Every year, around 16,800 children are born with a ventricular septal defect, or VSD, in the US, according to the Centers for Disease Control & Prevention. VSD account for nearly half of the 40,000 congenital heart defects diagnosed annually, making them the most common congenital abnormalities in America.
What Is VSD?
Ventricular septal defect is a hole in the wall (or “septum”) that normally separates the heart’s two lower chambers, the ventricles.
In healthy human hearts, a complete wall between these two chambers prevents oxygen-rich blood from mixing with oxygen-poor blood, preserving the heart’s efficiency.
But for children with a VSD, a hole in the septum allows oxygen-rich blood to flow directly from the left side of the heart to the right side. From here, it’s pumped back out to the lungs, but since some of the blood has already absorbed oxygen, the total amount of oxygen that eventually reaches the body is lower than normal.
That can force the heart to work harder than usual, increasing blood pressure in the lungs. In severe cases, the body tissues and organs that rely on blood for oxygen may be starved of nutrients.
How Does It Happen?
In specific cases, doctors rarely come to an adequate explanation. But researchers have identified two causal factors that likely contribute to the vast majority of congenital heart defects: genetics and environmental toxins.
Some VSD are likely hereditary, passed down from parent to child in the form of genetic information. Ventricular septal defects often accompany genetic syndromes, including Down syndrome. But most scientists believe that genetic abnormalities are only half of the story. These mutations, in other words, need a “push” to have an effect, and that push comes from the environment in which a human embryo develops.
We’ve long known that some chemicals, after being ingested by a mother, can come to affect her growing baby. Alcohol, for example, has been linked to an increased risk for ventricular septal defect, as have organic solvents, a class of chemicals used in industrial cleaning. Several prescription drugs have also been implicated as possible causes, including Zofran, a popular “off-label” morning sickness treatment.
Can Heart Defects Be Diagnosed Before Birth?
In some cases, yes.
Larger defects, ones that would be obvious to the naked eye, can often be spotted during pregnancy on a fetal echocardiogram, a sort of ultrasound test that creates images of an unborn baby’s heart.
Most VSD, on the other hand, are too small to be detected by this technique. While some heart defects will be missed entirely, until their effects become noticeable later in life, many are diagnosed relatively early, through physical examinations.
Ventricular septal defects create a loud sound, often described as “rumbling,” called a heart murmur. Doctors are often able to diagnose VSD based solely on this sound, because it’s very specific, and unlikely to be caused by a different heart defect.
You can listen to a murmur characteristic of ventricular septal defect over at the University of California Los Angeles.
How Can We Treat VSD?
Since the long-term complications of VSD, like pulmonary hypertension and heart failure, are quite severe, most large ventricular septal defects are repaired during infancy or early childhood. Open-heart surgery remains the standard treatment, although some holes can be patched through the use of a catheter, a less-invasive technique.
Surgical interventions for VSD are almost always successful. More than 99% of infants will survive their surgery, according to the Children’s Hospital of Philadelphia, and the vast majority will go on to live healthy lives.
Many ventricular septal defects, however, are so small that they close of their own accord, without the need for any medications or surgeries. When the outcome is still questionable, babies with smaller VSD are often placed on diuretics, medicines that encourage urination, and thus reduce the amount of fluids reaching the lungs, or Digoxin, a drug that can decrease the risk of abnormal heart rhythms.