ASTRONOMY

Also known as a 'ventricular assist device' (VAD), the pump is currently undergoing human trials with patients awaiting heart transplants. It is based in part on technology used in space shuttle fuel and oxidizer pumps. NASA computer engineers suggested improvements after simulating blood flow through the pump using a NASA computer that normally models the flow of fuel through rockets. "Johnson Space Center and DeBakey Heart Center of Baylor College of Medicine asked us to help them because of our experience with simulating fluid flow through rocket engines," said Dochan Kwak, chief of the NASA Advanced Supercomputing Applications Branch 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 normally spins as fast as 10,000 rpm. "The speed of fluid flow through a rocket engine is faster than blood flow, but very similar in many ways," Kiris noted. MicroMed Technology, Inc., Houston, manufactures the pump, now called the DeBakey VAD. It is intended as a long-term 'bridge' to a heart transplant, or as a long-term device to help patients move toward recovery and a more normal life. In European trials, the VAD was implanted in 115 people with no device failure. U.S. trials will involve 178 implants; 21 have been performed successfully to date. During initial development of the one-inch by three-inch implantable axial rotary heart pump, engineers noticed two major problems. Friction led to damaged blood cells because the device created high shear flows through pump parts. Further, there were stagnant regions in the pump that caused blood clotting, a major problem with ventricular assist devices. Following supercomputer simulations, NASA computer scientists were able to reduce red blood cell damage to an amount comfortably below acceptable limits. The improved blood flow pattern also reduced 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," Kiris said. NASA Ames scientists first began assisting the NASA/Baylor team in 1993, and continue to collaborate with them. In keeping with its mission of transferring space-based technology to the private sector, in 1996 NASA granted exclusive technology rights to MicroMed Technology Inc. after a period of intense competition. "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. Within two years of receiving the NASA license for the pump, 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 VAD in November 1998, in Berlin. The pump functioned normally and to its design specifications, Anderson said. The device has been implanted for periods of up to one year in individual patients, thus far. "There are three groups who made this effort successful," Kwak said. "The medical team led by Dr. Michael DeBakey and Dr. George Noon, the systems engineers at Johnson Space Center, and the Ames computational team that used NASA supercomputer know-how to help develop the VAD." The concept for the pump began years ago with talks between DeBakey and one of his heart transplant patients, David Saucier, a NASA Johnson engineer who passed away in 1996. Six months after his 1984 heart transplant, Saucier was back at work. With fellow NASA employees, as well as DeBakey, 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.