Of the 5.7 million US people experiencing heart failure (costing the country about $32 billion/year), over 2000 receive transplants, and the others usually die expecting a donor as the transplant waiting list is extensive. Henceforth there has always been a need to propose ways to extend these patients’ lives. Scientists and researchers have come up with ventricular assist devices (VADs) and cardiac sleeves to deal with the problem, but the former has higher risks of coagulation and lethal or crippling strokes, and the latter was abandoned, being nowhere near perfect. So, we needed something much, much better. And that’s how, after years of research and experimentation, we came up with soft robots.
Though the word first brings to our minds solid bodies resisting intergalactic combat, medicine envisages them as devices made of elastomers, fibers, and other filler materials that can interact closely and dexterously with our body structures.
As we’d turned away from the idea of developing heart compressions instead of those blood-pumping VADs owing to technological hindrances; we can simply turn back now as we have progresses in soft robotics, which can be applied to clinical needs and possibly decrease heart disease load and improve quality of life for patients.
How are they designed?
Comprising non-rigid, lightweight, able-to-achieve-complex-motions, bio-compatible materials, and sitting outside the heart (meaning they do not contact the blood directly), soft robots have pneumatically powered ‘air muscles’ called actuators, working as artificial muscles, like the outer cardiac muscular layers. Plus, there are pressure-detecting sensors. The elastic silicone sleeve/funnel is secured to an external pump for powering actuators by air.
How does it fit around the heart?
This is accomplished via suction devices, sutures and a gel interface (to combat friction) combined. Being less than a millimeter thick, it hugs the heart from bottom, actuators making rings around the sleeve and helical coils from top to bottom, mechanically expanding and contracting when occupied with pressurized air.
How does it work?
It not only compresses but also twists – unlike earlier sleeves – the heart exactly like normal ventricles. Being able to re-create 97% of the original cardiac output when experimented on six cardiac arrest-induced pig hearts, it has surpassed VADs and former sleeves.
How is it better than its predecessors?
Roche believes that we can self-sufficiently control device portions – because heart failure usually occurs on one side – and alter assistance to patient’s needs, as actuator pressure can be increased/decreased over time according to patient’s condition. Hence it is beneficial in short-term cardiac rehabilitation besides long-term therapy. Influentially far-reaching, soft robots can safely interact with soft tissues giving support, helping with function augmentation, and possibly even recovery.
However, this innovation is not without limitations. Though eliminating risks of coagulation and serious infections as were with VADs, soft robots cause heart surface inflammation, the most vulnerable sites being where the suction-cup tethers the device to the heart. Hydrogel has been only slightly effective. Moreover, it is bulky, composed of a heart sleeve plus external air compressor, which isn’t yet portable. We need a pressurized air store small enough to fit in a backpack or worn on a waist-belt; yet there will be cables protruding from the chest to connect the sleeve to the power supply, just like VADs. Hence, we still need something completely implantable.
Possibly, with softer materials like rubber or elastic-plastic, and better adhesives than hydrogel, soft robots can emerge as significant breakthroughs in cardiac medicine with incredible lifesaving properties for transplant-awaiting cardiac patients. Who knew hugs could have so much healing power!