Erythrocyte-Rich Thrombus Is Associated with Reduced Number of Maneuvers and Procedure Time in Patients with Acute Ischemic Stroke Undergoing Mechanical Thrombectomy

Abstract

Background: Only few studies have investigated the relationship between the histopathology of retrieved thrombi and clinical outcomes. This study aimed to evaluate thrombus composition and its association with clinical, laboratory, and neurointerventional findings in patients treated by mechanical thrombectomy due to acute large vessel occlusion. Methods: At our institution, 79 patients were treated by mechanical thrombectomy using a stent retriever and/or aspiration catheter between August 2015 and August 2016. The retrieved thrombi were quantitatively analyzed to quantify red blood cells, white blood cells, and fibrin by area. We divided the patients into two groups – a fibrin-rich group and an erythrocyte-rich group – based on the predominant composition in the thrombus. The groups were compared for imaging, clinical, and neurointerventional data. Results: The retrieved thrombi from 43 patients with acute stroke from internal carotid artery, middle cerebral artery, or basilar artery occlusion were histologically analyzed. Erythrocyte-rich thrombi were present in 18 cases, while fibrin-rich thrombi were present in 25 cases. A cardioembolic etiology was significantly more prevalent among the patients with fibrin-rich thrombi than among those with erythrocyte-rich thrombi. Attenuation of thrombus density as shown on computed tomography images was greater in patients with erythrocyte-rich thrombi than in those with fibrin-rich thrombi. All other clinical and laboratory characteristics remained the same. Patients with erythrocyte-rich thrombi had a smaller number of recanalization maneuvers, shorter procedure times, a shorter time interval between arrival and recanalization, and a higher percentage of stent retrievers in the final recanalization procedure. The occluded vessels did not differ significantly. Conclusions: In this study, erythrocyte-rich thrombus was associated with noncardioembolic etiology, higher thrombus density, and reduced procedure time.

Platelet-rich emboli are associated with von Willebrand factor levels and have poorer revascularization outcomes

“…These results are in agreement with a recent study on the structural analysis of acute ischemic stroke that found that red blood cell-rich clots are composed mainly of densely packed red blood cells supported by a thin fibrin network, whilst platelet-rich clots contain dense fibrin structures aligned with vWF and packed with platelets [22]. We demonstrate that platelet-rich clots correlated with a poor revascularization outcome and previous studies have also shown that fibrin/platelets rich clots are more difficult to retrieve that than red blood cell-rich clots [23]. Contracting (activated) platelets have been shown to actively remodel the fibrin network of thrombi leading to an increase in fibrin density and a consequential decrease in clot volume and increase in clot stiffness [24].…”

Why we fail: mechanisms and co-factors of unsuccessful thrombectomy in acute ischemic stroke

“…Recent literature also shows inconclusive findings concerning this aspect [24]. There are studies and histological analysis that come to a similar result [25,26], while other investigations indicate the opposite: cardiogenic thrombi seem to have a higher proportion of fibrin compared to other stroke etiologies, associated with worse interventional recanalization rates [27][28][29]. More studies on thrombus etiology and thrombus composition must be performed.…”

Structural analysis of ischemic stroke thrombi: histological indications for therapy resistance

“…Emerging evidence indicates that RBC-rich stroke thrombi are more easily retrieved via endovascular procedures in comparison to more complex fibrin/platelet-rich thrombi. 14,38 Even though it may seem intuitive that the retriever devices and techniques available today favor more soft thrombi, the mechanisms that render platelet-rich thrombi more resistant to thrombectomy are not completely understood. Weafer et al have recently shown that the degree of clot integration into the thrombectomy device is decreased in fibrin-rich thrombi, making these thrombi more resistant to mechanical removal.…”