Verapamil in prophylaxis of paroxysmal atrioventricular nodal reentrant tachycardia.

We examined by electrophysiologic study and clinical follow-up the use of verapamil as a prophylactic agent in 13 patients with refractory paroxysmal supraventricular tachycardia due to atrioventricular (AV) node reentry. Electrophysiologic variables and initiation and maintenance of AV nodal reentry were studied by programmed electrical stimulation. Observations were made before and after intravenous administration of verapamil, 0.15 mg/kg. Twelve of the 13 patients had previously not been controlled by other antiarrhythmic agents. Before verapamil, AV nodal reentry was induced in all 13 patients. Verapamil increased AV nodal transmission time (AH interval), as well as the effective and functional refractory periods of the AV node. Reentry could not be initiated in 5 of the 13 patients after verapamil and was nonsustained in a further 3. The echo zone for atrial premature beats which initiated tachycardia decreased in 2 of the remaining 5 patients. The rate of tachycardia was also significantly decreased. Over a mean follow-up period of 16 months, 11 of the 13 patients had definite symptomatic improvement, with decrease in frequency, duration, and/or associated symptoms of their arrhythmia. Only 1 patient had side effects which necessitated withdrawal of the drug. It was concluded that verapamil is a useful agent in the management of such patients.