Nicholas Cohrs and his colleagues at the Functional Materials Laboratory of ETH Zurich University in Switzerland have a new concept for what they call a soft artificial heart.
By developing an artificial heart that closely resembles a recipient’s own heart, Cohrs and his team hope to create a device that can keep patients alive for years without needing another risky transplant surgery.
For nearly 50 years, surgeons have transplanted artificial hearts into patients who would otherwise die of heart failure.
These devices are made of plastic and metal. They can sustain life for days, and even months, while patients await donor hearts.
In some cases, an transplant may be permanent and could last for several years, but the likelihood of surviving more than four years is . The record for the longest time living with an artificial heart is five years.
Complications that may occur from an artificial heart transplant include bleeding, infection, and organ failure.
A common problem with artificial hearts is their tendency to allow blood to clot due to their rigid composition.
Blood clots can lead to strokes.
Trying a soft, personalized touch
An artificial heart with less rigidity, then, could improve blood flow and lessen the chances of clotting.
Initially, Cohrs and his team experimented with a substance that is generally nonreactive, stable, and resistant to extreme environments. It also has several life science applications.
“Of course, silicone is an artificial material, which is not human tissue and cannot directly resemble it,” Cohrs told Dr.China. “However, it is a soft material and can mimic the material properties of human tissue to a certain extent. We use it because it is an established material for implants and available from many different suppliers.”
The silicone heart was designed using computer assisted design (CAD) software, producing a soft organ that resembles the human heart in composition, form, and function.
For an actual transplant, a CT scan of the patient’s heart would form the basis of the design, ensuring that it is a close fit.
Design modifications to the heart are required to allow it to move on its own, including a chamber that inflates and deflates with pressurized air.
In their Cohrs’ team used a 3D printer to create a plastic mold of the heart.
“We manufacture our artificial heart not directly by 3D printing, but we need 3D printers, because it is not possible to manufacture such a soft device with traditional manufacturing techniques,” Cohrs says. “We 3D print a negative of the heart and use this as a mold, which we later dissolve.”
Initially, the mold was filled with silicone, resulting in a 13-ounce heart — a device approximately one-third heavier than the average adult heart.
When implanted, it would be sutured to the valves, arteries, and veins, and powered by a portable, external pneumatic driver.
Cohrs and his team tested their silicone heart in April 2016 by placing it in a hybrid mock circulation machine. The results proved that the blood flow of the silicone heart mimicked that of a real human heart.
However, the silicone heart lasted about 3,000 heartbeats before rupturing from stress. At a resting heartrate of 60 beats per minute, the heart would fail in less than an hour.
The scientists published in the journal Artificial Organs
Looking beyond silicone
Since their initial experiments, Cohrs’ team has switched from silicone to other materials.
“We are testing different polymers to make the artificial heart more stable and increase the lifetime,” Cohrs said. “We also changed and optimized the geometry.”
Their latest heart lasts for 1 million heartbeats — or about 10 days’ worth of life.
Further modifications will improve the heart, although it may be decades before one is ready for real-life testing.
“Our ultimate goal would of course be a soft artificial heart which can produce a physiological, natural blood flow, has a sufficient lifetime, and does not cause adverse events,” Cohrs said. “Whether this is possible is still unknown, but we were happy with the first results.”
“Developing such a complex internal artificial implant is very difficult and takes a lot of time,” Cohrs added. “We cannot really predict when we could have a final working heart which fulfills all requirements and is ready for implantation. This usually takes years.”
“But with the publication of our research, we presented a proof-of-concept for softness in artificial heart therapy.”
The process Cohrs and his team have used — taking advantage of simple CAD software and 3D printing—could allow for widespread availability of personalized artificial hearts.
These hearts, in turn, could last longer than today’s devices — perhaps as much as 15 years, and hopefully for the rest of a recipient’s life.