PP.27.03

Abstract

Objective: Endothelial dysfunction is recognized as an independent risk factor for cardiovascular events. It is measured non-invasively as brachial artery flow-mediated dilation (FMD) and as reactive hyperemia index (RHI). This study aimed to address the relationship of these two methods for assessing endothelial function comparing the two possible techniques with lower (forearm) and upper (arm) cuff occlusion. Design and method: In 17 young healthy subjects (9 males, age 29 ± 4 years) FMD and RHI were measured simultaneously in two separate occasions by 5 minutes of ischemia with lower (L) and upper (U) cuff occlusion. FMD was measured by ultrasounds as maximum percentage increase in brachial diameter by an automated system (FMD studio, Quipu s.r.l., Pisa, Italy). Baseline and Hyperemic Shear rate (SR) were also computed. RHI was assessed by finger arterial tonometry (EndoPAT 2000, Itamar Medical, Israel) and log-transformed. Results: L-FMD (7.32 ± 4.87%) and L-RHI (0.61 ± 0.29%) were significantly lower (p < 0.05 and p < 0.01, respectively) as compared to U-FMD (10.48 ± 5.67%) and U-RHI (0.86 ± 0.23%). L-FMD was not related to U-FMD (r = 0.39; p = 0.12). No significant relation was found between L-RHI and U-RHI (r = 0.49; p = 0.06). L-FMD was significantly related to L-SR (r = 0.62; p < 0.01), but not to L-RHI (r = 0.17; p = 0.54). L-RHI was not significantly correlated with L-SR (r = 0.24; p = 0,38). U-RHI was related to U-FMD (r = 0.50; p < 0.05) and to U-SR (r = 0.50, p < 0.04). In multiple regression analysis (full model: r2 = 0.23) U-FMD but not U-SR was associated with U-RHI (r2 = 0.20; p = 0.05). Conclusions: In healthy subjects, the assessment of FMD and RHI with lower and upper cuff occlusion is not equivalent. L-FMD, but not U-FMD is related to SR increase, thus possibly representing a better marker for conduit artery endothelial function. Conversely, U-RHI and U-FMD are independently related, both providing similar information on vascular reactivity, although possibly less specifically for endothelial function. Thus, caution is deemed in interpreting studies on vascular reactivity conducted with different techniques and methodologies.