Wall shear stress at the initiation site of cerebral aneurysms.

A. J. GEERS; H. MORALES; I. LARRABIDE; C. BUTAKOFF; P. BIJLENGA; A. F. FRANGI

BIOMECHANICS AND MODELING IN MECHANOBIOLOGY

SPRINGER HEIDELBERG

Lugar: HEIDELBERG; Año: 2016 vol. 16 p. 97 - 115

1617-7959

Hemodynamics are believed to play an important role in the initiation of cerebralaneurysms. In particular, studies have focused on wall shear stress (WSS), which is akey regulator of vascular biology and pathology. In line with the observation thataneurysms predominantly occur at regions of high WSS, such as bifurcation apices orouter walls of vascular bends, correlations have been found between the aneurysminitiation site and high WSS. The aim of our study was to analyze the WSS field at ananeurysm initiation site that was neither a bifurcation apex nor the outer wall of avascular bend. Ten cases with aneurysms on the A1 segment of the anterior cerebralartery (ACA) were analyzed and compared with ten controls. Aneurysms were virtuallyremoved from the vascular models of the cases to mimic the pre-aneurysm geometry.Computational fluid dynamics (CFD) simulations were created to assess themagnitude, gradient, multidirectionality, and pulsatility of the WSS. To aid the inter-subject comparison of hemodynamic variables, we mapped the branch surfaces onto atwo-dimensional parametric space. This approach made it possible to view the wholebranch at once for qualitative evaluation. It also allowed us to empirically define a patchfor quantitative analysis, which was consistent among subjects and encapsulated theaneurysm initiation sites in our dataset. To test the sensitivity of our results, CFDsimulations were repeated with a second independent observer virtually removing theaneurysms and with a 20% higher flow rate at the inlet. We found that branchesharboring aneurysms were characterized by high WSS and high WSS gradients.Among all assessed variables, the aneurysm initiation site most consistently coincidedwith peaks of temporal variation in the WSS magnitude.