Long term use of flecainide in patients with supraventricular tachycardia.

The acute effects of intravenous flecainide on electrically-induced paroxysmal supraventricular tachycardia and the safety and efficacy of long term prophylaxis with orally administered flecainide were assessed in 37 patients with paroxysmal supraventricular tachycardia refractory to treatment with 'conventional' antiarrhythmic drugs. Over a mean treatment period of 14.2 months, flecainide 200 to 400mg daily completely suppressed paroxysmal supraventricular tachycardia in 9 of 20 patients with paroxysmal supraventricular tachycardia due to Wolff-Parkinson-White syndrome, while 3 patients reported only transient episodes of paroxysmal supraventricular tachycardia, and 1 patient had a decreased ventricular response to chronic atrial fibrillation. Of 17 patients with paroxysmal supraventricular tachycardia due to atrioventricular nodal re-entry, flecainide 200 to 500mg daily for a mean period approaching 26 months totally prevented episodes of paroxysmal supraventricular tachycardia in 8, and reduced the frequency and duration of episodes of paroxysmal supraventricular tachycardia in 3 others. Flecainide prolonged action potential refractoriness in a few patients in each group; however, an increased frequency of occurrence of paroxysmal supraventricular tachycardia occurred due to a simultaneous decrease in the re-entry circuit conduction velocity. In both patient groups the acute electrophysiological effects of flecainide were often predictive of the long term efficacy of the drug in the prophylaxis of paroxysmal supraventricular tachycardia. Side effects usually involved the central nervous system and were most commonly manifested by disturbances in vision, balance, and taste and increased nervousness. These side effects generally subsided following 1 to 2 months' treatment with flecainide. No abnormal trends were observed in laboratory analysis of blood samples taken from patients during long term treatment with flecainide.(ABSTRACT TRUNCATED AT 250 WORDS)