Biorobotic hybrid heart promises better cardiac devices
Researchers at MIT have come up with a bionic heart that can be used to test heart valves and other cardiac implants under realistic conditions. Built out of an actual living heart, the new device promises improved designs and less expensive development cycles.
Prosthetic heart valves have saved or dramatically improved the quality of life for countless people, with an estimated 280,000 valves installed worldwide each year. With an aging population, demand is expected to increase, but the design and testing of such valves and other devices is a major challenge for engineers.
According to MIT, the bottleneck in the process is the extensive testing of prosthetic valves that starts with bench-top simulators before moving onto animal and, eventually, human trials. This is not only expensive, but it also results in valves and other devices that still don't work as well as they should.
To create a more realistic testing device, a team led by MIT started out with a real biological heart, which had its muscle tissue replaced with soft robotic material that forms artificial muscles. These use inflatable bubbles, which make the bionic heart squeeze and twist in a way similar to that of a real one as it pumps blood.
The design of the bionic heart is a compromise of two earlier approaches. One was to use a chemically-preserved biological heart, which was set in a sleeve of soft, artificial actuators. This was realistic, but keeping the tissues alive was too difficult. The other approach was to make a completely artificial heart, which was more durable, but not as realistic.
Instead of either of these, the MIT team started with a living pig heart, then replaced the muscle tissue. Because the heart makes a very complex set of motions as it squeezes and twists along the outer myocardium, the bubble-wrap-like artificial tissues connected by thin air tubes had to be aligned in a large, spiral band of silicone that was simpler than that of the original heart's tissue but would cause blood to flow in a similar pattern. The bands were then sealed together using a new hydrogel-based adhesive called TissueSil.
Once the "biorobotic hybrid heart," was assembled, it was placed in a mold cast from the original heart, which was filled with silicone to form a uniform covering over the device. This gave the bionic heart a form very like that of a real heart and helped ensure the artificial muscles fit snugly around the real ventricle it was attached to. When the air was pumped into the tubes at frequencies like to those of a living heart, it contracted in a similar manner.
"Imagine that a patient before cardiac device implantation could have their heart scanned, and then clinicians could tune the device to perform optimally in the patient well before the surgery," says team member Chris Nguyen. "Also, with further tissue engineering, we could potentially see the biorobotic hybrid heart be used as an artificial heart – a very needed potential solution given the global heart failure epidemic where millions of people are at the mercy of a competitive heart transplant list."
The research was published in Science Robotics.