The outcomes of pediatric hypertrophic cardiomyopathy (HCM) associated to RASopathies are scarcely known.

To describe outcomes of pediatric HCM associated with RASopathy.

80 cases of children with a clinical phenotype of RASopathy and HCM were included. Age at diagnosis of HCM was 11.7 months (range 0 to 168). The HCM was diagnosed prenatally in 9 cases, and before one year of age in 58 cases. 67 had Noonan syndrome, 9 had Cardiofacio-cutaneous syndrome, 3 had Costello syndrome, and 1 had Noonan syndrome with multiples lentigines. The HCM was obstructive in 37 cases. Associated cardiac defects were right ventricular outflow tract obstruction in 40 children, polyvalvular dysplasia in 18, atrial septal defect (ASD) in 13, ventricular septal defect in 3, congenital mitral regurgitation in 2, persistent arterial duct in 2, left superior caval vein in 2, aortic arch anomaly in 2, coronary anomaly in 1, and systemic arteriovenous fistula in 1. Nineteen children underwent a Konno operation for obstructive HCM. Additional surgical procedures were 9 right ventricular outflow tract surgical reliefs, 9 percutaneous dilatations of pulmonary valve stenosis, 4 percutaneous closures of ASD, 1 tricuspid valve repair, 1 Brom procedure with aortic valve repair, 1 aortic valve replacement, and 1 coronary artery bypass. Overall mortality was 21%. Fourteen (82%) deaths occurred before 1 year of life. Causes of death were cardiac in 10 cases including two sudden deaths, related to respiratory diseases causes in 5, and in utero fœtal death in 1. Factors predicting mortality were diagnosis before 2 months of life (HR=4,33, p<0,001), fœtal diagnosis of HCM (HR=3,64, p<0,001), and surgery before one year of life (HR=3,43, p=0,001).

Mortality of children with HCM due to RASopathy is high and occurs early in life. Main risk factors are early diagnosis of HCM including prenatal diagnosis, and need for surgery before one year of life.