<p><strong>BACKGROUND: </strong>Previous estimates of life-threatening event (LTE) risk in Wolff-Parkinson-White (WPW) are limited by selection bias inherent to tertiary referral-based cohorts.</p>

<p><strong>OBJECTIVE: </strong>This analysis sought to measure LTE incidence in children with WPW in a large contemporary representative population.</p>

<p><strong>METHODS: </strong>A retrospective cohort study was conducted using claims data from the IBM MarketScan® Research Databases, evaluating WPW patients (age 1-18 years) from any encounter between 1/1/2013 and 12/31/2018. Subjects with congenital heart disease (CHD) and cardiomyopathy (CM) were excluded. The primary outcome was diagnosis of ventricular fibrillation (VF); a composite outcome, LTE, was defined as occurrence of VF and/or cardiac arrest. VF and LTE rates were compared to matched representative non-WPW controls (3:1 ratio).</p>

<p><strong>RESULTS: </strong>Prevalence of WPW was 0.03% (8,733/26,684,581) over median follow-up of 1.6 years (IQR 0.7-2.9). Excluding CHD/CM, 6,946 subjects were analyzed. LTE occurred in 49 subjects, including VF in 20. Incidence of VF was 0.8 events per 1000 person-years, and incidence of LTE was 1.9 events per 1000 person-years. There were no occurrences of VF in controls; rate of LTE was 70 times greater in WPW (0.7%, 95% CI: 0.5-0.9%) than in controls (0.01%, 95% CI: 0-0.02%).</p>

<p><strong>CONCLUSION: </strong>Use of a large claims dataset allowed for evaluation of VF and LTE risk in an unselected pediatric WPW population. The observed range of 0.8-1.9 events per 1000 person-years is consistent with prior reports from selected populations. Comparison of event rates to matched controls confirms and quantifies the significant elevation in VF and LTE risk in pediatric WPW.</p>