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ROCHESTER – Every year, about 1,000 babies are born in the United States with half a heart — a rare defect that requires a series of risky surgeries and, even then, leaves the infants with a strong likelihood that their hearts will wear out prematurely.

Now, the Mayo Clinic has received federal approval for a first-of-its kind clinical study to see if stem cells from the babies' own umbilical cords can strengthen their underdeveloped hearts and extend their lives.

If it works, the new technique could buy these children time as scientists scramble for a cure for the congenital defect called hypoplastic left heart syndrome (HLHS).

The Mayo study, which will begin as soon as 10 eligible candidates can be enrolled, could also pave the way for additional breakthroughs in stem cell treatments that would help the 19,000 children born each year with other heart defects. But for the time being, the doctors at Mayo are keeping their focus on those babies who need the most help now.

"We are not here to build an academic career out of science and technology,'' said Dr. Timothy Nelson, director of Mayo's HLHS research program. "We're really here to make a difference in children's lives who are living today with unmet needs."

Christina DeShaw of Clive, Iowa, was pregnant with fraternal twins when she learned during an ultrasound procedure that the left side of her daughter's heart was not developing properly.

"The world just started spinning," DeShaw said. "Our lives were forever changed from that moment on."

DeShaw and her husband, Brad Weitl, sought help from the Mayo Clinic for the baby they named Ava Grace.

They learned that children born with defects on the left side of the heart must undergo a series of three complex surgeries. The first is called the Norwood procedure: Within a few days of birth, surgeons reconstruct the heart so that the fully developed right ventricle can do both its own work of supplying blood to the lungs and the work of the defective left ventricle, which ordinarily would pump oxygenated blood back to the body.

Dr. Harold Burkhart, who is overseeing surgeries in Mayo's new study, said that when the procedure was developed in 1983, only about 30 percent of the patients survived. About 70 percent survive now, he said, and at Mayo, about 9 out of 10 make it through.

The second and third surgeries are much safer. They involve rerouting blood from the body directly to the lungs, bypassing the heart entirely to reduce the workload of the right ventricle.

Ava Grace Weitl was born by Caesarean section on May 8, 2012, then whisked away for her first surgery. "Her heart was the size of a walnut," DeShaw said. "She had less than a 40 percent chance of making it."

Ava remained under intensive care until Labor Day. DeShaw, who works at ING Financial Partners in Des Moines, spent months living in a Rochester hotel; her husband, a construction estimator, drove up on weekends. But their trauma didn't stop when they finally took their daughter home. Ava has suffered numerous complications and once had to be flown back to Mayo in a helicopter.

Unfortunately, Ava won't be eligible for the stem cell trial: The design calls for stem cells to be injected into the right ventricle during the second surgery, and Ava has already had hers.

Still, Ava's parents remain dedicated to helping with Mayo's research. "We wanted to participate, not only because we thought that at some point Ava might benefit, but we also wanted to help all the other babies … and to try to give them the best shot,'' DeShaw said.

Seeds of life

Cardiac stem cell treatments were pioneered in adult patients. Worldwide, some 5,000 to 6,000 people have received stem cell treatments for heart conditions, but those procedures relied on cells taken from the patients' bone marrow, said Dr. Atta Behfar, one of Mayo's leading researchers in the field.

Behfar, working with Dr. Andre Terzic, a Mayo cardiovascular specialist, found that stem cells typically lose their vitality as they age and apparently become "sick" along with the patient. Mayo just finished a clinical trial in Europe showing that they could kick-start those cells in a way that significantly improves the patient's health, cuts treatment costs and improves quality of life.

Nelson said he thinks stem cells taken from umbilical cord blood and placed into a growing heart will prove even more effective.

"I think of stem cells as seeds," Nelson said. "If you plant that seed into a rocky, dry soil, that seed may not grow nearly as well as if you plant it into a black, rich, fertile soil that gets watered, irrigated and fertilized," he said. "And so we think of this as planting these seeds into that fertile soil of a pediatric heart."

Also, Nelson said, stem cells from the umbilical cord seem to know when to stop producing heart cells, so they don't create the same cancer concerns that have been associated with the use of "pluripotent" embryonic cells or bioengineered cells in adult hearts.

Too few hearts

Nelson dedicated himself to finding a cure for hypoplastic left heart syndrome when he was studying to become a pediatric heart surgeon. He said it tore him up to know that babies who endured three open heart surgeries would often return as young children with irreparable heart damage and little likelihood of finding a donor heart in time to save them.

Some research suggested that half the children with HLHS don't make it to their 5th birthday, Nelson said, but there are also children living into their early 20s. "So there are wonderful success stories of the surgical practice," he said. "But obviously, the percentage of kids born that make it to that stage is far too low."

Joshua and Sandra Hughes of Ashburn, Va., said they learned about Mayo's pediatric heart research from a friend. Their 5-year-old daughter, Jaclyn, also has HLHS, and although she gets treated in Washington, D.C., they volunteered to participate in Mayo's research program.

Jaclyn underwent an MRI last week, and she and her parents each contributed skin tissue for genetic testing and other research. Mayo's Dr. Patrick O'Leary thanked them for spending two days in Rochester undergoing tests; he showed them images from Jaclyn's scan and said her heart is performing quite well after her third surgery.

"The stuff they're working on now may not be available for Jackie," Sandra Hughes said. "But it may be available for the next generation."

O'Leary interrupted her, voicing his optimism for the Mayo research.

"It may be available for her, too," he said.

Kaiser Health reporting intern Ashley Griffin contributed to this story.

Dan Browning • 612-673-4493