Incidence and mechanism of presyncope and/or syncope associated with paroxysmal junctional tachycardia

The objectives of this study were to: (1) define the incidence of presyncop e and/or syncope in patients with paroxysmal junctional tachycardias, (2) d etermine their causes, and (3) determine the outcome of symptoms. Syncope i s a frequent problem and is often caused by paroxysmal tachycardia. The mec hanism of hemodynamic instability is unknown. The population study consiste d of 281 patients, consecutively recruited because they had paroxysmal tach ycardia and a sinus rhythm on a normal electrocardiogram. Fifty-two patient s (group I) had presyncope and/or syncope associated with tachycardia. The remaining patients (group II) had no loss of consciousness. Transesophageal programmed atrial stimulation used 1 and 2 atrial extrastimuli, delivered in a control state, and if necessary, after infusion of 20 to 30 mug of iso proterenol. Arterial blood pressure was monitored. Vagal maneuvers and echo cardiogram were performed in all patients. Paroxysmal tachycardia was induc ed in 51 group I patients and 227 group II patients. Comparisons of groups I and II revealed that age (50 +/- 21 vs 49 +/- 17 years), presence of hear t disease (10% vs 10%), mechanism of tachycardia with a predominance of atr ioventricular nodal reentrant tachycardia (70.5% vs 76%), and rate of tachy cardia (196 +/- 42 vs 189 +/- 37 beats/min) did not differ between the grou ps. However, there were differences in both groups with regard to significa ntly higher incidences of positive vasovagal maneuvers (35% vs 4%, p < 0.01 ), isoproterenol infusion required to induce tachycardia (55% vs 17%, p < 0 .001), and vasovagal reaction at the end of tachycardia (41% vs 4%, p < 0.0 5). Thirty-seven group I patients underwent radiofrequency ablation of the reentrant circuit, which suppressed presyncope and/or syncope in 36 of the 37 patients. Thus, presyncape and/or syncope frequently complicated the his tory of patients with paroxysmal junctional tachycardia (18.5%). Several me chanisms ore implicated, but vasovagal reaction was the most frequent cause . Treatment of the tachycardia typically suppressed presyncape and/or synco pe. (C) 2001 by Excerpta Medica, Inc.