[Heparin-induced thrombocytopenia: implictions for cardiologist]

Heparin-induced thrombocytopenia (HIT) is one of the most life-threatening adverse effects of heparin administration. It is characterized by thrombocytopenia and may also be associated with venous or arterial thrombosis. HIT type 2 is caused by the binding of antibodies, most likely IgG, to a complex of heparin and platelet factor-4, these complexes IgG/PF4/heparin activate platelets causing the release of pro-thrombotic particles that promote thrombin generation. HIT and HIT-thrombosis are associated with high morbidity and mortality. Thrombotic events are most frequently venous and may manifest as pulmonary embolism or cerebral venous thrombosis. Arterial thrombosis leading to limb damage and amputation and to myocardial infarction or stroke may also occur. HIT is a clinical syndrome that requires clinical and laboratory findings to confirm the diagnosis. All forms of heparin treatment should be stopped once HIT is suspected and patients should be treated with an alternative anticoagulant to treat and prevent thrombotic complications. Available alternative anticoagulants include argatroban and lepirudin, a recombinant form of hirudin.