Challenges in neonatal ductal stenting: When to avoid tortuous ducts and pulmonary artery stenosis

Abstract

Ductal stenting (DS) is the preferred palliative approach to the Blalock–Thomas–Taussig shunt (BTTS) for neonates with duct-dependent pulmonary circulation. However, appropriate case selection remains a critical challenge. This report explores the limitations of DS through illustrative examples and defines the subset in which neonatal DS is better avoided. Tortuous ducts increase the risk of procedural failure, ductal spasm, and pulmonary artery (PA) jailing. These can generally be managed with wire techniques and stiff wires. If extreme curvature persists despite these measures, it is best to abandon the procedure. Bilateral PA stenosis needs careful strategic planning and is often better managed surgically. Procedural risk is significantly high when both branch PA stenosis and tortuosity coexist, necessitating a BTTS. This pictorial report specifies anatomical substrates that are unsuitable for neonatal DS to improve safety and efficacy. It is intended as a visual reference for interventionists facing comparable clinical scenarios, particularly in early career.

INTRODUCTION

Ductal stenting (DS) is the preferred mode of palliation for neonates with duct-dependent pulmonary circulation. This stems from its advantages, which include ease of application, reduced resource consumption, shorter intensive care unit (ICU) and hospital stays, and better survival to the next stage compared to Blalock–Thomas–Taussig shunt (BTTS).[1,2,3,4] The technique of DS has been described in detail elsewhere.[5,6,7,8] A consistent challenge faced by interventionalists is appropriate case selection. The general condition of the baby (weight, prematurity, and sepsis), size of the duct at the pulmonary end (whether it is adequately constricted to allow safe stent positioning), and the origin and orientation of the duct from the aorta (site of origin, vertical vs. horizontal) are some of the important considerations.

Comprehensive preprocedure assessment in our setting has been described previously, which emphasizes the role of echocardiography. A computed tomography scan is used when the anatomy is unclear on echocardiography.[4] The degree of tortuosity and presence of branch pulmonary artery (PA) stenosis are perhaps the most challenging aspects of DS. This brief report aims to provide a practical framework for addressing these two specific aspects and to identify anatomies best avoided through illustrative examples.

CLINICAL SITUATIONS AND DISCUSSION

What level of tortuosity is acceptable for neonatal ductal stenting?

Neonatal vertical ducts in the setting of pulmonary atresia universally exhibit some degree of tortuosity, with rare exceptions. Tortuous ducts lead to failure of DS, PA jailing, and unintended re-interventions.[9,10,11] These are prone to ductal spasm during catheter-wire manipulations and can be lethal if not identified and acted upon quickly. Technical challenges include difficulty crossing the duct, inaccurate measurement of the intended stent length, and changes in ductal configuration during wire/stent positioning. Assessment of tortuosity has largely been subjective, further complicating case selection. Attempts have been made to quantify tortuosity objectively.[10]

It is best to cross a tortuous duct using a floppy coronary wire with medium support, like a Whisper extra support wire (Hi-Torque Whisper Extra Support: Abbott Vascular, Santa Clara, CA, USA). A micro-catheter may be used for additional support if required. A floppy, hydrophilic wire, such as Whisper MS (Abbott Vascular, Santa Clara, CA, USA) or Runthrough NS (Terumo Corporation, 2-44-1 Hatagaya, Shibuya-ku, Tokyo, Japan), may be necessary when the medium support wire fails to negotiate the turns. A second, stiffer wire is then passed alongside the first wire or exchanged over a micro-catheter (Hi-Torque Iron Man Extra Support: Abbott Vascular, Santa Clara, CA, USA/Choice PT extra support guide wire, Boston Scientific, 300 Boston Scientific Way, Marlborough, MA, USA). Tortuous ducts generally straighten out upon passage of a stiff coronary wire across. Once this occurs, stenting can proceed with the usual steps [Table 1]. Occasionally, a duct may remain significantly tortuous despite the passage of a stiff wire [Figure 1]. Our practice is to abandon DS and proceed with a neonatal BTTS in such a scenario.[9] DS has a significant learning curve. It would be prudent to avoid ducts with 360° turns and complex ducts with multiple turns early on.

Table 1.

Technical strategies for addressing challenging ducts

Cross with a floppy hydrophilic coronary wire

Guide and microcatheter support for crossing

Buddy wire technique: Place an additional stiff wire parallel to the first one

Exchange floppy wire for stiff wire using a microcatheter

Use coronary balloons with markers to assess optimal length

Use coronary stents with excellent trackability

Figure 1.

A 36-week-old preterm neonate weighing 2 kg with tetralogy of Fallot and pulmonary atresia (a). Angiogram through the 5 French access sheath placed through the right carotid artery. The ductus arteriosus is vertical and tortuous with a 360° turn (2a). Ductus was crossed with a whisper extra support and a choice extra support wire through a 5-French Judkins right coronary guide catheter. Despite the passage of two stiff wires across, the duct failed to straighten out (b). Stenting was abandoned. The baby underwent Blalock–Taussig–Thomas shunt with a 3.5 mm polytetrafluoroethylene graft electively

How to approach ductal stenting in the presence of branch pulmonary artery stenosis?

Branch PA stenosis was traditionally considered a contraindication for DS.[9,12] However, a thorough assessment of anatomy before and during the procedure, along with strategies tailored to the specific anatomy, can enable successful DS. Unilateral branch PA stenosis is easier to address than bilateral branch PA stenosis during DS.

