Soft robot designed to mechanically pump failing hearts

Heart failure affects millions of people annually and the availability of donor organs, particularly hearts, is limited at best. Due to this current state, Engineers from Boston Children’s Hospital and Harvard University have spent several years developing a mechanical alternative.

Photo courtesy of courtesy of Ellen Roche/Harvard SEAS

The team has designed a soft robotic sleeve proof of concept product. The sleeve is fitted around the heart where it twists and compresses the heart’s chambers just like healthy cardiac muscle would do.

When it comes to life-sustaining medical devices, there are few options on the market. Currently, Ventricular assist devices (VADs) are used to sustain end-stage heart failure patients awaiting transplant. However, these VADs can cause serious complications.

“I’ve been implanting VADs in patients for a long time,” says Frank Pigula, MD, who took part in the research at Boston Children’s Hospital’s Heart Center. “The current generation systems directly expose a patient’s blood to artificial materials such as tubing and rotors, which makes necessary the use of blood thinning and anticoagulatory medications that are complication-prone.”

Although the medication is necessary for the body to tolerate the VAD implants, it increases the chance of having a stroke by up to 20 percent. The constant contact between blood and foreign material also carries the inherent risk of serious infection.

Pigula and his collaborators have designed a device that attaches to and snugly hugs the outside of the heart without having any contact with blood. The soft robotic sleeve mimics the heart’s natural compression motion using only non-rigid, biocompatible materials.

The team successfully tested the device on a pig’s heart, which is similar in size and structure to a human heart. Their tests showed that the device restores acutely failing hearts to 97 percent of their original cardiac output.

“This work represents an exciting proof-of-concept result for this soft robot, demonstrating that it can safely interact with soft tissue and lead to improvements in cardiac function,” says Conor Walsh, PhD, the John L. Loeb Associate Professor of Engineering and Applied Sciences at Harvard SEAS and a Core Faculty Member at the Wyss Institute. Walsh, a soft robotics expert, co-led the study with Pigula.

Utilizing pneumatically powered “air muscles,” different parts of the device bend and flex via remotely-controlled actuators that initiate the movement, mimicking the orientation of a heart’s contracting muscle fibers. One part of the device takes care of the twist, and another, the squeeze.

“The soft robotic actuators are essentially artificial muscles,” says Nikolay Vasilyev, MD, a staff scientist in cardiac surgery research at Boston Children’s Hospital and co-author on the recent study. “In this sense, the robotic sleeve mimics both ventricles of the heart.”

The soft robotic heart sleeve also contains sophisticated sensing abilities that measure pressure at specific points on the heart’s surface.

“We can independently control portions of the device and adjust assistance to a patient’s needs,” says Ellen Roche, PhD, the study’s first author. “I’m optimistic the soft robotic sleeve could potentially be used for short-term cardiac rehabilitation in addition to long-term therapy.”

“The cardiac field had turned away from idea of developing heart compression instead of blood-pumping VADs due to technological limitations,” says Pigula. “But now, with advancements in soft robotics, it’s time to turn back. Most people with heart failure still have some function left. One day. the robotic sleeve may help their heart work well enough that their quality of life can be restored.”

www.childrenshospital.org

www.seas.harvard.edu

In vivo demonstration of cardiac assist in a porcine model of acute heart failure (Video courtesy of Ellen Roche/Harvard SEAS)