Objective: To assess the short- and long-term safety and efficacy of oral flecainide therapy in patients with symptomatic tachycardia and an extranodal accessory pathway.
Design: Open-label, uncontrolled trial with a mean follow-up of 24 months.
Setting: Referral-based, teaching medical center.
Patients: Sixty-three patients with symptomatic tachycardia and an extranodal accessory pathway.
Interventions: Patients had electrophysiologic testing before and after the initiation of oral flecainide therapy and were followed long-term for the presence of symptoms, new physical limitations, and adverse effects of therapy.
Measurements and Main Results: Flecainide therapy prevented or slowed (324 ± 59 ms to 398 ± 55 ms; P < 0.001) inducible sustained atrioventricular reciprocating tachycardia in 44 of 63 patients (70%). Of the 44 patients discharged from the hospital, 33 (75%) have continued to receive flecainide therapy and have shown no adverse effects (mean follow-up, 24 ± 10 months). Adverse cardiac reactions (proarrhythmia or sinus node suppression) attributable to flecainide occurred in 11 of 63 patients (17%); in 9 (82%) of these 11 patients, events were detected during either in-hospital monitoring or the electrophysiologic study done before discharge. Structural heart disease was detected by two-dimensional echocardiography in 8 of 11 patients who had adverse cardiac events and in 6 of 52 patients who did not have such events (P < 0.001). Isoproterenol reversed the effects of flecainide therapy in 11 of 21 patients; 7 of the 11 patients had spontaneous clinical recurrences of tachycardia or palpitations during the follow-up period, but these symptoms occurred in only 1 of 10 patients who did not show isoproterenol-induced reversal (P = 0.02).
Conclusions: Oral flecainide therapy was effective in 33 of 63 patients who had tachycardia and an extranodal accessory connection. Hospital monitoring during initial therapy is recommended, and flecainide should be used with caution, if at all, in patients with structural heart disease. An isoproterenol challenge appears to be helpful in predicting late recurrence of tachycardia.