Whole blood viscosity and erythrocyte 1 deformability are related to 2 endothelium - dependent vasodilation and 3 coronary risk in the elderly 4 The Prospective Investigation of the Vasculature in Uppsala Seniors

It has previously been shown that a high hemoglobin value, a major determinant of whole blood viscosity (WBV), 9 predicts cardiovascular events. One putative mechanism might be an impaired endothelial function. Erythrocyte deformability is 10 another rheologic feature of the erythrocyte being of importance for the flow properties of the blood, especially in the capillaries. 11 The present study evaluates the relationships between blood viscosity, erythrocyte deformability assessed as erythrocyte fluidity 12 (EF), coronary risk and endothelial vasodilatory function. In the population-based PIVUS study (1016 subjects aged 70); 13 endothelium-dependent vasodilation (EDV) was evaluated by the invasive forearm technique with acetylcholine given in the 14 brachial artery and the brachial artery ultrasound technique with measurement of flow-mediated dilatation (FMD). WBV, plasma 15 viscosity (PV) and EF were measured in a random sample of 573 subjects. WBV and PV were positively and EF negatively 16 related to Framingham risk score. EDV was inversely related to both whole blood and plasma viscosity. FMD was not related to 17 any rheologic variable. In multiple regression analyses WBV and EF were significantly related to EDV independently of gender, 18 hypertension, smoking, hypercholesterolemia, obesity and diabetes. Acetylcholine-induced vasodilation in the forearm, but not 19 FMD, was negatively related to whole blood viscosity and positively related to EF independently of traditional risk factors in 20 elderly subjects, indicating a pathophysiological link between impaired hemorheology and coronary risk. 21