Patent ductus arteriosus: Patent ductus arteriosus (PDA) is a communication between the pulmonary artery and the aorta. This communication is normal present before birth (ductus arteriosus), but closes soon after birth. But if it remains patent, it leads to abnormal blood flow from the aorta to the pulmonary artery and the lungs. The extra blood returns from the lungs to the left atrium and then into the left ventricle. Patent ductus arteriosus overloads the left ventricle, which can fail in infancy.

Is PDA more common in premature infants?

Yes PDA is more common in premature infants. The more premature the baby, the higher the chance of having a PDA. Normally ductus arteriosus closes after birth in response to the higher oxygen content of blood once baby starts breathing. This response of ductus arteriosus to oxygen is not well developed in the premature baby. It does not respond well to the increased oxygen content in blood after birth. Often these respond to medications so that no surgery is required to close the PDA in a premature infant.

Should all PDAs be closed?

Many PDAs close spontaneously in infancy. Others can be closed by medications. Some of them may persist and produce heart failure due to the excessive blood flow through the lungs which return to the left atrium (upper chamber) and the left ventricle (lower muscular chamber). These have to be closed either by devices or by surgery. Device closure is done in a cardiac catheterization laboratory while surgery is done in an operation theater.

How is PDA detected in an infant?

Small PDAs will not produce any symptoms. They produce a heart murmur which is picked up by the doctor and the baby is examined for another reason, usually when the baby has fever. Very large PDAs may produce only soft murmurs, but they cause cardiac failure and baby develops breathlessness, poor weight gain and head sweating. Lower part of chest wall can be seen retracting during breathing due to the heavy water logged lungs due to heart failure. The diagnosis is usually confirmed by ultrasound examination of the heart (echocardiography).

Very small PDAs without a heart murmur can be detected during routine echocardiography. But they are generally left alone because they seldom produce any problems.