The heart of a newborn undergoes dramatic physical changes after birth, as the baby's circulatory system disconnects from the mother's and starts pumping blood on its own.

But the natural process in which an infant's heart is rewired can be disrupted if the baby is born early. As many as 12,000 preemies in the U.S. are born with a heart defect known as a patent ductus arteriosus (PDA), which happens when a temporary conduit between a major artery and a major vein fails to close as it should.

Now, a tiny medical device designed in Minnesota is offering a new treatment option for the smallest newborns with PDAs. Slightly larger than Roosevelt's ear on a dime, the Amplatzer Piccolo Occluder made by Abbott Laboratories is the first minimally invasive heart device approved for infants weighing as little as 2 pounds. The permanent implant is essentially a plug composed of tiny braided wire that gets covered with a thin layer of cells.

Implanted using a 1.3-mm catheter snaked through blood vessels instead of open-heart surgery, the Piccolo is the result of a long-running structural-heart program at Minnesota's St. Jude Medical, which Abbott Laboratories has continued to invest in after buying St. Jude in 2017.

"For me, the fascinating part about this device isn't the size or the shape, it's the indication — we've never had approval of a cardiac device for premature infants in the United States, in the history of the FDA," said Dr. Evan Zahn, director of pediatric cardiology at the Cedars-Sinai Heart Institute in Los Angeles, and principal investigator for a recent trial of the Piccolo.

The Food and Drug Administration's (FDA) approval of the Piccolo comes one year after the FDA approved the world's smallest mechanical heart valve for babies, also made by Abbott and based on a St. Jude innovation. In both cases, Abbott engineers took a device design that was well-understood for larger patients, and essentially shrank it down to "world's smallest" size so it could be used in infants and small kids.

Though the larger versions of the devices are already proven safe, the smaller versions still needed to be tested in clinical trials. Based on the results of the "ADO II AS" trial, the FDA approved Abbott's application to start selling the Piccolo for PDA in the U.S. last month. Another 150 Piccolo patients are being followed under a "clinical access protocol" for the device.

"The FDA really works well with us, especially when we're talking about pediatrics," said Rick Olson, a divisional vice president who leads product development in Abbott's structural heart business. "And we're committed to treating the pediatric market, so they are working with us to ensure that we are bringing these products to market."

Producing new medical devices for kids has long been a challenge for industry and a concern for regulators.

"The development of pediatric devices is underserved compared to adult devices due to factors such as relatively low return on investment, unique design considerations, small market and small sample size, reimbursement considerations, etc.," FDA officials wrote last year.

Anthony Daly said he was glad the Piccolo was available as a treatment option for his son, Anthony.

In September 2015, "Little Tony" was born at 26 weeks and 6 days. (A pregnancy is considered "full-term" after 39 weeks.) He weighed less than 3 pounds, and was in "an extremely fragile state," as the open PDA in his heart was causing potentially fatal problems in his bowels related to poor blood flow, Daly said. Although doctors took a "wait-and-see" approach, but after about two weeks the decision was made to close the PDA with a medical procedure.

Daly described his reactions to the situation: "It was horrifying and helpless, and then here's this device that could seemingly change his fortunes literally overnight. So we signed up. And did just that," Daly said in a phone interview from Nevada, where his family now lives. "It literally changed the trajectory of our son's recovery. He turned a corner and really never looked back."

The treating physician was Dr. Zahn, who had access to the still-unapproved device in 2015 via an FDA exemption for "humanitarian" cases. During the procedure, which took place in Los Angeles, Zahn threaded the narrow tool from an incision in Little Tony's leg, through his blood vessels, and into the place near his heart where two vessels were connected in a way that lets blood bypass the lungs.

Permanently inserting the braided-wire Piccolo device into the conduit caused it close off like is supposed to happen naturally. Although Little Tony stayed in the neonatal intensive care unit for another two months after the procedure, Daly said those months were mainly geared toward getting Little Tony ready for discharge.

"It obviously was a life-changing surgery, for him and for all of us," Daly said.

PDA is one of the most common birth defects in premature babies, affecting nearly 1 in 5 babies born prematurely with very low birth weight. The Amplatzer Piccolo Occluder was approved Jan. 11 for treatment of PDA in premature babies who are at least three days old. The device is not indicated for babies weighing less than 1.5 pounds, according to the device label.

Joe Carlson • 612-673-4779