Clinical characteristics and survival of children with hypertrophic cardiomyopathy in China: A multicentre retrospective cohort study.

Background: Few data on paediatric hypertrophic cardiomyopathy (HCM) are available in developing countries. A multicentre, retrospective, cohort study was conducted to profile the clinical characteristics and survival of children with HCM in China. Methods: We collected longitudinal data on children with HCM aged 0-18 years at three participating institutions between January 1, 2010 and December 31, 2019. Patients were identified by searching for the diagnosis using ICD-10 codes from the electronic medical records database. HCM was diagnosed morphologically with echocardiography or cardiovascular magnetic resonance imaging. The exclusion criteria were secondary aetiologies of myocardial hypertrophy. The primary outcomes were all-cause death or heart transplantation. The Kaplan-Meier method was used to estimate the survival rate of different groups. Findings: A total of 564 children were recruited, with a median age at diagnosis of 1.0 year (interquartile range, IQR: 0.4-8.0 years), followed for a median of 2.6 years (1977 patient-years, IQR:0.5, 5.9 years). The underlying aetiology was sarcomeric (382, 67.7%), inborn errors of metabolism (IEMs) (108, 19.2%), and RASopathies (74, 13.1%). A total of 149 patients (26.4%) died and no patients underwent heart transplantation during follow-up. The survival probability was 71.1% (95% confidence interval [CI], 66.3%-75.3%) at 5 years. Patients with IEMs or those diagnosed during infancy had the poorest outcomes, with an estimated 5-year survival rate of 16.9% (95% CI, 7.7%-29.1%) and 56.0% (95% CI, 48.8%-62.5%), respectively. Heart failure was the leading cause of death in the cohort (90/149, 60.4%), while sudden cardiac death was the leading cause in patients with sarcomeric HCM (32/66, 48.5%). Interpretation: There is a high proportion of patients with IEM and a low proportion of patients with neuromuscular disease in children with HCM in China. Overall, mortality remains high in China, especially in patients with IEMs and those diagnosed during infancy. Funding: National Natural Science Fund of China (81770380, 81974029), China Project of Shanghai Municipal Science and Technology Commission (20MC1920400, 21Y31900301).