Characterization of the In Situ Stress State of Blood Clots in Ischemic Stroke: The Effect of Initial Conditions and Arterial Interaction

Abstract

Ischemic stroke, caused by a blood clot lodging in cerebral vasculature, is a leading cause of death worldwide. The mechanics of vessel occlusion and the influence of residual stress on thrombectomy outcomes remain poorly understood. Most computational studies neglect arterial residual stress and the deformation a clot undergoes as it lodges, both of which elevate system stresses. Here, we introduce a method to simulate the initial state of a clot lodged in an idealized artery with residual stress. In this study, the artery is formulated as two concentric right cylinders with fibers embedded in an isotropic mesh, with a pre-deformation used to incorporate residual stress. A base equilibrium state of an elastic clot is simulated in continuous contact with the arterial wall. The opening angle of the artery, un-lodged-to-lodged dimensional ratios, and stiffness of the clot are varied in parametric sweeps to characterize the traction forces of the clot into the arterial wall. An aspiration pressure is applied to the proximal end of the clot to determine the pressures necessary to begin tensile detachment of the clot. As the artery opening angle increased, removal aspiration pressures increased, while the pressures decreased with increasing artery fiber orientation. The stress-free-to-lodged length ratio of the clot influenced the removal aspiration pressure, with pressures increasing nearly a thousand-fold with increased ratio. By incorporating different factors that contribute to the stress state of the system, this study provides a library of realistic initial conditions for simulating aspiration thrombectomy and validating new surgical techniques.