Electrophysiologic effects of adenosine-5'-triphosphate on atrioventricular reentrant tachycardia.

The effects of adenosine-5'-triphosphate (ATP) on atrioventricular reentrant tachycar- dia (AVRT) were studied in 18 patients. Nine patients had AV nodal reentrant tachycardia and the remaining nine patients had AVRT with an accessory pathway for retrograde conduction. After electrophysiologic control study, ATP was administered (20 mg iv, rapid bolus) during sustained tachycardia and during right ventricular pacing (150 beats/min). ATP terminated the tachycardia within 16 sec of administration in eight of nine patients with AV nodal reentry and in all patients with accessory pathways. Termination of the tachycardia was related to a block in the antegrade slow pathway in patients with AV nodal reentry and to a block in the AV node in patients with accessory pathways. In one patient with AV nodal reentry, ATP resulted in a slowdown of the rate of the tachycardia due to delayed conduction in the slow antegrade pathway. No change in the conduction in the retrograde fast nodal pathway or in the accessory pathway was noted in any patient before termination of the tachycardia. The administration of ATP during ventricular pacing resulted in transient complete ventriculoatrial (VA) block or slight prolongation of VA conduction in five of nine patients with AV nodal reentry. VA conduction was not affected in four of nine patients with AV nodal reentry nor in all patients with accessory pathways. Short-lived and benign side effects were commonly noted after administration of ATP. Transient episodes of second-degree or complete AV block and sinus bradycardia were noted in eight patients and did not require any treatment. These results suggest that intravenous ATP is a safe and effective drug for rapid termination of AVRT.