Patent Ductus Arteriosus

Disclaimer: this page is dedicated at the assessment of the PDA by echocardiography. It is not meant to discuss therapeutic strategies in the context of left to right PDA. There is current controversy in the literature regarding management strategies in the preterm newborn with a patent left to right ductus.

In the Patent ductus arteriosus view - modified upper parasternal short axis view - one may appreciate the patency of the ductus, its configuration, its course, its size and the direction fo the trans-ductal flow. Measurement should be at its narrowest diameters (usually closer to the pulmonary arterial end). Doppler (CW) should be done in order to evaluate its direction and velocity. A large ductus may be associated with rapid equalization of pressure on both side and with low velocity of flow. A restrictive small ductus with low velocity may be indicative of PA pressure closer to Aortic pressure. The large PDA will lead to rapid equalization of pressure on both side. As such, the PDA may be associated with excessive systolic and diastolic pressure and flow in the pulmonary compartment.

Left to Right Patent Ductus Arteriosus

2D view of a large patent ductus arteriosus (PDA) connecting from the main pulmonary artery (MPA) to the Aorta (Ao). The right (RPA) and left pulmonary artery (LPA) are visualized as well.

Colour box on the PDA confirms the left to right direction of the shunt (flow coming towards the probe; from the Ao to the MPA).

Example of left to right PDA by Colour Doppler

Example of left to right PDA by Colour Doppler

Diameter of the PDA

Measurement of the PDA at its narrowest point. Often, the PDA diameter is indexed to the left pulmonary artery diameter (or to weight).

Other example of PDA view with RPA, LPA and PDA.

Other example of PDA view with RPA, LPA and PDA.

Diameter of a small ductus measured in 2D and seen in colour on the right panel.

Small restrictive PDA by 2D ultrasound and restrictive profile (high-velocity) obtained by CW-Doppler.

In this A4C, the patient with a large PDA left to right has subjective increased LV size and LA size. This is secondary to the increased Qp:Qs with increased pulmonary venous return. The LV/LA dilation may lead to mitral regurgitation and, eventually, appearance of aortic insufficiency. Indeed, with dilation of the structures, these valves may loose some degree of coaptation.

Supra-sternal view to evaluate the arch in the context of large PDA. Presence or absence of underlying coarctation is always a chalenge when the ductus is open. Coarctation may progressively worsen as the ductus closes. PDA progressive closure may further tightened the tissue that surrounds the coarctation shelf. Indicators of coarctation are: posterior shelf, narrow isthmus diameter compared to transverse arch, the presence of bidirectional or right to left shunting via the ductus or a persistent forward flow during diastole by CW or PW Doppler in the descending aorta.

LA/Ao ratio

Large left atrium in the parasternal long axis view. M-Mode may be applied to measure the LA:Ao ratio.

M-Mode of the LA:Ao ratio. Measurement is usually done at aortic valve closure. Increase ratio may be indicative of increased LA diameter (or decreased Ao diameter, or both). Patients with large inter-atrial defect may not have LA dilation if there is sufficient unloading of the LA into the RA via the inter-atrial septum. As such, this is only one of the markers indicative of increased Left to right shunting via the PDA.

PDA Doppler Profile

Unrestrictive Doppler profile of a Left to right PDA. There is rapid equalization of pressure with a low diastolic velocity profile.

Unrestrictive L to R PDA, gradient of 19 mmHg at peak of systole. Rapid pressure transmission to pulmonary vasculature

Doppler Profile in Aorta, Cerebral Artery and Celiac Artery

Subcostal view indicating holo-diastolic retrograde flow in the context of a large left to right PDA with diastolic steal effect.

Subcostal view indicating holo-diastolic retrograde flow in the context of a large left to right PDA with diastolic steal effect.

Various degree of holo-diastolic retrograde flow in the descending abdominal aorta in the context of diastolic steal in patients with left to right PDA.

Holo-diastolic retrograde flow in the descending aorta observed in the subcostal view (PW-Doppler). This can be seen in a conditions with diastolic steal - such as significant left to right shunting via the PDA, as well as other cause of diastolic steal (Vein of Galen malformation, severe aortic insufficiency, aorto-ventricular tunnel, AP window, truncus arteriosus, etc.).

Anterior Cerebral Artery (ACA) PW-Doppler indicative of holo-diastolic retrograde flow. Resistive index (RI), where RI = (Peak Systolic Velocity - End Diastolic Velocity / Peak Systolic Velocity), can be calculated on the ACA or MCA Doppler. A RI > 0.80 has been associated with decreased diastolic velocities relative to systolic velocities in the context of diastolic steal effect from the PDA (or from other conditions with diastolic steal). When retrograde, velocity are considered negative. When absent, they are considered 0, and as such, the RI =1. Here, RI is 1.31.

