BACKGROUND AND PURPOSE:Mechanical behavior of the thromboembolus is one of the key factors that determine the efficacy of thrombectomy devices for revascularization in AIS. We characterized the mechanical properties and composition of thromboemboli from clinical cases and compared them with commonly used EAs.

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

Intracranial atherosclerotic disease (ICAD) is the most common cause of stroke throughout the world. Patients with severe arterial stenosis and a recent stroke or transient ischemic attack are at high risk of recurring stroke. In an attempt to improve the clinical outcome of patients with severe, symptomatic ICAD, percutaneous transluminal angioplasty and intracranial stenting have become treatment options over the last years. Follow-up imaging of patients with ICAD that underwent intracranial stenting is generally done using 2D digitally subtracted angiography. Since often the vessel path is curved and the neointimal hyperplasia (NH) is eccentric, in-stent restenosis (ISR) may be under- or overestimated using 2D techniques.

Introduction: Thrombectomy devices have become an integral tool in the armamentarium of neuro-interventionalists to treat acute ischemic stroke (AIS). Previous preclinical evaluation of these devices has not assessed their safety in the native cerebrovasculature. We assessed the operation of stent-trievers in the canine basilar artery (BA), with a goal to evaluate their vascular safety on angiography and histopathology. Methods: Four mongrel canines (female, mean weight:12.53kg,n=2 each arm) were randomly assigned to receive the Solitaire FR Revascularization device (4mm X 22mm;eV3, Plymouth, MN) or the Enterprise VRD (4.5mm X 22mm ;Codman Neurovascular, Raynham, MA). The canine basilar artery (BA) was accessed through the anterior spinal artery (ASA, control vessel). The device was deployed in the basilar artery and withdrawn in the expanded state to the vertebrobasilar junction. The ASA, in which only the microcatheter was deployed, served as the control. Angiographic scoring of the vasospasm and histopathological assessment using a quantitative grading of the scanning electron microscopy (SEM) and cross-sectional hematoxylin and eosin histology was used to assess for the vascular integrity. Results: The Enterprise VRD and the Solitaire performed equally with grade 3 vasospasm on the first pass, which quickly resolved with intra-arterial Nicardipine administration and minimal vasospasm on subsequent passes. Based on the qualitative histopathological and SEM assessment the Solitaire and the Enterprise VRD device performed comparably when tracked through the canine basilar artery. Based on the luminal surface assessment from the SEM, the most likely damage expected from an intervention with either of these devices is expected to be partial damage to the internal elastic lamina and an exposure of the smooth muscle cells. Microcatheter navigation in the control vessels induced focal endothelial injury along the path in which the catheter was tracked. Conclusion: In an attempt to emergently re-vascularize the ischemic vascular territory, the vulnerability of the cerebrovasculature to manipulation by thrombectomy devices is often overlooked. Deployment of stent-trievers induces intimal damage that does not impact vessel integrity.