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2.24.2012

Miller School Study Suggests Criteria for Defibrillators in Children

Underscoring the fact that children should not be treated as small adults, a study led by the Miller School’s Steven E. Lipshultz, M.D., professor and chair of pediatrics and executive associate dean for child health, found that less than 3 percent of children diagnosed with dilated cardiomyopathy die suddenly and unexpectedly.

The finding suggests that relatively few pediatric patients with weakened and enlarged hearts may benefit from cardioverter-defibrillators, the battery-powered devices that, based on recommendations for adults, are routinely implanted in some of these children to prevent sudden cardiac death.

Published this month in the prestigious Journal of the American College of Cardiology, the study also identified three key risk factors associated with sudden cardiac death in children diagnosed with dilated cardiomyopathy, about half of whom fail medical management and either receive a heart transplant or die. The risk factors — an age at diagnosis younger than 14 years, left ventricular dilation, and left ventricular wall thinning — could help clinicians decide which children, especially babies, would benefit from implantable cardioverter-defibrillators.

“There are 10 times more cases of dilated cardiomyopathy diagnosed in the first year of life than in the rest of childhood, and many of these children undergo placement of implantable cardioverter-defibrillators based on recommendations from studies in adult patients with dilated cardiomyopathy,’’ said Lipshultz, who is also chief of staff at Holtz Children’s Hospital.

“But it is not trivial to put these devices in children, especially babies,’’ Lipshultz continued. “As they grow, they need more surgeries to replace the wires to the device. There’s also a lot of maintenance and other risks associated with the devices, which we show may not be necessary. The placement of these devices can also cause unnecessary anxiety in parents about an unlikely event. This is another example of why adult studies cannot simply be extrapolated to children. They are not small adults.”

The study, “Incidence of and Risk Factors for Sudden Cardiac Death in Children With Dilated Cardiomyopathy: A Report from the Pediatric Cardiomyopathy Registry,’’ was based on an exhaustive analysis of the medical records of 1,803 children enrolled in the national registry Lipshultz established in 1994 with a grant from the NIH’s National Heart Blood and Lung Institute. To date, the Pediatric Cardiomyopathy Registry, which is based at the Miller School and coordinated by James D. Wilkinson, M.D., M.P.H., professor of pediatrics in the Division of Pediatric Clinical Research, has enrolled more than 3,500 children under 18 who have been diagnosed with cardiomyopathy at one of nearly 100 participating pediatric cardiac centers across North America.

By examining the records of the 1,803 children diagnosed at a participating center between 1990 and 2009, Lipshultz, Wilkinson and the study’s other co-authors concluded that the five-year rate of sudden cardiac death in children with dilated cardiomyopathy was 2.4 percent, well below the rate of more than 7 percent reported in adults.

The researchers also found that 30 of the 35 children known to have experienced sudden cardiac deaths were younger than 14 when diagnosed with dilated cardiomyopathy, and had both left ventricular dilation, and left ventricular wall thinning – the risk factors the study authors suggest should be considered for implanting cardioverter-defibrillators in children.

“Our study supports the concept that universal implantation of cardioverter-defibrillators is probably not warranted,’’ Lipshultz said, summarizing the conclusions. “However, risk stratification is possible and is strengthened by a patient’s condition meeting all the high-risk criteria for an extended period. In such situations, implantable cardioverter-defibrillator placement should be considered for pediatric patients with dilated cardiomyopathy.’’

In addition to Lipshultz, who is the lead author of the study and the principal investigator of the registry, and Wilkinson, other co-authors included researchers at 10 other institutions, including Children’s Memorial Hospital at Northwestern University, Harvard Medical School, Washington University in St. Louis, and the Hospital for Sick Children in Toronto, Canada.

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