Soft robots could revolutionize cardiac medicine.
Each year, more than 2,000 people in the United States receive heart transplants, and a staggering 5.7 million experience heart failure.
Heart failure occurs when either of the heart's ventricles can no longer fulfill their duty of pumping blood around the body.
The waiting list for heart transplants is long, and many people die before a donor is found. Designing ways to extend lives while patients wait for a new organ is therefore a priority.
Currently, ventricular assist devices (VADs) can be used to improve the health of patients with end-stage heart failure awaiting a transplant. However, they are not ideal.
VADs work by pumping blood from the heart and pushing it around the body. To work, the blood has to leave the confines of the blood vessels and travel through tubes and rotors.
Because of this contact with foreign material, the patient needs to take anticoagulants. These drugs can make VADs a viable solution, but they also increase the risk of stroke by 20 percent.
Besides VADs, cardiac sleeves are another option; they sit around the heart and squeeze it in order to replicate muscular contractions. These heart compression interventions are also far from perfect and, until recently, had been all but abandoned.
A new age of robots
Dr. Frank Pigula - from Norton Children's Hospital in Louisville, KY, but who participated in the research at Boston Children's Hospital in Massachusetts - explains that: "The cardiac field had turned away from the idea of developing heart compression instead of blood-pumping VADs due to technological limitations. But now, with advancements in soft robotics, it's time to turn back."
This week, a new proof of concept - published in the journal Science Translational Medicine - reopens the doors to heart compression devices. A team of biomedical engineers and clinicians from Harvard in Cambridge, MA, and Boston Children's Hospital has designed and tested a robotic sleeve that twists and compresses the heart in the same way that healthy ventricles would.
Although the classical image of a robot is a solid structure capable of withstanding interstellar warfare, the robots of modern medical research are the polar opposite. Made from elastomers, fibers, and other filler materials, a new wave of so-called soft robots are able to interact intimately and delicately with human anatomy.
Made exclusively from non-rigid, biocompatible materials, this groundbreaking cardiac sleeve sits outside of the heart, removing the need for anticoagulants while minimizing infection risks. It uses pneumatically powered "air muscles," called actuators.
According to Dr. Nikolay Vasilyev, co-author of the current paper: "The soft robotic actuators are essentially artificial muscles." The thin silicon sleeve is tethered to an external pump that uses air to power the actuators.
One section of the sleeve twists and the other squeezes, mimicking both ventricles of the heart. Earlier cardiac sleeves were limited in that they could only squeeze.
Soft robot's lifesaving potential
The study's first author, Ellen Roche, Ph.D. - who is now based at the National University of Ireland Galway - says that: "We can independently control portions of the device and adjust assistance to a patient's needs." So, if one side of a patient's heart is weaker, it can be modified accordingly.
She continues: "I'm optimistic the soft robotic sleeve could potentially be used for short-term cardiac rehabilitation in addition to long-term therapy."
The teams recently published their studies on pigs, in which they induced cardiac arrest in the animals then implanted the robotic device. They were able to demonstrate the sleeve's ability to restore the heart to 97 percent of its 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."
Study co-leader Conor Walsh, Wyss Institute, Massachusetts
As the device is refined, there is a real opportunity to save lives. Most patients with heart failure retain a certain degree of function in their heart, and the sleeve has the potential to restore quality of life to these people. Finally, because heart failure affects 41 million people globally, its impact could be far-reaching.