Misuse of intravenous verapamil in patients with ventricular tachycardia.

Intravenous verapamil is effective in the acute termination of supraventricular tachycardia but is also used for broad-complex tachycardia when the diagnosis is uncertain. This study analysed the responses to verapamil in 57 episodes of ventricular tachycardia, incorrectly diagnosed as supraventricular tachycardia, in 32 patients. Diagnostic electrocardiographic features of ventricular tachycardia were present in 81% of episodes. Intravenous verapamil (mean dose 9.8 mg) failed to terminate the tachycardia in 45 episodes (79%). 2 patients sustained cardiac arrest after verapamil (1 ventricular fibrillation, 1 asystole), and in 22 episodes severe hypotension occurred. At least one serious adverse effect occurred in 19 patients (59%). Sinus rhythm was restored after verapamil on 10 occasions in 6 patients. Verapamil is ineffective and potentially hazardous in most patients with ventricular tachycardia. It should not be used to treat broad-complex tachycardia unless a supraventricular origin has been established.