Does endoprosthesis design impact bleeding risk when using lumen-apposing metal stents for drainage of pancreatic fluid collections?

Lumen-apposing metal stents (LAMSs) were the answer to an urgent plea made in 2008 by an endoscopic ultrasound (EUS) working group for the development of dedicated devices to treat symptomatic pancreatic fluid collections (PFCs) [11]. The Axios platform (Boston Scientific) was designed to simplify, streamline, and improve the procedural safety of EUS-guided PFC drainage. While initial studies reported high technical and clinical success rates, delayed bleeding was observed in some patients. It was hypothesized that, unlike double-pigtail plastic stents (DPPSs), which migrate towards the gastric lumen with resolution of the PFC, the LAMS with its rigid spikes at both ends could erode into adjacent vasculature and precipitate bleeding [22]. Consequently, recommendations were made for timely removal of the LAMS [33]; however, the problem has not been fully eliminated [44].

Whether the Axios or Spaxus stents are associated with less bleeding risk must wait for a prospective, well-designed, large cohort study.

More recently, a new cautery-enhanced LAMS (Hot-Spaxus; Taewoong Medical) has been designed with rounded edges and foldable flanges to potentially minimize bleeding risk. To ascertain the benefit of this, an international team of collaborators conducted a retrospective propensity study to compare the technical and clinical performance, in particular the bleeding risk, of the Hot-Axios and Spaxus (cold and hot) systems [55]. Among the 264 analyzed patients (132/cohort), while there was no difference in the technical or clinical outcomes, the rates of overall adverse events (AEs; 9.8% vs. 3.0%; P=0.04) and clinically relevant bleeding (6.8% vs. 1.5%; P=0.03) were significantly higher in patients treated using the Hot-Axios system. Reported nonbleeding AEs included two cases of stent migration/misdeployment in each group and one case of perforation with the Hot-Axios. Bleeding was observed in nine patients with the Hot-Axios (five at the access site and four intracavitary) compared with two in Spaxus group (one at the access site and one intracavitary). All bleeding episodes occurred within 4 weeks, and the majority within the first 2 weeks, after undergoing intervention.

The issue is whether the Spaxus stent, by virtue of its unique design, is associated with a lower bleeding risk. Of the 11 bleeding events, six were localized to the access site and five to the intracavitary region. The Hot-Axios has a stiff 10-Fr cautery-enhanced delivery tip that can limit the flexibility of the distal end of an echoendoscope and potentially interfere with visualization of small intervening vasculature structures. This may explain why five patients in the Hot-Axios cohort had access-site bleeding. In contrast, this was observed in only one patient in the Spaxus group; however, Hot-Spaxus stents (recently released) were used for puncture in only 28% of patients in this cohort. In the majority, access was first gained using a 19G needle, followed by guidewire passage, cautery administration, and stent placement. This fine-needle aspiration (FNA)-based technique, although time-consuming, is significantly safer than puncture using a stiff 10-Fr cautery tip. Only a head-to-head comparison between the Hot-Axios and Hot-Spaxus systems will be able to resolve the conundrum of access-site bleeding – I very much doubt there will be a true difference as the delivery catheter dimensions are quite similar between the platforms.

Of the five intracavitary bleeding events, four were observed with the Hot-Axios stent and one with the Spaxus stent. It is rather surprising that all of the bleeding episodes occurred within 4 weeks of intervention in both cohorts. In a prior randomized trial that compared LAMSs and plastic stents, we observed that stent indwell time was proportionate to bleeding risk [22]. It is obvious that, while the 4-week cutoff for Axios removal may minimize the possibility of delayed bleeding, it is unlikely to eliminate the risk. In fact, bleeding was also observed in the Spaxus cohort in one patient within 8 days of intervention. Based on the presented data, does the Spaxus design confer a unique safety advantage over the Hot-Axios in preventing intracavitary bleeding? No – a simple two-table test does not demonstrate any statistical difference between the cohorts; however, small observations are important to take note and be mindful of.

A recent large retrospective study from the USA, including 1524 patients, reported no difference in AEs between Axios stents and DPPSs, particularly pertaining to bleeding [66]. Therefore, as the authors rightly observe, could factors other than stent design, such as a small pseudoaneurysm, precipitate some of these bleeding events? We simply don’t know. What we know is that, while multicenter retrospective studies can occasionally be insightful, they do not provide accurate answers for difficult questions, particularly when they are narrow or too focused. The answer as to whether the Axios or Spaxus stents are associated with less bleeding risk must wait for a prospective, well-designed, large cohort study.

Publication History

Article published online:
21 December 2023

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