IntroductionPrimary prevention (PP) ICD are increasingly placed in children with Hypertrophic Cardiomyopathy (HCM) to prevent SCD using adult criteria. The reliability of PPICD to prevent SCD is unclear.MethodsWe collected data on HCM children ≤20 years with PPICD. Risk factors (RF) for SCD were 1) family history (FH) of SCD 2) syncope; 3) maximal Left ventricular (LV) wall thickness (LVWT) Z value > 5; 4) non-sustained VT (NSVT) on ambulatory ECG; and 5) abnormal BP response to exercise (ABPR).ResultsOf 347 patients (age 14.61± 4.18), with PP-ICD, appropriate interventions (AI) occurred in 55 (16%). RF presence pre-ICD implant was FH-SCD in 114 (33%); LVWT in 230 (66%); NSVT in 25 (7%); ABPR in 105 (30%) and syncope in 84 (20%). Follow up after ICD implant was 0.07 to 32.95 (mean 8.82 ± 6.03) years and incidence of AI was 18.40 cases per 1000 person-years. AI incidence for each RF wasFH-SCD20/114 (17.5%); LVWT 36/230 (15.7%); NSVT 4/25 (16.0%); ABPR 18/105 (17.1%) and syncope 22/84( 26.2%). Risk of AI based on # of RF were5/31 (16%) for 0 RF; 16/126 (13%) for 1 RF; 20/146 (14%) for 2 RF; 12/36 (33%) for 3 RF and 2/8 (25%) for 4 RF.ConclusionsThe incidence of AI in HCM children with PP-ICD based on adult criteria was high. Syncope was the commonest RF associated with AI. All other RF’s had similar incidence in patients with AI. Presence of ≥ 3 RF was associated with AI.