Flow-mediated dilation (FMD) estimates endothelial function under the assumption that post-ischemic dilation represents a nitric-oxide mediated response to increase in wall shear stress, i.e. wall shear rate (WSR) times blood viscosity. Implementation of WSR measurements would expand the informative value of this technique.

Aim of the study was to provide preliminary clinical evaluation of a new ULtrasound Advanced Open Platform (ULA-OP, University of Florence) capable to record simultaneously arterial diameter and WSR based on a Multigate Spectral Doppler approach (Tortoli et al, UMB 2006).

Methods: The response of brachial artery diameter (FMD) and WSR to different forearm occlusion times was assessed by ULA-OP in twelve volunteers (age 25–29) undergoing two sequential exams (3 and 5-min occlusion) 30min apart each other in random order. Time variant arterial distension curves and WSR were obtained at baseline and during post-ischemic reflow.

Results: Mean percent changes observed in peak WSR (far wall) and diameter (FMD) after 3 and 5 min ischemia are below reported in Table, together with the corresponding time lags between peak WSR and peak diameter (D). The post-ischemic WSR peaks always preceded peak diameter increase.

Conclusions: WSR and D can be simultaneously measured during FMD studies by ultrasound. Compared to the standard 5-min occlusion, the post-ischemic response to a 3-min occlusion appears slightly delayed and lower, for both diameter and shear.Simultaneous recording of WSR and arterial distension may expand knowledge of the mechanisms regulating vascular responses to hemorheologic changes.