Pumps like Cheney's can extend lives of patients with congestive heart failure
Friday, July 16, 2010
The device, which takes over the work of the heart's main pumping chamber, should lessen discomfort and allow Cheney to do activities as strenuous as riding a bicycle. But it is far from a miracle cure for end-stage congestive heart failure, the condition from which he apparently suffers.
Cheney, 69, had a left ventricular assist device implanted last week at Inova Fairfax Heart and Vascular Institute. In a statement Wednesday, Cheney said he was "entering a new phase of the disease . . . and decided to take advantage of one of the new technologies available."
He has not made public key details of his treatment, including the exact type of device he received. It is not known whether a heart transplant is being considered. But experts on heart failure and published studies of ventricular assist devices sketch a general picture of his prognosis.
It is likely he received a HeartMate II LVAD, made by the California company Thoratec, which is approved as either a "bridge to transplantation" or as "destination therapy," which is permanent use. It is an electrical device implanted in the chest that draws blood from the left ventricle and pumps it into the aorta, the main artery leaving the heart.
A study published in December showed that 58 percent of patients who received the HeartMate II were alive two years later. Forty-six percent were alive, had not had a stroke (the chief complication) and had not needed a replacement.
Patients with a different Thoratec device -- one that pumps the blood in pulses, like the heart, rather than continuously -- did much worse, the study found. Twenty-four percent survived two years, and nearly all of them had had their devices replaced during that period.
The prognosis for people with end-stage congestive heart failure who get neither a transplant nor a pump is dismal. In a previous study, it was 8 percent after two years.
"We have taken a disease that had a terrible prognosis and given people a much improved prognosis and a better quality of life," said Samer Najjar, a cardiologist who heads programs on heart failure, heart transplantation and mechanical circulatory support at Washington Hospital Center.
The procedure to implant a pump normally requires a three-week hospital stay. A thin power cord runs from an external battery pack, which can be carried over the shoulder, through the abdomen to the pump. Infection is a constant risk.
The main hazard, however, is the formation of blood clots in the pump circuit. A clot can travel to the brain and cause a stroke. For that reason, people with pumps must take anticoagulant drugs.
The devices solve the problem of life-threatening left ventricle failure, but they do not help the right ventricle. That chamber is responsible for pumping blood to the lungs, where oxygen is picked up and carbon dioxide is released. In some patients, the right ventricle is so weak that it eventually fails, too.
Other causes of death in people with heart pumps are kidney failure, liver failure and respiratory failure, Najjar said.
About 4,000 people worldwide have received HeartMate II devices, which cost $100,000, said Thoratec spokeswoman Susan Benton Russell.
Cheney has had five heart attacks, the first when he was 37.