The ductus arteriosus is an opening between the two large blood vessels (the aorta and the pulmonary artery) leading out of the heart to the body and lungs. The ductus arteriosus normally closes shortly after birth. If it remains open after birth, it is called patent ductus arteriosus (PDA).
The ductus arteriosus in the fetus
Before birth, every fetus has this opening. Blood that is rich in oxygen flows to the fetus from the placenta. Since that blood does not need to pass through the lungs of the fetus to get oxygen, the blood is diverted away from the lungs to the rest of the body through the ductus arteriosus.
The ductus arteriosus after birth
After birth, as blood stops flowing from the placenta via the umbilical cord, the ductus arteriosus begins to close rapidly. It starts closing in minutes to hours after birth and is completely sealed and replaced with scar tissue in a few weeks, never to open again.
With some premature babies, this process of closure either does not happen at all or does not happen sufficiently, leaving a small opening. As a result, normal blood flow is affected. This condition is called patent ductus arteriosus (PDA). “Patent,” in this context, means “open.”
Signs and symptoms of PDA in babies
The signs and symptoms of a PDA depend on how much blood flows through it and on the effect that it has on a baby’s circulation and breathing.
Often, the first sign of a PDA comes from the sound of the baby’s heart and blood flow heard through an ordinary stethoscope. Blood flowing through a PDA is usually turbulent and will make a typical sound called a continuous murmur that can be heard through a stethoscope. At times, however, a PDA can be silent. If the opening is very large, sometimes there may not be any turbulence to cause a detectable murmur.
Babies with larger PDAs may have more strain on their heart and lungs if their heart must work harder to deliver oxygen to the body and if too much blood flows to their lungs through the PDA. They may develop symptoms such as breathing difficulty, very strong or bounding pulses that can appear in the leg or wrist, low diastolic blood pressure (i.e., low blood pressure when the heart relaxes between beats) and fast heart rates.
As the heart must work harder to oxygenate the body, it tries to compensate by pumping harder, which may lead to an increase in its size.
How common is PDA?
This condition is more common among extremely premature (less than 28 weeks' gestation) or extremely low–birthweight babies (birth weight less than 1000 grams).
How is PDA diagnosed?
While the health-care team may suspect a PDA based on a baby’s murmur, heart rate, pulses, blood pressure and breathing difficulty, a PDA is confirmed with an echocardiogram (echo). An echo is similar to an ultrasound and can provide more detailed information about the PDA, including its size, the amount of blood flowing through it and the effect of the PDA on the size of the chambers of the heart and amount of blood flow to other organs.
How is PDA treated?
Treatment for a PDA depends on the size of the opening and the effect the opening is having on the baby’s lungs and circulation.
The goal of treating a PDA is to close the blood vessel, allowing a normal supply of blood to the lungs and body. There are several ways to close a PDA. If the opening is small and the consequences of the abnormal blood flow are minimal, management of symptoms and giving the PDA time to close on its own may be all that are necessary. If the opening is large and abnormal blood flow is creating more significant problems with breathing and circulation, the health-care team may try to speed up the closure of the PDA using medication or a procedure.
PDA management and spontaneous closure
If a PDA is small and not interfering with blood flow to any great extent, waiting for it to close on its own (spontaneous closure) may be the best strategy. Most babies born with a PDA fit into this category. Under normal circumstances, a PDA will close within a few days. It may be that the premature baby needs extra time for the PDA to close on its own. Spontaneous closure is common, especially in babies who are only mildly premature.
Sometimes, the health-care team in the Neonatal Intensive Care Unit (NICU) will help a baby while waiting for the PDA to close. They may control the pressure of air flow and the volume of fluids given to a baby or administer diuretics to prevent too much blood flow to the lungs while ensuring enough blood flow to the vital organs.
Medications for PDA closure
If the PDA does not close on its own or it is large enough to be causing circulation or breathing problems, it may be closed with medication. There are several medications that can speed up the closure of a PDA. The most commonly used medication is ibuprofen. An alternative to ibuprofen is acetaminophen. In some babies, a repeat course of medication can be given if the first course of treatment does not close the PDA.
Closure of a PDA via cardiac catheterization or surgery
If medication is unsuccessful in closing a PDA or is not an option due to a premature baby’s medical condition, a PDA that is causing symptoms can be closed by other methods. There are two procedures that are available for PDA closure: percutaneous transcatheter PDA closure (performed by an interventional cardiologist) and surgical PDA ligation (performed by a paediatric cardiac surgeon). The method used to close the ductus arteriosus varies depending on the size of the baby, the size of the PDA and the effect the PDA is having on a baby’s heart and lungs. Each procedure has its own specific risks and benefits.
Possible complications of PDA
PDA may be associated with:
- bleeding in the lungs and brain
- chronic lung disease
- ventilator dependency
- pulmonary hypertension
- necrotizing enterocolitis
- acute kidney injury
What is the long-term outlook for children with patent ductus arteriosus?
In the vast majority of cases, when a PDA closes, it stays closed and there is a very low likelihood of the patent ductus returning. Babies with a small PDA that has not closed at the time of discharge from the NICU are referred to a cardiologist for outpatient monitoring and follow-up.