Heparin-induced thrombocytopenia pathophysiology

Heparin-induced thrombocytopenia
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2], Aric C. Hall, M.D., [3]

Overview

Heparin-induced thrombocytopenia is diagnosed when the platelet count falls by > 50% typically after 5-10 days of heparin therapy.

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.