Background: Low endothelial shear stress (ESS) elicits endothelial dysfunction. However, the relationship between ESS and aortic pulse wave velocity (PWV), a validated surrogate marker for cardiovascular disease, is unknown in humans. We developed a 3.0 Tesla magnetic resonance imaging (MRI) protocol to assess associations of ESS and PWV in healthy subjects.

Methods: Common carotid 3T-MRI measurements were performed in 55 subjects (aged 41±15years). Axial gradient echo Phase-Contrast images were acquired over 45 phases per heartbeat, using a 5cm single-element microcoil, with slice thickness 3mm, non-interpolated pixel size 0.6 × 0.6mm, velocity encoding 150cm/s. The mean ESS in the cardiac cycle was calculated: ESS=μ•WSR, μ is the blood viscosity (3.2 Pa•s), WSR was the slope of the velocities close to the artery wall assessed by second order curve fitting of the velocity profile.

Results: Mean ESS was 0.89(0.23)N/m², and PWV was 7.21(1.58)m/s. ESS was inversely correlated with PWV (Pearsons’ r=−0.40, p=0.01). Multiple linear regression analysis accounting for age, gender and systolic blood pressure revealed that ESS was an independent predictors of the response variable PWV (regression coefficients [b]=−1.67N/m² per m/s, p=0.04).

Conclusion: Our carotid MRI data show that ESS is an important determinant of arterial stiffness in humans. The data warrant further studies to evaluate use of carotid ESS as a non-invasive tool to understand individual CVD risk and to assess novel drug therapies in cardiovascular disease prevention.