ABSTRACT
This chapter focuses on principles of thromboembolism, related pathophysiology, and clinical Thromboembolic (TE) disorders that mainly affect cats and dogs. Normal hemostasis depends on the interplay among several different factors that promote coagulation, inhibit coagulation, and promote fibrinolysis. A proper balance of these factors maintains blood fluidity and minimizes loss when vessels are damaged. Hemostasis involves the vascular endothelium, platelets, proteins of the coagulation cascade, and the fibrinolytic system. Intact vascular endothelial cells secrete substances that help prevent inappropriate thrombosis and participate in vasoregulation. The currently accepted model of coagulation is the cell-based model, in which coagulation occurs in overlapping steps: initiation, amplification, and propagation. Active tissue factor is the initiator of thrombin generation and ultimately, fibrin formation. Intact endothelium normally produces factors that have antiplatelet, anticoagulant, or fibrinolytic effects. Antithrombin deficiency is the most common cause of hypercoagulability.
