A patent ductus arteriosus is a heart defect that occurs when a blood vessel called the ductus arteriosus fails to close after birth, as it normally should.

The ductus arteriosus is an open channel in the heart present in every fetus. It allows blood to bypass the lungs, which are not used by a baby until after birth. Shortly after the baby’s first breath, the ductus arteriosus should close permanently, thus forcing blood into the lungs. If it does not, it is known as a patent, or open, ductus arteriosus (PDA).

Except for cases in which the baby has certain other heart defects that actually benefit from the presence of a PDA (e.g., tetralogy of Fallot), this condition can be harmful. If the PDA is very small, it may cause only mild symptoms or no noticeable symptoms. However, larger PDAs lead to breathing difficulty by the infant and poor growth. Particularly large PDAs can flood the lungs with blood, leading to acute heart failure.

Approximately 35,000 babies are born each year in America with heart defects, according to the American Heart Association. PDA is slightly more common among babies born at high altitudes and among females. It is most prevalent among premature and very low birth-weight (VLBW) babies. However, treatment is available. In premature infants, most PDAs can be closed with medication. Medication is not effective in full-term infants and older children, but catheter-based procedures or surgery is used to close the PDA in these patients.