Patent Ductus Arteriosus (PDA)
A PDA is a communication between the great arteries of the heart, which are the aorta and pulmonary artery. The PDA is a blood vessel that is present in all babies while still in the womb. It allows blood to bypass the lungs and flow from the pulmonary artery to the aorta.
The PDA usually closes within the first few hours or days of life. On occasion, however, this communication may not close on its own, which is referred to as a patent ductus arteriosus (PDA). This condition is more common in premature babies.
Only a small percentage of term babies will have a PDA that extends beyond the first few days of life. The incidence of a PDA is much higher in premature infants. The lower the gestational age, the higher the incidence (up to 75%). Premature infants may respond differently to changes in certain body substances that constrict the PDA. Pathologic samples have shown that the histology of a PDA in a premature infant is different than that seen in term infants.
A patent ductus arteriosus may be associated with other congenital heart defects. A PDA is more prevalent in high altitude places. It may also be seen with certain syndromes, such as rubella syndrome, and chromosomal abnormalities.
In patients with hypoplastic left heart syndrome, the PDA is crucial to allow adequate blood flow to the body. In other complex heart defects, such as pulmonary atresia, the PDA supplies the only adequate source of blood flow to the lungs so that oxygen can be delivered.
Cardiovascular tests include an electrocardiogram and echocardiogram. The color Doppler echocardiogram is used to diagnose a PDA. The echo is able to visualize blood flowing from the aorta (through the PDA) into the pulmonary artery. In addition, the echocardiogram will help determine the degree of heart size and function. Patients with a PDA may have other heart defects that can be detected by the echocardiogram.
A small PDA may not produce a murmur at all; however, a larger PDA may create turbulent blood flow from the high-pressure aorta to the low-pressure pulmonary artery and produce a characteristic continuous heart murmur that is heard on physical examination. The chest x-ray may show mild enlargement of the heart and evidence of an excessive amount of blood flow to the lungs. In older children, the chest x-ray may be completely normal.
In a newborn, the PDA still has the potential to close on its own without any intervention. Thus, in newborns, additional time is allowed for the PDA to close on its own unless the patient becomes symptomatic.
Virtually all patients with a small PDA will remain asymptomatic. If the PDA is large, the newborn may tire quickly, breathe rapidly, or catch pneumonia easily. In some infants, symptoms may develop after the first few weeks or months of life, while others may develop symptoms within the first few days of life, especially premature babies. Premature infants may benefit from Indocin or a special type of ibuprofen. They may respond to medications such as diuretics (water pill). In rare cases, a premature newborn that persists with symptoms may require surgical closure of the PDA.
Virtually all patients with a PDA will have mixing from the aorta into the pulmonary artery. This mixing is called a left to right ductal shunt. Patients with a moderate-large left to right shunt or who are symptomatic will benefit from closure of the PDA. If they are about 11 pounds or more in weight, they may undergo transcatheter closure by means of interventional cardiac catheterization. Another alternative would be to close it by surgery. The surgeon does not have to open the heart to close the PDA.
For those patients who remain asymptomatic and are over two years of age, they may undergo closure of the PDA by either method. However, if the PDA is rather small, then the other option would be to leave it alone.
Patients with a small PDA lead a normal life and have no restrictions. Optimal dental hygiene and routine dental cleanings are recommended. There is a very small risk of developing endocarditis. It is no longer necessary for patients with a small PDA to take antibiotics prior to dental visits.
Patients who undergo closure of a PDA may require antibiotics for only a limited time depending on the procedure used to close it.
There are potential complications in patients with a larger PDA. The complications may include:
Failure to grow or gain weight
Higher incidence of pneumonia
Development of pulmonary hypertension (high pressures in the blood vessels of the lungs)
Aneurysmal formation (dilation) of the pulmonary artery
Left heart enlargement and/or left ventricular hypertrophy
Infection at the PDA (endarteritis)