Risk of distal embolization with stent retriever thrombectomy and ADAPT

Abstract

Background: There is a discrepancy in clinical outcomes and the achieved recanalization rates with stent retrievers in the endovascular treatment of ischemic stroke. It is our hypothesis that procedural release of embolic particulate may be one contributor to poor outcomes and is a modifiable risk. The goal of this study is to assess various treatment strategies that reduce the risk of distal emboli.

Methods: Mechanical thrombectomy was simulated in a vascular phantom with collateral circulation. Hard fragment-prone clots (HFC) and soft elastic clots (SECs) were used to generate middle cerebral artery (MCA) occlusions that were retrieved by the Solitaire FR devices through (1) an 8 Fr balloon guide catheter (BGC), (2) a 5 Fr distal access catheter at the proximal aspect of the clot in the MCA (Solumbra), or (3) a 6 Fr guide catheter with the tip at the cervical internal carotid artery (guide catheter, GC). Results from mechanical thrombectomy were compared with those from direct aspiration using the Penumbra 5MAX catheter. The primary endpoint was the size distribution of emboli to the distribution of the middle and anterior cerebral arteries.

Results: Solumbra was the most efficient method for reducing HFC fragments (p<0.05) while BGC was the best method for preventing SEC fragmentation (p<0.05). The risk of forming HFC distal emboli (>1000 µm) was significantly increased using GC. A non-statistically significant benefit of direct aspiration was observed in several subgroups of emboli with size 50-1000 µm. However, compared with the stent-retriever mechanical thrombectomy techniques, direct aspiration significantly increased the risk of SEC fragmentation (<50 µm) by at least twofold.

Conclusions: The risk of distal embolization is affected by the catheterization technique and clot mechanics.

Keywords: Device; Intervention; Stroke; Thrombectomy.

Figure 1

Schematic illustration of the flow loop (arrows indicate the direction of flow). The common carotid artery (CCA) is connected to the flow pump and divided to form internal and external carotid arteries (ICA and ECA, respectively). The vascular phantom includes collateral circulation via the posterior communicating artery (PComA) and a small anastomosis with the distal middle cerebral artery that represents leptomeningeal collateral supply. Inset shows digital subtraction angiography before (A) and after (B) clot introduction. Note that the PComA flow is toward the anterior circulation during the occlusion and is transiently opacified due to a forceful injection of contrast. All distal emboli are captured in the effluent of the middle and anterior cerebral arteries.

Figure 2

Cumulative size distribution of (A) hard and (B) soft clot fragments generated during the procedure. The majority of the clot fragments have size <20 µm. The x-axis is shown in log scale to indicate the large range of the data.

Figure 3

(A) Total number of hard fragment-prone clot (HFC) emboli. (B, C) Number of HFC clot fragments with size >1000 µm (B) and 200–1000 µm (C). The risk of large clot fragmentation (>1000 µm) is increased with the use of the guide catheter (GC). Average number of HFC fragments with size <200 µm collected during the experiments shown is in D (100–200 µm), E (50–100 µm) and F (<50 µm). The ADAPT technique generates more clot fragments than the other three mechanical thrombectomy techniques (D, E). *p<0.05, **p<0.01, ***p<0.001, ****p<0.0001.

Figure 4

(A) The total number of soft elastic clot (SEC) emboli is reduced with the use of the balloon guide catheter (BGC). Similar to the findings observed in the hard fragment-prone clots groups, the least number of SEC fragments with size >1000 µm (B) and 200–1000 µm (C) is found in the ADAPT group. The average number of SEC fragments with size 100–200 µm, 50–100 µm, and <50 µm is presented in D, E, and F, respectively. *p<0.05, **p<0.01, ***p<0.001, ****p<0.0001.

Figure 5

(A) Partial flow restoration after deployment of stentriever. There is a significant increase in partial flow restoration after deployment of the Solitaire FR device in the hard fragment-prone clots (HFC) group compared with the soft elastic clot (SEC) group. (B) Using the guide catheter (GC) achieves the greatest middle cerebral artery (MCA) flow restoration after device deployment.****p<0.0001.

Figure 6

(A) With the representative collateral circulation, temporary internal carotid artery (ICA) occlusion provided by the balloon guide catheter (BGC) during mechanical thrombectomy does not significantly change the restored middle cerebral artery (MCA) flow. (B) Flow reversal in the MCA due to aspiration during clot retrieval is observed in the BGC and ADAPT groups. *p<0.05, ****p<0.0001.