patent ductus arteriosus
Before birth, a short blood vessel called the ductus arteriosus acts as a bypass channel, letting blood skip the unused lungs by connecting the pulmonary artery directly to the aorta. It is meant to clamp shut within the first days after birth, like a temporary detour that is supposed to close once the main road opens. A patent ductus arteriosus is this detour staying stubbornly open.
After birth the lungs take over and pressures shift, so an open ductus now lets blood flow from the high-pressure aorta back into the pulmonary artery, a left-to-right shunt. A small one may be harmless, but a large persistent ductus overloads the lungs and left heart, producing a continuous machinery-like murmur, bounding pulses, and, in infants, fast breathing and poor feeding.
Closure can be encouraged with medication in premature newborns or achieved with a catheter-delivered coil or plug in older children and adults. Left open and untreated, a large ductus carries the same long-term risk of irreversible lung damage as other large shunts.
A premature infant with a continuous murmur and bounding pulses is diagnosed with a patent ductus arteriosus and treated with medication to encourage closure.
A continuous machinery murmur is the hallmark of a patent ductus arteriosus.
In a few rare congenital defects, an open ductus is briefly lifesaving because it is the only path for blood to reach the lungs or body; in such cases doctors may deliberately keep it open with medication until surgery.