We analysed data from the Pediatric
Cardiomyopathy Registry, which collected longitudinal data for 1085 children with
hypertrophic cardiomyopathy from 1990 to 2009. Our goal was to understand how patient factors measured at diagnosis predicted the subsequent risk of the primary outcome of death or
heart transplantation. The Kaplan-Meier method was used to calculate time-to-event rates from time of diagnosis to the earlier of
heart transplantation or death for children in each subgroup. Cox proportional-hazards regression was used to identify univariable and multivariable predictors of death or
heart transplantation within each causal subgroup.
FINDINGS: The poorest outcomes were recorded for the 69 children with pure
hypertrophic cardiomyopathy with
inborn errors of metabolism, for whom the estimated rate of death or
heart transplantation was 57% (95% CI 44-69) at 2 years. Children with mixed functional phenotypes also did poorly, with rates of death or
heart transplantation of 45% (95% CI 32-58) at 2 years for the 69 children with mixed hypertrophic and
dilated cardiomyopathy and 38% (95% CI 25-51) at 2 years for the 58 children with mixed hypertrophic and
restrictive cardiomyopathy. For children diagnosed with
hypertrophic cardiomyopathy at younger than 1 year, the rate of death or
transplantation was 21% (95% CI 16-27) at 2 years. For children diagnosed with
hypertrophic cardiomyopathy and a malformation syndrome, the rate of death or
transplantation was 23% (95% CI 12-34) at 2 years. Excellent outcomes were reported for the 407 children who were diagnosed with idiopathic
hypertrophic cardiomyopathy at age 1 year or older, with a rate of death or
heart transplantation of 3% (95% CI 1-5) at 2 years. The risk factors for poor outcomes varied according to
hypertrophic cardiomyopathy subgroup, but they generally included young age, low weight, presence of
congestive heart failure, lower left ventricular fractional shortening, or higher left ventricular end-diastolic posterior wall thickness or end-diastolic ventricular septal thickness at the time of
cardiomyopathy diagnosis. For all
hypertrophic cardiomyopathy subgroups, the risk of death or
heart transplantation was significantly increased when two or more risk factors were present and also as the number of risk factors increased.
INTERPRETATION: FUNDING: