Clinical features and outcomes of childhood hypertrophic cardiomyopathy - Results from a national population-based study

Background - Population- based studies have provided insight into the natural history of adult hypertrophic cardiomyopathy, but comparable information for affected children is lacking. Methods and Results - All Australian children who presented with primary cardiomyopathy at 0 to 10 years of age between January 1, 1987, and December 31, 1996, were enrolled in a longitudinal cohort study. A single cardiologist reviewed serial cardiac investigations on each subject. A total of 80 subjects with hypertrophic cardiomyopathy were identified. An underlying syndromal, genetic, or metabolic condition was identified in 46 subjects ( 57.5%). There were no cases of sudden death at presentation. Left ventricular outflow tract obstruction was present in 32 subjects ( 40%); right ventricular outflow obstruction was present in 10 ( 12.5%). Freedom from death or transplantation was 83% ( 95% CI, 73 to 90) 5 years after presentation and 76% ( 95% CI, 62 to 86) 10 years after presentation. By proportional- hazards regression analysis, risk factors for death or transplantation included concentric left ventricular hypertrophy, age at presentation < 1 year, lower initial fractional shortening Z score, and increasing left ventricular posterior wall thickness relative to body surface area. At the latest follow- up, 54 of 65 surviving subjects had no symptoms, and 46 were receiving no regular medication. Conclusions - Syndromal, genetic, and metabolic causes predominate in children with hypertrophic cardiomyopathy. Ventricular outflow tract obstruction is common. The clinical status of long- term survivors is good. This population-based study identifies children with hypertrophic cardiomyopathy who are at risk of adverse events.