title: Estimation of wall shear stress dynamic fluctuations in intracranial atherosclerotic lesions using computational fluid dynamics.
abstract: OBJECTIVE
  Intracranial stenosis (IS) is associated with significant morbidity and mortality from hypoperfusion and thromboembolism. We used computational fluid dynamic methods to analyze luminal patterns of wall shear stress (WSS), a known critical modulator of endothelial function, within patient-based IS lesions undergoing percutaneous angioplasty and stenting.
  
  
  METHODS
  High-resolution three-dimensional rotational angiographic data sets were reconstructed to yield a fine-resolution computational mesh allowing application of pulsatile computational fluid dynamic analysis with a non-Newtonian realistic model of blood. WSS and its gradient were analyzed spatiotemporally in five IS lesions before and after percutaneous angioplasty and stenting.
  
  
  RESULTS
  WSS within the stenosis reached average shear magnitudes of 1870 +/- 783 dyn/cm with rapidly reversing direction to oscillating low values in the recirculation zone. WSS vectors revealed complex dynamic directional and amplitude oscillations not seen in healthy segments with time-dependent convergence and divergence strips sweeping back and forth across the lesion during the cardiac cycle. These areas also underwent extreme temporal WSS oscillation of 2052 +/- 909 dyn/cm over a short time interval. The endothelial mechanotransductive response to such extreme WSS magnitudes and gradients, which were normalized by percutaneous angioplasty and stenting in the current study, remains undefined.
  
  
  CONCLUSIONS
  Computational fluid dynamic analysis of IS has uncovered a complex and hostile microhemodynamic environment characterized by wide and rapid shear variations in time and space. Characterization of the mechanical forces acting on the wall can help in determining the molecular transduction response of the luminal endothelium to these extreme stresses and may lead to better understanding of the hemodynamic contribution to stenosis pathophysiology.
authors.affiliation: Department of Neurosurgery, Cerebrovascular and Endovascular Division, Tufts Medical Center, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
authors.forename: Clemens M
authors.initials: CM
authors.lastname: Schirmer
authors.forename: Adel M
authors.initials: AM
authors.lastname: Malek
mesh_terms: D000368:Aged; D017073:Atherectomy / Q000379:methods / Q000706:statistics & numerical data; D001783:Blood Flow Velocity / Q000502:physiology; D019295:Computational Biology / Q000379:methods* / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods / Q000706:statistics & numerical data; D002537:Intracranial Arteriosclerosis / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery; D008297:Male; D008875:Middle Aged; D011859:Radiography; D033081:Shear Strength; D013314:Stress, Mechanical