Adverse Outcomes of Underuse of β-Blockers in Elderly Survivors of Acute Myocardial Infarction

Objectives. —To study determinants and adverse outcomes (mortality and rehospitalization) of β-blocker underuse in elderly patients with myocardial infarction; and whether the relative risks (RRs) of survival associated with β-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 β-blockers. Main Outcome Measures. —β-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 β-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 β-blocker after their AMIs. Advanced age and calcium channel blocker use predicted underuse of β-blockers. Controlling for other predictors of survival, the mortality rate among β-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 ≥85 years) and consistent with the results for elderly subgroups of 2 large RCTs. β-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 β-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 β-blockers. Conclusions. —β-Blockers are underused in elderly AMI survivors, leading to measurable adverse outcomes. These data suggest that the survival benefits of β-blockade after an AMI may extend to eligible patients older than 75 years, a group that has been excluded from RCTs.