0037: Is the risk of atrial fibrillation dependent on the mechanism of tachycardia in patients with history of paroxysmal supraventricular tachycardia?

Abstract

to evaluate the role of the mechanism of paroxysmal supraventricular tachycardia (SVT) on the incidence of spontaneous atrial fibrillation (AF). The relation between SVT and AF is well-known but its frequency could depend on the mechanism of SVT. 1559 patients, mean age 49±19 years, with SVT and without anterograde conduction over an accessory pathway (AP) were referred for electrophysiological study (EPS), performed in control state and after isoproterenol. SVT was related to atrioventricular nodal re-entrant tachycardia (AVNRT) in 1262 patients (group I), either typical (n=1180)(group IA) or atypical (n=183)(group IB). In 297 patients SVT was related to atrioventric-ular re-entrant tachycardia (AVRT) due to a concealed AP (group II). At the initial evaluation 47 group I patients (4%)(44 of group IA, 4%, 3 of group IB, 2%), 6 of group II (2%) had presented at least one episode of sustained AF (NS). During follow-up (mean 3±2 years), 97 patients developed AF, 86 of group I (7%)(71 of group IA, 6%, 15 of group IB, 8%),11 of group II (4%). AF risk was higher in group I than in group II (p<0.045); differences remain significant for group IA/IB. When patients with AF at first study were excluded AF risk was similar in all groups: 5% of group I)(4% of group IA; 6.5% of group IB)(0.06) and 3% of group II. Ablation of slow pathway/AP was performed in 1099 patients, 67% of group I (69% of group IA, 51% of group IB), 64% of group II (NS). AF risk was paradoxically higher in patients in whom ablation was performed in group I (6.7% in group I, 7% in group IA, 13% in group IB), compared to patients without ablation (4% in group I, 4% in group IA, 3% in group IB)(p<0.022) and was unchanged in group II (4% after ablation and 3% in patients without ablation). AF-related SVT was rare (3%), independent on the mechanism of SVT. The risk of subsequent AF after a follow-up of 3 years increased to 6% and was near 5% in patients without AF at initial evaluation; it was only higher in patients with atypical AVNRT than in patients with AVRT. The risk was not affected by the ablation of the slow pathway or the AP.