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Mechanical Device Helps Kids Waiting for Heart Transplant
Pediatric ventricular assist device buys time for young patients with severe heart failure
Wednesday, August 8, 2012
New research has shown, however, that a new device called the Excor pediatric ventricular assist device (or Berlin Heart) often can help the youngest heart-failure patients live long enough to receive a heart transplant. In the past, the only available treatment for those children -- who would otherwise die waiting for a heart -- could keep them alive only about two to three weeks. In the current study, the longest a child lived on the new ventricular assist device was 192 days.
"I don't think any of us predicted the results would be as good as they were," said the study's lead author, Dr. Charles Fraser Jr., surgeon-in-chief at Texas Children's Hospital and a distinguished professor and chairman of congenital heart surgery at Baylor College of Medicine in Houston.
"Ninety percent of these children survived or made it to transplant ... and these were kids who were dying," he said. "It's really striking when you look at the survival curves, not to mention the effect on quality of life and the ability to become ambulatory again."
Results of the study, which was funded by Berlin Heart (the German device maker) and a grant from the U.S. Food and Drug Administration's Office of Orphan Product Development, are published in the Aug. 9 New England Journal of Medicine. The FDA approved the device for pediatric use in December 2011.
Before the pediatric ventricular assist device, the only option to keep alive a child who was dying of heart failure was a procedure known as extracorporeal membrane oxygenation (ECMO).
"ECMO is a pretty precarious arrangement," Fraser said.
It involves tubes in the heart, chest or neck, and an artery, he said. Blood is then circulated through an artificial lung and pumped back into the body. Infants and children on ECMO have to be in the intensive care unit, and they almost always have to be completely anesthetized and often are on a mechanical ventilator. Children on ECMO can't get up and move around, they can't do any physical therapy and they don't get normal nutrition.
At best, ECMO gives a child a few more weeks of survival, Fraser said. The hope is that during those few extra weeks, a donor heart will become available.
"Once you put a child on ECMO, the clock is ticking quickly," Fraser said. Unfortunately, the average time to transplant is 119 days for infants, according to background information in the study. Only between 40 percent and 60 percent of children on ECMO survive long enough to receive a transplant.
About 20 years ago, a device became available for adults with heart failure that helped them get extra time to wait for a transplant. Called the left ventricular assist device, it helped the patient's heart pump more efficiently. Although it has helped many adults, getting the device sized for children presented many challenges, Fraser said.
"Children aren't just scaled-down adults," he said. "The complexity of the engineering and the logistics and geography in the chest of a child are all different. Plus, they needed to size devices to work from newborn size and up."
The current trial included two groups of 24 children aged 16 and under who were in severe heart failure. Children in each group received the pediatric ventricular assist device. These groups were then compared to previous heart failure patients with similar disease severity who had received ECMO.
The average age was 1 year in the first group of children. The longest duration of support in this group for the pediatric ventricular assist device was 174 days, compared with 21 days for ECMO. At 21 days, 25 percent of the children on ECMO had died after coming off the device. At 174 days, 88 percent of the children on the assist device were able to survive to transplantation or be weaned off the machine.
The average age in the second group of children was about 9 years old. The longest duration of support with the pediatric ventricular assist device was 192 days, compared with 28 days for ECMO. At 30 days, 33 percent of children on ECMO had died; at 192 days, only 8 percent of children on the assist device had died.
The pediatric ventricular assist device isn't a panacea. It carries significant risks of major bleeding, infection and strokes, according to the study.
"This is definitely not something to be undertaken with light consideration," Fraser said. "But for those desperate children who likely wouldn't survive to transplant, clearly the benefits of the device outweigh the risks."
Fraser added that children who receive the pediatric ventricular assist device can usually be taken off mechanical ventilation. They can typically get out of bed and move around, take part in physical therapy and eat normally. All of these things help make them stronger and healthier before surgery.
"This device is designed to rescue children whose hearts are failing so severely that the benefits outweigh the risk," said Dr. Daphne Hsu, chief of pediatric cardiology at Children's Hospital at Montefiore, in New York City.
She has experience with the device, and said "it's wonderful that there is a device to treat children now. There has not been much emphasis on treating heart failure in children."
The only drawback for the new device compared to ECMO is cost, she said. Although she didn't know the exact figures, she thought the new device initially cost about $50,000, compared with several thousand dollars for ECMO. But, she said, the cost of the assist device may have already come down, and might come down further as it gains more widespread use.
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