Malignant ventricular tachyarrhythmias in association with propafenone treatment

During treatment with the class Ic antiarrhythmic agent propafenone, the drug appeared to cause malignant ventricular tachyarrhythmias in five patients. Sudden cardiac death occurred in two of them. Three patients exhibited a transition from non-self-terminating ventricular tachycardia to ventricular fibrillation. In the other two patients electrocardiography during syncope revealed ventricular fibrillation. The observed malignant arrhythmias occurred within the first three days of treatment for chronic complex ventricular ectopic activity. Two of the five patients had markedly impaired left ventricular function. All patients received digoxin and low dose diuretic therapy. In contrast to drug induced arrhythmias encountered with other type I antiarrhythmic agents, the proarrhythmic effects of propafenone were not associated with marked QT prolongation. QRS duration was only slightly affected.