The overall incidence of congenital heart disease in the general population is 0.8 percent. The incidence of congenital heart disease in children with Down syndrome is up to 50 percent.
The types of heart defects in children with Down syndrome can be broken down into three broad categories:
Atrioventricular septal defects (AV Canal) are greatly over-represented in these children, making up approximately 60 percent of the congenital heart disease found in Trisomy 21. For comparison, AV canals account for only 2.9 percent of the congenital heart defects in the general population.
Ventricular septal defects, atrial septal defects, and patent ductus arteriosus comprise another 20 percent of the congenital heart disease associated with Down syndrome, although these defects are much more common in the general population compared to AV canals.
Other complex congenital heart diseases including Tetralogy of Fallot and hypoplastic left heart syndrome comprise the rest of the heart disease seen in Trisomy 21.
In addition to the heart defects associated with Down Syndrome, isolated elevated blood pressure in the lungs (pulmonary hypertension) is seen with higher frequency in patients with Down syndrome. This high pressure may be related to malformation of the lung tissue, although the exact cause is not known.
The higher pressures may limit the amount of blood flow to the lungs and therefore decrease the likelihood of symptoms of congestive heart failure seen in babies with complete AV canals or large ventricular septal defects. However, since the pulmonary hypertension can become irreversible, particularly if these large holes are not surgically corrected by a year of age, children with Down syndrome and AV canals or large ventricular septal defects are often referred for surgery earlier than a non-Down syndrome child with the same heart defect. If the baby does have evidence of high pressures in the lungs, it may complicate postoperative management and hence prolong the recovery time.
Depending on the type of heart defect, children with Down syndrome and heart disease may have a variety of symptoms.
Babies with complete AV canal defects may have signs and symptoms of congestive heart failure such as:
Children with partial AV canals can be asymptomatic because the extra blood flow to the lungs is not enough to cause symptoms of congestive heart failure.
Even babies with large ventricular septal defects as part of their heart disease who should have large amounts of extra blood flowing to their lungs may have no symptoms due to high pressures in the lungs. These babies must be watched carefully to determine the proper timing for surgery.
Most cardiologists would agree that all babies that have been diagnosed with Down syndrome should have a cardiology evaluation because of the high incidence of associated congenital heart defects. A good history and physical examination should be performed by an experienced cardiologist to rule out any obvious heart defect. Most cardiologists would perform an electrocardiogram, which can be very helpful in making the diagnosis of AV canal, even in the absence of physical findings. At least one echocardiogram may also be performed to rule out subtle heart problems.
If the diagnosis of congenital heart disease is made, the cardiologist will follow the child with office visits on a fairly regular basis. Most patients can be watched clinically to determine if the child is having difficulty due to the heart defect. Occasionally, a repeat electrocardiogram, chest X-ray, or echocardiogram is performed to further evaluate clinical changes. These tests are likely to be repeated before surgical repair is recommended.
Rarely, a cardiac catheterization is required for complete evaluation prior to corrective surgery, especially in patients where elevated pressures in the lungs are a concern.
Children with Down syndrome and symptoms of congestive heart failure can be initially managed medically with the use of diuretics, blood pressure medications to allow the heart to eject more blood out to the body rather than out to the lungs, and/or digoxin, a medication used to improve the pumping ability of the heart. If the baby is having difficulty with feeding and weight gain, nasogastric tube feedings with high calorie formula or fortified breast milk can be used to help with growth.
These are all temporary solutions to allow the baby to grow while deciding if and when surgery is indicated. In general, atrial septal defects, ventricular septal defects, and AV canal defects are closed surgically if the child is demonstrating congestive heart failure that cannot be controlled with medication.
If the baby has no signs of heart failure or is controlled well with medications, the decision for surgical closure can be delayed. AV canals are usually repaired electively between 3 and 6 months of age. Depending on the size of an atrial septal defect or a ventricular septal defect, surgery can be postponed even longer, keeping in mind the risk of developing irreversible high pressures in the lungs. The decision must be individualized to each child's physical state as well as the family's concerns.
Congenital heart disease is the most common cause of death in early childhood. Survival beyond one year of age is 85 percent in all children with Down syndrome. Over 50 percent of individuals with Down syndrome live to be greater than 50 years old. With improved medical and surgical care, these numbers continue to improve.