Efficacy and safety of class IC antiarrhythmic agents for the treatment of coexisting supraventricular and ventricular tachycardia.

Thirty-three patients with concurrent supraventricular (SVT) and ventricular tachycardia (VT) were treated with class IC antiarrhythmic agents. Twenty-two patients had atrial fibrillation (17 with paroxysmal and 5 with chronic fibrillation), 1 patient had ectopic atrial tachycardia and 11 patients had reentrant paroxysmal SVT (8 with atrioventricular node reentrant tachycardia, 3 with atrioventricular reentrant tachycardia). Of 5 patients with Wolff-Parkinson-White syndrome, 2 had only atrial fibrillation. Six patients had sustained VT and 27 had nonsustained VT. Twenty-nine patients had organic heart disease (16 with coronary artery disease, 8 with cardiomyopathy and 5 with valvular heart disease) and 4 had primary electrical disease. The mean ejection fraction was 40 +/- 14% (range 15 to 66%). The study population's arrhythmias were not controlled despite having received 2 to 5 (mean 3.1) previous drug trials. Eighteen patients were referred for treatment of SVT and 15 were referred for treatment of VT (mean symptom duration 107 months). Efficacy was determined in 13 of 33 patients with sustained SVT or VT by programmed electrical stimulation and in 20 of 33 by telemetry and 24-hour Holter response. Twenty-two flecainide and 15 encainide trials were conducted in the 33 patients. Four patients underwent trials with both drugs. Of 33 patients with coexisting SVT and VT, 15 (45%) were controlled with an IC agent alone and 3 continued therapy with an IC agent plus additional therapy (2 drugs, 1 antitachycardia pacing). During the follow-up period (mean 10.4 months), flecainide produced a complete response in 9 patients and encainide in 9 patients. SVT was not controlled in 7 patients and VT was not controlled in 7 patients. One patient had neither arrhythmia controlled. Atrial or ventricular proarrhythmia was seen in 9 of 33 patients (27%) (5 with ventricular and 4 with atrial arrhythmia). Noncardiac side effects were uncommon. Oral class IC agents may be effective therapy for some patients with coexisting VT and SVT of different mechanisms. Patients with such complex arrhythmias should be evaluated carefully because there is a potential for both atrial and ventricular proarrhythmia.