ArticlesRisk stratification at diagnosis for children with hypertrophic cardiomyopathy: an analysis of data from the Pediatric Cardiomyopathy Registry
Introduction
Cardiomyopathy is a rare but serious condition in infants and children. Hypertrophic cardiomyopathy is a heterogeneous group of disorders in childhood.1, 2, 3, 4, 5, 6, 7, 8, 9, 10 Paediatric hypertrophic cardiomyopathy encompasses conditions with diverse genetic origins and clinical phenotypes, including associations with inborn errors of metabolism, neuromuscular disorders, and malformation syndromes.7, 11 Few data are available to predict which patients with paediatric hypertrophic cardiomyopathy will progress to end-stage pump failure with subsequent death or need for heart transplantation or who will die from sudden cardiac death.12, 13, 14 Despite the relative rarity of this disorder, the incidence, morbidity, and mortality are higher in the first year of life by a factor of ten compared with the rest of childhood.9, 10, 12 Increased understanding of the factors contributing to a poor outcome in the various causal subgroups of paediatric hypertrophic cardiomyopathy is needed.
Using data from the Pediatric Cardiomyopathy Registry (PCMR) funded by the National Heart, Lung, and Blood Institute of the US National Institutes of Health, we have previously reported the demographic and clinical features of children with pure hypertrophic cardiomyopathy, as well as their clinical outcomes.12 In that report, all available annual follow-up data were used to categorise children into causal subgroups in as scientifically rigorous a manner as possible. Clinical outcome and survival were found to be dependent on the cause of hypertrophic cardiomyopathy and patient age. Although this report provided the most complete estimates of the causes of the disease, the effect of clinical characteristics at the time of diagnosis on outcome was not evaluated. Physicians treating children with hypertrophic cardiomyopathy must base their initial course of care on information collected at the time of diagnosis. Therefore, we have reanalysed the PCMR database to quantify clinical outcomes and their predictors on the basis of causal subgroups (including age at diagnosis and mixed phenotype hypertrophic cardiomyopathy) in children with hypertrophic cardiomyopathy at the time of diagnosis. Our goal was to understand how patient factors measured at the time of diagnosis will predict the subsequent risk of death or heart transplantation. Our hope is that this information will allow clinicians to more effectively stratify patients by risk, to improve family counselling and clinical planning development for these children, resulting in reduced morbidity and mortality.
Section snippets
Design
This study used PCMR data from patients seen between Jan 1, 1990, and Feb 28, 2009, at 98 participating paediatric cardiology centres in the USA and Canada. The design and implementation of the PCMR are described elsewhere.9, 15 Briefly, patients younger than 18 years who received a recent diagnosis of cardiomyopathy at participating centres were eligible for inclusion. Children with specific secondary causes of ventricular hypertrophy such as pulmonary parenchymal or vascular disease,
Results
Of the 1085 children with hypertrophic cardiomyopathy in the database, 69 also had characteristics of dilated cardiomyopathy, 58 also had characteristics of restrictive cardiomyopathy, and the remaining 958 had pure hypertrophic cardiomyopathy at the time of initial diagnosis. We divided the cohort of patients with pure hypertrophic cardiomyopathy into subgroups according to cause. In the subgroups of patients with neuromuscular disorders and familial hypertrophic cardiomyopathy, there were too
Discussion
Prediction of clinical outcome for paediatric patients with hypertrophic cardiomyopathy is challenging because of the substantial heterogeneity of the population. This study expands the earlier PCMR report on the epidemiological features and outcomes of paediatric hypertrophic cardiomyopathy to include the effect of demographic and clinical factors at the time of diagnosis on the subsequent outcomes of death and heart transplantation (panel).12 Specifically, the results of this analysis use
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