Numerical study on proximal ischemia

Brain artery occlusion is a major cause of cerebral stroke. During a stroke, perfusion decreases at tissues distal to the occlusion, but ischemia or hypoperfusion at tissues supplied by arterial branches proximal to the occlusion is not expected. However, ischemia proximal to the occlusion site has been observed without mechanical occlusion of the proximal branches. The mechanism of this unexpected ‘proximal ischemia’ is not well understood yet. In this study, transient three-dimensional computational fluid dynamics simulations of hemodynamic flow were performed to investigate ‘proximal ischemia’ using three non-Newtonian models and Newtonian model of a simple blood vessel consisting of an artery with one branch. Blood velocity of the artery dropped sharply after occlusion, resulting in shear rates low enough to cause red blood cell aggregation. The average shear rate in a cross-section of the artery during diastole was around 0.1 s⁻¹, resulting in large red blood cell clots. Large aggregates formed in the artery have the potential to block the artery or the entrance of the branch.