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Mortality in patients treated with flecainide and encainide for supraventricular arrhythmias
1Department of Medicine (Division of Clinical Pharmacology and Cardiology), Duke University Medical Center, Durham, North Carolina.
Insights
Class Ic antiarrhythmic drugs encainide and flecainide did not show increased mortality risk in patients with supraventricular arrhythmias. This contrasts with findings in patients experiencing myocardial infarction and ventricular arrhythmias.
Area of Science:
- Cardiology
- Pharmacology
- Clinical Trials
Background:
- Class Ic antiarrhythmic drugs, encainide and flecainide, were previously linked to increased mortality in myocardial infarction patients with ventricular arrhythmias.
- Concerns exist regarding the safety profile of these drugs in different patient populations.
Purpose of the Study:
- To evaluate the mortality risk associated with encainide and flecainide in patients treated for supraventricular arrhythmias.
- To determine if the increased mortality risk observed in other patient groups extends to those with supraventricular arrhythmias.
Main Methods:
- Retrospective analysis of mortality data from pharmaceutical sponsor protocols for encainide and flecainide in supraventricular arrhythmia patients.
- Comparison of mortality rates between combined encainide-flecainide patient groups (n=579) and a control group from a research arrhythmia clinic (Duke population, n=154).
- Kaplan-Meier survival analysis and hazard ratio estimation to compare survival functions between groups.
Main Results:
- Nine deaths occurred in the combined encainide-flecainide group (average follow-up 488 days) versus 10 deaths in the Duke population (average follow-up 1,285 days).
- Kaplan-Meier survival analysis showed no significant difference in 6-year survival functions between the groups (p = 0.62).
- The estimated hazard ratio for the encainide-flecainide group relative to the Duke population was 0.6 (95% CI: 0.2, 1.7).
Conclusions:
- The use of encainide and flecainide in patients with supraventricular arrhythmias did not demonstrate an excess mortality risk compared to a control arrhythmia population.
- These findings suggest that the arrhythmogenic potential of Class Ic drugs may be context-dependent, varying with the underlying cardiac condition.
- Further research may be warranted to fully elucidate the risk-benefit profile of encainide and flecainide across diverse cardiovascular patient groups.
Abstract:
In a recent clinical trial, the class Ic antiarrhythmic drugs encainide and flecainide were found to be associated with an increased mortality risk in patients with new myocardial infarction and ventricular arrhythmias. The purpose of this study was to assess whether an increased mortality risk also accompanied the use of these drugs to treat patients with supraventricular arrhythmias. Data were obtained from the respective pharmaceutical sponsors on the mortality observed with each drug in United States and foreign protocols enrolling patients with supraventricular arrhythmias. Mortality in the encainide population (343 patients) and the flecainide population (236 patients) was compared with that in a research arrhythmia clinic, the Duke population (154 patients). Nine deaths occurred in the combined encainide-flecainide population and 10 deaths occurred in the Duke population; the follow-up periods averaged 488 days and 1,285 days, respectively. The 6-year survival functions of these 2 populations, estimated by the Kaplan-Meier technique, did not differ significantly (p = 0.62). The hazard ratio for the combined encainide-flecainide population relative to the Duke population was estimated to be 0.6 with a 95% confidence interval of 0.2, 1.7. These descriptive comparisons did not demonstrate any excess mortality when flecainide and encainide were used in patients with supraventricular arrhythmias.