Adverse outcomes of underuse of beta-blockers in elderly survivors of acute myocardial infarction

Abstract

OBJECTIVES: To study determinants and adverse outcomes (mortality and rehospitalization) of beta-blocker underuse in elderly patients with myocardial infarction; and whether the relative risks (RRs) of survival associated with beta-blocker use were comparable to those reported in the large randomized controlled trials (RCTs). SETTING: New Jersey Medicare population. DESIGN: Retrospective cohort design using linked Medicare and drug claims data from 1987 to 1992. PATIENTS: Statewide cohort of 5332 elderly 30-day acute myocardial infarction (AMI) survivors with prescription drug coverage, of whom 3737 were eligible for beta-blockers. MAIN OUTCOME MEASURES: beta-Blocker and calcium channel blocker use in the first 90 days after discharge and mortality rates and cardiac hospital readmissions over the 2-year period after discharge, controlling for sociodemographic and baseline risk variables. RESULTS: Only 21% of eligible patients received beta-blocker therapy; this rate remained unchanged from 1987 to 1991. Patients were almost 3 times more likely to receive a new prescription for a calcium channel blocker than for a new beta-blocker after their AMIs. Advanced age and calcium channel blocker use predicted underuse of beta-blockers. Controlling for other predictors of survival, the mortality rate among beta-blocker recipients was 43% less than that for nonrecipients (RR=0.57; 95% confidence interval [CI], 0.47-0.69). Effects on mortality were substantial in all age strata (65-74 years, 75-84 years, and > or = 85 years) and consistent with the results for elderly subgroups of 2 large RCTs. beta-Blocker recipients were rehospitalized 22% less often than nonrecipients (RR=0.78; 95% CI, 0.67-0.90). Use of a calcium channel blocker instead of a beta-blocker was associated with a doubled risk of death (RR= 1.98; 95% CI, 1.44-2.72), not because calcium channel blockers had a demonstrable adverse effect, but because they were substitutes for beta-blockers. CONCLUSIONS: beta-Blockers are underused in elderly AMI survivors, leading to measurable adverse outcomes. These data suggest that the survival benefits of beta-blockade after an AMI may extend to eligible patients older than 75 years, a group that has been excluded from RCTs.