Computational fluid dynamics analysis and correlation with intraoperative aneurysm features

Introduction. There are many controversies about computational fluid dynamics (CFD) findings and aneurysm initiation, growth, and ultimate rupture. The aim of our work was to analyze CFD data in a consecutive series of patients and to correlate them with intraoperative visual aneurysm findings. Methods. Hemoscope software (Amin, Ziosoft Corporation, Minato ward, Tokyo, Japan) was used to process images from 17 patients who underwent clipping of 18 aneurysms. Pressure (P), wall shear stress (WSS) gradient and vectors, normalized WSS, and streamlines (SL) direction and velocity were assessed. CFD data were compared to intraoperative visual findings. A total of 39 aneurysm wall areas were assessed. Results. Red, thin aneurysm wall areas were more often associated with low WSS. However, the association of low WSS with high P, diverging WSS vectors, direct impact of SL, and high SL velocity more frequently matched with yellow, atherosclerotic aneurysm walls. Conclusions. Low WSS alone is not sufficient to determine the thickness of an aneurysm wall. Its association with other parameters might enable one to distinguish preoperatively atherosclerotic, thick areas (high P, diverging WSS vectors, high flow velocity) from thin areas with higher rupture risk (parallel WSS vectors, lower flow velocity). The changing balance between these parameters can modify the features and the risk of rupture of aneurysm wall over time.