What is CHD?
A congenital heart defect (CHD) is a heart defect present at birth. Approximately 40,000 babies are born with CHD in the United States each year. With more than 35 different types, little is known about the causes of most of them.
Possible Causes of CHD
According to Dr. Carl Backer, the surgical director of the Heart Transplant Program of Children's Memorial Hospital in Chicago, causes for CHD are hard to pinpoint. Alcohol and drug use and smoking during pregnancy and some infections have long been blamed.
"But I think it's genetic, though we've been unable to specify, except for a very few lesions, the chromosomal problem," says Dr. Baker, who's a professor of surgery at Northwestern University's Feinberg School of Medicine and a Medical Advisory Board chairperson for the Children's Heart Foundation. "It's generally something that's probably in the genetic makeup and not controllable by environmental issues."
In most cases, Dr. Backer says that CHD are diagnosed in the newborn period. "There are clearly some cases diagnosed by fetal echoes, and the further along in pregnancy the better it can be diagnosed, but the majority are diagnosed after the baby is born," he says. "Fetal echoes are difficult, so an obstetrician may or may not see a subtle heart defect. But after the baby is born, a doctor can do a full exam and check the child's oxygen levels and do a cardiac exam."
Still, there are some patients who aren't diagnosed until much later in life, Dr. Backer admits. However, with improved screening in the childhood years, this number grows smaller and smaller.
Signs in Newborns
So what would a doctor—or parent—see in a child with a CHD? "One of the first things they would see is that the child's color is not normal, the baby would have blue cyanosis," Dr. Backer says. "You see this blue coloring in about 50 percent of heart defects. The other major issue or problem you might see is if the child doesn't gain weight and has, what we call, failure to thrive."
Other signs include newborns who breathe in short, fast breaths and are prone to upper respiratory tract infections. "Still some of these babies go into full cardiovascular shock within the first couple of days or weeks of life," he says. "When a child is in utero, the mother provides oxygen, but in the first seven or 14 days after birth there's a valve that connects the two arteries (the Patent Ductus) and it falls off, forcing the arteries to work independently. When this valve falls off and the child's heart is unable to function properly, the infant will turn grey and limp—and that child is going to die unless he or she gets immediate medical care. This is why newborns need a careful screening exam in the neonatal unit before they're discharged."
Part of the reason CHD are so complicated is that there are some 35 different defects. Dr. Backer says typically patients fall into one of two categories. The first includes patients who suffer from pulmonary atresia, tricuspid atresia and hypoplastic left heart syndrome. "These make up about 50 percent of my practice," he says. "The other group of patients has two ventricles but endure malformations, such as a hole between the upper or lower chambers of the heart."
The most widely used treatments for such defects are accordingly complex and varied. But in most cases, any holes between the chambers are closed. And those patients with one chamber go through a series of surgeries starting with a shunt-type operation, which connects an artery from the arm to the lungs. Later the Glenn procedure gets rid of the shunt, and finally the Fontan operation returns a patient's oxygen level to around 95 percent.
"Heart transplants are relatively uncommon," Dr. Baker says. "I do maybe 10 a year out of 500 surgeries. Heart transplants are an end-stage treatment when all else fails."