What to Know About Jimmy Kimmel’s Son’s Heart Defect

Jimmy Kimmel’s newborn son underwent emergency open-heart surgery just a few days after birth, the late-night host revealed Monday in an emotional Jimmy Kimmel Live monologue.

William “Billy” Kimmel was only about three hours old when a nurse noticed he had a heart murmur and looked slightly discolored, Kimmel said. Doctors soon determined he had a congenital defect, called tetralogy of Fallot with pulmonary atresia, that was preventing his lungs from getting enough oxygen.

Kimmel assured his audience that the story had a happy ending, but the comedian struggled through tears as he recounted the harrowing tale and shared a photo of his son hooked up to wires and machines. “He went in there with a scalpel and did some kind of magic I couldn’t even begin to explain,” he said of his son’s cardiac surgeon at Children’s Hospital Los Angeles. “It was the longest three hours of my life.”

The surgery was a success, Kimmel said, but his son will need another procedure in a few months, and a third as a teenager. Fortunately, the prognosis for most patients with tetralogy of Fallot is very good. Here are a few things to know about this fairly common heart defect, and how it’s treated in infants just a few days old.

Health.com: WATCH: Jimmy Kimmel Tearfully Reveals Newborn Son Billy Underwent Open Heart Surgery

About 1% of babies are born with congenital heart defects

Structural problems with the heart, known as congenital heart defects, occur in just under 1% of babies. Among babies born with heart problems, about 10% have tetralogy of Fallot—the most common reason for children to have lower than normal oxygen levels and be “cyanotic,” or have a bluish coloring. About 20% of those babies have the most severe form of the disease, tetralogy of Fallot with pulmonary atresia.

“Overall, the incidence of this specific diagnosis is somewhere less than 1 in 10,000,” says Dr. Mary Donofrio, director of the Fetal Heart Program at Children’s National Health System in Washington, D.C. (Donofrio is not involved in Baby Kimmel’s care, but she has treated babies with the same condition.)

While genetics can sometimes play a role, most cases of congenital heart defects, including most cases of tetralogy of Fallot, are unexplained.

Tetralogy of Fallot is four defects in one

The disease Kimmel’s son was diagnosed with is named for the doctor who first described it (Fallot), and the four (“tetra”) different defects that it entails: First, a hole exists between the bottom two ventricles, or chambers, of the heart. Second, the pulmonary valve or arteries are narrowed or blocked, keeping blood from getting to the lungs. Third, the aorta, the large artery that carries blood away from the heart, is slightly out of place.

The fourth defect is called hypertrophy, which means that the heart becomes thicker and more muscular because it has to work harder to pump blood. This complication isn’t generally seen in the United States, however, because the other three problems are fixed before the fourth can occur.

Most babies are diagnosed with tetralogy of Fallot in the hospital shortly after birth, either because they have a bluish discoloration or because their blood oxygen levels (as recorded by a pulse oximeter device) are low. “We really try not to have a child be discharged after birth without a diagnosis, because some of those children might get very sick once they’re home,” says Dr. Joseph Rossano, executive director of the cardiac center at Children’s Hospital of Philadelphia. (Rossano is also not involved in Baby Kimmel’s care.)

When a baby is also diagnosed with pulmonary atresia, this means the blood flow to their lungs is completely blocked, rather than partially obstructed. “This is the most severe form, and the baby will be blue,” says Donofrio. “In this case, the problem needs to be fixed right away, right after birth.”

Surgery success rates are excellent, even in newborns

A person’s heart is about the size of their fist, says Rossano, so one only has to think of the size of a baby’s hands to appreciate the job of a pediatric cardiac surgeon. “There are very technical challenges, but at high-quality centers all over the world, the vast majority of children survive this procedure and have excellent outcomes,” he says.

Heart surgery on infants often involves smaller-scale instruments and materials, says Donofrio, and doctors use special glasses that magnify tiny infant organs and blood vessels. Besides surgeons, an entire care team is also needed to tend to the unique needs of newborns, many of whom are already sick.

For a baby with tetralogy of Fallot, “the surgeon closes the hole in the heart’s wall just like you would sew a patch onto a pair of pants,” Donofrio says. “Sometimes fabric is actually used to seal it off.”

Several procedures are usually required

Depending on the severity of a child’s condition, more procedures may be needed as he or she gets older. More extensive surgeries are often delayed until a child is a few months old and their heart is larger and stronger.

If artificial valves or connectors are used in these surgeries, they’ll likely need to be replaced at least once more. “Unfortunately, these materials don’t grow along with the rest of the heart,” Donofrio says. “Hopefully someday we’ll develop materials that will grow and expand over time.”

This is one reason Rossano cautions against saying that surgery can “cure” congenital heart defects. “We can definitely treat it, and many patients live with these conditions and do very well,” he says. “But they do need lifelong care.”

Most babies grow up healthy

Even when infants are operated on shortly after birth, most are discharged from the hospital within a week or two, says Donofrio. They’ll need follow-up appointments at least annually, and should be monitored closely for complications, both physical and developmental. (Neurological problems are sometimes linked to surgeries at very young ages.)

But in general, Donofrio says, children with this disease—and their parents—have a lot to be optimistic about. “They can run around, they can go to school, they can be athletes,” she says. “This is something we see often, and with advances in modern medicine and surgery, it’s something we can take care of.”

Rossano agrees that patients with congenital heart disease can grow up fairly normally. “I don’t want parents to think their child will be so fragile they have to live in a bubble,” he says. “Our goal is to have these children living healthy, active lives.”

This article originally appeared on Health.com