In a proof-of-concept study, scientists have created a soft robotic sleeve that wraps around the heart and mimics ventricular contractions to help move blood to through body. The robot was also shown to support heart function in a pig model of heart failure.
Heart failure, or the inability of the heart to pump enough blood to the body, affects more than 40 million people globally. Heart transplants are the best option for many patients at the end stages of heart failure but the lack of available donor organs often results in death. Mechanical circulatory support can help extend the lives of patients awaiting transplantation.
The heart consists of four main chambers – two atrial chambers that collect blood as it flows into the heart and two ventricular chambers that pump blood to the lungs and the rest of the body. Currently, there are numerous ventricular assist devices that mechanically help the ventricles pump blood out of the heart, but do not mimic the natural contractions of the heart and often require the patient to take anticoagulants because the devices come in contact with blood.
In a recent report in Science Translational Medicine, a group of researchers have used soft robots made from a combination of elastomers, fibers, and other filler materials to develop a robotic heart sleeve. The robot sleeve is chemically attached and wraps around the lower, ventricle portion of the heart. When attached, it looks a bit like a cup with a heart in it.
The soft robot sleeve mimics the natural twisting and compression movements of the heart muscles using two layers of soft materials with actuators that trigger specific directional movements. The implanted sleeve is connected to a custom electro-pneumatic instrumentation system that monitors and records physiological parameters like heart rate and flow rate, and more importantly, synchronizes the movements of the sleeve with the natural heart cycle so the device can provide disease-specific assistance.
The soft robotic sleeve was successful in displacing physiological volumes of water from a synthetic heart model made of silicone and increased heart ejection output in the hearts of pig cadavers. To demonstrate that the robot sleeve could provide cardiac assistance in disease states, acute heart failure was induced in 6 pig animal models. Cardiac output was recorded prior to heart failure (baseline), during heart failure, and with assistance from the robot sleeve. Cardiac output was reduced to 45% of baseline under heart failure conditions, but with assistance from the sleeve, recovered to 97% of baseline. This demonstrates that the robot sleeve can support and help recover cardiac output after heart failure.
Further work, however, is needed to optimize the implanted robot sleeve before it can be tested in a clinical environment. In addition to the miniaturization of the instrumentation system, in vivo experiments using a larger number of animals, longer implantation durations, and chronic heart failure models are needed to investigate the efficacy of the device. The biocompatibility of all of the materials should be investigated and an effective bio-adhesive developed to ensure the sleeve stays in place.
Overall, the soft robotic sleeve offers a promising and versatile platform to mechanically manipulate the heart to target cardiac rehabilitation or recovery, as well as the potential to prolong the life of a heart failure patient awaiting transplantation.
Written By: Fiona Wong, PhD