People whose hearts are failing and are on a waiting list for a donor heart often need to buy time until a suitable human heart for transplantation can be found. Depending on their condition, there is a range of devices that can keep their heart functioning until a new heart becomes available. Is the tital articial heart the best?
Yes. Most patients who need a transplant have a disease process that involves the entire heart muscle, such as cardiomyopathy. They require total support. I feel a patient must have fairly severe biventricular failure with disease affecting the whole heart to be a bona fide transplant candidate.
Most bridge researchers agree that the total artificial heart is indicated for graft candidates dying of right-and-left-sided failure. They tend to favor a univentricular device for patients with a normal right heart and left-sided failure. The latter may have had a severe myocardial infarction. If there's a chance both sides of the heart may fail, I'd rather use a total artificial heart than two univentricular devices with four big tubes going through the chest wall. A total artificial heart has just one set of lines.
Total replacement gives you more control. You don't have to depend on the patient's own heart. With an univentricular device, you have to treat the failing heart with drugs that can worsen cardiac problems and change renal function.
The patient on a total replacement is off heart drugs. You control his cardiac output by how much fluid you give and how you set the drive pressures and pumping rate.
Also, most cardiomyopathy patients who deteriorate rapidly have pulmonary edema. This may elevate pulmonary vascular resistance, which is no problem with a total device but a catastrophe with partial support. -- Jack G. Copeland, MD Professor of Surgery and Chief of Cardiovascular and Thoracic Surgery, University of Arizona, Tucson
No. Both systems have served as successful bridges. But with today's technology, I favor using either one or two prosthetic ventricles. They offer more choices. To use a total artificial heart, you must remove the patient's own heart. With the ventricles, we aren't forced to make an early irrevocable decision.
In at least one case, prosthetic ventricles were used for a patient expected to have a transplant, and then his own heart improved. The pumps were removed, and he was able to lead a normal life without tranplantation.
We often don't have to replace the whole heart. For a left- or a right-sided problem, we use one device. Half of the prosthetic-ventricle bridges done so far required a pump on just one side. This avoids therapeutic extravagance and cuts implant risks. Also, we aren't limited by size. Since we don't put prosthetic ventricles inside the chest, it isn't necessary to fit them where the heart was.
Furthermore, applying prosthetic ventricles isn't a big operation. It can sometimes be done without heart-lung support, and there's less morbidity. That's important since we don't want to jeopardize the patient's opportunity for transplantation. The total heart was expected to carry a lower risk of infection, but experience shows mediastinitis is a significant danger. Prosthetic ventricles have proved amazingly free of infection.
Worldwide results are very good. Of the 34 patients bridged with the devices, 25 got transplants and 23 became long-term survivors. And using one prosthetic ventricle costs $10,000 less than a total artificial heart. -- J. Donald Hill, MD Chairman, Department of Cardiovascular Surgery, Pacific Presbyterian Medical Center, San Francisco