Heparin-induced thrombocytopenia pathophysiology


 * Associate Editor(s)-In-Chief: Priyamvada Singh, M.B.B.S. [mailto:psingh@perfuse.org]

Overview
Heparin-induced thrombocytopenia is diagnosed when the platelet count falls by > 50% typically after 5-10 days of heparin therapy. It is caused by antibodies to complexes between heparin and platelet factor 4 (PF4). These antibody complexes stimulates the procoagulant pathways due to activation of platelet and endothelium.

Pathophysiology

 * It is caused by antibodies to complexes between heparin and platelet factor 4 (PF4).
 * More than 90% patients have these anti–PF4-heparin antibodies in their plasma.
 * These antibodies bind to the platelet's surface and induce their activation by cross-linking Fc IIA receptors and bind to the surface of the endothelium, inducing procoagulant activity.
 * Platelets activated with these antibodies, increase their release of platelet factor 4 (PF4). Thus, a viscous cycle continues.