An injured athlete can rest on the couch to recover before returning to sports, but an injured heart doesn't have the same luxury - at least not yet.
One Ohio State University Medical Center surgeon predicts that within 10 years, mechanical support devices for the heart will be put to use temporarily to allow a damaged heart to rest and recover itself. Right now, such heart pumps, known commonly as ventricular assist devices, or VADs, are typically used as bridges to transplant and in some cases as long-term therapies for chronically ill patients.
"I see this as a huge potential therapy for many heart failure patients who will have the opportunity 10 years from now to recover their own hearts," says Dr. Benjamin Sun, chief of cardiothoracic surgery at Ohio State's Medical Center and director of cardiac transplantation and mechanical support.
Why is he so confident? Because he and other physicians have seen the kind of heart healing a VAD can provide. Functioning essentially as surrogate pumps for the heart, the devices have been used for years to help patients who are poor candidates for transplantation regain enough physical and nutritional health to make them strong and successful transplant recipients.
These early patients' experiences demonstrated that for some, the pumps could be better therapy than a transplant, Sun said. "This became the jumping-off point for patients who were not good candidates for transplantation. Some people now can go home with these pumps for years and live a very good quality of life. And they can be walking around in public without anyone knowing they have a pump."
Ohio State's Medical Center has one of the largest and most successful cardiac mechanical support programs in the country, managing patients with 10 different types of mechanical support devices (including a total artificial heart), and slated to participate in a worldwide study of a new, apricot-sized investigational device this year.
The devices differ in size and portability - some patients on VADs must remain hospitalized while others are able to live at home with the implanted devices and an accompanying power pack. Why so many? "We don't have the perfect pump for every indication now. We use a variety of pumps for very different diagnoses," Sun says.
The pumps' functions also differ, depending on patient need. Some provide volume displacement, meaning they squeeze blood out of the heart chambers; others operate on a high-speed rotor to provide a continuous flow of blood. The latest generation of VADs operate with magnetic levitation bearings to move blood, meaning the parts never touch each other, which results in a potentially lower risk for clots and less wear on the device itself.
The Ohio State program's strength and size is largely attributable to its status as an academic medical center.
"As an academic institution we are not married to a single manufacturing company or a single device. We have a strong desire to participate in the future of the field. We analyze the devices and compare them in an unbiased environment," Sun said.
In animal studies, researchers at Ohio State are using the devices to exercise the heart to see if recovery can be achieved in a chronically ill heart. "For people after an acute attack, we definitely can use devices on them and see recovery. But for people with multiple heart attacks, cardiomyopathy or chronic heart failure, we are still trying to determine whether we can mechanically support them, and recover the heart after the pump gives their heart a rest," Sun said. "We do see people's hearts getting stronger with these pumps, but so far they're not strong enough to come off the pump."
Researchers also are exploring whether the devices could be combined with stem cell transplants or gene therapy. And there is still a lot to learn about the heart function itself.
"We understand the damage that occurs to the heart during and after a heart attack. But with other causes of damage, such as chemotherapy and some viruses, we don't know how to stop or reverse that damage, or even what molecular or cellular mechanism caused the damage in the first place," Sun said. "We're hoping we'll reach a point where mechanical support can rest the heart while we learn what's going on and can intervene to make the heart better. We could then take all the hardware out, letting the patient walk away from this with their heart truly 'recovered'"