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Risk Stratification at Diagnosis for Children With Hypertrophic Cardiomyopathy: An Analysis of Data From the Pediatric Cardiomyopathy Registry
Study Questions:
What risk factors for death and transplant are present in children with hypertrophic cardiomyopathy (HCM) at the time of diagnosis?
Methods:
Data from the Pediatric Cardiomyopathy registry were analyzed. This registry collected longitudinal data for 1,085 children with HCM between 1990 and 2009. The primary outcome was death or heart transplantation. Pure HCM was categorized as idiopathic diagnosed <1 year of age (n = 252), idiopathic diagnosed ≥1 year of age (n = 407), HCM associated with malformation syndromes (n = 60), and HCM associated with inborn errors of metabolism (n = 69). Mixed HCM was categorized as HCM with dilated cardiomyopathy (n = 69) and HCM with restrictive cardiomyopathy (n = 58).
Results:
The highest risk group was children with HCM with inborn errors of metabolism, with an estimated rate of death or heart transplantation of 57% (95% confidence interval [CI], 44-69) at 2 years. The outcomes for children with mixed functional phenotypes were also poor, with an estimated rate of death or transplant of 45% (95% CI, 32-58) at 2 years for children with mixed hypertrophic and dilated cardiomyopathy, and an estimated rate of death or transplant of 38% (95% CI, 25-51) at 2 years for children with mixed hypertrophic and restrictive cardiomyopathy. For infants with HCM diagnosed <1 year of age, the rate of death or transplantation was 23% (95% CI, 12-34), while the rate of death or transplantation for children diagnosed at 1 year of age or older was 3% (95% CI, 1-5). The risk factors for poor outcomes were dependent on HCM subgroup, but generally included young age, low weight, 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 diagnosis.
Conclusions:
In children with HCM, the highest risk groups are those presenting as infants with inborn errors of metabolism, or those with mixed hypertrophic and dilated or restrictive cardiomyopathy.
Perspective:
This study used the Pediatric Cardiomyopathy Registry to determine risk factors at the time of diagnosis for poor outcomes in infants and children with HCM. The highest risk groups are patients with inborn errors of metabolism, as well as those with a mixed picture of HCM with dilated or restrictive cardiomyopathy. It is possible that some infants with metabolic and mitochondrial diseases may have been included in the idiopathic HCM group of infants less than 1 year of age, leading to poorer outcomes in this group. The study also identified important patient-specific risk factors, including young age, low weight, congestive heart failure, greater left ventricle wall or septal thickness, and poorer systolic function. These risk factors may assist in identifying patients who would benefit from aggressive medical therapy and/or early listing for cardiac transplantation.
Keywords: Heart Defects, Congenital, Ventricular Septum, Cardiomyopathy, Hypertrophic, Risk Factors, Heart Transplantation, Heart Diseases, Mitochondrial Diseases, Cardiomyopathy, Restrictive, Pediatrics, Heart Failure, Metabolism, Inborn Errors, Hypertrophy, Heart Ventricles, Cardiomyopathy, Dilated, Death, Sudden, Cardiac
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