AV nodal reentrant tachycardia using three different AV nodal pathways.

In a patient with frequent paroxysmal supraventricular tachycardia, an electrophysiologic study was performed. Although by programmed atrial stimulation only double AV nodal pathways could be documented, three distinct forms of AV nodal reentrant tachycardia could be induced. By programmed atrial stimulation a typical AV nodal reentrant tachycardia was initiated, by programmed ventricular stimulation, an AV nodal reentrant tachycardia was induced with an antegrade conduction time of 215 ms and a retrograde conduction time of 160 ms. Furthermore, a third form of tachycardia was induced with alternating cycle length due to two different antegrade conduction times, whereas retrograde conduction time was almost identical, irrespective of the antegrade conduction time. The patient received betaxolol (20 mg day-1); during a second electrophysiologic study, the tachycardia could not be induced, and it did not occur spontaneously during a follow-up period of 14 months.