When there is unilateral branch PA stenosis [Figure 2a], the wire is passed into that side, and the duct is stented into the stenosed PA, covering the entire ductus and just enough of the stenosis, which is usually at the origin. The contralateral PA is intentionally jailed and allowed to fill via the struts of the coronary stent, which generally has an open-cell design [Figure 2b]. Sluggish or reduced flow in a jailed PA not only leads to hypoxia by itself, but can also predispose to stent thrombosis. When flow is compromised in the jailed contralateral PA, it can be wired through the stent struts and redilated. Recrossing and redilatation are technically demanding. It is recommended to use a balloon that is no more than 60% of the stent’s size to minimize the risk of stent distortion.[8] Simultaneous kissing balloon inflation, with one balloon placed in the stent to the stenosed PA and another in the contralateral jailed PA, can also help. The size of the guide catheter is a major limitation of this technique in the newborn. In addition, manipulation after DS can dislodge or distort the initially placed stent.

Figure 2.

A term baby weighing 2.6 kg was diagnosed with Tetralogy of Fallot and pulmonary atresia. Angiogram done from the 5 French access sheath in the right axillary artery shows a vertical duct with minimal tortuosity (a). Note the stenosis at the origin of the right pulmonary artery (PA). The wire was placed in the right PA through a 5-French Judkins right coronary guide catheter. A 3 × 13 Biomime drug-eluting stent was positioned such that the stenosis is covered. Poststenting angiogram (b) shows unobstructed flow to both branch Pas

Occasionally, redilatation may fail, or differential blood flow may persist after redilatation. When significant hypoxia persists, an emergency BTTS will be required. Another challenge is unilateral pulmonary edema [Figure 3a-d]. This usually settles with meticulous ICU management. Strategies in such a situation include high positive end-expiratory pressure ventilation, diuretics, vasodilators, and single lung ventilation.

Figure 3.

A 27-day-old neonate weighing 3.4 kg with a double outlet right ventricle and pulmonary atresia, (a) Angiogram done through the 5-French access sheath placed in the right axillary artery. Vertical duct with stenosis of both branch pulmonary artery (PA) origins, right more than left, (b) A 3 × 13 Biomime coronary stent was placed into the right PA. Through a 5 French Judkins right coronary guide catheter. The left PA is filling via the stent struts, (c) Chest X-ray taken in the intensive care unit postprocedure showing differential blood flow, unilateral pulmonary edema on the right, (d) Chest X-ray at discharge showing resolution of the same

Bilateral branch PA stenosis is challenging to address in the catheterization laboratory. The classic approach is to stent into either branch PA, preferably the more stenosed one. Once stented, flow to the contralateral PA is established as described above [Figure 4]. Recrossing through the stent struts is challenging and unpredictable. Unless emergency bailout options are available in the event of a catastrophe, bilateral branch PA stenosis is best addressed surgically.

Figure 4.

A term baby weighing 2.5 kg was diagnosed with Tetralogy of Fallot and pulmonary atresia, (a) Angiogram done through the 5 French access sheath in the left axillary artery shows a straight vertical duct, constricted at the pulmonary artery (PA) insertion. There is a narrowing of both the branch PA origins, (b) Angiogram after placement of a 3.5 × 13 Biomime stent into the left PA through a 5-French Judkins right coronary guide catheter. Note the persistent narrowing of the origin of the right PA, (c) A coronary wire is passed into the right PA through the struts of the stent and dilated with a 3 mm coronary balloon, (d) Final angiograms show good caliber of the origin of the right PA. Both lungs are filling equally and well

How to approach when tortuosity and branch pulmonary artery stenosis coexist?

Another scenario in which DS may need to be abandoned is when extreme tortuosity coexists with branch PA stenosis. In this illustrative example [Figure 5], the vertical tortuous duct insertion was complicated by severe stenosis of the origin of the right PA. Two technical challenges prompted the abandonment of the procedure. First, the stent would have to be placed through the tortuous duct, across the stenosis, into the right PA, making it an almost 360° turn. Secondly, in the event of reduced flow to the left PA, the chances of recrossing through the side struts of the curved stent were grim. In any case, the risk of abrupt closure of the right PA and the duct during catheter-wire manipulation, leading to hemodynamic collapse, was high. Once it happens, the likelihood of placing a quick stent to restore normal pulmonary circulation is low in this complex anatomy. For all these reasons, the baby underwent an elective BTTS.

Figure 5.

A 34-week preterm baby weighing 1.94 kg was diagnosed with situs solitus, congenitally corrected transposition of great arteries with pulmonary atresia. Angiogram done through an access sheath placed in the right carotid artery. The vertical ductus is tortuous (upward arrow). There is severe stenosis of the origin of the right PA (downward arrow)

CONCLUSIONS

A systematic assessment using echocardiography and, when required, CT can inform case selection in neonatal DS. Nevertheless, preliminary angiograms are the backbone of technical planning. Tortuous ducts, particularly those that turn 360° or have multiple turns and do not straighten with the passage of a stiff wire, are best abandoned. A stent directed to the stenosed PA, with a backup plan of side-strut dilatation, is the preferred strategy for unilateral PA stenosis. Bilateral branch PA stenosis is better addressed surgically. A combination of extreme tortuosity and branch PA stenosis is another red flag for DS. By illustrating case selection and technical strategies through images, this brief report provides valuable insights, particularly for early-career interventionists facing similar situations.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.