MECHANISMS OF AV NODE REENTRANT TACHYCARDIA IN YOUNG-PATIENTS WITH AND WITHOUT DUAL AV NODE PHYSIOLOGY

Recent advances in electrophysiological mapping and radiofrequency cat heter ablation have demonstrated the participation of perinodal atrial tissue or pathways in atrioventricular node reentrant tachycardia (AV NRT). Current concepts of the role of these pathways in the genesis of the various forms of AVNRT continue to evolve. in view of these recen t advances, this study investigated the electrophysiology of AVNRT in young patients, and factors potentially associated with variant forms of this arrhythmia. Detailed programmed stimulation and catheter mappi ng were performed in 35 consecutive young patients with AVNRT. This gr oup consisted of 15 male and 20 female patients, with a mean age of 12 .1 +/- 4.2 years (range 3-18 years). Of the 35 patients, 23 demonstrat ed dual AV node physiology, either in response to a critically timed e xtrastimulus (n = 17) or to rapid pacing(n = 6). The common form (ante grade slow-retrograde fast) of AVNRT was demonstrated in 21 of these 2 3 patients. Antegrade fast-retrograde slow (n = 1) and antegrade slow- retrograde slow (n = 1) forms of AVNRT were identified in the 2 other patients. In contrast, only 5 of the 12 patients who did not demonstra te dual AV node physiology had the common form of AVNRT (P = 0.03). Fi ve of these patients also had the slow-slow form of AVNRT, while 1 pat ient each had a fast-slow and fast-fast form of AVNRT. Patients with d ual AV node physiology were older (14.2 +/- 2.0 years) and more likely to be female (26 of 23) than patients in whom dual AV node physiology was not identified, where the mean age was 10.6 +/- 4.2 years and onl y 4 of 12 patients were female (P = 0.02 for age and P = 0.07 for gend er). These observations suggest that the physiology of Av node reentry may evolve as a function of age, with slow-fast AVNRT prevalent in ad olescents. However, absence of dual AV node physiology should not prec lude diagnosis of AVNRT in young patients with supraventricular tachyc ardia, in whom atypical forms of AVNRT may be common.