OU Medicine Named Member of National HLHS Consortium

For its surgeons’ expertise in treating babies born with hypoplastic left heart syndrome, OU Medicine has earned membership in the national HLHS Consortium.

The achievement was led by OU Medicine pediatric cardiothoracic surgeon Harold Burkhart, M.D., who is leading a clinical trial studying a promising new treatment for babies born with the heart defect. OU Medicine’s success with the treatment led to membership in the consortium – a network of institutions across the United States that specialize in treating HLHS.

“We are excited about joining the HLHS Consortium because it establishes OU Medicine as a site where families can receive the latest research-based treatment for their children who are born with HLHS,” Burkhart said. “We will serve as a regional center for families to receive care closer to home.”

Babies with hypoplastic left heart syndrome are usually diagnosed in utero. In HLHS, the left ventricle is significantly underdeveloped, and the heart can’t pump sufficient blood through the body. A set of three surgeries, conducted from birth through about age 2, stabilizes infants for the short term, but until now, surgeons have not had a long-term option for strengthening a baby’s heart.
In the clinical trial, Burkhart and his team study the effects of injecting the baby’s own umbilical cord blood cells into the heart muscle in the hopes that it will cause the muscle to strengthen and multiply. The treatment is an example of cutting-edge regenerative medicine.

“Families of children with heart anomalies want to know that we’re not just resting where we are. We need to keep pushing forward to come up with newer treatments,” Burkhart said. “This trial is exciting because it is showing good results, and it is the epitome of a bench-to-bedside research project.”

Babies in the trial receive the injection of umbilical cord blood cells during the second of their three surgeries. Each surgery takes an important step in stabilizing the baby’s heart. The first surgery, called the Norwood, is conducted within the first few weeks of life in order to keep the baby alive. Burkhart reconstructs the aortic arch, inserts a shunt to deliver blood to the lungs, then ensures the atrial septum is wide open. This allows the right ventricle to pump blood to the lungs and to the rest of the body.

The second surgery, the Glenn, is performed when the baby is 4 to 6 months old. In this procedure, Burkhart sews the superior vena cava directly to the right pulmonary artery. This allows the blue blood to go directly to the lungs to become oxygenated, instead of both blue and pink blood mixing in the single pumping chamber. While the heart is beating, Burkhart injects the umbilical cord blood cells directly into the heart.

In the final surgery, the Fontan, the inferior vena cava (the vessel carrying blood from the bottom part of the body) is connected to the right pulmonary artery. This allows the blue blood to go directly to the lungs; after it becomes oxygenated there, it heads back to the single pumping chamber as red blood that travels to the rest of the body.

Although the combined three surgeries provide the baby with 100 percent saturation, the approach isn’t a long-term solution. The right ventricle is designed to pump to the lungs at a lower pressure. Because it must pump to the whole body at a higher pressure, it may wear out as the child grows older. Some require a heart transplant to save their lives.
That’s where the umbilical cord blood cells enter the picture. The hypothesis is not that the cells themselves will grow bigger and stronger, but that they emit a signaling pathway that causes the actual muscle of the heart to strengthen and multiply, Burkhart said.

“If this can make the right ventricle stronger than it normally is, by stimulating it to have more cell growth and more hypertrophy of the cells, then we hope babies can tolerate the high-pressure pumping better,” Burkhart said. “Then, because of that improved cardiac function, we hope we can avoid or prolong having to do a transplant for some of these children.”

Thus far, Burkhart and his team have provided the treatment to six babies in the clinical trial. The results of the trial have been very encouraging and are being reviewed for publication in a top cardiovascular surgery journal.

Many different health care providers play a big role in the care of babies with HLHS, from the intensive care team and cardiologists to researchers and other cardiothoracic surgeons at OU Medicine, including Jess L. Thompson, M.D. The entire team is gratified to be playing a role in the development of a potential new treatment for HLHS. Babies are resilient, Burkhart said, and the regenerative capabilities of their tiny hearts may yield enormous results.

“The beauty of working with babies is that their hearts are so adaptable. They’re ready to change, based on what’s taking place from a stimulus standpoint at the cellular level,” he said. “That’s one of the things that made us think about injecting umbilical cord blood cells – these babies’ hearts can respond and adapt much more so than adult hearts. So let’s inject the cells early rather than waiting until they show signs of heart failure or to trying to reverse the process when they’re older. It’s an incredible possibility for babies.”