While more than 2,000 heart transplants are performed each year in the United States, thousands more adults would benefit from a heart transplant if more donor hearts were available. But new cardiac technology is making it possible to extend the lives of many of these patients who suffer from heart failure and give them greater quality of life as well.
According to the American Heart Association, advanced heart failure claims more than 700,000 American lives each year, but ventricular assist devices (VADs) are helping many patients by restoring the flow of oxygenated blood throughout the body. By restoring the hemodynamic performance of the heart, the devices provide oxygenated blood to adequately perfuse vital organs.
In Alabama, VAD therapy is available only at the University of Alabama at Birmingham, which is one of only 22 academic medical centers nationwide offering this treatment option. Dr. James Kirklin, director of cardiothoracic surgery and cardiac transplantation at UAB, said they use VADs as a bridge to transplantation for short-term support while a patient awaits a donor heart.
"There just aren't enough donors, and often we just can't find a heart to match the patient," Kirklin said.
For patients who are not able to receive a heart transplant, these devices are used as long-term support, also known as destination therapy. "In these cases, the device is intended for permanent lifelong support for circulation in patients where transplantation is not appropriate," Kirklin said.
Patients with acute myocarditis who previously would have died also are using VADs to extend their lives. "In all three of these areas, these devices have had a massive impact in terms of lives saved," he added.
Kirklin and UAB cardiothoracic surgeon Dr. William Holman served as principal investigators for ventricular assist devices in the Randomized Evaluation of Mechanical Assistance in Congestive Heart Failure (REMATCH) clinical trial. REMATCH compared two treatment options for congestive heart failure: the traditional medication regimen versus an implantable heart pump. Both are encouraged about the heart pump technology and the possibilities it brings to the field of cardiac surgery.
Holman is excited about the evolution that is already taking place in this area of cardiac technology. He said they currently use pumps designed by MicroMed and Thoratec, both of which have been approved by the Federal Drug Administration. These VADs are the size of a large cell phone and are implanted in the abdominal cavity. Electric leads run across the skin to the battery support that provides a power supply that's never interrupted as long as the batteries are replaced.
A new generation of VADs currently being trialed is designed with rotary pumps that, Holman said, last longer that the pulsatile pumps on the current devices. "The new devices are smaller, quieter and more durable," he said. Because the current devices last only 18 to 24 months, destination therapy patients must have their pumps replaced every couple of years, which can cause problems.
"Many of these patients don't survive long because of the need to replace the devices," said Holman. "They can have complications from the implantation of the next device and they can also have other problems not related to the device, like intracranial bleeds."
One patient who has beaten the odds with heart-pump technology is Sherri Selph of Sumter, S.C., one of the longest surviving persons in the United States on an implantable heart pump. Selph was 41 when she was diagnosed with stage two congestive heart failure in 1994. By 1999, her health was diminishing so rapidly that she was diagnosed with end-stage heart disease and not expected to live beyond six months.
Kirklin said Selph has had four pump changes and is now on the heart transplant waiting list. "She's broken a record, I'm sure. This technology isn't perfect but we're fortunate to have it for patients like Sherri," he said. "To be totally candid, mechanical circulation support will never replace heart transplantation. Heart transplants are wonderful."
Several of the new rotary pumps are expected to be FDA approved in the next couple of years, Kirklin said. "Rotary pumps are the wave of the future. These new devices will have major advances in quality of life for the patient," he said. "The drive lines are smaller and the patient can wear it like a shoulder harness so they are fully ambulatory."
Holman and Kirklin are involved in FDA trials for Thoratec's HeartMate® II and the DeBakey pump from MicroMed. Holman said a main goal for mechanical circulation support is a device that can provide chronic support, "which is another way of saying permanent placement of VADs," he added. "We're heading toward smaller pumps and totally implantable systems."
Kirklin reiterated that even under the best circumstances, pumps are not as effective as heart transplantation. "In the U.S., we can offer transplants to only about 2,500 patients a year. With these devices, we can just take them off the shelf and treat three times that many," he said. "While VAD technology doesn't replace heart transplantation, it does widen the options for end-stage heart disease patients."
February 2007
