How to choose a snare and how to create a snare in complex PCI scenarios

A problem-solving step by step tutorial

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Summary

A snare is an endovascular device that consists of one or more radiopaque loops of wire inserted in a catheter, which, when extended, flower out, and, when withdrawn into the catheter, collapse. Its main function is to capture, within the extended loop/loops, any lost or malpositioned devices, with the final aim to retrieve and/or reposition them once its loop/loops are collapsed (Figure 1. A-C).

Once vascular access is obtained, the snare is usually inserted through a guiding catheter and placed in proximity to the capturable device.

There are several scenarios in which snare is useful, in particular in the retrieval of a lost device e.g dislodged coronary stent, broken coronary wire, etc.

Many types of snare are available. They vary according to different characteristics: the size of the catheter, its length, and the number and working diameter of its loops. Based on the numbers, snaring systems can be classified into single configurations (e.g Amplatz Goose Neck, Medtronic, or One Snare, Endovascular snare), or multiple overlapping loop configurations (e.g. En Snare, Endovascular snare). Both configurations are available in several different working loop diameters, ranging from a few millimeters (2 to 7 mm, also called microsnare) to some centimeters (up to 35-45 mm) (Figure 1. D-E).

The Problem

The choice of snare type and size largely depends on the type and location of the embolized devices, and the planned retrieval technique.

Although capturing a small device, or one of its small components, may be feasible with a small-diameter loop snare, it appears challenging to succeed if the embolized device is not over a wire, or if its coaxiality with the snare is difficult to achieve. On the contrary, if the purpose is to encircle the entire device, a large snare is required.

On the other hand, the localization of the capturable device, in terms of vessel or cardiac dimensions, is pivotal to safely choose the size of the snare and to avoid traumatic lesions. 

The most frequent scenarios in which a snare is useful are depicted below.

Retrieval of a lost coronary stent

This is a potential scenario encountered in the context of PCI for calcified coronary artery disease¹. In order to select the proper technique and size, two key aspects should be evaluated:

• Localization of the dislodged stent (inside or outside the coronary vessel)
• Persistence of the dislodged stent on the coronary wire (“total stent loss but guidewire in situ” or “total stent and guidewire loss”)

In general, snaring a lost stent is easier in case of proximal dislodgement in the coronary tree. It is therefore recommended that the free end of the stent be carefully located under fluoroscopy.

The persistence of the stent on the wire (“guidewire in situ”) makes it possible to apply a technique based on the use of microsnare, to reduce the risk of coronary vessel damage (Figure 2. A-D and Video 1)².

The microsnare is loaded onto the 'in situ' guidewire and advanced close to the lost stent until a perpendicular position is reached (Figure 2. A). Before securing the dislodged stent, the operator must ensure that the snare has correctly encircled the stent (Figure 2.B). The exchange catheter is then advanced and the embolised stent bends as the snare is engaged. To avoid potential crushing of the stent, it is recommended that the stent is wrapped around the proximal segment. When the stent is secured by the snare, the whole assembly is pulled back and extracted (Figure 2. C-D).

This simple technique is not replicable in case of both total stent and guidewire loss (Figure 2. E-H and Video 2). In this scenario, it is important to understand whether the stent partially protrudes from the coronary tree, which opens up the possibility of using a larger loop snare (Figure 2. E-F). The first step is to secure the coronary vessel with an additional guidewire. The most crucial phase of recovery is obtaining proper coaxiality between the snare and the dislodged stent. If the stent is partially protruding from the left main, insertion of a second guiding catheter with a second guidewire (to stabilize the system) through a contralateral vascular access may allow optimal alignment of the snare and the stent (Figure 2. G-H). Once the operator is confident that the snare has properly encircled the lost device, the retrieval steps are the same as those previously described³.

Principal idea

Snaring is not often used in daily practice but, as seen before, it can be an important tool. Due to its infrequent use, desired dimensions of snare devices in the cathlab are limited and not always suitable for the specific situation. It may be of interest to know that a “homemade” snare can be created in few steps [also called KAM-snare^_7,8]. The homemade snare is size-adjustable and can be applied to catch different foreign bodies.

Material needed

The material used for a homemade snare is depicted in Figure 3 and consists of:

• A conventional (workhorse) 0.014” guidewire
• A 2.0 mm semi-compliant balloon catheter
• A 6 Fr guide catheter extension (GCE)
• A balloon indeflator

Method step-by-step

Step 1

The 0.014” guidewire is inserted into the wire lumen of the 2.0 mm semi-compliant balloon and advanced until it protrudes 20-30 mm from the balloon tip.

Step 2

The guidewire tip is folded back towards the balloon in a loop fashion, then the whole system is inserted in the 6 Fr GCE (Figure 4. A) and advanced up to 10 mm from the tip (Figure 4. B-C)

Step 3

The folded guidewire is trapped by balloon inflation (usually 8-12 atm) into the GCE.

Step 4

Advancement of the guidewire shaft will produce a size-adjustable snare loop (Figure 4.D and Video 3)

Points of specific attention

• For setting up the homemade snare, various PCI balloons are suitable, as long as their size do not exceed the inner diameter of the GCE (However, a 2.0 mm semi-compliant balloon is recommended).
• To avoid vessel damage, selection of a soft guidewire is preferable. Moreover, using the floppy part at the tip of the guidewire further improves safety.
• In rare cases, the wire lumen of the balloon collapses during inflation, making wire movement impossible. For this reason, an initial functional test of the constructed snare system built outside the body is suggested.
• To adjust the size of the snare loop, simply pulled the snare wire backwards and push it forward (Video 3).
• A case of homemade snare used to retrieve a lost wire in the left subclavian artery is shown in Video 4.

 

A word from the reviewer - Alexander Völz

References

1. Giannini F, Candilio L, Mitomo S, et al. A practical approach to the management of complications during percutaneous coronary intervention. JACC Cardiovasc Interven. 2018;11(18):1797‐1810. https://www.pcronline.com/Cases-resources-images/Complications/Implant-loss/Stent-loss
2. Restivo A, Stanzione A, Maffeo D, Buono A. Ping-pong snaring of a totally dislodged stent across left main ostium: "All is not lost". Catheter Cardiovasc Interv. 2023 Sep 13. doi: 10.1002/ccd.30833. Epub ahead of print. PMID: 37702150.
3. Buono A, Medda M, Cesna S, Davidavicius G, Casilli F, Bande M, Pellicano M, Tespili M, Ielasi A. Snaring the Transcatheter Heart Valve Delivery System During Aortic Valve Replacement: When and Why. Cardiovasc Revasc Med. 2021 Jul;28S:81-84. doi: 10.1016/j.carrev.2021.02.018. Epub 2021 Feb 16. PMID: 33674218.
4. Mashayekhi K, Valuckiene Z, Neuser H, Akin I, Reifart N, Toma A, Neumann FJ, Behnes M. Wire externalisation techniques for retrograde percutaneous coronary interventions of chronic total occlusions. EuroIntervention. 2017 Dec 8;13(12):e1489-e1490. doi: 10.4244/EIJ-D-16-00009. PMID: 29208580
5. Yokoi K, Sumitsuji S, Kaneda H, Siegrist PT, Okayama K, Ide S, Mizote I, Kumada M, Kuroda T, Tachibana K, Sakata Y, Nanto S. A novel homemade snare, safe, economical and size-adjustable. EuroIntervention. 2015 Mar;10(11):1307-10. doi: 10.4244/EIJV10I11A220. PMID: 24642569

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