Transient hemorheology, application to cardiovascular diseases

Rheological properties of blood play an important role in blood flow physiology. From a mechanical point of view, blood does not exhibit a classical behaviour. In addition to a non-newtonian behaviour (shear-thinning) /1/ which is generally attributed to concentrated suspensions of small particles (polymer solutions, colloids, …), blood exhibits, under transient flow conditions, viscoelasticity and thixotropy /2, 3/. In order to explain these phenomena, it is necessary to take into account RBC (Red Blood Cell) ability to aggregate into a complex network with tangled rouleaux. Shear stresses separate the rouleaux, stretch and divide them into single cells. This organization of RBC at rest depends on the presence of plasma proteins such as fibrinogen and globulins. RBC aggregation is due to macromolecular bridging between the surface of adjacent cells /4/.