Patent ductus arteriosus (PDA) is the failure of a duct, or passageway, between two specific blood vessels to close. The blood vessels involved are the pulmonary artery and the aorta, two of the largest arteries in the body. It is a congenital heart disease, or a heart defect present at birth.

What is going on in the body?

The pulmonary artery carries blood to the lungs. The aorta receives all the blood from the left ventricle of the heart and sends it to the rest of the body. In the normal heart, the passageway that connects these two blood vessels, called the ductus arteriosus, closes soon after birth. The closing of the duct helps keep the blood flowing in the right direction.

If the duct does not close, patent ductus arteriosus results. In PDA, some of the blood flows out of the aorta back into the duct instead of going to the rest of the body. This forces the lungs and heart to work much harder.

What are the causes and risks of the condition?

The cause of patent ductus arteriosus is unknown. One theory about the cause of PDA has to do with the action of a chemical made by the body. In the normal heart, levels of this chemical drop, and the duct closes soon after birth. But in PDA, the chemical remains active, and the duct stays open. The rubella virus has also been associated with a higher risk of developing PDA.