If a surgeon "just opened things up and decided on the fly what to do, it could be extraordinarily difficult," he said.
Also known as additive printing, 3-D printing can create almost any shape by building its structure one layer at a time, like laying a brick house from bottom to top. Instead of ink, a 3-D printer uses materials such as plastic, metal, or even sugar.
While the technology has been around since the 1980s, only in the last few years have printers become commercialized and more affordable. Their popularity has spiked as the number of applications keeps rising: from car prototypes and blood vessels to artworks.
Since the purchase of a 3-D printer 18 months ago, the Children's Hospital cardiac team can print a patient-specific replica that they can take apart, cut, and sew up to find the best approach.
"Imagine your child needs heart surgery, and instead of looking at your child's heart on the computer, I can actually give the surgeon the heart and he can hold it in his hand," said Children's Hospital cardiologist Mark Fogel, who lobbied for the purchase of the $250,000 printer three years ago.
He wanted Children's Hospital to join the ranks of medical facilities that are taking part in the growing 3-D printing movement. Fogel and Dori are part of a multicenter trial to assess the effects of printed-heart pre-surgical planning.
Arizona State University bioengineer David Frakes, a pioneer of the technique, has printed about 100 hearts since 2008. For the doctors at Phoenix Children's Hospital, where his lab is located, it is now an integral part of their planning.
"They work with their hands, so the value of having a physical model is immense," he said. "This clinical trial at [Children's Hospital] could be a great example of how to show this stuff matters."
Made by the Israeli firm Objet Geometries, the Connex500 printer at Children's Hospital is a top-of-the-line model that can re-create a heart with high resolution using both hard and soft polymers. For hollow areas, it prints a support material that can be washed away with a stream of water after the replica is produced. So far, the doctors have printed five patients' hearts, with each one taking three to four hours to make.
Dori - who got a Ph.D in chemical engineering before medical school - gives the team a replica of the patient's malformed heart as well as a version with repairs already made, such as patches to plug up certain areas.
"For routine cases we wouldn't need it, but there are very complex hearts that generate a lot of discussion, and a 3-D model would help," said Children's Hospital cardiothoracic surgeon Christopher Mascio.
Congenital heart defects are the most common type of birth defect in the United States, affecting nearly 1 percent of babies born each year. The defects can be complicated and diverse, and vary widely in severity, from a small hole between chambers to the absence of entire chambers.
"The malformations that we deal with are incredibly complex," said Dori. "That's the world of pediatric cardiology."
The intricacy can result in disagreements among doctors making decisions on how to proceed, and a pre-operative 3-D model might clarify the better path.
There's a stressful, time-crunch element to the procedure too. Surgeons must stop the baby's heart and circulation to do the surgery, and generally, said Fogel, the faster the surgery, the better the outcome. Knowing the heart's architecture inside and out beforehand should save time.
The project's next phase will go beyond surgical planning. For a given patient, they will print a few possibilities for the surgically modified heart and then use an MRI-compatible fluid pump that can simulate blood flow.
A special MRI sequence will map the flow inside each heart so doctors can quantify which surgical approach would best help the patient's circulation.
Mascio said such experiments may reveal why some children have complications after surgery, despite imaging that shows nothing unusual.
Other doctors see many uses for the printer. Fetal surgeons want it to practice in utero procedures that involve threading a needle through an unborn baby's tiny heart. An otolaryngologist wants to make custom cochlear implants for children with difficulty hearing.
Despite the interest, Fogel said the team lacks the funds to take the printer to full capacity.
Frakes had the same experience. "It's a concept that is a little bit out there for the traditional funding agencies," he said. "We kind of had to bootstrap it and do it on our own."
A few years ago, Frakes launched his own start-up, Heart in Your Hand, that sells hearts with congenital defects printed from actual patients. They also can create custom-made hearts for a new patient.
"It's almost like individualized medicine," Fogel said. "They're slowly but surely coming around."