Risk factors for atrioventricular tachycardia degenerating to atrial flutter/fibrillation in the young with Wolff-Parkinson-White.

BACKGROUND: Atrioventricular reciprocating tachycardia (AVRT) is common in patients (pts) with Wolff-Parkinson-White (WPW) syndrome but atrial flutter/fibrillation (AF) with rapid ventricular response (RVR) is rare. Although AF occurs in 18% of adult WPW pts, its incidence in children is unknown. We sought to determine risk factors for AVRT spontaneously degenerating to AF during electrophysiologic studies (EPS) in children with WPW.

METHODS: This was a retrospective study of children with WPW referred for accessory pathway (AP) ablation without clinical AF. Standard electrophysiologic protocols were performed to induce AVRT. To determine if AF degeneration was associated with patient characteristics, 2-sample t-tests, Chi-square, and Fisher's exact were used.

RESULTS: There were 53 (31 males) WPW pts studied. During EPS, AVRT degenerated to AF in 27/53 (51%). RVR was seen in 18/27 (67%) patients. The ventricular cycle length (CL) during AF was shorter with RVR (211 + 24 ms) than without (313 + 65 ms) (P = 0.01). AF occurred more commonly among patients with right anterior AP (P = 0.05). Patient gender, age, height, weight, body surface area, persistence of preexcitation on exercise testing, baseline CL, AVRT conduction, and AP number were not significant AF determinants. The AVRT CL was significantly shorter in patients with (265.2 + 41.5 ms) versus those without (308 + 59 ms) AF (P = 0.01). Preliminary data suggest that AP location may be related to patient ethnicity.

CONCLUSION: AF with RVR occurred following AVRT induction during EPS in 34% of our WPW patients, typically associated with right-sided AP locations. Time intervals for RVR to degenerate into ventricular fibrillation and lead to SCD are yet to be determined.