February 2006
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Children with heart defects can benefit from exercise
Children with serious congenital heart defects are typically urged to restrict their activity, but a pilot study at Children's Hospital Boston, published in the December Pediatrics, indicates that most of these children can benefit from cardiac rehabilitation. The study enrolled 19 children, aged 8 to 17, in a 12-week program of stretching, aerobics and light weight/resistance exercises. All the children had disease severe enough to consider restricting their activity, and all showed reduced cardiac function on exercise tests, but none had test findings that raised safety concerns, such as arrhythmias or chest pain. Still, it was a sick group: all 16 children who completed the program had undergone heart surgery or a nonsurgical procedure in the past, and 11 of the 16 had just one functional ventricle.
"These kids haven't exercised much. They've been told by coaches, doctors, parents and teachers, 'Oh, you can't exercise,'" says Children's cardiologist Jonathan Rhodes, MD, who led the study.
The hour-long sessions, held twice weekly, were tailored to the children's interests and included dance, calisthenics, kick boxing and jump rope. Balls, music, games, relay races and age-appropriate prizes helped keep the kids motivated, and sessions were moved outdoors whenever possible.
"One game they particularly enjoyed was 'punch the doctor'," says Rhodes, referring to a game in which children threw punches at pieces of matting. "A lot of the kids were timid in the beginning, but being with other kids with heart disease who had never exercised helped melt away a lot of their anxiety. It was quite a metamorphosis."
Heart rates were checked initially and two to three times during each session. A pulse oximeter and external defibrillator were available on site, but were never needed, since there were no adverse events.
At the program's end, 15 of 16 children had significantly improved peak work rate, peak oxygen consumption, or both—their hearts pumped more blood with each beat, and their muscles used more oxygen. Functional improvements were as high as 20 percent on some parameters.
Follow-up exercise testing, roughly seven months after program completion, showed that participants' cardiac benefits were sustained, whereas non-participating children had a slight decline in cardiac function. Participants reported exercising more than in the past and had higher behavioral, emotional and self-esteem scores.
Children's plans to launch a formal cardiac rehabilitation program in fall 2006 or spring 2007, when facilities at Children's Hospital Boston at Waltham are complete. Rhodes believes that some two-thirds of children with serious congenital heart disease will be eligible to participate. "With the approval of a pediatric cardiologist, and after careful exercise testing, exercise is generally safe and tolerable," he says.
Non-coding parts of genome are important, too
About 5 percent of mammals' genetic makeup has remained virtually unchanged by evolution. Surprisingly, less than a third of these "conserved" portions of the genome contain genes that code for proteins. The rest, known as conserved noncoding sequences (CNCs), is of growing interest to scientists: there's growing suspicion that these areas aren't just filler, but contain functional bits of genetic sequence whose variation may contribute to human disease.
Seeking to prove this suspicion, researchers, led by Joel Hirschhorn, MD, PhD, of Children's Department of Genetics, and associate member of the Broad Institute, combined two databases: the recently released HapMap database, which catalogues variants in human genome sequences, and the chimpanzee genome sequence. By comparing the two databases, the researchers were able to identify new mutations—those appearing in humans, but not in chimps. They then compared the pattern of new mutations in the CNCs versus the rest of the genome. They reasoned that if the CNCs had a preponderance of rare mutations, and fewer mutations common to many individuals, that would indicate that some of the mutations were harmful, and that natural selection was weeding them out. And that is what their computational analysis showed—providing the most direct evidence to date that CNCs perform important functions in the genome. The work, a collaboration with the Sanger Institute in England, was published in the December 25 online edition of Nature Genetics.
Have a research news you would like to share?
E-mail nancy.fliesler@childrens.harvard.edu or call ext. 5-2426
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