Po-03-125 ventricular preexcitation and pediatric hypertrophic cardiomyopathy: etiology and accessory pathway characteristics

The etiology of pediatric hypertrophic cardiomyopathy (HCM) is varied. Ventricular preexcitation (VPe) is well recognized, yet little is known regarding the specific etiology, and accessory pathways (AP) characteristics. Define the etiology of HCM in patients with VPe and the characteristics of the responsible APs. Retrospective cohort study of patients <21 years of age with HCM/VPe from 2000-22. The etiology was defined as sarcomeric/non-sarcomeric (isolated HCM), storage disorder, metabolic disease, or genetic syndrome. AP were designated as atrioventricular (AV) or fasciculoventricular fibers (FVF) using standard invasive EP study criteria when available. AV APs were defined as high risk if any of the following were <250 ms: shortest preexcited RR interval in AF, shortest paced preexcited cycle length, or APERP. ECG characteristics were compared in patients with VPe exclusively secondary to an FVF to those with anteroseptal AP-mediated VPe. From a total of 345 patients with HCM, 28 (8%) had VPe and proportion with VPe varied significantly between etiologic groups: isolated HCM 10/220 (5%), storage 8/17 (47%), metabolic 5/19 (26%), genetic syndrome 5/89 (6%), p < 0.001. Six (21%) had clinical AF (1 with SPPRI <250 ms, 4 with storage disease). Invasive EP study was performed in 22, identifying 39 APs (23 AV AP, 16 FVF; fig 1). VPe resulted exclusively from an FVF in 8 (36%) patients. Multiple AV APs were seen in 8 (36%) and AV AP plus FVF in 10 (45%). Five (23%) patients had AV APs with high-risk conduction properties (≥1 in each etiologic group). Ablation was acutely successful in 13/14 patients with recurrence in 3. The only complication was a single case of heart block after ablation of a high-risk midseptal AP. Patients with storage disease had larger QRS amplitudes (median 42.3 v. 23.0 mm, p < 0.01). The delta wave amplitude did not discriminate between anteroseptal AP and FVF (median 4.3 v. 4.1 mm, p = 0.92). VPe and high risk or multiple AP may be associated with any etiology of childhood HCM. This is most common in storage disorders associated with high QRS amplitudes and clinical AF, with important implications for prognosis and management.