Artificial Heart Helps People Awaiting Transplants

By Michelle Meadows

The FDA has approved a partial artificial heart that keeps people alive in the hospital while they wait for a heart transplant. The SynCardia CardioWest Temporary Total Artificial Heart is intended to be a "bridge to transplant" for people who don't respond to other treatments and who could die from non-reversible biventricular heart failure, a condition in which both the left and right sides of the heart are not functioning properly. The device, cleared for marketing in October 2004, is the first of its kind authorized to be sold in the United States.

Heart failure occurs when the heart can't pump enough blood through the body. "People with Class IV biventricular failure are considered to be at the highest stage of severity of heart failure," says Marvin J. Slepian, M.D., a cardiologist and president of SynCardia Systems in Tucson, Ariz., which manufactures the artificial heart. "Even at rest, these patients are having symptoms such as shortness of breath."

Slepian says the artificial heart is like a safety net for some patients, making them a better candidate for transplantation. The goal is to improve blood function, as well as lung and kidney function.

Surgeons remove the bottom half of the patient's heart and sew the artificial heart to the remaining top half, called the atria. The device is made of a plastic material called polyurethane.

"Each of the two artificial ventricles is separated into two parts, an air chamber and a blood chamber," says Michael Berman, Ph.D., a senior medical reviewer in the Food and Drug Administration's Division of Cardiovascular Devices. "One side of each ventricle fills up with blood and gets ejected, respectively, to the lungs or to the rest of the body when air pressure is applied to the air chamber."

Tubes called drivelines are connected from the heart through the chest wall to a console, which operates and monitors the device. Slepian says the console, which is on wheels, is the size of a small washing machine.

About 4,000 people in the United States await heart transplants each year. During a typical year, only about 2,200 donor hearts become available. Some of the 4,000 people awaiting heart transplants have non-reversible biventricular failure and could be candidates for the new artificial heart, Berman says.

The FDA approved the device based on clinical studies of safety and effectiveness conducted by SynCardia Systems and on the recommendation of a panel of outside experts convened by the FDA to review the device.

SynCardia studied the artificial heart in 81 transplant patients with severe biventricular heart failure at five medical centers in the United States. In the studies, nearly 80 percent of patients implanted with the heart remained alive for 79 days, long enough to receive a donor heart, demonstrating that the artificial heart could successfully serve as a bridge to transplant.

"We found that about four days after the procedure, 75 to 80 percent of patients were up out of bed," Slepian says. "In a week, most were walking 100 feet. By the end of a month, they really wanted to get moving."

Seventy-two percent of those in the study developed infection. Other complications included bleeding, a neurological event such as a major or minor stroke, and device malfunctions. There were 17 patients in the study who died before a donor heart became available. The FDA is requiring SynCardia Systems to conduct a post-approval study to monitor the device's performance in commercial use. The device should not be used in those who are not eligible for a heart transplant, who do not fit the device, or who have heart failure only on one side.

Though researchers have been working on artificial hearts that could permanently replace diseased hearts, there are no such devices approved for permanent use. Slepian says his firm has plans to make a portable console system so that patients could use the temporary artificial heart for longer periods in an outpatient setting.

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