In contrast, this is a patient with normal ACA flow pattern, with a RI = (0.31-0.09)/0.31 = 0.71. As such, the profile has forward diastolic flow.

Sweep from the anterior fontanelle in sagittal view of the neonatal brain. One may observe the lateral ventricles and the anterior cerebral artery pulsation by colour ultrasound.

Normal flow in the anterior cerebral artery. Normal diastolic flow (forward) in an extreme premature newborn.

Flow in the anterior cerebral artery by colour ultrasound.

ACA PW-Doppler indicating some decrease end-diastolic flow.

Subcostal view of the descending aorta with colour flow. An umbilical arterial catheter is observed with the tip at the level of the diaphragm. The flow in the celiac artery is seen.

Sweep in the subcostal view outlining the flow in the celiac artery.

Normal flow in a celiac artery obtained in the subcostal view. In patients with significant diastolic steal, one may also observe absence end-diastolic flow, or reverse diastolic flow.

Example of celiac artery PW-Doppler indicating that there is absent end-diastolic flow in the context of a patient with a large left to right PDA.

Celiac artery flow with adequate diastolic flow.

In this patient, one can appreciate absent end-diastolic flow, or decreased diastolic flow.

Absent end-diastolic flow in the celiac artery.

2D and Colour ultrasound for visualization of the celiac artery coming off the descending abdominal aorta.

Restrictive Left to Right PDA

Left to right PDA with a different configuration that is tortuous. Sweep outlining its path from the Ao to the PA.

Example of a sweep with colour of a small restrictive left to right PDA.

Example of high velocity restrictive profile of the left to right PDA. Here the gradient is estimated at 49 mmHg. One shall beware that the Bernoulli equation may under or over-estimate since the PDA is not a pinpoint structure, but rather a tubular structure.

Example of high velocity restrictive profile of the left to right PDA. Here the gradient is estimated at 27 mmHg.

Small restrictive PDA left to right.

Restrictive PDA left to right, with a peak systolic gradient of 14 mmHg between the Ao and PA.

Small restrictive PDA left to right.

Restrictive L to R low-velocity PDA, gradient of 6 mmHg at peak of systole. PA pressure infra-systemic but 6 mmHg less than systemic. This may be secondary to systemic low pressures, increased pulmonary pressures, or a mix.

Left to Right PDA Scoring Systems

Signifiance of the PDA (Left to Right) by Sheperd and Noori:

Stead Family Children’s Hospital, Iowa City - PDA screening and management guideline for ELBW infants - Available from the NHRC website

Left to Right ductus is considered significant if:

  • Ductal diameter is > 1.5mm AND

  • Predominant (>90%) left-to-right transductal flow AND

  • PDA shunt volume score is ≧ 6

PDA significance table from the NPE/TNE Teaching manual - The Rotunda Hospital, Dublin, Ireland - Available on the NHRC website

Assessing the "need" for PDA ligation

Application of NPE in the assessment of a patent ductus arteriosus (van Laere D et al.). Pediatric Research (2018) 84:S46 – S56

Bidirectional PDA

Bidirectional PDA by Colour.

Right to left gradient in systole indicating that PA pressure are 30 mmHg higher than Ao pressure at peak of systole.

Examples of bidirectional flow via the ductus. This profile may be seen in the context of iso-systemic PA pressures. This could be secondary to high pulmonary pressures, low systemic pressures, a mix, or a large PDA with rapid equalization of pressure on both side of the PDA.

Examples of large PDA with bidirectional shunts. On the first clip, one may appreciate the retrograde flow in diastole within the descending aorta.

Right to left PDA

Right to left PDA indicating that there is supra-systemic PA pressure. This could be due to increased PA pressure, low systemic pressure or a mix of both component.

Example of CW-Doppler in the Right to Left PDA, indicating that the PA pressure is 46 mmHg above the Ao pressure at peak of systole.

Large PDA right to left

Right to left PDA (restrictive profile) with peak at a gradient of 31 mmHg (peak of systole).

Restrictive right to left PDA

Patient with restrictive right to left ductus, with a diagnosis of severe acute pulmonary hypertension.

The same patient with now a bidirectional PDA after initiating therapies for the acutre PH.

Newborn with unrestrictive right to left ductus found in the context of severe hypoxic respiratory failure. Patient was started on iNO and PDA became bidirectional. Inhaled nitric oxide weaned rapidly after reversal of shunt.

Right to left ductus (unrestrictive)

Doppler (right to left) - Continuous Wave

Right to left ductus (unrestrictive)

Bidirectional PDA (unrestrictive) - after iNO exposure.

Bidirectional PDA (CW-Doppler) - after iNO exposure.

Bidirectional PDA (Color M-Mode)

Created by Gabriel Altit - Neonatologist / Créé par Gabriel Altit (néonatalogiste) - © NeoCardioLab - 2020-2021 - Contact us / Contactez-nous