Mechanical pumps originally designed to supplement the pumping action of a failing heart and keep the patient alive until a transplant could be found have taken a major step toward becoming a permanent treatment - a development that could expand their use to tens of thousands of patients in the United States.
Results presented Tuesday at the Orlando, Fla., meeting of the American Heart Association showed that a new type of device doubled the two-year survival of heart failure patients. The key to the improvement was the development of a smaller, quieter, more reliable pump that is less likely to break down and need to be replaced, an outcome that requires the patient to undergo a second major surgery.
The pumps are called left ventricular assist devices, or LVADs. They are not meant to replace the entire heart, only to assist in the pumping action of the left ventricle, which pushes blood out the aorta to the body.
Researchers originally thought that LVADs had to mimic the action of the heart, pushing out blood in a series of pulses that were timed to coincide with pulses from the heart itself. That required complex machinery to produce the pulses and sophisticated electronics to synchronize them with the heart.
Such devices had a high propensity to fail.
But more recently, researchers have concluded that a simple, continuously operating pump can work just as well, if not better. Such pumps typically have only one moving part - the impeller - and don't need to be synchronized with the heart, so their reliability is much greater. They are also much smaller, typically only about one-seventh the size of older models.
The findings presented Tuesday were of one such device, manufactured by Thoratec Corp. of Pleasanton, Calif., and called the HeartMate II. The device is currently approved by the Food and Drug Administration only as a temporary bridge to a transplant.
"We had a sense that these smaller devices were going to have better long-term outcomes, and this trial proves it," said Dr. Alfred A. Bove, president of the American College of Cardiology, who was not involved in the research, in an e-mailed statement. "These devices have come a long way in five years. I expect that technology will continue to move things forward and they will be even better five years from now."
The need is great. An estimated 150,000 Americans have advanced heart failure that could be treated with a heart transplant, but there are only about 2,100 donors available in a given year.
The big issue in the future may be not the availability of the devices but the fiscal strain that they will put on the health care system. The Thoratec pump costs about $80,000 and the surgery to implant it an additional $45,000. With thousands of patients needing the device, costs could mount quickly.
In the new trial, headed by researchers from Duke University Medical Center and the University of Louisville, researchers at 38 centers in the United States enrolled 200 heart failure patients between ages 26 and 81. All had failed medical therapy for their condition and were considered too sick to be candidates for a transplant. About two-thirds of the patients received the HeartMate II, and the rest received an older version that pumps in pulses.
The team reported in Orlando and in an article published online in the New England Journal of Medicine that patients receiving the new pump lived longer and had a higher quality of life than those receiving the older one.
One year after the original surgery, 68 percent of those with the new pump were still alive, compared with 55 percent of those who received the older pump. But at two years, the results were much more dramatic: 58 percent of those who received the HeartMate II were still alive, compared with 24 percent of those receiving the older pump.