Adjunctive use of beta-adrenergic blockers, calcium antagonists and other therapies in coronary thrombolysis

Hemorrhagic potential of combined diltiazem and recombinant tissue-type plasminogen activator administration

In the Thrombolysis in Myocardial Infarction (TIMI) phase II study, use of calcium channel antagonists at study entry was associated with an increased risk of intracerebral hemorrhage. Whether the observed association was due solely to chance, underlying cerebrovascular disease, or an effect of calcium channel antagonists themselves was not determined. Accordingly, blood loss from standardized ear incisions was measured in six groups of anesthetized New Zealand white rabbits: (1) saline control, (2) intravenous diltiazem (20 micrograms/kg/min x 60 minutes), (3) intravenous recombinant tissue-type plasminogen activator (rTPA) (1.0 mg/kg over 60 minutes, 10% bolus), (4) diltiazem plus rTPA, (5) diltiazem daily for 3 consecutive days, and (6) diltiazem (3 days) plus rTPA given on day 3. The combination of rTPA plus diltiazem (3 days) resulted in significantly more blood loss than rTPA alone, diltiazem (60-minute infusion), or rTPA plus diltiazem (60-minute infusion) (p = 0.003). Similarly, diltiazem (3 days) resulted in more blood loss than either agent alone or rTPA plus diltiazem (60-minute infusion) (p < 0.05). Thus, in this animal model, prolonged exposure to diltiazem with or without rTPA was associated with increased bleeding. The potential for chronic use of oral calcium channel antagonist to increase hemorrhagic risk after rTPA administration requires further investigation.

Beta-blocker therapy in acute myocardial infarction: evidence for underutilization in the elderly

PURPOSE

To assess the impact of patient age on the use of beta-blocker therapy in the management of acute myocardial infarction.

PATIENTS AND METHODS

The population studied consisted of 4,762 patients hospitalized with validated acute myocardial infarction in 16 hospitals in the Worcester, Massachusetts, Standard Metropolitan Statistical Area during the years 1975, 1978, 1981, 1984, 1986, and 1988. Logistic regression analysis was employed to control for relevant demographic and clinical variables in evaluating the independent effect of patient age as a determinant of receipt of beta-blocker therapy during the hospitalization.

RESULTS

A consistent trend toward reduced use of beta-blocker therapy in older patients was demonstrated. After adjustment for demographic and clinical variables (gender; prior history of angina, hypertension, or diabetes mellitus; myocardial infarction characteristics; complications including congestive heart failure and shock; and use of digoxin and diuretics), odds ratios for receipt of beta-blocker therapy relative to patients less than 55 years of age were 0.61 for those 55 to 64; 0.52 for those 65 to 74; 0.36 for those 75 to 84; and 0.26 for those 85 or older. Analyses performed for each study year demonstrated results consistent with those for the overall study population.

CONCLUSION

The results of this population-based study suggest that there are substantial opportunities for expanded use of beta-blocker therapy in elderly patients who have sustained an acute myocardial infarction.