As reported throughout the media this past week, former vice president Dick Cheney had surgery to place a pump in his heart. During the procedure, a left ventricular assist device (LVAD) was implanted in his chest. The technology of the implanted LVAD—now marketed through Thoratec Corporation and named the HeartMate II (pictured)—was developed through a collaborative effort that included engineers and clinical scientists of the McGowan Institute for Regenerative Medicine
The device is a miniature rotary pump with axial flow bearings and is intended for patients with end-stage heart failure. Typically the device is used mainly for short periods, to buy potential heart transplant candidates time as they await a donor organ. However, since the FDA’s approval of the device in January 2010, they are also used as a permanent therapy—destination therapy—for people with severe heart failure who aren't transplant candidates.
A key feature of the design is a sophisticated control system developed by researchers at the McGowan Institute that senses when to increase or decrease the rate of blood flow. Other approved and experimental devices require manual adjustments. The controller was the brainchild of McGowan Institute affiliated faculty member James Antaki, PhD, associate professor in Biomedical Engineering at Carnegie Mellon University and adjunct professor in the University of Pittsburgh’s Departments of Surgery and Bioengineering. The control system involves a patented algorithm that permits the LVAD to respond to the needs of the patient based on the level of activity, generating up to10 liters of blood flow per minute, a rate that would be required to climb stairs, for example.
McGowan Institute faculty member Robert Kormos, MD, Director Artificial Heart Program, Co-Director Heart Transplantation at UPMC, and Medical Director of Vital Engineering, said the key was to design an internal propeller, or "impeller," that would pump just the right amount of blood at the right rate through the heart. Engineers spent countless hours on computers refining the blades on a shaft that looks very much like a corkscrew, he said, so that they had correctly engineered angles and heights.
"In the case of jet engines, you're trying to design a rotor that produces the least amount of friction to the air so it doesn't generate undue drag," Dr. Kormos said. "The same is true with moving blood. You don't want a Waring blender in there, you want something that won't damage blood cells and is compatible with blood."
While a heart transplant is still the best treatment out there for those with congestive heart disease, 75 percent of those who have received an LVAD are still alive after 3 years -- a survival rate approaching those who received new hearts, Dr. Kormos said.
"We're not talking about these pumps replacing the need for a heart transplant, but they keep alive those people who would be dying before getting a transplant, or who can't have one," he said.
Illustration: Thoratec Corporation.
The Pittsburgh Channel w/video (07/15/10)
The Heart.org (07/15/10)
Pittsburgh Post-Gazette (07/16/10)
McGowan Institute for Regenerative Medicine In the News: McGowan Institute for Regenerative Medicine Design Technology Receives FDA Approval
Bio: Dr. James Antaki
Bio: Dr. Robert Kormos