Exacerbation of ventricular tachycardia by tocainide

Exacerbation of ventricular arrhythmias by antiarrhythmic drugs the lignocaine‐type has not been reported previously. In this paper we describe three patients with a variety of ventricular arrhythmias who were treated with tocainide and developed worsening of the ventricular arrhythmias. In one patient, frequent ventricular ectopic beats were converted to sustained ventricular tachycardia (VT) in another, nonsustained VT was converted to sustained VT, and in a third, monomorphic VT was converted to multimorphic VT. These patients illustrate the need for careful supervision of antiarrhythmic therapy for VT, even when lignocaine‐like drugs are being used.