Parameters of blood viscosity do not correlate with the extent of coronary and carotid atherosclerosis and with endothelial function in patients undergoing coronary angiography.

While the role of physical forces on the control of atherogenesis and the modulation of endothelial function is well known, studies investigating the impact of shear stress on the extent of central atherosclerosis and flow-mediated dilation in humans produced controversial results. We investigated the relationship between viscosity, coronary atherosclerosis, carotid intima-media thickness and flow-mediated dilation in patients undergoing coronary angiography. 451 patients (306 males, mean age 66 ± 10) were enrolled. Viscosity, which was calculated using a validated formula, showed a positive association with platelet activation (P = 0.01), leukocyte counts (P = 0.006) and C-reactive protein (P = 0.03), a marker of inflammation; surprisingly, visocsity showed a negative association with FMD (FMD decreased 0.14 ± 0.05% per each cPoise increase in viscosity) but only in patients without coronary artery disease. Viscosity showed no association with the extent of coronary or carotid artery disease. We provide cross-sectional data on the relationship between whole blood viscosity and parameters of vascular structure and function. While viscosity correlated with parameters of vascular inflammation, it showed no relationship with the presence and severity of central atherosclerosis.