Engineers are working on custom, 3D-printed hearts that look and pump just like the real thing. 

There is a lot of variation in the size and shape of the human heart, and these differences can be particularly pronounced for people living with heart disease.

But scientists are now looking to tailor treatments to patients’ specific heart form and function, with a custom robotic heart. 

A team at MIT has developed a procedure to 3D print a soft and flexible replica of a patient’s heart. They can then control the replica’s action to mimic that patient’s blood-pumping ability.
The procedure involves first converting medical images of a patient’s heart into a three-dimensional computer model, which the researchers can then 3D print using a polymer-based ink. The result is a soft, flexible shell in the exact shape of the patient’s own heart. 

The team can also use this approach to print a patient’s aorta - the major artery that carries blood out of the heart to the rest of the body.

To mimic the heart’s pumping action, the team has fabricated sleeves similar to blood pressure cuffs that wrap around a printed heart and aorta. The underside of each sleeve resembles precisely patterned bubble wrap. When the sleeve is connected to a pneumatic system, researchers can tune the outflowing air to rhythmically inflate the sleeve’s bubbles and contract the heart, mimicking its pumping action. 

The researchers can also inflate a separate sleeve surrounding a printed aorta to constrict the vessel. This constriction, they say, can be tuned to mimic aortic stenosis - a condition in which the aortic valve narrows, causing the heart to work harder to force blood through the body.

The team is producing custom replicas of actual patients’ hearts using polymer-based ink that, once printed and cured, can squeeze and stretch, similarly to a real beating heart.

Medical scans are converted into a three-dimensional computer model of the patient’s left ventricle (the main pumping chamber of the heart) and aorta, which is then fed into a 3D printer to generate a soft, anatomically accurate shell of both the ventricle and vessel.

The team has also fabricated sleeves to wrap around the printed forms. They tailor each sleeve’s pockets such that, when wrapped around their respective forms and connected to a small air pumping system, the sleeves could be tuned separately to realistically contract and constrict the printed models.

The researchers showed that for each model heart, they could accurately recreate the same heart-pumping pressures and flows that were previously measured in each respective patient.

Taking the technique further, the team has tested whether the printed heart and vessel respond in the same way to a real human heart. 

Valve implants are often used to widen the aorta in patients with aortic stenosis. Researchers implanted similar valves in the printed aortas, and when they activated the printed heart to pump, they observed that the implanted valve produced similarly improved flows as in actual patients following their surgical implants.