Heparin-Induced Thrombocytopenia Diagnosis and Management

Heparin-induced thrombocytopenia (HIT) is an adverse drug reaction characterized by thrombocytopenia and a high risk for venous or arterial thrombosis.1 It is caused by heparin-dependent, plateletactivating antibodies that recognize a “self” protein, platelet factor 4 (PF4), bound to heparin. The resulting platelet activation is associated with increased thrombin generation (Figure).2 Typically, the platelet count fall begins 5 to 10 days after starting heparin, although a rapid platelet count fall can occur in a patient who has antibodies from recent heparin use.3 Remarkably, transience of HIT antibodies permits safe heparin reexposure in selected patients (for example, heart surgery patients) despite a history of HIT.3,4