researchers recently were awarded a $5 million contract from the National Heart, Lung, and Blood Institute of the National Institutes of Health to develop a pediatric heart assist device.
"This contract will allow us to develop two blood pumps small enough to provide heart support for infants, children and teens," said William J. Weiss, Ph.D., principle investigator for the project and associate professor of surgery and bioengineering, Penn State College of Medicine, Penn State Milton S. Hershey Medical Center. "Our multidisciplinary team combines expertise from faculty in several Penn State colleges to develop an effective, safe, pediatric heart assist system. Our goal is to make the product available for clinical use in about five years."
Few heart assist pumps have been developed or adapted specifically for use in children. Most currently-available heart assist devices were designed for adults and are too large for pediatric patients. Currently, short-term heart or heart/lung support is available for children via extracorporeal membrane oxygenation, or ECMO, and the Bio-Pump, but both provide support for only a few days to, at most, a few weeks. Other devices either are not available in the United States, or are adaptations of adult technology, which are not useful for very small children and infants.
Development of a child-size heart assist device started in 1986 at Penn State College of Medicine under the direction of William S. Pierce, M.D., a pioneer in the development of mechanical heart assist devices.
Although the research team has continued to work on certain aspects of the pump, a lack of industry and federal funding slowed development of the device.
"Since the late 1980s, there have been numerous successes with adult heart assist devices such as the Arrow LionHeartTM," Weiss said. "That has sparked renewed interest in funding research and development of a pediatric version of a heart assist device."
Children in need of heart support typically are suffering with congenital heart diseases like hypoplastic left heart syndrome, in which the left part of the heart is underdeveloped, or left ventricle dysfunction due to infection or inflammation of the heart. This heart assist device will provide support for at least six months until the heart recovers or until a donor heart can be found.
Challenges with this type of device include developing very smooth materials and making seamless connections between parts to ensure red blood cells and platelets will not collect in crevices and seams where clots can form, break loose, travel through the blood stream and cause a stroke. Heart assist pumps also can create stress in the blood. When blood undergoes fluid stress it may become activated and begin to clot, or red blood cells may rupture.
Pediatric heart assist devices pose even more complex problems. Due to the smaller size of the blood pump, blood flow in the smaller version is completely different than in the larger adult heart devices.
"Making these pumps smaller is not just a matter of shrinking everything. We really have to be careful about how we design the pump. When you make blood pumps, or even grafts or tubes, the fluid dynamics change as the size changes," Weiss said. "In the smaller pumps, dead zones, or low-rate flow zones, can form inside the blood pumps. This slow-flowing blood can create clots. Our challenge is to be sure the blood is neither too active or too slow."
Penn State researchers have acquired significant expertise in the design, development, clinical use and technology transfer of circulatory support systems. Among their accomplishments are the adult-sized Pierce-Donachy pneumatic ventricular assist device manufactured by Thoratec Corporation, Pleasanton, Ca., the Arrow LionheartTM, a fully-implantable ventricular assist device developed at the College of Medicine in cooperation with Arrow International, Reading, Pa., and currently in clinical trials, and the Penn State Total Artificial Heart currently under further development by Abiomed, Inc., Danvers, Mass. http://www.psu.edu/