Background: The benefit of β-blocker use beyond 3 years after a myocardial infarction (MI) has not been clearly determined.
Methods and results: 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).
Conclusions: 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.
Keywords: Medicare; heart failure; myocardial infarction; probability; stroke.