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Encainide for atrial fibrillation associated with Wolff-Parkinson-White syndrome
R L Rinkenberger1, G V Naccarelli, W M Miles
1Electrophysiology Laboratory, University of Texas Medical School, Houston 77225.
Insights
Encainide effectively treats atrial fibrillation in patients with Wolff-Parkinson-White syndrome, reducing atrioventricular reciprocating tachycardia episodes. This study confirms encainide
Area of Science:
- Cardiology
- Electrophysiology
Background:
- Atrial fibrillation and Wolff-Parkinson-White syndrome (WPW) pose significant risks.
- Existing treatments for WPW with atrial fibrillation have limitations.
- Encainide's role in WPW requires further investigation.
Purpose of the Study:
- To evaluate the efficacy and safety of encainide in patients with WPW and atrial fibrillation.
- To assess encainide's impact on accessory pathway conduction and tachycardia induction.
Main Methods:
- Thirty-six patients with WPW and atrial fibrillation received oral encainide (175 +/- 44 mg/day).
- Baseline electrophysiologic studies were performed drug-free.
- Patients were followed for a mean of 30.1 months to assess clinical response and side effects.
Main Results:
- Encainide demonstrated efficacy in 67% of patients (14 completely effective, 7 partially effective).
- Anterograde accessory pathway block occurred in 40% of patients; retrograde block in 10 of 24.
- Inducible atrioventricular reciprocating tachycardia (AVRT) decreased from 29 to 19 patients.
- Noncardiac side effects were mild; only one patient discontinued due to side effects.
- Ventricular tachycardia occurred in 3 patients, but 2 had a prior history.
Conclusions:
- Encainide is an effective and safe oral agent for managing atrial fibrillation in WPW patients.
- Encainide reduces the inducibility of AVRT in this patient population.
- The drug is generally well-tolerated, with manageable side effects.
Abstract:
Thirty-six patients with a history of atrial fibrillation and Wolff-Parkinson-White syndrome were treated with oral encainide, 175 +/- 44 mg/day, after undergoing baseline drug-free electrophysiologic studies. The mean age was 38 +/- 15 years, with structural heart disease present in only 3 patients. Nine patients had only paroxysmal atrial fibrillation and 27 patients had both atrial fibrillation and atrioventricular reciprocating tachycardia (AVRT). Symptoms were present for a mean of 195 +/- 168 months and were treated with an average of 2.7 +/- 1.6 drugs before encainide. Anterograde block in the accessory pathway occurred in 12 of 30 patients (40%) and retrograde block accessory pathway occurred in 10 of 24 patients in whom comparison could be made. AVRT was initiated in 29 of 36 patients during the control study and could be initiated in 19 of 29 patients while receiving encainide. Drug efficacy was determined by the clinical response judged completely effective, partially effective or ineffective. During a mean follow-up of 30.1 +/- 25 months, 24 patients (67%) continued to take encainide. Encainide was completely effective in 14 of 24 patients and partially effective in another 7 patients. Noncardiac side effects were mild and generally resolved, and required discontinuance in only 1 patient. More frequent AVRT occurred in 2 patients, but was managed with dose reduction and the addition of a beta blocker. Three patients had ventricular tachycardia requiring discontinuance; however 2 of 3 patients had a history of ventricular tachycardia before receiving encainide. Encainide is an effective and safe agent for treating atrial fibrillation in patients with Wolff-Parkinson-White syndrome.