Blood viscosity, red-cell flexibility, haematocrit, and plasma-fibrinogen in patients with angina.

Whole-blood viscosity, haematocrit and plasma-fibrinogen concentration were measured in 22 patients with angina and 22 controls. All four variables were significantly higher in patients with angina. When the viscosity was corrected to a standard haematocrit (45%), however, there was no significant difference in the mean viscosity of the two groups, indicating that the higher viscosity in patients with angina is the result of the higher haematocrit. Increased red-cell flexibility tends to counteract the effect of increased plasma-fibrinogen concentration, which tends to increase blood-viscosity.