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Background and Purpose: Wall shear stress (WSS) is the frictional force exerted by the circulating blood on the endothelium. Low systolic WSS is identified as an atherosclerotic risk factor. Recently, also the importance of diastolic WSS has been described. Still, it is unknown whether diastolic WSS carries similar cardiovascular risk factors compared to systolic WSS., Methods: Of 379 subjects (70-82 years, 56% male) diastolic and systolic WSS in the internal carotid arteries was determined., Results: After adjustment for age and gender, diastolic blood pressure was associated with systolic WSS (p = 0.02). Body mass index was associated with diastolic WSS (p = 0.04). Smoking was associated with diastolic WSS (p = 0.05). Myocardial infarction was associated with both systolic WSS (p = 0.04) and diastolic WSS (p < 0.01). No associations between cholesterol, HDL, LDL, triglycerides, history of diabetes, hypertension, angina pectoris, claudication, stroke, or any vascular disease were found with systolic or diastolic WSS., Conclusions: Our data indicates different cardiovascular risk factors for diastolic WSS compared to systolic WSS., (2009 S. Karger AG, Basel.)

Purpose: To verify whether wall shear stress (WSS) can be assessed in a reproducible manner using automatic model-based segmentation of phase-contrast MR images by determination of flow volume and maximum flow velocity (Vmax) in cross-sections of these vessels., Materials and Methods: The approach is based on fitting a 3D paraboloid to the actual velocity profiles and on determining Vmax. WSS was measured in the internal carotid arteries of two groups of healthy young volunteers. The reproducibility of rescanning and repositioning was studied in the first group. In the second group a 1-week and a 1-month interval was investigated. Reproducibility was calculated by the intraclass correlation (ICC)., Results: The flow volume, Vmax, and WSS averaged over the cardiac cycle were found to be 287.8 +/- 29.7 mL/min, 37.0 +/- 4.6 cm/s, and 1.13 +/- 0.16 Pa, respectively. The diastolic WSS varied between 1.00 +/- 0.21 Pa without averaging to 0.88 +/- 0.16 Pa with temporal and spatial averaging. Systolic WSS was 1.67 +/- 0.33 Pa without averaging and 1.67 +/- 0.25 Pa with averaging. ICC varied between 0.58 and 0.87 without averaging and between 0.75 and 0.90 with averaging for WSS., Conclusion: WSS in MR images of the internal carotid artery can be assessed semiautomatically with good to excellent reproducibility without inter- or intraobserver variability using model-based postprocessing., ((c) 2007 Wiley-Liss, Inc.)

Background and Purpose: Despite speculations, it is unknown whether statins affect wall shear stress (WSS). Therefore, the effect of pravastatin on WSS was investigated., Methods: In 355 elderly individuals participating in the PROSPER study (follow up after 3 years), the effect of 40 mg pravastatin on WSS was assessed in the internal carotid artery using magnetic resonance imaging., Results: WSS and blood velocity decreased both in the pravastatin group and in the placebo group but decreased faster in the pravastatin group (P<0.04, P<0.02). Blood volume flow did not differ between the groups., Conclusions: In elderly subjects, the WSS and blood velocity of the internal carotid artery declines significantly over time and this decline is more pronounced in subjects treated with 40 mg pravastatin compared with the placebo group.