Trans-Catheter PDA Closure

PDA measurements in anticipation of cath-based closure

These measurements are obtained on the intra-procedural (or immediately pre-procedural) transthoracic echocardiogram to give the interventionalist the numbers required for device type and size selection, and to establish the baseline flow velocities against which a satisfactory deployment is judged. Whenever possible, echo and angiographic measurements are used together; if the two disagree, device sizing is generally based on the modality giving the larger dimension, because instrumentation-induced ductal spasm and TTE length underestimation both bias toward undersizing (Sathanandam et al., Pediatric Cardiology, 2021).

Window and image optimization

1. Use the high left parasternal short-axis window — the "ductal view" — with the duct elongated along its long axis (Mohammad Nijres et al., Pediatric Cardiology, 2025; Paudel et al., Journal of the American Society of Echocardiography, 2021).

2. Optimize a 2D grayscale/B-mode image first. Make all primary caliper measurements on 2D without color when image quality allows; add color Doppler only when the unenhanced 2D image does not permit satisfactory quantification of the narrowest segment (Mohammad Nijres et al., 2025).

3. Obtain a full cine loop rather than a single frame so the narrowest reproducible segment can be selected.

The three device-defining measurements - Report all three, labeled clearly, in millimeters:

1. Narrowest ductal diameter (pulmonary end). The single most important number for device size — it is usually located at or near the junction of the PDA with the main pulmonary artery. Measure the narrowest internal diameter, inner edge to inner edge, perpendicular to the long axis of the duct (Mohammad Nijres et al., 2025; Paudel et al., 2021). TTE agrees closely with angiography for this dimension (mean difference ≈ 0.4 mm), so it is the most reliable echo-derived input for sizing (Mohammad Nijres et al., 2025).

2. Aortic end / ampulla width. Measure the diameter at the insertion of the PDA into the aorta. Note that TTE tends to underestimate this dimension relative to angiography, so interpret it as a lower bound (Paudel et al., 2021; Mohammad Nijres et al., 2025).

3. Ductal length. Measure from the aortic end to the pulmonic end. A straight-line length underestimates the true (angiographic) length; a curvilinear trace following the axis of the duct matches angiography much more closely and is preferred when the duct is non-tubular (Paudel et al., 2021). Report the method used.

Timing convention

For transcatheter sizing, these dimensions are conventionally measured in systole, when the duct is maximally distended (Mohammad Nijres et al., 2025; Paudel et al., 2021). This differs from the end-diastolic convention used for HsPDA characterization; state the timing explicitly in every report so the two contexts are not confused.

Baseline velocities to record before deployment

Document these as the reference for judging the result after device release:

• Left pulmonary artery (LPA) origin peak velocity.

• Proximal/descending aortic peak velocity.

A satisfactory deployment is defined as an intraductal device position with no residual peri-device shunt, no device-related LPA obstruction (LPA peak velocity < 2.5 m/s), and no device-related descending aortic obstruction (descending aorta peak velocity < 2.5 m/s) (Baruteau et al., JACC Advances, 2024).

Morphology to communicate to the interventionalist

• Ductal shape/type (e.g., conical/type A vs. tubular/type F), since morphology influences whether a given occluder is appropriate — some morphologies are poorly suited to a particular device (Sathanandam et al., 2021).

• Shunt direction and flow pattern on color and pulsed-wave Doppler.

• The angle of the duct into the descending aorta, which affects the risk of aortic-disc protrusion and coarctation, particularly in the smallest infants (Sathanandam et al., 2021).

Reproducibility and reporting

• Select the narrowest reproducible frame; avoid the color-bloomed jet as the primary diameter, as color overestimates luminal width.

• Where feasible, have measurements confirmed by a second reader from the same clip, given documented interobserver variability.

• In the final report, list: narrowest diameter, aortic-end width, length (with method), LPA and descending-aorta baseline velocities, ductal type/morphology, shunt direction, and the measurement timing convention used.

Post-deployment confirmation (pre-release checklist)

Before device release, confirm on TTE: intraductal position with no significant residual shunt or flow acceleration; LPA peak velocity < 2.5 m/s; descending aorta peak velocity < 2.5 m/s. After release, reassess for new or worsening tricuspid regurgitation and for pericardial effusion (Baruteau et al., 2024; Wei et al., Catheterization and Cardiovascular Interventions, 2025).

Why undersizing is the dominant hazard

The most common causes of device embolization are improper positioning and selection of a waist smaller than the minimal ductal diameter — most often when ductal spasm or poor imaging causes underestimation of the true diameter. This is the practical reason to size to the larger of your echo and angiographic measurements: both TTE underestimation and instrumentation-induced spasm bias toward undersizing. Conversely, in infants >2 kg with a vasoactive, high-flow, conical duct, embolization risk is actually higher than in smaller infants with a tubular duct. 

