ABSTRACT
Thrombosis is a major cause of mortality and morbidity in polycythemia vera (PV).
The wide range of thrombotic events reflects the complex picture in PV. There are
multiple factors involved in thrombogenesis in this disease, including increased hematocrit,
thrombocytosis, impaired fibrinolytic activity, platelet activation, leukocyte activation,
endothelial damage, interactions between platelets and endothelium, various modalities
of therapy, and increased in whole-blood viscosity. Among them, the increase in blood
viscosity, and hence the impairment of blood flow, is the major factor. In this article,
the role of hyperviscosity in PV is reviewed. A high hematocrit occurs under PV and
many other conditions with abnormal red blood cell aggregation. The impaired capillary
blood flow results in neurological manifestations and increased bleeding risk in PV.
Thrombotic complications can also occur in both arteries and veins and manifest as
stroke, myocardial infarction, deep vein thrombosis, or pulmonary embolism. The hemodynamic
principle is aptly applied in the management of PV. The most important objective is
the reduction of the patient's hematocrit.
KEYWORDS
Hyperviscosity - polycythemia vera - red cell aggregation - thrombosis - rheology