How to build a child's heart … with a 3-D printer
The development of 3-D printers, which use computer designs to create solid objects, are revolutionizing the way engineers make prototypes, models and even some consumer goods. The practical applications for the health-care industry are huge — and they’re starting to happen in St. Louis.
At Cardinal Glennon Children’s Medical Center in St. Louis, two doctors named Nadeem Parkar and Wilson King work with children who have severe congenital heart defects. These abnormalities in their patients' hearts can be corrected, but it requires invasive heart surgery. Sometimes, operations must be performed on infants, just a few days old.
Most surgeons rely on MRI images of their patient’s hearts to plan the surgery. But for the most complex cases, Dr. King says he and his colleagues wanted something more.
"Surgeons are looking at images right now, but [this gives] them a model that they can hold in their hand. This is about personalizing technology to the patient so surgeons have a very good understanding of what they would be encountering in the operating room," King said.
King builds the designs for the printer out of MRI images taken of a patient’s heart. The first design took him 18 hours to complete.
"The blood is white, and the walls of the heart are darker. You can see the heart beating, and you see what chambers look like, how the walls contract in each chamber," Dr. Parkar said.
The designs are then sent to the 3-D printing lab at Saint Louis University's engineering school, led by Sridhar Condoor, one of the department chairs. Usually, his students use the printers for engineering projects, like building spare parts for small, remote-controlled planes. Printing a model heart takes eight to 12 hours, so the lab technicians usually let the machines run overnight.
A 3-D printer at work smells slightly sweet — as if your toddler just put her fruit snacks in the microwave. A hard plastic resin gets melted, sprayed and cured into incredibly thin layers. Each one is laid on top of the other to build the model, so printers can create incredibly complex objects that would be nearly impossible to build any other way.
And, like a 2-D printer, the machine dings when it's done.
When SLU graduate student Federico Garcia-Lorca uses a scraper to pull a newly printed model off of the plate. It jiggles slightly, because the model is actually encased in a type of gel that served as a temporary mold during the printing process.
"You can’t build a house from the roof, you need the foundation first. So all this gel, you see how it breaks off very easily? In half an hour of work we’ll have the actual model just ready to go," Garcia-Lorca said.
Graduate student Vignan Reddy remembers the first time he held one of the model hearts.
"I look at it as, you just helped someone to save a life," Reddy said.
Models to use for surgery
Dr. Charles Huddleston, a cardiothoracic surgeon at Cardinal Glennon, used one of the models to help prepare for a surgery.
"We take the patient to the operating room, and a lot of times we'll take this with us," he said, holding one of the completed models. "As we start the operation we'll refer back to this to see how well what we're seeing is represented in this image."
In one case, a patient had a complex web of blood vessels between the lungs and heart, which were hard to discern from a 2-D X-ray.
"When you're actually in the chest, there's a lot of other stuff there. That's what the 3-D models helped us with immensely," Huddleston said. "I'd say I felt a lot more comfortable doing that dissection, knowing from the 3-D picture where things were lying."
King and Parkar say the models are accurate within one millimeter of the original.
3-D Printers in the Medical World
King and Parkar don't plan to stop here.
They've created model hearts for four of their patients with severe congenital heart defects and a couple models of brain aneurysms for their colleagues in neurosurgery. They've also had requests to map kidney tumors, and for models that can be sterilized so they can be held by the doctor during a surgery.
With 3-D printers, engineers can build medical implants that are personalized for the size and shape of a patient’s organs, like the pacemaker-type device that’s being developed at Washington University. Some researchers have even gotten 3-D printers to build things using human tissue.
But funding can be a challenge. Parkar and King are currently working with funds from a Saint Louis University grant.
"Right now, this is not paid for by anybody. The insurance companies don’t pay, Medicare doesn’t pay. So you have to either use innovation funds if a hospital or university can provide that, or you have to write a grant for research," Parkar said.
The resin for one of these hearts costs about $800, but the doctors say it’s a fraction of what it would cost if they sent the designs to a company that specializes in printing 3-D models. That doesn't mean the cost won't go down as demand increases and technology improves.
Parkar said the four patients they’ve created models for have done well after their operations. But when it comes to complex open heart surgeries like these, doctors need all the help they can get.
"When the surgery’s done and they restart the heart, everyone is waiting for the heart to start beating again … the amount of silence that’s there is almost deafening," Parkar said.
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An earlier version of this story incorrectly identified Dr. Charles Huddleston as Dr. Charles Huddlesworth.