Engineers from MIT have created a robotic replica of the right ventricle of the heart, replicating the beating and blood-pumping functions seen in live hearts. This robotic ventricle incorporates a combination of real heart tissue and synthetic balloon-like artificial muscles. These artificial muscles allow scientists to control the contractions of the ventricle while studying the functioning of its natural valves and other intricate structures.
The synthetic ventricle is versatile and capable of mimicking both healthy and diseased states. The research team manipulated the model to simulate conditions associated with right ventricular dysfunction, such as pulmonary hypertension and myocardial infarction. Additionally, the model was utilized for testing cardiac devices. For example, a mechanical valve was implanted by the team to repair a malfunctioning natural valve, and the resulting changes in the ventricle’s pumping were observed.
The engineers believe that this innovative robotic right ventricle, known as RRV, serves as a realistic platform for studying right ventricle disorders. It can also be employed to test various devices and therapies designed to treat these disorders.
“The right ventricle is particularly susceptible to dysfunction in intensive care unit settings, especially in patients on mechanical ventilation,” says Manisha Singh, a postdoc at MIT’s Institute for Medical Engineering and Science (IMES). “The RRV simulator can be used in the future to study the effects of mechanical ventilation on the right ventricle and to develop strategies to prevent right heart failure in these vulnerable patients.”
Singh and her team have published the specifics of the innovative design in a freely accessible paper featured in today’s issue of Nature Cardiovascular Research. The co-authors of the paper include Associate Professor Ellen Roche, a key member of the Institute for Medical Engineering and Science (IMES) and the associate head for research in the Department of Mechanical Engineering at MIT. Other contributors are Jean Bonnemain, Caglar Ozturk, Clara Park, Diego Quevedo-Moreno, Meagan Rowlett, and Yiling Fan from MIT, Brian Ayers from Massachusetts General Hospital, Christopher Nguyen from Cleveland Clinic, and Mossab Saeed from Boston Children’s Hospital.
A Ballet of Beats
Among the heart’s four chambers, which include the left and right atria, as well as the left and right ventricles, the left ventricle takes on the role of the primary pump. With its robust, cone-shaped musculature, it is designed to efficiently pump blood throughout the entire body. In contrast, the right ventricle is likened to a “ballerina” by Roche, carrying a lighter yet equally vital load in its function.
“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 motion.”
This anatomical complexity has made it difficult for clinicians to accurately observe and assess right ventricle function in patients with heart disease.
“Conventional tools often fail to capture the intricate mechanics and dynamics of the right ventricle, leading to potential misdiagnoses and inadequate treatment strategies,” Singh says.
In an effort to enhance comprehension of the less-explored chamber and expedite the advancement of cardiac devices for addressing its dysfunction, the team developed an authentic and operational model of the right ventricle. This model not only replicates the anatomical intricacies of the right ventricle but also mirrors its pumping function.
Incorporating real heart tissue into the model was a deliberate choice by the team. This decision was motivated by the fact that natural structures within the heart are too intricate to be accurately reproduced through synthetic means.
“There are thin, tiny chordae and valve leaflets with different material properties that are all moving in concert with the ventricle’s muscle. Trying to cast or print these very delicate structures is quite challenging,” Roche explains.
A Heart’s Shelf-life
In a recent study, the team describes the process of extracting a pig’s right ventricle, treating it meticulously to preserve its internal structures. Subsequently, they applied a silicone wrapping around it, serving as a soft, synthetic myocardium or muscular lining. Within this lining, the team embedded elongated, balloon-like tubes strategically positioned around the real heart tissue. These positions were determined through computational modeling to optimize the reproduction of the ventricle’s contractions. Each tube was connected to a control system, programmed to inflate and deflate at rates mimicking the natural rhythm and motion of the heart.
To evaluate its pumping capability, the team introduced a liquid with a viscosity similar to blood into the model. This transparent liquid allowed engineers to use an internal camera to observe how internal valves and structures responded as the ventricle pumped the liquid through.
The findings revealed that the artificial ventricle exhibited pumping power and internal structure functionality akin to observations in live, healthy animals, affirming the model’s realistic simulation of the right ventricle’s action and anatomy. Additionally, the researchers could adjust the frequency and power of the pumping tubes to replicate various cardiac conditions, including irregular heartbeats, muscle weakening, and hypertension.
“We’re reanimating the heart, in some sense, and in a way that we can study and potentially treat its dysfunction,” Roche says.
To demonstrate the utility of the artificial ventricle in testing cardiac devices, the team conducted surgical procedures to implant ring-like medical devices of varying sizes aimed at repairing the tricuspid valve of the chamber. The tricuspid valve, characterized by its leafy structure, functions as a one-way valve permitting blood entry into the right ventricle. When this valve is compromised, either due to leakage or physical damage, it can lead to conditions such as right heart failure or atrial fibrillation, manifesting symptoms like reduced exercise capacity, leg and abdominal swelling, and liver enlargement.
In the experiments, the researchers surgically manipulated the robo-ventricle’s valve to simulate the aforementioned condition. Subsequently, they either replaced the valve by implanting a mechanical alternative or repaired it using ring-like devices of various sizes. The team closely observed and recorded the impact of each device on the fluid flow within the ventricle as it continued its pumping action.
“With its ability to accurately replicate tricuspid valve dysfunction, the RRV serves as an ideal training ground for surgeons and interventional cardiologists,” Singh says. “They can practice new surgical techniques for repairing or replacing the tricuspid valve on our model before performing them on actual patients.”
At present, the RRV can accurately replicate realistic functions for a limited duration of a few months. The team is actively engaged in efforts to enhance this performance, aiming to enable the model to operate continuously for extended periods. Additionally, they are collaborating with designers of implantable devices to assess and test prototypes on the artificial ventricle, potentially expediting the development process for these devices and their availability to patients.
Looking ahead, Roche envisions a future where the RRV is paired with a corresponding artificial and functional model of the left ventricle. The group is presently fine-tuning this left ventricle model, paving the way for a comprehensive understanding and simulation of both ventricles in the heart.
“We envision pairing this with the left ventricle to make a fully tunable, artificial heart, that could potentially function in people,” Roche says. “We’re quite a while off, but that’s the overarching vision.”
This research was supported, in part, by the National Science Foundation.