Sudden cardiac death in childhood RASopathy-associated hypertrophic cardiomyopathy: validation of HCM Risk-Kids model and predictors of events

Abstract RASopathies represent an important proportion of hypertrophic cardiomyopathy (HCM) cases presenting in childhood. Despite this, there are no published risk factors for sudden cardiac death (SCD) in this cohort of patients. Our primary aim was to validate the HCM Risk-Kids model in children with RASopathy-associated HCM and to investigate additional predictors of SCD in a cohort of 169 patients from 15 international paediatric cardiology centres (UK, Ireland and Germany). Eleven (6.5%) patients experienced a SCD equivalent event [5 (45.5%) an aborted cardiac arrest; 3 (27.3%) SCD; 2 (18.2%) sustained ventricular tachycardia (VT); and 1 (9.1%) appropriate implantable cardioverter-defibrillator (ICD) shock] at a median age of 12.5 months (IQR 7.7-28.64). The calculated SCD equivalent event incidence was 0.78 (95% CI 0.43 – 1.41) per 100 patient years. Six patients (54.54%) with a SCD equivalent event were in the low-risk category according to the HCM Risk-Kids model. Harrell’s C index was 0.5959 (95% CI 0.26-1.22) with a sensitivity of 9.09%, specificity of 63.92%, positive predictive value of 1.72%, and negative predictive value of 90.99%; there was poor distinction between the different risk groups. Unexplained syncope (HR 102.63 (95% CI 14.94 – 704.99), p<0.001) and non-sustained VT [NSVT (HR 5.67 (95% CI 1.30 – 24.70), p=0.021)] were independent predictors of SCD. The HCM Risk-Kids model should not be used for patients with RASopathy-associated HCM but NSVT and unexplained syncope appear to be predictors of SCD in this population. Larger multicentre collaborative studies are required to further investigate predictors of SCD in this group of patients.