Prototype heart pump. (via Harvard)
The inevitable future of bionic humans is one step closer with the engineering of a robotic heart “sleeve” by a team of American and European scientists. The sleeve is the newest model of ventricular assist devices (VADs), or devices that help hearts plagued by heart failure to beat properly.
Heart failure is not a total cessation of the heart’s activity as its name would suggest, but the inability of the heart to pump enough blood. This can cause exhaustion and even leaky blood vessels, leading to fluid buildup and congestion. As of 2012, an estimated 5.7 million American adults suffered from heart failure, and that number is projected to increase to over 8 million by 2030. Compare these numbers to how many heart transplants are performed in the U.S. each year, about 2,100, and the need for an alternative to transplant is clear.
To address this problem, the team sought to improve on the design limitations of current VADs that pump blood through tubes piercing the heart and major blood vessels. The biggest problem with these devices is that they directly contact the blood and cause it to clot. Even with blood-thinning medications, this increases the risk of stroke. Another issue with current devices is their tendency to slightly distort the curvature of the heart, leading to less-than-perfect synchronization with the heart’s natural movement.
The aim of the sleeve’s design was to circumvent these limitations by taking inspiration from the biology of the heart itself.
Cardiac muscle is made up of interlocking, contractile cells circling around the heart, embedded in an extracellular matrix. To mimic the heart’s outer two muscle layers, polymer copies of cardiac cells were set in a sticky, stretchy matrix. The result was a silicon device that, when powered by compressed air, can twist and squeeze a heart just like cardiac muscle can.
The robotic heart sleeve’s design mimics that of cardiac muscle. (image from BBC)
Besides the major advantage that the sleeve does not contact blood and so does not produce blood clots, the device collects biofeedback so that its motion can be synchronized with a heart’s unique beating pattern. This is a major bonus as each heart’s malfunctioning is different, so a one-size-fits-all device just wouldn’t cut it. The sleeve can also be adjusted to provide partial or full assistance to one side or both sides of the heart, providing further customization.
The sleeve was used successfully to assist pumping and even stop cardiac arrest in pig hearts, but it still has a long way to go before it can be tested in humans. Namely, longer-term testing in animals with heart failure is required, and a portable compressed air supply must be designed so that people with the device implanted can move freely. However, once this is achieved, this robotic heart sleeve will be a huge boon to healthcare.
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