MIT engineers have developed a robotic replica of the heart’s right ventricle that mimics the beating and pumping of blood by a living heart.
The robo-chamber combines real heart tissue with synthetic, balloon-like artificial muscles, allowing scientists to control the ventricle’s contractions while observing the functioning of its natural valves and other convoluted structures.
The artificial ventricle can be tuned to mimic robust and diseased states. The team manipulated the model to simulate states of right ventricular dysfunction, including pulmonary hypertension and myocardial infarction. They also used the model to test cardiac devices. For example, the team implanted a mechanical valve to repair a naturally failing valve, then watched as the ventricle’s pumping changed in response.
They say the modern right ventricular robot, or RRV, can be used as a realistic platform to study right ventricular disorders and test devices and therapies to treat them.
“The right ventricle is particularly susceptible to dysfunction in the intensive care unit setting, especially in patients undergoing mechanical ventilation,” says Manisha Singh, an assistant professor in MIT’s Institute for Medical Engineering and Science (IMES). “The RRV simulator could be used in the future to study the effects of mechanical ventilation on the right ventricle and develop strategies to prevent right ventricular failure in these vulnerable patients.”
Singh and her colleagues provide details of the modern project in an open-access article article that will be published today in . Its co-authors are assistant professor Ellen Roche, who is a member of the IMES board and deputy chair of research in the Department of Mechanical Engineering at MIT; as well as Jean Bonnemain, Caglar Ozturk, Clara Park, Diego Quevedo-Moreno, Meagan Rowlett, and Yiling Fan of MIT; Brian Ayers of Massachusetts General Hospital; Christopher Nguyen of the Cleveland Clinic; and Mossab Saeed of Boston Children’s Hospital.
Ballet of Rhythms
The right ventricle is one of the four chambers of the heart, along with the left ventricle and the left and right atria. Of the four chambers, the left ventricle is the heavyweight, because its stout, conical muscles are built to pump blood throughout the body. The right ventricle, Roche says, is the “ballerina” by comparison, because it carries a lighter but no less significant load.
“The right ventricle pumps deoxygenated blood to the lungs, so it doesn’t have to pump as hard,” Roche notes. “It’s a thinner muscle with more complex architecture and movement.”
This anatomical complexity makes it challenging for physicians to accurately observe and assess right ventricular function in patients with heart disease.
“Conventional tools often fail to capture the complex mechanics and dynamics of the right ventricle, which can lead to misdiagnosis and inappropriate treatment strategies,” Singh says.
To better understand the lesser-known ventricle and accelerate development of cardiac devices that could treat its dysfunction, the team designed a realistic, functional model of the right ventricle that not only reflects its anatomical complexity but also replicates its pumping function.
The model contains real heart tissue, which the team decided to include because it preserves natural structures that are too convoluted to replicate synthetically.
“There are thin, tiny valve strings and leaflets with different material properties that move in unison with the ventricular muscle. Trying to cast or print these very delicate structures is quite difficult,” Roche explains.
The shelf life of a heart
In the modern study, the team reports on an explant of a pig’s right ventricle that had been treated to carefully preserve its internal structures. It was then fitted with a silicone wrap that acted like supple, synthetic heart muscle or muscle lining. Within this lining, the team placed several long, balloon-like tubes that surrounded real heart tissue, in positions that the team determined using computer modeling were optimal for reproducing the contractions of the ventricle. The researchers connected each tube to a control system, which they then set to inflate and deflate each tube at a rate that mimicked the rhythm and movement of the real heart.
To test its pumping ability, the team injected a liquid with a viscosity similar to blood into the model. This particular liquid was also limpid, which allowed engineers to observe, via an internal camera, how the valves and internal structures reacted as the chamber pumped the liquid.
They found that the artificial ventricle’s pumping force and the function of its internal structures were similar to what they had previously observed in living, robust animals, showing that the model can realistically simulate the function and anatomy of the right ventricle. The researchers could also tune the frequency and power of the pumping tubes to mimic different heart conditions, such as irregular heartbeats, muscle weakness and high blood pressure.
“In a sense, we are resuscitating the heart in a way that allows us to study and potentially treat its dysfunction,” Roche says.
To show that the artificial ventricle could be used to test cardiac devices, the team surgically implanted ring-shaped medical devices of varying sizes to repair the ventricular tricuspid valve, a leafy, one-way valve that lets blood into the right ventricle. When this valve is leaky or physically damaged, it can cause right ventricular failure or atrial fibrillation and leads to symptoms such as reduced exercise capacity, leg and abdominal swelling, and an enlarged liver.
The researchers surgically manipulated the robo-ventricle valve to simulate this condition, then either replaced it by implanting a mechanical valve or repaired it with variously sized annular devices. They observed which device improved fluid flow in the ventricle while it continued to pump.
“With its ability to accurately replicate tricuspid valve dysfunction, the RRV provides an ideal training ground for surgeons and interventional cardiologists,” says Singh. “They can practice new surgical techniques for tricuspid valve repair or replacement on our model before performing them on real patients.”
Right now, the RRV can simulate realistic function for months at a time. The team is working to expand that performance and allow the model to run continuously for longer periods. They’re also working with implantable device designers to test their prototypes on the artificial ventricle and possibly speed their path to patients. And looking farther into the future, Roche plans to pair the RRV with a similar artificial, functional model of the left ventricle that the group is currently refining.
“We envision combining this with the left ventricle to create a fully tunable artificial heart that could potentially function in humans,” Roche says. “We’re still quite a ways off, but that’s the overarching vision.”
This research was partially funded by the National Science Foundation.