Hemorheological parameters as independent predictors of venous thromboembolism.

The role played by hemorheological alterations in the development of deep vein thrombosis (DVT) has often been overlooked. Although marked rheological alterations and the relationship with thromboembolic events are well-defined in patients with hematological diseases such as myelom, Waldenström disease and polycythemia vera, the relationship is not so clear in patients without hematological diseases. In the present review, we analyzed studies evaluating the rheological profile in DVT patients. Among the cardiovascular risk factors, only hyperlipidemia, metabolic syndrome, tobacco and obesity increase DVT risk and, in addition, a disturbed rheological profile is shown which could further increase this risk. The significance of hematocrit and fibrinogen, the main factors influencing blood viscosity, is not sufficient to increase blood viscosity in any of the studies analyzed. DVT patients show increased fibrinogen levels and erythrocyte aggregation throughout all the studies despite patients not being in an acute reactant phase. In addition to rheological alterations, it is necessary to consider local conditions at pockets of venous valves which undergo deterioration with aging and play an important role equally to alterations in the rheological profile. Moreover, it is necessary to take into account that systemic rheological alterations are not comparable to those in low shear rate areas where minimum disturbances could be more relevant. It would be convenient to perform multicentric studies with the same rheological methodology and pre-analytical procedures to evaluate, in order to obviate the effect of thrombophilic and circumstantial risk factors, rheological parameters in patients with spontaneous DVT to elucidate their real contribution to the development of thromboembolic events.