Custom, 3D-printed heart replicas

The size and shape of the heart can vary from one person to the next and these differences can be particularly pronounced for people living with heart disease. MIT engineers are hoping to help doctors tailor treatments to a patient’s specific heart form and function with a 3D-printed (3DP) soft, flexible replica that can be controlled to mimic that patient’s blood-pumping ability.

First, medical images of a patient’s heart are converted into a 3D computer model, then printed using a polymer-based ink, resulting in a soft, flexible shell in the exact shape of the patient’s own heart. The team can also use this method to print a patient’s aorta.

The team fabricated sleeves similar to blood pressure cuffs that wrap around the 3DP heart and aorta. The underside of each sleeve resembles precisely patterned bubble wrap, and when 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. Researchers can also inflate a separate sleeve surrounding a printed aorta to constrict the vessel, mimicking aortic stenosis.

Doctors commonly treat aortic stenosis by surgically implanting a synthetic valve to widen the aorta’s natural valve. In the future, the team says doctors could use their new procedure to print a patient’s heart and aorta, then implant a variety of valves into the model to see which design results in the best function and fit for that patient.

“All hearts are different,” says Luca Rosalia, a graduate student in the MIT-Harvard Program in Health Sciences and Technology. “There are massive variations, especially when patients are sick. The advantage of our system is that we can recreate not just the form of a patient’s heart, but also its function in both physiology and disease.”

Rosalia and his colleagues report their results in a study appearing in Science Robotics. MIT co-authors include Caglar Ozturk, Debkalpa Goswami, Jean Bonnemain, Sophie Wang, and Ellen Roche, along with Benjamin Bonner of Massachusetts General Hospital, James Weaver of Harvard University, and Christopher Nguyen, Rishi Puri, and Samir Kapadia at the Cleveland Clinic in Ohio.

Print and pump

The team took advantage of 3DP to produce custom replicas of actual patients’ hearts, using medical scans of 15 patients diagnosed with aortic stenosis. The researchers showed for each model heart, they could accurately recreate the same heart-pumping pressures and flows previously measured in each respective patient.

“Being able to match the patients’ flows and pressures was very encouraging,” Roche says. “We’re not only printing the heart’s anatomy, but also replicating its mechanics and physiology. That’s the part that we get excited about.”

Going a step further, the team aimed to replicate some of the interventions a handful of the patients underwent, to see whether the printed heart and vessel responded in the same way. Some patients had received valve implants designed to widen the aorta. Roche and her colleagues implanted similar valves in the printed aortas modeled after each patient. When they activated the printed heart to pump, they observed the implanted valve produced similarly improved flows as in actual patients following their surgical implants.

Finally, the team used an actuated printed heart to compare implants of different sizes, to see which would result in the best fit and flow – something they envision clinicians could potentially do for their patients.

Roche says the patient-specific replicas could help develop and identify ideal treatments for individuals with unique and challenging cardiac geometries.

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