LAUSR

Introduction: Guidelines for electrophysiology study (EPS) and catheter ablation in Wolff-Parkinson-White syndrome (WPW) are based on age. Size is an established factor in ablation risk and may be the more appropriate factor to consider when deciding timing of EPS. Hypothesis: Weight <30 kg is associated with higher rates of major adverse events (MAE) and deferred ablation, and lower rates of success. Methods: A multicenter retrospective cohort study was performed on children age 1-21 years with WPW and first-time EPS data in IMPACT from 4/16-12/19, excluding those with congenital heart disease, cardiomyopathy, and > 1 ablation target. MAE were defined as cardiac arrest, stroke, tamponade, permanent pacemaker, or unplanned cardiac / vascular surgery. Ablation success was evaluated in those with attempts. Multivariable logistic regression models were used to adjust for measurable confounders - accessory pathway (AP) type, AP location, and use of cryoablation (cryo). Results: 4456 subjects from 84 centers were evaluated, with 14% <30 kg. Subjects <30 kg were more likely to have pre-operative SVT (45% vs. 29%, p<0.001) and inducible SVT (71% vs. 61%, p<0.001), more likely to have left non-septal APs (46% vs. 37%, p<0.001), and less likely to have right septal APs (25% vs. 33%, p<0.001, Table). No difference was seen in the likelihood of deferred ablation based on weight (9.5% vs. 12%, p=0.07). Ablation success was higher in <30 kg: 95% vs. 92% (p=0.009). This effect persisted after adjusting for measurable covariates (OR 1.7, 95% CI 1.03-2.7, p = 0.04). Left non-septal AP location was also associated with success (OR 2.9, CI 1.9-4.2, p <0.0001), and cryo was negatively associated (OR 0.4, CI 0.3-0.5, p<0.0001). MAE were rare, though with higher incidence in <30 kg (0.3% vs. 0.05%, p=0.04). Conclusions: In this analysis of WPW patients with ablation data in IMPACT, weight <30 kg was associated with increased ablation success; a higher incidence of MAE (which were rare) was observed.