Clinical electrophysiology, efficacy and safety of chronic oral cibenzoline therapy in refractory ventricular tachycardia.

The electrocardiographic (ECG) and electrophysiologic (EP) effects, clinical efficacy and safety of oral cibenzoline therapy were evaluated using a twice-daily dosing regimen in patients with refractory ventricular tachycardia (VT). Twenty patients underwent EP studies in the control (drug-free) state and after cibenzoline therapy using an incremental dose-titration protocol. Oral cibenzoline (2.4 to 5.8 mg/kg/day) was administered in doses of 130, 160 or 190 mg at 12-hour intervals. ECG and EP variables, 24-hour ambulatory ECG monitoring and programmed electrical stimulation studies were obtained in the control state and after 11 +/- 4 days of cibenzoline therapy. Cibenzoline therapy prolonged the mean PR interval (from 179 +/- 29 to 201 +/- 36 ms, p less than 0.001), the mean QRS duration (from 107 +/- 21 to 130 +/- 25 ms, p less than 0.001), and the mean QTc interval (from 422 +/- 25 to 460 +/- 42 ms, p less than 0.001). It increased the mean HV interval (from 50 +/- 17 to 65 +/- 20 ms, p less than 0.01) and mean right ventricular effective refractory period (from 245 +/- 24 to 266 +/- 27 ms, p less than 0.01). After cibenzoline therapy, 5 patients (25%) had suppression of inducible sustained VT during programmed electrical stimulation. High-degree atrioventricular block occurred in 2 patients. Chronic cibenzoline therapy (mean follow-up 24 +/- 3 months) remained effective in long-term suppression of VT in 4 patients. Two patients had to discontinue therapy because of gastrointestinal intolerance. Cibenzoline is effective in suppression of refractory VT in selected patients using a twice-daily dosing schedule.