Preemies born with a common but dangerous heart defect are gaining better chances at survival and good health through a new technique performed at the University of Minnesota Masonic Children’s Hospital.

The technique involves plugging up a cardiac blood vessel that is vital to circulation before birth, but doesn’t always close on its own — as it is supposed to — in the hours after birth.

Babies born prematurely and at low birthweights are at higher risk for this problem, known as Patent Ductus Arteriosus (PDA), and for potentially fatal disruptions to heart and lung function when the vessel doesn’t close.

“The babies we’re treating today, they wouldn’t have survived” two decades ago, said Dr. Gurumurthy Hiremath, the U’s director of pediatric cardiac catheterization.

Not all cases require treatment to close the ductus arteriosus, a vessel that promotes fetal growth by bypassing blood around the fluid-filled lungs that don’t work until after birth. Simple Tylenol can hasten closure of the blood vessel. But when medication fails, doctors often try surgery to close it.

Already fragile, preemies can suffer infections and complications from surgery, Hiremath said. Those risks led to the development of the new technique, by which specialists thread a plug through the groin and inside blood vessels to the heart.

Earlier attempts used larger plugs that could only fit in the arteries of preemies, which presented complications because of the disruption of blood flow, Hiremath said. But Medtronic’s expandable MVP plug, created in 2013, is small enough to thread through preemies’ 1-millimeter veins, which are easier and safer than arteries to navigate to the heart.

“Veins are forgiving,” Hiremath said. “Veins are stretchy.”

Several medical centers have added the technique; the U is the first in Minnesota to do so. Hiremath reported eight cases so far of preemies gaining stable lung function and weaning off ventilators after the procedure.

Adding complexity is the fact that preemies are less tolerant to radiation or to the contrast dye that is used for high-resolution imaging. Doctors instead use lower-resolution ultrasound and X-ray imaging to guide the plug through the blood vessels.

“It is extremely delicate,” Hiremath said.