Background: Wall Shear Rate (WSR) is a main determinant of shear stress (WSS), the viscous drag exerted on the arterial wall by the flowing blood. In human studies WSR is only roughly estimated by a static measurement of diameter and centerline systolic flow velocity. A double beam multigate Doppler (MGD) system, capable to provide simultaneous monitoring of arterial diameter and WSR, was recently developed and validated by our group.

Aim: To investigate in man the relations between WSR, age, arterial geometry and distension in common carotid artery (CCA) by MGD.

Methods: Twentyfive normotensive subjects, age 30–53, underwent CCA scan by an ultrasound system (Esaote Megas, 7.5–10.0 MHz probe) interfaced with MGD. Ultrasound beams were setted transversely for diameter assessment, and at an interbeam angle of 35° for flow velocity profile and WSR determination. Autocorrelation algorithm and spectral analysis of backscattered signals from walls an erithrocytes were used for estimating distension and WSR, respectively. IMT was also measured.

Results: Mean CCA diameter and distension were 6.9 ± 0.6 mm and 499 ± 188 μm; WSR (average through cardiac cycle) was 335 ± 87 s⁻¹ and 283 ± 80 s⁻¹ at near and far wall. WSR was inversely related (r from −0.47 and –0.52) to age, diastolic BP, CCA diameter and IMT, and directly to distension (r =0.41). Significant relations with age were confirmed for BP, carotid diameter and IMT.

Conclusion: Our findings are in keeping with the hypothesis that an age-related reduction of WSR, possibly associated to vessel dilation, may represent a mechanism underlying the age-related IMT increase.