Novel Assessment of Accessory Pathway Function in Patients with Wolff-Parkinson-White Syndrome.

Abstract

Surrogates for the shortest pre-excited R-R interval in atrial fibrillation (SPERRI) such as the accessory pathway effective refractory period (APERP) and shortest pre-excited paced cycle length (SPPCL) are flawed assessments of accessory pathway function in patients with WPW. Multi-extrastimulus pacing may have the theoretical advantage of more accurately mimicking the clinical reality of atrial fibrillation and thus may serve to better assess accessory pathway function. This cross-sectional study included 25 consecutive patients, aged≤18years, undergoing electrophysiology study for WPW. The longest S1S2, S2S3, S3S4 coupling intervals at which the antegrade AP refractoriness occurred, SPERRI, and SPPCL were recorded. Induction of atrial fibrillation was attempted in all patients and induced in 8 (32%, 4 SPERRIbaseline (265ms±61ms), 4 SPERRIIsuprel (258ms±41ms)). At baseline, the lower value of the S3ERP or S4ERP (274ms±52ms) was lower than the SPPCL (296ms±54ms, p<0.0001) and APERP (296ms±41ms, p<0.0001). More patients had S3ERP or S4ERP≤250ms (12/25, 48%) compared to those with APERP≤250ms (2/25 8%), p=0.0016), SPPCL 5/24, 20%), p=0.008 or either (6/25, 24%), p=0.0143). With Isuprel, the lower value of the S3ERP or S4ERP (221ms±36ms) trended to be lower than the APERP (252ms±36ms, p=0.0001) and the SPPCL (266ms±57ms, p=0.001). With Isuprel, there was no statistical difference in the proportion of patients with S3ERP or S4ERP<250ms (12/16, 75%) compared to those with APERP≤250ms ((9/16, 56%), p=0.08), SPPCL≤250ms ((9/16, 56%), p=0.08), or either ((10/16, 63%), p=0.16). Multi-extrastimulus pacing protocols demonstrate that accessory pathways are less refractory than as defined by single extrastimulus pacing and straight decremental pacing.