Aug 18 2009
The National Institutes of Health (NIH) has awarded a $4.1 million grant to the Texas Heart Institute at St. Luke’s Episcopal Hospital (THI at SLEH) to determine the effect of pulseless blood flow on bodily functions. This knowledge will be used in the development of a total artificial heart (TAH) that produces continuous, pulseless blood flow.
The new TAH will be an important advance over current heart replacement devices. It will be more durable (lasting for at least 10 years without needing replacement), and its small size will allow it to be implanted in small adults. Current artificial hearts fit only very large adults.
As a type of ventricular assist device, or VAD, continuous flow pumps were first introduced for partial support of the failing heart. They have worked well for partial heart support but have never been used for total heart replacement, which is needed for many patients with heart failure. In the THI study, the heart will be replaced experimentally by two small, continuous flow blood pumps that operate according to the principle of centrifugal force. Compared to existing assist devices, the new TAH will function more like a natural heart, in that it can adjust how much blood it pumps depending on how much blood is in the heart. Assessing how the device responds to the body’s changing needs for blood—such as during exercise—is an important objective of the study.
Over the past four decades, substantial effort has been expended to develop a TAH, but technical hurdles have been prohibitive. However, the introduction of continuous flow VADs over the last 8 years has revolutionized cardiac support. These pumps are smaller and more durable than earlier devices. In 1988, Dr. Frazier was the first to implant a continuous flow pump in a patient. This work ultimately led to continuous flow VADs being used worldwide as the preferred method of support for the failing heart. More than 4,000 patients have now been treated with continuous flow VADs; one of the first such pumps to be implanted functioned well, without any sign of wear, for more than seven years.
Translational (from the lab to the bedside) research in the development of mechanical circulatory support devices began more than 40 years ago at THI. Under the direction of Dr. O. H. Frazier (chief of Cardiopulmonary Transplantation, chief of The Center for Cardiac Support, and director of Surgical Research at THI, and director of Transplant Service at SLEH), physician scientists at THI have amassed the world’s most extensive experience in the development and use of heart assist devices to help patients with severe heart failure. More than 700 patients have received such devices at THI since the research program began.
“The availability of an effective, reliable mechanical replacement for the failing human heart would have an enormous impact on health care,” said Dr. Frazier. “Congestive heart failure is the most common cause of premature death in America, claiming the lives of nearly 300,000 persons a year, including more than 10,000 young adults (under the age of 40), and imposing a financial burden of billions of dollars. The development of this new TAH could allow many of these patients to live long, productive lives. For example, one young man has been supported by a left ventricular assist device developed at THI for more than 10 years. During that time, he has worked, has had two children, and has been productive in every sense of the word. The ultimate goal of the NIH grant is the development of a TAH that will allow patients to have the same functional capacity as patients with successful heart transplants, but without the transplant patient’s dependency on the availability of a donor and on anti-rejection medications.”
The grant (R01HL090521) was awarded by the National Heart, Lung, and Blood Institute (NHLBI) of NIH through a special program that encourages collaborations among medical and engineering experts. Dr. Frazier will lead a collaborative team from THI, Thoratec Corporation, and Beth Israel Deaconess Medical Center/Harvard Medical School. The preliminary studies for this program were initially supported by grants from the John S. Dunn Research Foundation and the John M. O’Quinn Foundation.
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