Whole blood viscosity and erythrocyte fluidity are related to endothelium-dependent vasodilation and coronary risk in the elderly

Background: It has been shown that an elevated blood viscosity predicts cardiovascular events. One putative mechanism might be an impaired endothelial function. Further, erythrocyte fluidity, representing erythrocyte deformability, is a characteristic rheologic feature of importance for the flow properties of the blood, especially in the smallest vessels.The present study evaluates the relationships between erythrocyte fluidity, whole blood and plasma viscosity, coronary risk and endothelial vasodilatory function.Methods and results: In a population-based study on 1016 subjects aged 70, endothelium-dependent vasodilatation (EDV) was evaluated by a) the invasive forearm technique with acetylcholine given in the brachial artery, b) the brachial artery ultrasound technique with measurement of flow-mediated dilatation (FMD) and c) pulse wave analysis with beta-2-agonist (terbutaline) provocation. Erythrocyte fluidity, and whole blood and plasma viscosity were measured in a random sample of 573 subjects.Whole blood and plasma viscosity were related to Framingham risk score (r=0.20, p< 0.0001). EDV was inversely related to both whole blood and plasma viscosity (r= -0.16, p=0.0004 and r= -0.14, p=0.0015, respectively). So was also the pulse wave response (r= -0.20, p<0.0001 and r= -0.09, p=0.045, respectively), but not FMD (r= 0.01-0.02).Erythrocyte fluidity was inversely related to the Framingham risk score (r= - 0.12, p=0.0009), EDV (r= 0.12, p=0.0064) and to the pulse wave response (r= -0.17, p=0.0002), but not to FMD (r= -0.01).Multiple regression analysis showed whole blood viscosity and erythrocyte fluidity to be significantly related to EDV and the pulse wave response independently of haematocrit, gender, hypertension, smoking, hypercholesterolemia, obesity and diabetes.Conclusion: Whole blood and plasma viscosity as well as erythrocyte fluidity were related to coronary risk. Acetylcholine-induced vasodilatation in the forearm and terbutaline-induced changes in pulse wave reflection were both inversely related to whole blood viscosity and erythrocyte fluidity independently of traditional risk factors in elderly subjects, indicating a pathophysiological link between impaired haemorheology and coronary risk.