U-M study: Implanted heart-assisting device yields excellent survival for patients with failing hearts
An implanted pumping device that helps a failing heart may improve survival for desperately ill patients and allow them to go home from the hospitalwhether they're waiting for a heart transplant or aren't eligible for one, a new study finds.
And, as hospitals gain experience in determining who the device can help, survival is rising while problems and hospital stays related to the device are dropping.
Those are the conclusions from a new six-year prospective study of 100 heart failure patients who received the implanted device, called a HeartMate, at the U-M Health System (UMHS). The study results were presented Nov. 19 at the 75th Annual Scientific Sessions of the American Heart Association by Dr. Francis Pagani, the cardiac surgeon who leads the U-M HeartMate team.
UMHS has performed more HeartMate operations than all but two hospitals in the United States. This gives its team valuable experience in the selection, care and follow-up of those who receive the device, which improves the outlook for patients.
Now that the Food and Drug Administration (FDA) has approved HeartMate both for patients awaiting new hearts and those who can't tolerate a heart transplant, the UMHS team hopes to put that experience to work in even more patients. On Nov. 6, the FDA approved the device as a permanent option for patients who are too old or ill, or have too many other health conditions, to qualify for a heart transplant.
"We find that the use of this therapy results in excellent one-year survival that approaches that of heart transplantation," says Pagani, an associate professor of surgery who also leads the Heart Transplant Program at the Cardiovascular Center. "And we saw good survival for those who used the device for more than a year, either while waiting for a new heart or as their destination therapy."
The HeartMate device is part of a class of technology known as LVADs, or left ventricular assist devices. LVADs don't replace the heart, but rather help do the job of the heart's main pumping chamber. Early HeartMates ran on a pneumatic air pump, but recent versions use an electric motor powered by a wearable battery pack.
In all, the 100 patients who got a HeartMate device at U-M between Oct. 1996 and May 2002 lived a total of 9,241 days on the devicemore than 57 percent of them at home. As the team's experience grew, results improved: the 50 most recent patients lived 6,600 days with the device, 75 percent of the days at home. Eighty-two percent of the last 50 patients, and 58 percent of all patients, were able to go home.
Seventeen patients who received the HeartMate at UMHS died, nearly all within three weeks of receiving the device, and nearly all because of circulatory system failure. This rate may have been related to the critically ill state of many patients just before they received their HeartMate implant; 45 percent had been on life support, a ventilator or temporary cardiac assist devices.
The median hospital stay immediately following the operation to implant a HeartMate was three weeks, and just under half of patients were readmitted at least once. But patients treated more recently had shorter hospital stays and fewer days in the intensive care unit.
Problems with the device did occur, especially in earlier versions of the technology. But more than four-fifths of patients went six months without a major device failure. About half of patients who had the device for a full year, whether because no suitable heart had been found or because they were ineligible for a transplant, experienced a significant device failure, such as a pump stoppage or failure of the valve that lets blood into the device's pumping chamber.
In all, the prospects for HeartMate recipients have improved significantly as doctors at UMHS and other major centers gain experience in the overall management of these patients.
"Improvements in patient selection and follow-up care, along with the trend toward implanting the device earlier in a patient's illness, have helped cut the death rate and length of post-implant hospital stays significantly," Pagani says.
According to the American Heart Association, 4.79 million Americans have congestive heart failure, a potentially lethal condition marked by progressive failure of the muscle that makes up the heart's pumping chambers. Heart failure can be brought on by the oxygen-depriving effects of a heart attack or by cardiomyopathy (heart muscle disease) caused by unknown factors; 41 percent of the 100 HeartMate patients at Michigan had this kind of "idiopathic" heart failure.
LVADs offer a promising solution for many patients, Pagani says, though the technology still can be improved to reduce problems and to allow more patients to receive the device. Eighty percent of the patients in the UMHS study were men, mainly because the device's canteen-like size and shape means it can't be implanted in many women.
Pagani and his colleagues look forward to implanting HeartMate devices in many more patients as a "bridge" to transplant or as a permanent therapy. Because of their experience with LVAD therapy since the early days of HeartMate clinical trials, they also look forward to participating in clinical trials for the next-generation devices now in development.
In addition to Pagani, the study's authors are research coordinator Susan Wright, a registered nurse, and cardiologists Dr. David Dyke and Dr. Keith Aaronson, medical director of the U-M heart transplant program. Many of the patients were participants in clinical trials sponsored by HeartMate manufacturer Thoratec Corp.