Two times before his first birthday, Mac Grieb had his chest cracked open for heart surgery, and physicians warned his parents he would someday need to go through the grueling process again.

Instead, last year at age 16, the New Jersey youth underwent an experimental procedure that allowed him to go home the next day. At Children's Hospital of Philadelphia, cardiologists inserted a catheter through a vein in the teenager's groin up into his heart, implanting an artificial valve to regulate the blood flow to his lungs.

Mac was born with a cluster of heart abnormalities called tetralogy of Fallot, the same condition that was diagnosed last year in the infant son of talk-show host Jimmy Kimmel.

Most children with this and other congenital heart defects live well into adulthood, thanks to a variety of surgeries developed decades ago. Many also go on to develop complications, ranging from subtle developmental delays to complex circulatory problems that can require follow-up procedures.

Physicians are increasingly coming up with strategies to help delay or even avoid surgery, such as the valve implant that Mac received. But some patients — especially older ones — never got the message that they need to keep careful tabs on their heart health, said Paula Miller, senior education manager at the Philadelphia-based Adult Congenital Heart Association.

"We hear from people who thought they were fixed, or cured, and never had to go back to the doctor," she said.

Not Mac. By age 16, he had so much experience with the medical system that he knew to speak up when something did not seem right.

‘Out of it’

Mac was born with VACTERL association, a genetic syndrome that can include abnormalities in as many as six bodily systems, denoted by the letters in its name: vertebral, anal, cardiac, tracheal-esophageal, renal (the kidney), and limbs.

Mac had issues with all of these except the A. In addition to the two open-heart surgeries during infancy, he had surgery to correct problems with his stomach and spinal cord, among other procedures. He was born with just one kidney and is missing a bone in one forearm.

So when he started to feel short of breath two years ago, he told his mom right away.

"I felt winded and exhausted," he said. "Kind of out of it."

They saw a physician near their home in Brielle, N.J., who recommended an appointment at CHOP. Victoria Vetter, a pediatric cardiologist at the Philadelphia hospital, detected an abnormal heart rhythm and performed a corrective procedure called an ablation.

But there was more: An MRI revealed that Mac's right ventricle was enlarged — a frequent consequence for those with tetralogy of Fallot, and for some patients with other congenital heart defects.

Such patients are born with a narrow (or even nonexistent) connection between the heart's right ventricle and the pulmonary artery — the vessel that delivers "blue" blood from the heart to the lungs to be enriched with oxygen the body needs to function. That is one of four hallmarks of the disorder, hence the prefix tetra-, from the Greek for four. (Fallot is the name of the French physician who described it.)

Surgeons typically enlarge this connection during infancy, improving blood flow to the lungs. But because the valve inside this vital passageway still does not work well, some of the blue blood flows backward into the heart — a condition that over time can stretch and enlarge the right ventricle to the point where it is no longer able to pump properly.

Tricky timing

Traditionally, that development has meant open-heart surgery to implant a new valve. But the timing is tricky, said Matthew J. Gillespie, an interventional cardiologist who treated Mac at CHOP.

If the surgery is done in time, the right ventricle returns to its normal size. Yet if heart failure begins to set in, it may be too late. As in older patients with heart failure, the term does not mean the heart stops pumping, but that it becomes too weak to keep up with the demands of circulation.

"It's a conundrum," Gillespie said. "If you wait till the point where people are really having severe symptoms, or you start to see the function of the heart is going downhill, there's a good chance they won't get the benefit of having the new valve."

This prosthetic heart valve is designed for patients with tetralogy of Fallot, the condition Jimmy Kimmel’s son was born with.
Medtronic
This prosthetic heart valve is designed for patients with tetralogy of Fallot, the condition Jimmy Kimmel’s son was born with.

Yet the prospect of another open-heart surgery may be an unwelcome surprise to a patient who does not feel especially bad, said Gillespie, associate director of CHOP's cardiac catheterization lab.

Mac and his family had a new option: the experimental Harmony valve, an hourglass-shaped implant made with a metal frame and tissue from a pig heart, inserted via catheter through a vein.

Gillespie told the Griebs he had helped conduct a study of the valve in sheep, funded by the hospital and private donors, and another study of 21 human patients, funded by the device maker Medtronic. Early results were promising.

The family needed little convincing.

"We were so ecstatic that we could possibly not have to go through another open-heart surgery," said Stacy Grieb, Mac's mom. "We were all in."

In April 2017, Mac became the first patient at CHOP to get the Harmony valve. The procedure took just two hours, and the teenager was home the next day. An avid drummer, he was soon back playing along with the music of Led Zeppelin and other classic bands.

Mac felt pretty good that summer, then really started to notice an improvement in the fall at school, in gym class.

"I was running around with my buddies," he recalled. "I noticed I was running at the same pace as they were. They were out of breath, but I wasn't."

Continuing care

Tetralogy of Fallot is among the most common congenital heart defects, occurring in 2,500 U.S. babies born each year.

Other heart defects can lead to complications later in life as well. Abnormal heart rhythms are a common consequence of infant surgery, and patients also are more likely to suffer hearing loss. One disorder, called single-ventricle disease, can lead to scarring in the liver and abnormal flow in the lymphatic system, which can be treated with a catheterization.

Such findings illustrate the need for ongoing surveillance, said Miller, of the Adult Congenital Heart Association.

A pediatric nurse by training, Miller also knows the importance of her advice personally. She, like Mac and Billy Kimmel, was born with tetralogy of Fallot. Now 67, she had two corrective surgeries in childhood, and needed a valve replacement as an adult. But in her late 40s, she was seen by a general cardiologist who knew little about treating adults who had survived infant heart surgery.

"You're lucky to be alive," the doctor told her in 1999, Miller recalled. "There's nothing more we can do."

Instead, she went online and found the patient association for which she now works. The group helped her find a specialist, and she had surgery in 2004 to get a new pulmonary valve.

Gillespie, the CHOP cardiologist, thinks someday all such valve replacements will be implanted via catheter, as Mac's was. He predicted that will happen for Billy Kimmel, the son of the talk-show host — assuming the device is approved by the U.S. Food and Drug Administration in a few years.

In short: conditions that once could mean a shortened life expectancy often can be managed, Gillespie and Miller say. Look no further than another famous tetralogy of Fallot patient, Olympic snowboarder Shaun White.

On his ABC talk show, Kimmel asked White about his experience with the disease, and jokingly worried that his son would become a snowboarder.

"That is a side effect, yes," White replied.

No treatment for that one. Yet.