Quantifying Stent Wall Shear Stress for Assessing Stent and Flow Diverter Performance for Treating Intracranial Aneurysms

Abstract

Analysis of flow diverting intracranial aneurysm repair devices has traditionally focused on reducing intrasaccular blood flow velocity and aneurysm wall shear stress (WSS) as the primary metrics for improved perceived device performance. However, the interpretation of this data has been debated, particularly with regard to the specific biological benefits of high or low aneurysm WSS. Therefore, this research proposes an additional parameter of WSS at the stent struts that could provide valuable insight regarding the device's potential to promote occlusion at the aneurysm neck by indicating locations of increased platelet activation and microparticle shedding. Fluid flow effects were evaluated for two flow diverters (Pipeline™ and FRED™) and three stents (Enterprise™, Atlas™, and LVIS™) using computational fluid dynamics (CFD) models developed from two patient-derived CTA datasets with aneurysms in the middle cerebral artery (MCA) and basilar artery (BA), respectively. The device WSS data provides an additional metric for evaluating the ability of the device to constrain the blood flow within the main vessel, as well as indicating potential locations of the initiation of aneurysm occlusion. It is hypothesized that high device WSS close to the aneurysm neck creates a higher likelihood of thrombus formation and aneurysm occlusion due to platelet activation and microparticle shedding, while high device WSS proximal or distal on the device would indicate a higher likelihood of undesirable daughter vessel occlusion. Conversely, low-to-moderate device WSS throughout the device length could be interpreted as a reduced likelihood of complete occlusion of the aneurysm over time, resulting in lesser device performance.