When pediatric interventional cardiologist John Thomson was planning a recent procedure for a patient with congenital heart disease, he made use of a 3D-printed plastic model of that patient’s heart. By holding and turning this replica of the patient’s complex anatomy, Thomson was able to study the heart’s blood vessels up close and determine what type of stent would be needed to fix the problem — where blood was being diverted from the heart into a lung artery.

“It allowed me to almost re-create the intervention and fit a stent in there to work out how we could do things — and if it was doable,” Thomson says. “Indeed it was, and we managed to get him successfully treated with a good result.”

It’s just one example of how Thomson and others at Johns Hopkins Children’s Center have been employing the heart models for some patients.

The surgeons says the models help ensure that they have all needed materials before starting an operation and make them more confident of what they can achieve through surgery when they counsel families during preoperative visits.

Just as people use GPS navigation systems to direct where they’re going, the 3D models provide an added depth perspective, explains pediatric cardiologist Sruti Rao, who oversees MRI and CT imaging that is used to construct the models. “In reality, we see everything in 3D, but most of our imaging techniques are usually 2D,” she says. “We have to reconstruct that 3D part in our head.”

Rao is part of a multidisciplinary team involved in the printing efforts, with engineers and colleagues including Stacy Fisher, director of the Adult Congenital Heart Disease Center; Juan Garcia, from the Department of Art as Applied to Medicine; and radiologist Jeff Hirsch from the University of Maryland. The process involves translating cross-sections of images into precise dimensions for the 3D printer. That part can take as many as 15 hours; the printing itself adds another 10–15 hours.

Models can be printed from a hard resin, which allows the team to assign different colors to different parts of the heart or use silicone to make a pliable, clear model through which cardiac specialists can practice routing a patch or inserting a catheter.

In some cases, Thomson and Fisher say, it allows experts to plan procedures using a catheter that previously could only be done in the operating room. Because newborn babies’ hearts are so tiny, the team can create models scaled 1.5 to two times larger for study.