Imagine, if you will, a tiny heart. This heart, no bigger than a walnut, has some real problems. It belongs to a baby who, without surgery, would never survive. How do you fix it? Where do you start?
While good quality imaging is the first step, some details that appear in even the best 3D ultrasound and CT imaging may be small and hard to visualize on a screen, but still quite serious. Perhaps the child has one ventricle doing the work of two. Maybe the child needs a baffle between them, but also what septum there is may be full of holes and not correctly oriented to function. Whatever the case, sometimes the more complex the problems with the heart, the more surprises the surgeon finds on the operating table.
In an attempt to provide better care for complex cases, surgical teams are turning to physical 3D printed models of hearts to provide them with tangible roadmaps, allowing them to handle the heart before a single scalpel is used.
Heart like a maze
For New York-Presbyterian Hospital, that first case had immediate impact.
“The child on whom we did this first model was one day old when we did the cardiac CT,” says Anjali Chelliah, MD, pediatric cardiologist at New York-Presbyterian and Morgan Stanley Children’s Hospitals in New York. Before birth, the baby had been diagnosed at 35 weeks with a rare and potentially fatal congenital heart defect, a double outlet right ventricle. The blood going to the baby’s lungs and to the rest of the body were both coming off the right ventricle.
In addition, Chelliah notes, “The baby also had a narrowing of the aorta that was abnormal. Because you have two vessels coming off of one ventricle, they get a little crowded and so one often is small.” In this case, that was the child’s aorta.
While the imaging was good, it only went so far in providing the surgeon with a full understanding of the baby’s condition. Congenital defects, she says, are not homogenous. Because they’re each unique, they’re very difficult to repair.
“This baby’s heart had holes, which are not uncommon with congenital heart disease, but it was in such an unusual formation, that it was basically like a maze in terms of trying to connect everything to where it belonged from a surgical standpoint,” Chelliah says. Even with excellent imaging, “What often happens and what has happened with patients like this in the past, is that typically at birth it is very difficult to not only visualize the anatomy, but also to be able to tell the surgeons what to do because you need to be able to visualize in three dimensions what’s going on.”
At only a week old, the child weighed a little shy of 7 pounds, which with the heart the size of his fist—only as big as a walnut—meant the patient was very small, leaving no margin for mistakes. This was a case that required something extra to help the surgeon determine the best approach and minimize the amount of time the child needed to be on bypass.
Heart in hand
Chelliah says that they performed multiple fetal echocardiograms, a postnatal echocardiogram and a low radiation CT scan in preparation for the surgery. “Despite all of these modes of imaging, it was still difficult to figure out exactly how you could connect the left ventricle to the aorta and the right ventricle to the pulmonary artery because of the very unusual configuration.”
Making the 3D printed heart for the baby didn’t require any extra imaging than had already been planned. Using the results from a chest CT, Materialise, the company that printed the plastic model, first created a digital model. Once compiled, the digital image was reviewed and the physical model created. Two days after the company received the data, physicians at New York-Presbyterian had the copy of the heart.
“It’s kind of astounding how after all of that imaging we did, nothing really even came close to the visualization that was made possible by holding a physical-scale 3D model of the heart in your hand,” she says.
Challiah’s colleague, Emile Bacha, MD, director of congenital and pediatric cardiac surgery at New York-Presbyterian and Columbia University Medical Center, says being able to see a heart like this ahead of time is a great advantage.
Bacha found that the model allowed him to better see the relationship between the maze of holes and the great arteries. He also was able to see the shape of the patches that needed to go in and where they needed to be. “In this particular case, I had to enlarge a hole and enlarge it in the correct direction. I could see in the model [how] I needed to do that. I went into this heart [surgery] knowing I was going to have to do that.”
He adds that the model was quite lifelike. “I knew that this [3D heart] was sort of gravy because the child needed to be operated on,” Bacha says. “A month ago or six months ago, I would have done it the old-fashioned way.” When the manufacturer sent the model, physicians were able to go back and ask for a different view—a different cut, as it were, to allow them to see the heart structures better.
The model cost a few thousand dollars, but allowed the surgeon to fix everything that was wrong with the heart in only one surgery. The charitable foundation Matthew’s Hearts of Hope provided a grant to pay for the model. While it currently isn’t covered by insurance, it is a cost Bacha and Chelliah foresee being worth coverage.
“In this patient, it was pretty apparent that the 3D printing actually saved the patient additional surgeries and additional ICU time,” says Chelliah, “If anything, we think that this is highly cost effective. Not just good for the patient but also good for medicine in general.”
Part of the good these hearts will do for medicine is the ability to continue after as teaching tools. Following surgery, the team intends to create an in-house library of hearts for future cardiologists to learn from. “When I was training we had to go to the pathologists and actually look at human hearts from cadavers and try to make sense of what we saw,” says Bacha. “And now we can have 3D printed hearts.”
Guide to teaching tool
The New York team is not alone in their intent to harness these cases to teach others.
Matthew L. Bramlet, MD, director of the congenital heart disease MRI program at the University of Illinois College of Medicine in Peoria, discussed three successes at the American Heart Association’s 2014 scientific sessions in November. He and his team have experienced similar victories from the start of using 3D printed models to reveal heart anatomy to the surgeons they work with.
They’ve done several now. But from the beginning, the models improved how surgeons were able to do their jobs. “We’re at a point right now where our surgeons won’t go to surgery without the model being printed on the complex cases,” Bramlet says. “They know that their knowledge of the anatomy increases so much. It may not change the plan on every one of them, but by their understanding increasing dramatically, it’s taking away the chance that they’re going to be thrown a curveball in surgery, which does happen.”
In their first case, the surgeon noticed a Swiss cheese ventricular septal defect on the model that they hadn’t seen on the MRI. While larger holes previously had been detected, a larger one that the surgeon knew needed a patch obscured it.
For Bramlet and his team, an important step with each heart is confirming the printed heart is the actual anatomy. This means having the best quality imaging possible and rechecking the heart against the scans.
Bramlet is a champion for visualizing anatomy via 3D printed hearts. “There are kids out there with criss-crossed hearts that there may be a decision to take a single ventricle route where, if they understood a component of it, they would have changed that opinion and turned it into a ventricle repair, which has a dramatic life expectancy difference,” he says.
He envisions a national printed heart library and teamed up with the National Institutes of Health to provide hearts and case studies for their 3D print exchange. Each heart in the exchange will undergo a review process to ensure accuracy. “The best thing we can do is improve our understanding of these hearts, but our greatest pitfall is creating false information about the anatomy that would then change the way somebody evaluates it.”
While it’s still in the early stages, Bramlet sees 3D modeling as an opportunity for all cardiologists and surgeons to learn from each other’s experiences when dealing with congenital heart defects and improve decision making. Bramlet says, “Anything that can improve decision making is worth fighting for.”