5 Keys to Assessing a Patent Ductus Arteriosus in Preterm Infants

A patent ductus arteriosus (PDA) is a common condition in premature babies. But when should a PDA be treated—and when will it close on its own? Finding that answer is often not a simple task.

“It’s challenging because there still is no universally accepted definition of a hemodynamically significant PDA,” notes Shahab Noori, MD, MS CBTI, RDCS, a neonatologist at Children’s Hospital Los Angeles and an international expert in neonatal hemodynamics. “And a standard echocardiography report may not contain enough information to make that decision.”

To help neonatologists better evaluate PDAs in these babies, Dr. Noori and CHLA neonatologist Caroline Noh, MD, MSEpi, were among the co-leaders of a special hands-on training April 28 at the 2025 Pediatric Academic Societies meeting in Honolulu.

The training, which included 15 manikin-based echocardiographic simulators, focused on how to use targeted neonatal echocardiography (TNE) to assess the significance of a PDA. Dr. Noori, Dr. Noh, and Jennifer Shepherd, MD—Medical Director of the Steven & Alexandra Cohen Foundation Newborn and Infant Critical Care Unit (NICCU) at CHLA—share five key takeaways.

1. Measure the direction and magnitude of the shunt.

When using TNE, one key factor to evaluate is the flow pattern of the PDA, or shunt. Two patterns to watch out for: a growing or pulsatile left-to-right shunt, with blood flowing from the aorta to the lungs.

“A shunt that is going in that direction means there is too much blood going to the lungs, often causing pulmonary edema and a need for more ventilatory support,” Dr. Noori says.

Neonatologists can also use TNE to measure the diameter of and pressure across the ductus, which will help them estimate the amount of that flow—an important factor in the assessment. “For example, if the shunt direction is left to right, but there’s little pressure difference between the two circulations, then not a lot of blood is getting through,” he notes.

2. Assess heart and pulmonary volume overload.

The degree of left heart volume overload can help determine if a PDA is hemodynamically significant. “But it’s important to interpret volume overload in the broader clinical and echocardiographic context,” says Dr. Shepherd. “Certain measurements may be high or low due to other cardiac factors.”

In addition, left pulmonary artery flow dynamics can help identify too much blood flow in the lungs. One marker of this overflow: an increased end-diastolic flow velocity (greater than 20 centimeters per second).

3. Look for a ‘steal phenomenon.’

“A steal phenomenon means that the blood that was supposed to go to the body is going to the lungs, so other organs such as the kidneys may be receiving less blood flow than they should,” Dr. Noori explains.

TNE can estimate the amount of this reduced blood flow to the body, which can lead to shock. Blood flowing toward the heart in the descending aorta—combined with a ductus diameter of 1.5 millimeters or above—often indicates a hemodynamically significant PDA in extremely preterm infants.

4. Consider the patient’s age.

It’s important to put any echocardiographic findings in the context of the individual baby, including whether the baby requires mechanical ventilation. One key factor is age—both gestational and chronological.

“A significant ductus for a baby born at 28 weeks is different than one born at 23 weeks, and it’s different for one born at 23 weeks who is now 2 weeks old,” Dr. Noh says.

For example, extremely preterm infants born at less than 26 weeks have the highest risk of having a PDA that does not resolve on its own. Studies have shown that spontaneous closure can take a median of 71 days in these infants. Given this high risk, the threshold for treating a PDA should be lower in those patients.

5. Seek advanced training.

While the PAS training was an excellent introductory course, the CHLA team recommends that neonatologists seek out additional in-depth training and find a mentor—either from cardiology or neonatology—who can guide them.

“It’s important for neonatologists to have this skill because they are the ones at the bedside, and they have a more comprehensive picture of what is going on with the baby,” Dr. Shepherd says.

Dr. Shepherd and Dr. Noori also co-authored a paper, published in 2018, that details specific echocardiographic values and markers that can help physicians determine when a PDA is hemodynamically significant, requiring treatment.

“Neonatologists sometimes have concerns that doing these point-of-care echocardiograms will make the baby unstable,” Dr. Shepherd adds. “But in the hands of an experienced neonatologist, these studies can be done very quickly and safely. They provide invaluable information to help make the best treatment decision for each baby.”