Thrombectomy in Acute Ischemic Stroke: Challenges to Procedural Success

Abstract

The overwhelming clinical benefit of intra-arterial stroke therapy owes to the major advance in revascularization brought on by the current generation of thrombectomy devices. Nevertheless, there remains a sizeable proportion of patients for whom substantial reperfusion cannot be achieved or is achieved too late. This article addresses the persistent challenges that face neurointerventionists and reviews technical refinements that may help to mitigate these obstacles to procedural success. Insights from in vitro modeling and clinical research are organized around a conceptual framework that examines the interaction between the device, the thrombus and the vessel wall.

Keywords: Acute ischemic stroke; Endovascular therapy; Intra-arterial therapy; Thrombectomy; Thrombus.

Figure 1.

Evolution of mTICI 2b-3 rates. First generation device = Merci. Second generation = initial smaller bore Penumbra catheters. Third generation = stent-retrievers and large-bore aspiration catheters (e.g., Penumbra 5 MAX ACE and larger). mTICI, modified Treatment in Cerebral Ischemia.

Figure 2.

Evolution of procedural times. First generation device = Merci. Second generation = initial smaller bore Penumbra catheters. Third generation = stent-retrievers and large-bore aspiration catheters (e.g., Penumbra 5 MAX ACE and larger).

Figure 3.

Variability in angiographic and clinical outcomes in the recent randomized trials of thrombectomy. TICI: Treatment In Cerebral Ischemia; mRS: modified Rankin Scale.

Figure 4.

Device-thrombus-vessel interaction.

Figure 5.

Line-of-force challenge. Top left image demonstrates a stent retriever deployed within a thrombus on the distal limb of an S-shaped curve. Top right image, taken during retraction of the stent retriever without an intermediate catheter, shows ineffective force transmission where some of the force deforms the original course of the vessel (depicted with the dotted lines). Bottom left image shows a stent retriever delivered through an intermediate catheter and deployed across a thrombus, again on the distal limb of an S-shaped curve. Bottom right image, taken during retraction of the stent retriever and with the intermediate catheter just proximal to the thrombus, demonstrates effective force transmission without deformation of the vessel.

Figure 6.

ADAPT. Long thrombus retrieved from a cervical internal carotid artery occlusion using the ADAPT technique through a Penumbra ACE 68 catheter.

Figure 7.

Combined stent-retriever/aspiration. (A) Baseline image of right MCA M1 segment occlusion. (B) Thrombus within the stent-retriever is partially captured within the aspiration catheter and removed as a single unit. (C and D) Final AP and lateral image demonstrating mTICI 2c reperfusion. Notice the S-shaped configuration of the supraclinoid ICA and M1 segment. MCA, middle cerebral artery; AP, FULL NAME; mTICI: modified Treatment In Cerebral Ischemia; ICA, internal carotid artery.

Figure 8.

Risk of thrombus shearing when pulling the stent-retriever fully through the aspiration catheter (Courtesy of Neuravi Inc.). BG, balloon guide catheter.

Figure 9.

Thrombus compression after stent-retriever attempt (Courtesy of Neuravi Inc.).

Figure 10.

Relationship between thrombus compression and coefficient of friction (Courtesy of Neuravi Inc.).