NASA computer experts have been using a supercomputer to improve the NASA/DeBakey miniature heart assist pump, leading to on-going human trials with patients awaiting heart transplants. The experts suggested improvements after simulating blood flow through the pump using a NASA computer that normally models rocket fluid flow.
To date, physicians have implanted the heart assist pump in 25 patients during European clinical trials. MicroMed Technology, Inc., Houston, TX, manufactures the pump, now called the DeBakey VADª.
"Johnson Space Center, Houston, TX, and DeBakey Heart Center of Baylor College of Medicine, Houston, asked us to help them because of our experience with simulating fluid flow through rocket engines," said Dochan Kwak, a researcher at NASA's Ames Research Center in California's Silicon Valley. He and colleague Cetin Kiris analyzed blood flow through the battery-powered heart pump whose blade spins as fast as 12,500 rpm. "The speed of fluid flow through a rocket engine is faster than blood flow, but very similar in many ways," Kwak noted.
During initial development of the one-inch by three-inch implantable rotary heart pump, engineers noticed two major problems. Friction damaged blood cells because the device created turbulent flows through many pump parts; and there were stagnant regions in the pump that caused blood clotting, a major problem with ventricle assist devices.
Following supercomputer simulations, the NASA researchers were able to reduce red blood cell damage to an amount comfortably below acceptable limits. The improved blood flow pattern also reduces the tendency for blood clots to form.
"We worked with the team to make the blood flow more smoothly through the pump; that also removed the stagnant regions," Kwak said. NASA Ames scientists first began assisting the NASA/Baylor team in 1993, and will continue to help this year and possibly for a longer period.
"Without the support of the NASA supercomputer design experts, the pump would not function as efficiently as it has," said Dallas Anderson, president and CEO of MicroMed, the company to which NASA granted exclusive rights for the pump in 1996.
In the two years after receiving the license for the pump from NASA, MicroMed gained international quality and electronic standards certifications, got permission to begin clinical trials in Europe and implanted the first device. The first patient, a 56-year-old man, received the DeBakey VADª in November 1998, in Berlin. The pump functioned normally and to its design specifications, Anderson said.
The device can pump more than 10 liters of blood per minute, about twice a normal heart's pumping needs. The pump has been in patients for as long as four months thus far. Eight of the patients have already gone on to have heart transplants.
"MicroMed will soon submit documentation to the Food and Drug Administration (FDA) for permission to conduct human clinical trials of the pump in the United States," Anderson said.
The pump is based in part on technology used in Space Shuttle fuel pumps. Developers predict that the heart pump will not only be a long term "bridge" to transplant, but will serve as a more permanent device to help recovering patients lead a more normal life. The concept for the pump began years ago with talks between Baylor College of MedicineÕs Dr. Michael DeBakey and one of his heart transplant patients, the late David Saucier, a NASA Johnson engineer who died in 1996.
Six months after his 1984 heart transplant, Saucier was back at work. With fellow NASA employees, as well as Dr. DeBakey, Dr. George Noon and other Baylor staff, Saucier worked evenings and weekends on the initial pump design.
"Since my own transplant, I have spent a lot of time visiting people who are waiting for a donor heart," Saucier said at the time. NASA began funding the project in 1992.
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