Blind Exchange With Mini-Pinning Technique Using the Tron Stent Retriever for Middle Cerebral Artery M2 Occlusion Thrombectomy in Acute Ischemic Stroke

Abstract

Introduction: The usefulness of the blind exchange with mini-pinning (BEMP) technique has recently been reported for mechanical thrombectomy in patients with stroke owing to medium vessel occlusion (MeVO). The Tron stent retriever can be delivered and deployed through a 0.0165-inch microcatheter. This retriever has potential as an effective and safe treatment for acute ischemic stroke (AIS) due to occlusion of the M2 segment of the middle cerebral artery (MCA). Here, we report the outcomes of the BEMP technique using Tron stent retrievers for M2 occlusion thrombectomy. Methods: Consecutive patients with AIS owing to M2 occlusion who underwent the BEMP technique using 2 × 15-mm or 4 × 20-mm Tron stent retrievers were included. The technique involves deploying a Tron stent retriever through a 0.0165-inch microcatheter, followed by microcatheter removal and blind navigation of a 3MAX or 4MAX aspiration catheter over the bare Tron delivery wire until the aspiration catheter reaches the clot. A Tron stent retriever is inserted into the aspiration catheter like a cork and subsequently pulled as a unit. We assessed procedural outcomes [first-pass expanded thrombolysis in cerebral infarction (eTICI) score 2c/3 and 2b/2c/3], safety outcomes [symptomatic intracranial hemorrhage (sICH)], and clinical outcomes (good outcome rate defined as modified Rankin Scale score 0-2 at 90 days and mortality at 90 days). Results: Eighteen M2 vessels were treated in 15 patients (six female, median age: 80 years, and median National Institutes of Health Stroke Scale score: 18). The BEMP technique was performed successfully in all cases. Whether to use a 3MAX or 4MAX catheter was determined by considering one of the following target vessels: dominant, non-dominant, or co-dominant M2 (3MAX, n = 9; 4MAX, n = 9). The first-pass eTICI 2c/3 and 2b/2c/3 rates were 47 (7/15) and 60% (9/15), respectively; sICH was not observed. Seven patients (47%) achieved good outcomes, and one patient (7%) died within 90 days. Conclusions: The Tron stent retriever was safely and effectively used in the BEMP technique for acute MCA M2 occlusion and can be combined with a 0.0165-inch microcatheter, which may be useful for treating MeVO, in general.

Keywords: BEMP technique; M2 occlusion; Tron stent retriever; acute ischemic stroke; thrombectomy.

Figure 1

The details of the Tron stent retriever. Photograph of the Tron stent retriever, which is constructed of two types of cells. There are a radiopaque marker in the proximal end (white arrowhead) and two markers attached to the distal end (black arrowheads). The large cell (pink) captures the thrombus, and the small cell (blue) reduces stent extension at the flexion.

Figure 2

Illustrative cases of the blind exchange and mini-pinning technique using a Tron stent retriever to remove a clot. Illustration of blind exchange and mini-pinning using the Tron stent retriever in a dominant and proximal middle cerebral artery M2 occlusion. (white arrow: proximal end of the clot) (A) Lateral angiogram showing an M2 occlusion. (B) A 0.0165-inch microcatheter in place after deployment (white arrowhead: distal end of the retriever). (C) The 3MAX aspiration catheter is advanced into the face of the clot (black arrowhead) over the bare retriever delivery wire. (D) Final angiogram showing successful reperfusion. (E) Mini-pinning (2-mm Tron stent retriever and 3MAX aspiration catheter) with “corking” of the thrombus.

Figure 3

Blind exchange and mini-pinning using a Tron stent retriever to retrieve a clot. Illustrative example of the blind exchange and mini-pinning technique using a Tron stent retriever to treat a middle cerebral artery M2 occlusion. We routinely place a large-bore balloon guide catheter in the cervical internal carotid artery. (A) The biaxial system, including the microcatheter and microguidewire, is advanced as a unit, with the microcatheter and guidewire traversing the occluded segment. The Tron stent retriever is deployed via a 0.0165-inch microcatheter distal to the clot. (B) In the next step, the microcatheter is removed from the body. (C) A 3MAX or 4MAX aspiration catheter, as a distal aspiration catheter, is blindly navigated over the bare Tron delivery wire (“blind exchange”) until the aspiration catheter reaches the clot. (C, left) The Tron stent retriever is pulled into the distal aspiration catheter like placing a bottle cork, and the pinned clot with the stent retriever and the distal aspiration catheters then forms a single unit. (C, right). (D) The Tron stent retriever and aspiration catheter are subsequently retracted as a unit to retrieve the clot.

Figure 4

Study flowchart. ACA, anterior cerebral artery; BA, basilar artery; BEMP, blind exchange with mini-pinning; BGC, balloon guide catheter; CCA, common carotid artery; EVT, endovascular therapy; ICA, internal carotid artery; MCA, middle cerebral artery; NCVC, National Cerebral and Cardiovascular Center; PCA, posterior cerebral artery; VA, vertebral artery.