Heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia with or without thrombosis has been recogn ized increasingly as a serious complication of heparin use. This article re views type II heparin-induced thrombocytopenia, which is mediated by an ant ibody that in most cases has specificity for a complex between heparin and platelet factor 4, a secreted platelet alpha-granule protein. The antibody- heparin-platelet factor 4 complex can activate platelets and endothelial ce lls, thereby initiating thrombosis. Clinical thrombosis in this syndrome ma y be arterial or venous. Treatment of the syndrome requires discontinuation of heparin and institution of an alternative anticoagulant.