Cardiomyopathy Often Develops during First Year of Life

Contrary to claims in medical textbooks, children who develop cardiomyopathy are more likely to do so in the first year of life than later in childhood, according to a study to be published in the April 24 issue of the New England Journal of Medicine. The study - of nearly 500 children at 38 sites nationwide - also finds that gender, race, and region play a role in determining who develops the disease.

Pediatric cardiology textbooks say it is highly unusual for children to develop cardiomyopathy - an uncommon and potentially devastating disease in which children have weak heart muscle, or too much heart muscle - before they are teenagers. That couldn't be further from the truth, says Steven Lipshultz, M.D., chief of pediatric cardiology at the University of Rochester (N.Y.) Medical Center's Golisano Children's Hospital. As director of its Children's Heart Center, Lipshultz oversees the care of more than 500 children who have cardiomyopathy, some of whom have come from as far away as Pakistan. He led the national team that did the research being presented in the New England Journal of Medicine.

"This study shows that expert opinion from around the world is not a viable substitute for examining the data," Lipshultz says. "A pediatrician who is concerned about a child potentially having a heart problem may consult some of today's most popular cardiology textbooks, and he or she will read that it is unusual for a young child to get cardiomyopathy. This study shows that children are about 10 times more likely to develop cardiomyopathy during their first year of life than ages 2-18 combined."

In addition, the study shows that cardiomyopathy may occur more often than shown in previous studies. "Our prospective incidence rates are higher than those reported in the retrospective Finnish study (published in 1997 and 1998), but the Finnish rates were based on idiopathic cases," Lipshultz says. "A preliminary review of the retrospective cohort in the Pediatric Cardiomyopathy Registry showed that 69 percent of the patients had idiopathic cardiomyopathy and 31 percent had a known cause of cardiomyopathy. The overall annual incidence of cardiomyopathy may have been underestimated by 45 percent." An editorial in the April 24 issue of the New England Journal of Medicine discusses these findings, as well as those in an independently done Australian study that is also featured in this week's edition.

The current study was based on 467 children who have cardiomyopathy. All patients presenting to pediatric cardiologists in 18 centers in New England and 20 centers in the Central Southwest (Texas, Oklahoma, and Arkansas) were identified and entered into a database. Every child in those regions who was diagnosed with cardiomyopathy between 1996 and 1999 is included in the study.

Many of the symptoms of cardiomyopathy are vague, so a pediatrician who sees an infant who is not happy, not feeding well, and is breathing hard may elect to prescribe antibiotics and recheck the child in a few weeks. "Clinical impressions can be misleading, and a child like this could die of cardiomyopathy," Lipshultz says. "If pediatricians don't know to look for cardiomyopathy, they won't find out the child has it."

Knowing that most cases of cardiomyopathy develop within the first year of life is crucial, because 40 percent of children who have the symptomatic form of the disease will either die or need a heart transplant within two years. "It's important to know when this disease presents, so if we see a child who has signs and symptoms of cardiomyopathy - shortness of breath, less of a desire to drink formula - we can address it," Lipshultz says.

If cardiomyopathy is detected early enough, there is hope for children who have the disease. During the past year, Lipshultz published a study in the Journal of Clinical Oncology that showed when doctors give medication known as enalapril to someone who has cardiomyopathy but is asymptomatic, children will experience up to eight additional years of improved heart function.

Until recently, population-based data on the incidence of pediatric cardiomyopathy was rare because of the lack of large, prospective studies. This new study is based on information culled from the North American Pediatric Cardiomyopathy Registry, which was started in 1995 by Lipshultz and his colleagues at Golisano Children's Hospital at Strong. The database contains invaluable information about children in the United States and Canada who have the disease, which affects 12 in 1 million U.S. children and is the leading cause of childhood heart transplantation. Studies such as this weren't possible prior to the creation of the database.

In the mid-1990s, studies showed outcomes for children with cardiomyopathy weren't better than they were three decades prior. In 1950, children experienced the same outcomes as they do today. In the poorest countries and the richest countries, the outcomes are the same. "This study provides the best assessment to date of the incidence of this serious disease in children," says Claude Lenfant, M.D., director of the National Heart, Lung, and Blood Institute, which funded the study and funds the registry. "The analysis of the Pediatric Cardiomyopathy Registry data also provides important information about the development of the disease that could aid in diagnosis, management, and identification of underlying cause."

In addition to disproving the widely held belief that cardiomyopathy rarely occurs in young children, the new study shows that gender, race, and region play a role in determining who developed the disease.

"We determined the incidence of pediatric cardiomyopathy in two regions of the country, and found that the incidence was higher in New England than in the Central Southwest," Lipshultz says. "We also found that the incidence of cardiomyopathy was higher among boys than girls, and among black and Hispanic children than among white children.

"This leads us to believe that genetics may be an important reason children develop cardiomyopathy," Lipshultz says. "But the study also suggests that different parts of the country have different rates of cardiomyopathy. Children in New England, for example, have significantly more cardiomyopathy than children living Texas, Oklahoma, and Arkansas. The regional differences are important because that suggests there may be environmental factors at play in those regions."

Now that physicians have pinpointed when children are most likely to developed cardiomyopathy, they can focus attention on how we can better help them. Thanks to a grant from the Children's Cardiomyopathy Foundation, which based in Tenafly, N.J., Lipshultz is further studying the nuances of cardiomyopathy in children. "We're looking at the data available when a child first presents with cardiomyopathy, trying to determine which factors can help us predict who is going to get better, who is not going to get better, and who is going to need a transplant," Lipshultz says.