Device availability across morphologies: The Piccolo was the single most-used device in the IMPACT registry of infants ≤2 kg (44.2%), but roughly a quarter received a microvascular plug, and others the ADO II AS or AVP II — reflecting that ductal morphology, not just diameter, drives final device choice. The figure in the article by Sathanandam SK et al. catalogs the available Piccolo waist/disc/length combinations against a scale ruler, which is the practical reference for matching a measured narrowest diameter to a device size. One caveat worth flagging: no fixed millimeter oversizing formula is published for the ≤2 kg population equivalent to the ">50% larger" rule used above 2 kg — sizing in ELBW infants is governed by the manufacturer's weight- and diameter-indexed chart plus the requirement for complete intraductal seating, rather than a single oversizing percentage. 

Indications and Complications to consider

Complications of Persistent PDA in term or post-term infants:

If a large PDA persists and causes significant left heart dilation, it can ultimately lead to cardiac failure. Long-term, unrepaired large shunts can cause permanent damage to the pulmonary arteries, leading to pulmonary hypertension and potentially Eisenmenger syndrome. PDA is also a predisposing factor for infective endocarditis due to turbulent blood flow. Less commonly, especially in adults, aneurysms of the ductus arteriosus and aortic dissections have been described.

Treatment of Persistent PDA

Historically, surgical ligation or section/suture was the preferred treatment for PDA. The first surgical closures date back to the early 20th century, and surgery remained the primary option until the late 20th century, including for premature infants from the 1970s. The surgical approach typically involves a left posterolateral thoracotomy, allowing access to the ductus under the scapula. Surgical complications can include haemorrhage due to proximity to large vessels. There is also a risk of nerve damage, particularly to the left recurrent laryngeal nerve (leading to vocal cord paresis or paralysis) and the left phrenic nerve (causing diaphragmatic paralysis). Injury to the thoracic duct, which drains lymph, can result in chylothorax (persistent fatty drainage). Although rare, inadvertent coarctation of the aorta or closure of the left pulmonary artery or aortic arch during surgery has been reported. In premature infants, surgery can significantly major their haemodynamic and respiratory instability due to positioning and manipulation of the lung. Currently, percutaneous closure via catheterization is the emerging standard for treating PDA in most patients at term or post-term. The first descriptions of catheter-based closure date back to the 1990s. This method avoids a surgical scar and allows for the closure of increasingly larger ducts in smaller infants using a variety of available prostheses, such as Amplatzer Duct Occluders (ADO 1, ADO 2, Piccolo) or coils.

Indications for PDA closure in term or term-corrected age newborns generally include:

• Symptomatic PDAs or large PDAs with evidence of significant Qp:Qs (e.g., left heart dilation).

• It is contraindicated to close a PDA that is bidirectional or exclusively right-to-left, as this indicates severe pulmonary hypertension where the ductus acts as a vital "safety pop-off valve".

Complications of percutaneous closure include:

• Prosthesis migration or embolization, which can obstruct the pulmonary artery or aorta.

• Iatrogenic coarctation or left pulmonary artery stenosis if the prosthesis is too large or extends beyond the ductal opening.

• Residual shunts (either through or around the prosthesis) are common but often resolve. However, persistent periprosthetic shunts may indicate an inappropriate prosthesis choice. Residual shunts can also cause haemolysis.

• Local complications at the access site, such as aneurysms, arteriovenous fistulas, or haematomas. Vascular injury to the limb. 

• Infections, bleeding. 

• Anesthesia complication.

• Valvular injury, myocardial injury. 

• Tricuspid regurgitation (due to guide wire trauma to chordae or leaflets). Other risks include failure to close the ductus (if it's very spastic or large, or if closure risks creating a coarctation or pulmonary artery stenosis), prosthesis embolization, and local access site complications.

• The success rate of percutaneous closure is generally over 95%. Recent advancements include the increasing use of venous access instead of arterial access (especially in small infants) to reduce the risk of arterial complications. Miniaturized and standardized equipment has enabled closure in very small infants. The ultimate goal is to perform echo-guided closures without the need for contrast injections or X-ray radiation.

• For specific ductus-dependent congenital heart conditions (e.g., tricuspid atresia, pulmonary atresia), it may be necessary to keep the ductus arteriosus open. This can be achieved through stenting of the ductus via catheterization. However, these stents often require repeated redilations as the child grows.

Intraprocedural echocardiographic criteria 

Intraprocedural echocardiographic criteria used to confirm satisfactory Amplatzer Piccolo Occluder position before device release, including thresholds for aortic and left pulmonary artery obstruction:

Satisfactory position before release is confirmed by four echocardiographic criteria: 

1. Complete ductal occlusion with no peri-device residual shunt (a central shunt through the device is acceptable, a shunt tracking around the device is not), 

2. A stable device with correct intraductal shape and orientation, 

3. No aortic obstruction, and 

4. No LPA obstruction — with the key numeric threshold being a Doppler velocity >2.5 m/s combined with an obstructive flow pattern signaling protrusion that warrants repositioning. These criteria come primarily from the Sathanandam et al. (reference above)

Pre-release imaging maneuver

Before assessing position, pull the delivery catheter back so the floppy segment of the delivery wire is exposed, removing superior tension on the device — this same maneuver is repeated immediately before release. Do not release if position is unstable or if device shape/orientation is incorrect. A recognized trade-off exists: spending too long on TTE while the device is still attached can pull it anteriorly out of position, so assessment must be efficient.

