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Effect of propranolol in patients with myocardial infarction and ventricular arrhythmia
Insights
Propranolol did not show a specific benefit in reducing sudden death for heart attack patients with complex ventricular arrhythmias. However, these arrhythmias still indicate a higher risk for mortality.
Area of Science:
- Cardiology
- Clinical Trials
- Pharmacology
Background:
- The Beta-Blocker Heart Attack Trial (BHAT) investigated propranolol's efficacy post-myocardial infarction.
- Arrhythmias are common in post-myocardial infarction patients and associated with increased mortality risk.
Purpose of the Study:
- To evaluate if propranolol offers a specific mortality benefit in post-myocardial infarction patients with complex ventricular arrhythmias.
- To determine if arrhythmias identify a high-risk subgroup for mortality.
Main Methods:
- A placebo-controlled, randomized, double-blind trial involving 3,837 patients post-myocardial infarction.
- 24-hour ambulatory electrocardiograms were used to assess arrhythmias at baseline in 85.7% of patients.
- Four arrhythmia classifications were analyzed, with a focus on complex ventricular arrhythmias.
Main Results:
- The hypothesis that propranolol would preferentially reduce sudden death in patients with complex ventricular arrhythmias was not supported.
- Propranolol showed a relative benefit of 28% in reducing sudden death for the arrhythmia subgroup versus 16% for the non-arrhythmia subgroup (nonsignificant difference).
- Arrhythmia presence consistently identified patients at higher risk for total mortality, coronary heart disease mortality, and sudden cardiac death.
Conclusions:
- Propranolol does not appear to offer a special relative benefit in reducing mortality for post-myocardial infarction patients with ventricular arrhythmias.
- Ventricular arrhythmias identify a high-risk group, suggesting other mechanisms for propranolol's mortality reduction beyond antiarrhythmic effects.
Abstract:
The Beta-Blocker Heart Attack Trial was a placebo-controlled, randomized, double-blind clinical trial of the long-term administration of propranolol hydrochloride to patients who had had at least one myocardial infarction. Among 3,837 patients followed up for an average of 25 months, 3,290 (85.7%) had 24 hour ambulatory electrocardiograms performed at the baseline examination. Four classifications of arrhythmia were examined. One of these, the presence of complex ventricular arrhythmias (at least 10 ventricular premature beats/h, or at least one pair or run of ventricular premature beats or multiform ventricular premature beats) was the subgroup of major interest. Regardless of the classification, the presence of arrhythmia identifies a group of patients with a higher risk of total mortality, coronary heart disease mortality, sudden cardiac death and instantaneous cardiac death. The a priori subgroup hypothesis that sudden death would be preferentially reduced by propranolol in patients with complex ventricular arrhythmias was not supported. The relative benefit of propranolol in reducing sudden death for this subgroup was 28 versus 16% for the subgroup without ventricular arrhythmia (relative risk of 0.72 versus 0.84, a nonsignificant relative difference of 14%). There were similar findings for two of the three other classifications of arrhythmia and for the other response variables. Although propranolol does not appear to be of special relative benefit in patients with ventricular arrhythmia, the presence of the arrhythmia does identify a high-risk group. The mechanism by which propranolol reduces mortality is still unclear, but is probably not solely an antiarrhythmic one.