P5.08: Normalisation for Wall Shear Stress Stimulus Improves Accuracy in the Assessment of Glucose-Induced Changes in Flow-Mediated Dilation

Background In healthy arteries, acute changes in wall shear stress (WSS) elicit a vessel dilation response, through endothelial NO-release and smooth muscle relaxation (flow-mediated dilation, FMD). Metabolic or pharmacologic agents might modulate FMD, but may also interfere with the transient WSS stimulus utilised to assess FMD. We hypothesized that glucose-induced changes in FMD can be detected with greater sensitivity by normalising FMD for the WSS stimulus. Methods & Results Twenty-two healthy volunteers (24±6 yrs, BMI 24±7kg/m 2 ) underwent a standard oral glucose tolerance test during which brachial FMD was assessed by simultaneous B-mode/PW-Doppler ultrasound at baseline (twice), at 30 and at 75min post glucose intake. FMD was defined as the peak increase in diameter relative to baseline diameter (ΔD peak /D baseline ) and as the response/stimulus ratio: nFMD = FMD/(ΔWSS mean /WSS baseline ). Subjects underwent this protocol twice, resulting in four baseline FMD measurements to estimate intra-class correlation coefficients, which were 0.57 and 0.63 for nFMD and FMD, respectively. Effect of the oral glucose tolerance test: Comparison between nFMD and FMD baseline 30min 75min p-value* glucose [mmol/l] 4.7 ± 0.3 6.6 ± 1.0 5.9 ± 1.3