Residual shunt criteria

• A central residual shunt through the device body on color Doppler is acceptable and expected to occlude over time.

• A shunt seen to track around the device indicates either an undersized device or malposition — reposition and reassess. If the peri-device shunt persists despite correct orientation, upsize by one device size.

• Baruteau et al. add that persistent antegrade diastolic flow or color aliasing on adjacent vessels should also trigger reloading/repositioning.

Aortic and LPA obstruction thresholds

• The actionable intraprocedural threshold is a Doppler velocity >2.5 m/s with an obstructive waveform pattern plus 2D/color evidence of protrusion — this should not be ignored and warrants repositioning if it can be done safely.

• Expected normal post-closure pattern: descending aortic velocity typically decreases, LPA velocity increases slightly, and in most cases remains below 2 m/s.

• Intraprocedural Doppler velocity alone is not a fully reliable predictor of later obstruction and must be integrated with 2D/color imaging and the other landmarks.

• If aortic or LPA protrusion is present, recapture the entire device and reposition to an intraductal position. A partial-recapture "packing" redeployment can work for LPA protrusion but is discouraged for aortic obstruction, where complete recapture is recommended. If it cannot be repositioned, the device is likely too large — downsize or pursue an alternative.

Note the commonly cited grading scale for obstruction severity (from Tomasulo et al.): none <1.5 m/s, mild flow acceleration 1.5–2 m/s, and stenosis/coarctation >2 m/s — a slightly lower cutoff than the >2.5 m/s intraprocedural repositioning trigger, reflecting that the two serve different purposes (severity grading vs. intraprocedural action).

Adjunctive confirmations (especially when no arterial access for aortography)

• Assess femoral pulses and lower-extremity pulse oximetry before and after deployment to detect aortic obstruction; compare upper- vs lower-extremity blood pressure (a differential ≥20 mmHg is significant).

• Use fluoroscopic landmarks: the esophageal temperature probe/NG tube marks the aortic isthmus/ampulla, and an SVC central-line tip marks the PA end of the duct — the device should sit entirely intraductal between them in infants ≤2 kg.

• After release, do not advance the wire/catheter (embolization risk), and continue monitoring for several minutes before sheath removal, with repeat TTE attention to tricuspid valve function and the pericardial space.

Review Presentation PDF on Trans-Catheter Ductal Closure

During the Neonatal Cardiology Academic Rounds of April 17, 2024 at the Montreal Children's Hospital, Dr. Mohammed Alamer (Pediatric Interventional Cardiology Fellow) and Mrs. Laila Wazneh (Neonatal Nurse Practitioner) presented "Trans-Catheter Ductal Closure – What the NICU Should Know" to our group. This topic, a focal point of active research, involves considerable debate regarding the optimal timing, candidates, and methods for addressing patent ductus arteriosus (PDA) in premature infants in the NICU. They provided a thorough review of the practical considerations for trans-catheter ductal closure. The presentation is available here. This presentation was not intended to guide patient selection or promote a specific approach but offered insights into the realities and perspectives of interventional cardiologists concerning the procedure, the data available from published studies, and the aspects to monitor post-procedure if this method is chosen for certain patients. Our site practices a conservative approach to duct management in premature infants, pending further data from trials on mechanical closures using a trans-catheter method. We described a high spontaneous closure rate in our population with only about 10% of our cohort, who have large residual shunts that do not close spontaneously, with follow-up in cardiology, and intervention considered by a handful of these patients from our cardiology colleagues just before or after discharge.

Lors des séances académiques de cardiologie néonatale du 17 avril 2024 à l'Hôpital de Montréal pour enfants, le Dr Mohammed Alamer (fellow en cardiologie pédiatrique et interventionnelle) et Mme Laila Wazneh (infirmière praticienne néonatale) ont présenté à notre groupe "Fermeture ductale par cathéter - Que doit savoir la NICU ?". Ce sujet, au cœur de recherches actives, suscite de vifs débats concernant les candidats appropriés, le moment optimal et les méthodes pour traiter le canal artériel persistant (CAP) chez les prématurés en NICU. Ils ont effectué une revue approfondie des considérations pratiques concernant la fermeture ductale par cathéter. Cette présentation est disponible ici. Cette présentation n'avait pas pour but de fournir des directives sur la sélection des patients ni de préconiser une approche spécifique, mais elle a offert des perspectives sur la réalité et le point de vue des cardiologues interventionnels concernant la procédure, les données disponibles issues des études publiées et les éléments à surveiller après la procédure si cette méthode est choisie pour certains patients. Nous avons une approche conservatrice de la gestion du canal chez les prématurés, en attente de données supplémentaires issues d'essais sur les fermetures mécaniques par méthode trans-cathéter. Nous avons décrit un taux de fermeture spontanée élevé dans notre population avec seulement environ 10 % de notre cohorte, qui présentent des shunts résiduels importants qui ne se ferment pas spontanément, avec un suivi en cardiologie et une intervention envisagée par une poignée de ces patients de la part de nos collègues en cardiologie. juste avant ou après la sortie.