Effects of smoking and hypertension on wall shear stress and oscillatory shear index at the site of intracranial aneurysm formation

Singh, Pankaj K.; Marzo, Alberto; Howard, Bethany; Rufenacht, Daniel A.; Bijlenga, Philippe; Frangi, Alejandro F.; Lawford, Patricia V.; Coley, Stuart C.; Hose, D. Rodney; Patel, Umang J.

doi:10.1016/j.clineuro.2009.12.018

« Previous Next »Clinical Neurology and Neurosurgery
Volume 112, Issue 4 , Pages 306-313, May 2010

Effects of smoking and hypertension on wall shear stress and oscillatory shear index at the site of intracranial aneurysm formation

Pankaj K. Singh
- Department of Medical Physics, Royal Hallamshire Hospital, Sheffield, UK
- Department of Neurosurgery, Royal Hallamshire Hospital, Sheffield, UK
- Corresponding author at: Department of Neurosurgery, Royal Hallamshire Hospital, Glossop Road, Sheffield S10 2JF, UK. Tel.: +44 114 2712180; fax: +44 114 2713314.
Alberto Marzo
- Academic Unit of Medical Physics, School of Medicine and Biomedical Sciences, University of Sheffield, Sheffield, UK
Bethany Howard
- Academic Unit of Medical Physics, School of Biomedical Sciences, University of Sheffield, Sheffield, UK
Daniel A. Rufenacht
- Department of Neuroradiology, Institute of Radiology, University Hospital Basel, Petersgraben, Basel, Switzerland
Philippe Bijlenga
- Clinic of Neurosurgery, Department of Clinical Neurosciences, Geneva University Hospital, Switzerland
Alejandro F. Frangi
- Center for Computational Imaging & Simulation Technologies in Biomedicine, Universitat Pompeu Fabra (UPF), Barcelona, Spain
- Center for Networked Biomedical Research on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Spain
- Institució Catalana de Recerca i Estudis Avaçats (ICREA), Barcelona, Spain
Patricia V. Lawford
- Academic Unit of Medical Physics, School of Medicine and Biomedical Sciences, University of Sheffield, Sheffield, UK
Stuart C. Coley
- Department of Neuroradiology, Royal Hallamshire Hospital, Sheffield, UK
D. Rodney Hose
- Academic Unit of Medical Physics, School of Medicine and Biomedical Sciences, University of Sheffield, Sheffield, UK
Umang J. Patel
- Department of Neurosurgery, Royal Hallamshire Hospital, Sheffield, UK

Received 5 August 2009; received in revised form 6 November 2009; accepted 28 December 2009.

Abstract

Objective

The mechanisms by which smoking and hypertension lead to increased incidence of intracranial aneurysm (IA) formation remain poorly understood. The current study investigates the effects of these risk factors on wall shear stress (WSS) and oscillatory shear index (OSI) at the site of IA initiation.

Methods

Two (n=2) IAs from two patients with history of smoking and hypertension were artificially removed with the help of software @neuFuse (Supercomputing Solutions^®, Bologna, Italy) and the vessel geometry reconstructed to mimic the condition prior to IA formation. Two computational fluid dynamics (CFD) analyses were performed on each data-set by using in turn the normal physiological values of blood viscosity (BV), and high BV values specific to smoking and hypertension, obtained from literature.

Results

At normal BV, high WSS (>15Pa) was observed at the site of IA initiation in both patients. When BV values specific to smoking and hypertension were used, both the areas affected by high WSS (>15Pa) and the maximum WSS were increased whilst the magnitude and distribution of OSI showed no significant change.

Conclusions

Long-term exposure to high WSS may result in an increased risk of IA development. An incremental increase in areas of high WSS observed secondary to smoking and hypertension may indicate a further increase in the risk of IA initiation. Interestingly, the relationship between BV and the area of increased WSS was not linear, reflecting the need for patient-specific CFD analysis.

Keywords: Blood viscosity, Computational fluid dynamics (CFD), Hemodynamics, Hypertension, Initiation, Intracranial aneurysm, Smoking, Wall shear stress (WSS), Oscillatory shear index (OSI)