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Risk Stratification in Pediatric Hypertrophic Cardiomyopathy

SEPTEMBER 05, 2013
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A new study in this week's The Lancet may profoundly change whether children, especially infants, with hypertrophic cardiomyopathy are evaluated for a heart transplant.  Until now, children with hypertrophic cardiomyopathy were generally treated with medication and monitored. The multicenter study led by the University of Miami Miller School of Medicine’s  Dr Steven E. Lipshultz et al indicates that treatment options, including immediate wait-listing for heart transplantation, should be based on likely outcomes following a risk stratification analysis.

While fairly common in adults, hypertrophic cardiomyopathy is rare in children. The disease is characterized by abnormal growth of the heart muscles and the area(s) of the heart with the greatest growth can further subdivide the condition (ie, asymmetric septal hypertrophy, symmetric ventricular hypertrophy, apical hypertrophy).  Children with hypertrophic cardiomyopathy are at risk for arrhythmias and cardiac arrest.

Treatment and long term prognosis varies greatly for these children due to the large variance in age at diagnosis and etiology of pediatric cardiomyopathy. Some children can be managed with heart failure medications or pacemakers while more severe cases may require heart transplants.  The uncertainty regarding the long term outcomes for these children led Dr Lipshultz and colleagues to analyze data from the NHLBI-funded Pediatric Cardiomyopathy Registry to look for risk factors that may better predict outcomes.  The study looked at longitudinal data on 1085 children with hypertrophic cardiomyopathy from 1990 to 2009. The purpose of the study was to understand how patient factors measured at diagnosis predicted the subsequent risk of the primary outcome of death or heart transplantation.

Results. The estimated minimum rates of death or heart transplantation at 2 years were: 

  • 57% for children with pure hypertrophic cardiomyopathy with inborn errors of metabolism
  • 45%  for children with mixed hypertrophic and dilated cardiomyopathy
  • 38% for children with mixed hypertrophic and restrictive cardiomyopathy
  • 21% for children diagnosed before the age of 1 year
  • 23% for children hypertrophic cardiomyopathy and a malformation syndrome
  • 3% for children with idiopathic hypertrophic cardiomyopathy at age 1 year or older.

The study also looked at risk factors that predicted poor outcomes and found that while there was a great deal of variance for the various subgroups generally poorer outcomes were associated with the following at the time of diagnosis:

  • young age
  • low weight
  • presence of congestive heart failure
  • lower left ventricular fractional shortening (poorer cardiac function)
  • higher left ventricular end-diastolic posterior wall thickness or end-diastolic ventricular septal thickness. (more cardiac hypertrophy).

More importantly, the study found that for all hypertrophic cardiomyopathy subgroups, the risk of death or heart transplantation was significantly increased when two or more risk factors were present. For example, children with pure hypertrophic cardiomyopathy with inborn errors of metabolism AND two risk factors had an 89% estimated rate of death or heart transplantation after two years. In contrast, the same group of children with no risk factors had a 55% rate of poor outcomes. Similarly, children with mixed hypertrophic and dilated cardiomyopathy AND two risk factors had a rate of 57% compared to 0% for those with no risk factors and 50% for those with one risk factor. In a press release, lead author Steven Lipshultz stated, “Before this study, nobody knew which factors were more or less important in predicting dismal outcomes," adding, "Based on our experience with adults, we do not think of HCM as a cause for heart transplant. Yet for a select group of high-risk children with HCM, transplant is key for survival."

For more information about this study, please click here.

Reference

Lipshultz SE, Orav EJ, Wilkinson JD, et al. Risk stratification at diagnosis for children with hypertrophic cardiomyopathy: an analysis of data from the Pediatric Cardiomyopathy Registry The Lancet, 2013 [Epub ahead of print] doi:10.1016/S0140-6736(13)61685-2

 

Image of idiopathic cardiomyopathy gross pathology courtesy of wikimedia commons.



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