-blocker use. Results were also consistent in patients with and without heart failure or systolic dysfunction ( P interaction =0.30). In this observational analysis, β-blocker use beyond 3 years post-MI, regardless of the dose achieved, was not associated with improved outcomes. The role of prolonged β-blocker use, particularly in older adults, needs further investigation.