Electrophysiologic and antiarrhythmic effects of oral flecainide in patients with inducible ventricular tachycardia

Flecainide has demonstrated unsurpassed antiarrhythmic activity in patients with stable ventricular arrhythmias, but its effects in those with ventricular tachycardia or fibrillation have not been evaluated. Electrophysiologic and hospital evaluation of oral flecainide therapy (150 to 200 mg every 12 hours for 4 to 6 days) was performed in 15 patients with clinically documented ventricular tachyarrhythmias treated unsuccessfully with an average of 3.7 (range 1 to 10) antiarrhythmic drugs. Plasma flecainide concentrations averaged 769 ng/ml (range 377 to 1,152). Cardiac conduction times increased; AH interval changed by + 29%, HV interval by +42%, PR interval by +25%, QRS duration by +14% (all p < 0.01). Ventricular refractory period increased by 10% (p < 0.01) and corrected sinus node recovery time lengthened by 153 ms (p < 0.02). During baseline programmed stimulation, sustained ventricular tachycardia was induced in six patients and nonsustained tachycardia (from 6 beats to 30 seconds' duration) in nine patients using up to three premature ventricular stimuli. Flecainide prevented tachycardia induction in 9 (60%) of 15 patients and improved response (marked increase in cycle length or difficulty of induction) in 2 (13%) of 15, for a 73% overall response. Cycle length of induced rhythms increased by 141 ms after drug administration in those with inducible responses. Antiarrhythmic response rate was higher in patients without coronary artery disease.Outpatient experience in 10 patients has been generally concordant with in-hospital evaluation at a median of 6.5 months. Flecainide has been well tolerated. Unexpected arrhythmias have included exercise-initiated tachycardia in one patient and slow, hemodynamically stable tachycardia (110 beats/min) in another patient. Oral flecainide is an important antiarrhythmic agent for the management of inducible ventricular tachyarrhythmias. Cardiac conduction times and ventricular refractoriness increase; favorable responses to programmed stimulation are frequent and generally predict outpatient safety and efficacy