The Patent Ductus Arteriosus Explained
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The Ductus Arteriosus is a vascular structure that is present before birth which allows blood in the fetus to avoid going through the lungs since a fetus does not need to breathe or to have blood pass through the lungs to obtain oxygen. In most cases the Ductus Arteriosus closes within hours to days after a baby is born and starts to breathe. The blood which previously was bypassing the lungs now needs to go to the lungs to pick up oxygen. Once the oxygen levels start to rise in the bloodstream because a baby has started to breathe air, the oxygen causes the Ductus Arteriosus to start contracting until it closes. In some infants the Ductus Arteriosus does not close (it stays “patent” or open). In these infants it can cause problems since some of the pumping effort of the heart is wasted because the left heart is pumping part of the blood into the lungs (unnecessarily). A Patent Ductus Arteriosus(or PDA) is a common heart problem and occurs in many infants(up to 8% of infants may have a PDA)–especially infants that have other heart problems and infants that are born prematurely.
Reasons why a Patent Ductus Arteriosus(PDA) is a problem:
The pulmonary blood flow is greater than normal which can cause high pressures in the pulmonary artery. The pulmonary artery is normally a low pressure system and the high pressures are an irritant that damages these blood vessels.
The left heart is pumping blood to the Aorta AND the pulmonary artery which is an extra workload on the left ventricle.
The patient has an increased risk of endocarditis–a bacterial infection of the lining of the heart.
The size of the Patent Ductus Arteriosus(PDA) determines the severity of the problems caused by the PDA. A large PDA means lots of extra flow and high pulmonary pressures. A small PDA may cause less serious problems. While most patients with PDA have few symptoms, a large PDA can cause signs of congestive heart failure which include:
- Congestion or fluid in the lungs
- Fast breathing
- Shortness of breath
- Heart murmur
- Enlargement of the heart
- Fatigue with exercise
- Increased chances of developing pneumonia
- Poor growth or weight gain
- Poor feeding (infant tires while feeding)
How do you diagnose a PDA?
Chest X-ray: pulmonary arteries, pulmonary veins, and left heart are larger than normal. Also, the ascending aorta may be enlarged.
Echocardiography: This is an ultrasound image of the heart which shows continuous flow from the aorta into the main pulmonary artery through the PDA.
Listening with a stethoscope: A heart murmur may be heard with a large PDA.
How is a PDA treated?
Medication such as indomethacin is often used to cause PDA closure. Indomethacin will often be all that is needed to make a PDA close. Ibuprofen is also given to cause PDA closure and both of these drugs work by inhibiting prostaglandins in the bloodstream-the naturally occurring prostaglandins may keep the PDA open. Drugs such as indomethacin are not without some risks and may cause decreased kidney function, bleeding into the gastrointestinal tract, bleeding into the brain, and problems with blood clotting.
Cardiac catheterization procedures can be performed by a pediatric cardiologist to make a PDA close. A small tube or catheter is inserted through a blood vessel in the leg and a coil or other device is released into the PDA to block blood flow through the vessel.
Surgery is also an option to close a PDA if the first medication or cardiac catheterization are not possible. The patient has a small incision in the chest and a surgical clip or a suture is used to clamp the vessel shut.
All of these approaches have risks and benefits, so the choice of treatment is tailored to the individual needs. The PDA should be closed before permanent damage is done to the heart or lungs. Also it my need to be closed if the infant is not eating and growing normally. If the child appears fairly healthy it is usually done when they are between 6 months and 3 years old.
