Epidemiology and cause-specific outcome of hypertrophic cardiomyopathy in children - Findings from the Pediatric Cardiomyopathy Registry

Background - Current information on the epidemiology and outcomes of hypertrophic cardiomyopathy (HCM) in children is limited by disease diversity and small case series. Methods and Results - The Pediatric Cardiomyopathy Registry has collected prospective and retrospective data on children diagnosed with HCM since 1990. We identified the various causes of HCM in childhood and determined the relationship between outcomes, cause, and age at presentation. Of 855 patients < 18 years of age with HCM, 8.7% (n = 74) had inborn errors of metabolism, 9.0% (n = 77) had malformation syndromes, 7.5% (n = 64) had neuromuscular disorders, and 74.2% (n = 634) had idiopathic HCM. Children with HCM associated with inborn errors of metabolism and malformation syndromes have significantly worse survival than the other 2 groups. Patients with idiopathic HCM diagnosed before 1 year of age (n = 227) had worse survival from the time of diagnosis than those diagnosed after 1 year of age (n = 407). Patients with idiopathic HCM who survived to at least 1 year of age, however, had an annual mortality rate of 1% that was similar regardless of whether they were diagnosed before or after 1 year of age. Conclusions - In children, HCM is a diverse disorder with outcomes that depend largely on cause and age. Patients presenting before 1 year of age have the broadest spectrum of causes and the poorest outcome. In those children with idiopathic HCM who survive beyond age 1, however, survival is independent of age at diagnosis, with an annual mortality rate (1%) that is much lower than previously reported in children and is not different from has been found in population- based studies in adults.