Congenital heart defects: Ventricular septal defects

A ventricular septal defect is the most common heart defect seen in newborns. They account for up to 25% of all cases of congenital heart disease seen in children. The severity of a ventricular septal defect can vary tremendously from child to child. In over 75% of cases these defects correct themselves by the age of 10. There are medical and surgical therapies available to fix the problems if they do not resolve on their own.
The heart begins development in a fetus at a very young age. Approximately twenty-two days after conception, the heart becomes sufficiently developed to be capable of beating. This corresponds roughly to the fifth week of pregnancy - pretty fast, isn't it? When it first begins forming in the fetus, the heart is a straight tube. This tube then twists and turns itself into the structure that we know as the heart. Sometimes these twists and turns do not form properly. This can lead to the development of a ventricular septal defect.

A fully formed heart has four chambers. The two upper chambers are called the atria. The two lower chambers are the ventricles. Separating the ventricles is a wall of heart muscle known as a septum. Ventricular septal defects occur when there is a small hole in the wall between the two lower chambers of the heart. From time to time, this septum will not develop properly, leaving a small hole that blood can flow through.

There are several sub-types of ventricular septal defects, depending on the exact location of the hole. Sometimes one of the heart valves (usually the mitral or tricuspid valves) will be involved in the defect.

Most ventricular septal defects will close without medical intervention. By age 3, over 40% of ventricular septal defects will heal themselves. By age 10, over 75% of infants born with a ventricular septal defect will have complete resolution of the problem. In some cases it may be necessary to perform surgery to close the hole.

The severity of the ventricular septal defect is related to how large the hole is. Obviously, larger holes cause more problems than smaller holes. Small holes allow extra blood to flow from the left side of the heart, which is typically at higher pressures, to the right side. If the hole is large enough, a series of pressure alterations in the vasculature involving the heart and lungs can cause the blood to start flowing from the right side to the left. This is a more severe condition, which actually has a name - Eisenmenger's Syndrome.

(This is a great answer to an obscure trivia question - What is the name of the syndrome caused by a large VSD where the shunt of blood goes from right to left? Answer: Eisenmenger's Syndrome! Think of the hit you'll be at parties!)

Symptoms are also related to the size of the hole. Small holes will generally be unnoticed by the infant. If the heart of the effected infant is listened to, it is often possible to hear a murmur. Although murmurs are very common in newborns and distinguishing a harmful one from a transient "normal" murmur can be quite difficult. ECGs and echocardiograms are the most useful tests to find a ventricular septal defect in a newborn.