The difference of the influence of autonomic nervous activation caused by reactive hyperemia on two different endothelial function tests

Background: While reactive hyperemia is used for the assessment of endothelial function in clinical settings, this maneuver is stressful and may affect autonomic nervous system activity. Two different methods to assess endothelial function are available {i.e., conduit arterial endothelial function: flow-mediated vasodilatation (FMD), micro-vascular endothelial function: reactive hyperemia index assessed by both (left/right) finger-tips arterial tonometry (RHIendPAT)}, but influence of the changes of autonomic nervous activity related with reactive hyperemia on these two methods has not been clarified. Objects: The present study was conducted to examine the influence of the changes of autonomic nerve activitiy caused by reactive hyperemia on micro-vascular and conduit arterial endothelial function. Methods: In 108 hypertensive patients, FMD and RHIendPAT were measured simultaneously. The analysis of heart rate viability (HRV) {high frequency domain (HF), low frequency domain (LF) and their ratio (LF/HF)} were performed throughout this reactive hyperemia in these patients. Results: By reactive hyperemia, LF was increased in 60 patinets (LFinc group) and was not increased in 48 patinets (LFdec group). RHIendPAT was lower in the former group (LFinc group) (2.2±0.5) than that in the latter group (LFdec group) (2.5±0.7) (p<0.05). However, no difference was found in FMD between these groups (3.4±2.0% vs 3.9±2.5%, p=0.28). Multivariate linear regression analysis demonstrated that the change of LF by reactive hyperemia was a significant determinant for RHIendPAT (β= -0.23, p<0.05), but not for FMD (β= -0.10, p=0.33), independent of conventional risk factors for cardiovascular disease. Conclusion: The influence of the changes of autonomic nerve activity by reactive hyperemia might be significant on RHIendPAT, but not on FMD, even with the adjustment of simultaneous both sides (left and right fingers) measurements of finger-tip tonometry.