Ultrashort-Segment Embolization of High-Flow Vessels Using a Coil Packing Technique in an Amplatzer Vascular Plug

Introduction

Ultrashort-segment embolization is a highly useful technique^1–4; however, its application in large-diameter target vessels is very difficult because the flow through these vessels is very high. The Amplatzer Vascular Plug 1 (AVP1; Abbott Vascular, Redwood City, CA, USA) is one of the best devices for short-segment embolization, but vessel occlusion can be delayed or fail altogether under certain circumstances, especially in the presence of antiplatelet and/or anticoagulation therapy. In situations where occlusion of the target vessel using a single AVP1 device is difficult, an additional occlusion device such as a coil and/or glue might be needed, resulting in longer segment occlusion.

Unlike the multilayered mesh of the AVP2 and the AVP4, the single layer of the AVP1 allows a microcatheter with a small-diameter tip to pass through it. We hypothesized that very tight coil packing of an AVP1 could accelerate formation of a stable occlusion in high-flow vessels. A preliminary experimental study was performed before application of this technique in a clinical case.

Technique

An experimental vascular model was constructed using 12-mm-diameter soft polyvinyl chloride tubing; a 4-mm-diameter stenotic lesion measuring 2 mm long was created. The model was perfused with warm saline using pulsatile flow, and a 12-mm AVP1 was deployed into this stenotic lesion. Before detachment of the AVP1, a 2.2-F microcatheter (Progreatβ ³ ; Terumo, Tokyo, Japan) was inserted into the 6-F delivery guiding sheath of the AVP1 in parallel with the plug’s delivery wire. The microcatheter was inserted into the AVP1 through its mesh using a 0.014-inch guidewire; 5 hydrogel microcoils (AZUR, AZUR CX; Terumo) were tightly inserted into the AVP1 (Figure 1), and the plug was detached. After the procedure, the pulsatile flow had almost stopped.

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Figure 1.

Experimental study model, (A) A 12-mm Amplatzer Vascular Plug 1 (AVP1) was placed in a model with a 4-mm-diameter stenosis. Before the detachment of the plug, the tip of a 2.2-F microcatheter was inserted into a 6-F delivery guiding sheath in parallel with the delivery wire; this microcatheter was inserted into the AVP1 via its mesh. The lumen of the plug was then embolized using 5 hydrogel microcoils. (B) After the procedure, the pulsatile flow had almost stopped.

The technique was applied in a 64-year-old man who had undergone a thoracic endovascular aortic repair (TEVAR) with single vessel debranching for a type B aortic dissection. A residual type II endoleak had developed via the left subclavian artery (LSA). The LSA had been occluded using an AVP1 in the TEVAR procedure, but this AVP1 had been deployed in the false lumen, and a major residual type II endoleak had arisen via the true lumen. The left vertebral artery (VA) arose from the proximal portion of the LSA, and the length from the LSA orifice to the left VA orifice was relatively short for additional embolization. For these reasons, occlusion of the AVP1 was planned using tight coil packing.

A 5-F guiding sheath (Destination; Terumo) was inserted via the left brachial artery, and the left VA exhibited antegrade flow. After LSA angiography, a 10-mm-diameter AVP1 was deployed at the proximal LSA. Before plug detachment, a microcatheter with 1.6-F tip (Marvel S; Tokai Medical Products, Aichi, Japan) was inserted into the plug through its mesh using a 0.014-inch guidewire (CHIKAI; Asahi Intecc, Aichi, Japan), and the lumen of the plug was tightly embolized (Figure 2A) using 4 electrolytic microcoils (TargetXL360; Stryker, Kalamazoo, MI, USA). After the procedure, the residual endoleak had completely disappeared, and the left VA flow became retrograde (Figure 2B). At 9-month follow-up, the chest radiograph showed no signs of coil or plug migration.

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Figure 2.

In the clinical case (A) a 10-mm Amplatzer Vascular Plug 1 was placed at the proximal position of the left subclavian artery stenosis. Before detachment of the plug, the tip of a 1.6-F microcatheter was inserted into the plug through its mesh, and the lumen of the plug was embolized using 4 electrolytic microcoils. (B) In a completion angiogram, the residual endoleak had completely disappeared, and the left vertebral artery flow was retrograde.

Discussion

Short-segment embolization is a relatively difficult procedure, and various techniques have been reported.^1–4 Yunaiyama et al ¹ used a double-balloon technique in an experimental model; however, coil embolization is associated with a risk of coil migration in high-flow vessels, and more stable embolization methods are needed, such as a microvascular plug. Koganemaru et al ⁴ reported an internal coil packing method for a mesh occlusion device, which is similar to our procedure. However, they embolized the internal plug space after detachment of the plug, and it is our opinion that a stable and tight coil embolization would be difficult to perform in vivo using their technique. In contrast, our method employed a plug anchoring technique reported by Onozawa et al ⁵ during intraplug embolization. This anchoring technique enabled robust and tight internal coil packing without migration of either the microcatheter or the coils.

Our technique can achieve robust ultrashort-segment embolization in preoperative embolization of the LSA and/or celiac trunk for TEVAR or preoperative embolization of the common hepatic artery for a distal pancreatectomy with celiac axis resection. ³

The thrombotic status of Japanese patients differs from Western populations. This “Japanese paradox” as reported by Gorog et al ⁶ features a more favorable thrombotic profile (longer occlusion time) but markedly reduced thrombolytic activity. Based on these points, the Japanese patient needs a more definitive embolization procedure than a Westerner. Furthermore, residual LSA flow after a zone 2 TEVAR causes distal embolization, ⁷ and the incidence of endoleak is significantly increased when undergoing LSA revascularization. ⁸ Therefore, we add preemptive LSA occlusion during a zone 2 TEVAR with LSA revascularization.

In cardiovascular areas, a transcatheter plug closure of postoperative paravalvular leaks (PVL), pseudoaneurysms, and shunts would be useful options in high-risk patients; however, failure/complications or recurrence can occur in some cases.^9–11 These devices use a mesh device such as AVP2, and this mesh structure can cause residual leaks and/or recurrences. The vascular model in our study resembled a PVL, and the shape of the post-deployed AVP1 was ideal for the treatment of PVL. Our first clinical case was not a PVL occlusion but an LSA embolization, since we believe that more clinical experience is needed to adapt this technique for PVL cases in the presence of a beating heart. Bare electrolytic microcoils were used in our case, but for even tighter packing we strongly recommend the use of hydrogel coils. We think that this technique is very useful and robust for ultrashort-segment embolization for vessels with a relatively large diameter and high flow.

Conclusion

Based on an experimental study and initial experience in vivo, tight packing of an AVP1 using a plug anchoring technique might be a robust option for ultrashort-segment embolization.