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Beta blockade early in acute myocardial infarction
Insights
Early intravenous beta blockers significantly reduce mortality in acute myocardial infarction patients, especially when administered within two hours of symptom onset. This treatment is safe, effective, and cost-effective.
Area of Science:
- Cardiology
- Pharmacology
- Clinical Trials
Background:
- Intravenous beta blockers show promise in reducing complications of acute myocardial infarction (AMI).
- Previous studies, including ISIS-1, indicated a potential mortality benefit with intravenous beta blockade, though with wide confidence intervals.
Purpose of the Study:
- To assess and compare the effects of early intravenous atenolol versus control treatment on mortality in patients with AMI.
- To evaluate the safety and cost-effectiveness of early intravenous beta blockade in AMI.
Main Methods:
- A large-scale randomized controlled trial involving 16,027 patients with AMI.
- Patients received either early intravenous atenolol or control treatment.
- Primary endpoint was vascular death, with follow-up at 1 week and 1 year.
Main Results:
- A significant 15% decrease in mortality was observed, primarily within the first 24-36 hours.
- Mortality at 1 week (313 vs. 365 deaths) and 1 year favored the atenolol group.
- Treatment initiated within 2 hours of pain onset showed a highly significant mortality reduction.
- Excess inotrope use (1-2%) and emergence of heart block were noted as potential concerns.
Conclusions:
- Early intravenous beta blockade is a safe and effective strategy for managing acute myocardial infarction.
- The benefits are most pronounced when treatment is initiated rapidly.
- This approach is considered cost-effective compared to oral beta blockade post-discharge.
Abstract:
Intravenous beta blockers given early in acute myocardial infarction have been shown to reduce chest pain, enzyme release and incidence of arrhythmias. Data published before the first report of the ISIS-1 group (International Studies of Infarct Survival) showed a 12% decrease in the probability of death using intravenous beta blockade but with large confidence limits. This study assessed and compared the effects of early intravenous atenolol and control treatment in the first week and first year after acute myocardial infarction in 16,027 patients. The principal endpoint was vascular death; most of the 15% decrease in mortality occurred in the first 24 to 36 hours with a significant difference at 1 week (313 vs 365 deaths in the atenolol and control groups, respectively). There was no rebound effect after stopping treatment after 7 days. Mortality at 1 year also showed a significant difference in favor of the atenolol group. Subgroup analysis found no significant difference in mortality by age, sex, initial heart rate, diabetes or entry electrocardiogram but data-derived analysis revealed a highly significant decrease in mortality if treatment began within 2 hours of the onset of pain. There was a significant 1% to 2% excess in inotrope use in the atenolol group in the first 36 hours, and first-degree heart block and bundle branch block emerged as relative contraindications to this treatment. The results suggest that early intravenous beta blockade in acute myocardial infarction is safe and effective and also cost effective in comparison with postdischarge oral beta blockade therapy.