Whole blood viscosity in microvascular angina and coronary artery disease: Significance and utility

Introduction and Objectives: Whole blood viscosity (WBV) is the intrinsic resistance of blood flow in vessels, and when elevated induces endothelial shear stress and endothelial inflammation and can accelerate the atherosclerotic process. This study aims to compare WBV levels in patients with microvascular angina (MVA), patients with coronary artery disease (CAD), and normal controls, and to identify the relationship between WBV and high-sensitivity C-reactive protein as a marker of inflammation in MVA and CAD. Methods: A total of 573 patients were studied. The MVA group consisted of 189 subjects, the CAD group consisted of 203 subjects, and the control group consisted of 181 age- and gender-matched individuals. WBV was calculated from hematocrit and plasma protein concentration at a low shear rate (0.5 s(-1)) and high shear rate (208 s(-1)) by a validated equation. Results: Patients with CAD and MVA had significantly higher WBV at both tow and high shear rates compared to the control group. Correlation analysis revealed a significant relationship between high-sensitivity C-reactive protein and WBV at tow (r=0.556; p<0.001) and high shear rates (r=0.562) in the CAD group and at low (r=0.475) and high shear rates (r=0.493) in the MVA group. Conclusions: Overall, this study demonstrated a significant and independent association between blood viscosity and the existence of endothelial inflammation and the atherosclerotic process. (C) 2020 Sociedade Portuguese de Cardiologia. Published by Elsevier Espana, S.L.U.