A new study published in the Journal of the American Medical Association confirms that screening of critical congenital heart disease (CCHD) using a simple test called pulse oximetry can lead to a dramatic decrease in infant deaths. In eight states that adopted the mandatory screening, deaths from CCHD decreased more than 33 percent. And deaths from other or unspecified cardiac causes decreased by 21 percent. In states that had voluntary screening policies or no screening policies at all, there was no reduction in infant deaths during the same time period.
CCHD is a surprisingly common birth defect, occurring in roughly 2 per 1,000 births. It accounted for 6 percent of infant deaths in the U.S. from 1999 to 2006, even though surgery to correct heart defects is very successful when performed early enough in the baby’s life.
CCHD encompasses a number of defects in the way the heart is formed. “The heart is a very complex organ,” says Daphne Hsu, professor of pediatric cardiology and chief of the Division of Pediatric Cardiology at Albert Einstein College of Medicine/Montefiore Health System. “With four valves, four chambers, connections to the lungs and to veins coming back from the head and the body — there are a lot of opportunities for the ‘plumbing’ to go wrong. That’s what CCHD is.”
CCHD is caused by a genetic mutation or mutations that affect the development of the heart, which is fully formed by twelve weeks of pregnancy. It was first noticed in babies born with trisomies, or an extra chromosome, who have a very high incidence of CCHD. “That was the first inkling that this was in fact a genetic disease,” Hsu says. Most babies with CCHD, however, do not have a trisomy. They have mutations in other genes that control the development of the heart, she says.
While there are roughly twenty defects that occur most commonly, there are many more ways that CCHD can manifest, many of them unique. Hsu says that during pregnancy, there isn’t usually any kind of clinical sign or symptom that points to heart defects, because the mother’s heart is still doing all the work for the fetus. Some defects can be found with a routine ultrasound during pregnancy. But nearly 20 percent go undiagnosed at birth — a situation that can quickly become dangerous if not discovered within the first couple of days of life, Hsu says.
In the first seven days after birth, a baby’s ductus arteriosis, starts closing gradually. This channel normally allows a mother’s blood to flow to the baby in utero, bypassing its lungs. But when the lungs start functioning after birth, and the baby can oxygenate its own blood, the extra vessel shrinks and closes on its own.
“Babies with CCHD often rely on that extra blood vessel to supply blood to the part of the heart that didn’t grow well,” says Hsu. While the vessel is open, the baby might have low oxygen saturation, but otherwise look normal. That is why normal nursery exams may be unable to detect any serious heart problems, and babies may be discharged with undiagnosed CCHD. Once the ductus arteriosis closes, however, symptoms can go from subtle to dangerous very quickly, and can result in organ damage.
“If we can diagnose the defect right away, we can keep the ductus open with medication, keep them stabilized until surgery, then make them better,” says Hsu.
Pulse oximetry accurately detects the lower oxygen saturations associated with CCHD by simply shining an infrared light through a baby’s fingers or toes. It is an easy, painless screening tool for detecting how well a newborn’s heart is working that was recommended by the American Academy of Pediatrics and the American Heart Association in 2012.
For the new study, researchers looked at data from newborn screenings between 2007 and 2013. They found that in states where the pulse oximetry screening was implemented, a significant decrease in infant deaths was observed. Since that time, nearly all states have adopted mandatory screening policies.
Mortality among babies with CCHD has also dropped dramatically in the past few decades as physicians have become more skilled at surgery, post-op management, and lifelong care. While the surgery is very successful, children with CCHD must still be followed medically through adulthood and often have complex medical needs.
The study results serve as a reminder of the importance of CCHD screening in hospitals, as nearly 120 babies may be saved each year by adopting nationwide CCHD screening, according to the Centers for Disease Control and Prevention.