ELECTROPHYSIOLOGICAL EVALUATION OF MORICIZINE IN PATIENTS WITH SUSTAINED VENTRICULAR TACHYARRHYTHMIAS - LOW EFFICACY AND HIGH-INCIDENCE OF PROARRHYTHMIA

In patients with history of sustained ventricular tachyarrhythmias, th e efficacy and safety of moricizine have not been systematically evalu ated by electrophysiological studies. We performed electrophysiologica l testing in these patients in the drug-free state and then after mori cizine loading, and evaluated the safety profile of moricizine during in, hospital loading and follow-up. The study population comprised of 31 patients with clinically sustained ventricular tachyarrhythmia. The underlying heart disease was coronary in 25 patients, cardiomyopathy in 5 patients, and none in 1 patient. The left ventricular (LV) ejecti on fraction ranged from 15%-69% (mean 39 +/- 15%). During the baseline drug-free electrophysiological testing, sustained ventricular tachyca rdia was inducible in 27 patients, ventricular fibrillation in 1 patie nt, and reproducible, nonsustained ventricular tachycardia (15-25 sec) in 3 patients. All 31 patients received moricizine to the maximum tol erated dose (851 +/- 185 mg) over a period of 2-7 days. Six patients d eveloped ventricular proarrhythmia within the first 4 days. Proarrhyth mia required multiple cardioversions in three patients, was not associ ated with QT prolongation, and spontaneously resolved 6-24 hours after withdrawal of moricizine. Of the remaining 25 patients, 24 underwent electrophysiological testing on moricizine and 4 patients (16%) were r endered noninducible. The VT cycle length in the other 20 patients slo wed from 243 +/- 30 msec to 299 +/- 60 msec (P < 0.09). Four noninduci ble patients, two patients with inducible but slowed VT and one patien t who had refused further testing were discharged on moricizine. Among these seven patients, recurrent arrhythmic events occurred in two pat ients, ventricular proarrhythmia in one patient, complete AV block in one patient, and severe disabling headache in one patient. Only two pa tients have continued to take moricizine without side effects or recur rent arrhythmic events during a follow-up of 4 months and 9 months, re spectively. Moricizine is only rarely effective for long-term treatmen t of patients with spontaneous sustained ventricular tachyarrhythmias. It renders ventricular tachyarrhythmias noninducible in a small minor ity (16%) and is associated with a high incidence (23%) of ventricular proarrhythmias.