Submitted on September 10, 2006
Accepted on April 19, 2007
ANALYSIS OF COMPLEX FLOW AND THE RELATIONSHIP BETWEEN BLOOD PRESSURE, WALL SHEAR STRESS AND INTIMA-MEDIA THICKNESS IN THE HUMAN CAROTID ARTERY
Alexander Augst1, Ben Ariff2, Simon AMcG Thom2, Yun Xu3, and Alun D Hughes2*
1 Chemical Engineering, Imperial College London, London, London, United Kingdom
2 NHLI, Imperial College London, London, United Kingdom
3 Chemical Engineering, Imperial College London, London, London, United Kingdom; Imperial College London, London, London, United Kingdom
* To whom correspondence should be addressed. E-mail: a.hughes{at}imperial.ac.uk.
Background: Previous studies have observed relationships between increased intima-media thickness (IMT) in the carotid artery, elevated blood pressure, and low wall shear stress (WSS) calculated by Poiseuille equation. This study used numerical methods to more accurately determine WSS in the carotid artery and to investigate possible determinants of increased IMT.
Methods: IMT (common carotid artery (CCA) and bulb), CCA flow velocity, brachial systolic (SBP) and diastolic blood pressure (DBP) and carotid systolic pressure (cSBP) were measured in 14 healthy subjects (age 44 ±16yrs). Flow patterns in the carotid bifurcation were determined by computational fluid dynamics (CFD) based on 3-dimensional ultrasound geometry. Instantaneous and time-average wall shear stress (WSSav), oscillatory shear index (OSI), and wall shear stress angle gradients (WSSAG) were calculated.
Results: IMT was positively related to SBP and WSSAG and inversely related to WSSav in the CCA. In the bulb IMT was positively related to SBP (p = 0.007), but was not significantly related to WSSav, or WSSAG. IMT was unrelated to OSI in either the CCA or the bulb.
Conclusion: In the CCA and bulb, IMT is most closely related to blood pressure suggesting that increased carotid artery IMT in healthy subjects with no evidence of focal plaques is primarily a response to elevated pressure rather than low shear stress.
