CMU researchers develop muscle-powered cardiac device

Dennis Trumble, an assistant research professor in the Biomedical Engineering Department at Carnegie Mellon University and a member of the Center for the Neural Basis of Cognition (CNBC), received a $1.2M NIH R01 grant to support his research on developing a totally self-contained, biologically powered, implantable cardiac assist device to treat the rapidly growing population of patients suffering from congestive heart failure.

The prevalence of congestive heart failure (CHF) on a worldwide scale provides a clear application for Trumble’s research. “Congestive heart failure is a highly debilitating and progressive illness that afflicts tens of millions of people worldwide,” Trumble stated in his research strategy, which was composed specifically for the R01 grant. “In the United States over 5.8 million people currently suffer from this condition, and it is estimated that CHF will ultimately affect one in every five Americans.”

Trumble’s research strategy also noted the need for innovative treatments for CHF. “With over 500,000 new cases diagnosed each year in the United States alone, CHF is a rapidly growing public health problem that has proved difficult to treat. Current pharmacologic therapies can relieve symptoms in most patients but do not appreciably stem the course of the disease,” Trumble said. “At present, heart transplantation remains the most effective treatment, but this approach is limited by a small donor pool and the serious side effects of immunosuppressive drugs. A safe and effective permanent ventricular assist device would be a powerful tool.”

Trumble’s research focuses on left ventricular assist devices (LVADs), which have been shown to effectively reverse the effects of CHF when used short-term, but give rise to complications when used over long time periods. Trumble ultimately hopes to develop and test a non-blood-contacting muscle-powered LVAD system without these complications.

“As a first step toward this goal, we have developed an implantable muscle energy converter (MEC) capable of transforming contractile energy into hydraulic power,” Trumble wrote in the project’s abstract. “The objective of this project is to assemble and test a non-blood-contacting ventricular assist system powered by this device.” The R01 grant has been approved for the next four years and will hopefully carry the project to the animal research stage.

In an interview with The Tartan, Trumble discussed two distinct features of his design. First, it’s a non-blood contacting device that avoids blood congestion problems. Most cardiac assisting devices are blood pumps, so they have to be in contact with the blood in order to achieve their functions. But blood has a tendency to clot, and blood clots tend to form inside these devices. Blood clots that get big enough can break free and travel from the device to other parts of the body. If they end up in the patient’s head, they can give the patient a stroke; similarly if they end up in the patient’s organ, they can lead to organ damage.

Because of these issues, doctors have to give the patients drugs to prevent the blood from clotting, but these drugs can have adverse effects. Often the drugs overcompensate, which can lead to patients losing too much blood since their blood is unable to clot if they are bleeding or injured. Trumble’s device solves this dilemma by not touching the blood at all. A part of the device goes around the aorta, the main artery that comes out of your heart, and squeezes the artery to displace the blood instead of pumping blood in the vessel.

The second key feature of Trumble’s device is that it’s a muscle-power-driven device that avoids infection caused by skin drivelines. Most cardiac assisting devices are electrical devices that have an electric cord that goes through the skin. The cord, which is called a driveline, can get infected and lead to death. Trumble’s device fixes this issue as it is totally internal and has no contact with the skin, which removes the risk of infection; the device is instead driven by muscle power.

Researchers connect the muscle-power device to the latissimus dorsi (LD) muscle and provide stimulants to activate the muscle so it does not fatigue. But trade-offs are that the muscle works slower and may not have enough power to completely facilitate the whole device. Fortunately, the research has proved that though energy output decreases, it’s still enough to sustain the device.

The idea of harnessing muscle power originated from Trumble’s prior studies at both Allegheny General Hospital and Carnegie Mellon University. Despite the team’s recent success, developing and modifying the device to its current design has been a long process. The first cylinder piston design was only able to last about 100 million cycles. The team’s recently completed research was focused on the seventh version of the original design.

Trumble’s device has a variety of possible future applications, including the development of a device that squeezes the heart directly. The research still needs time to be tested on patients before it becomes commercially available, but the researchers hope that the results from the research supported by the R01 grant will demonstrate the viability of harnessing energy from in situ muscle for long-term circulatory support, which has the potential to drastically reduce the cost of long-term cardiac support.