Heparin-induced thrombocytopenia: Impact of bovine versus porcine heparin in HIT pathogenesis

Heparin-induced thrombocytopenia ( HIT) is a complication of heparin therapy in cardiovascular/ hematologic indications. Heparin is a mixture of sulfated mucopolysaccharide with heterogeneity and is capable of forming multiple complexes with platelet factor 4 ( PF4), released from activated platelets. HPF4 antibodies may cause platelet/ endothelial cell activation to promote HIT pathogenesis. HIT is a clinico-pathologic syndrome and its diagnosis primarily remains a clinical one; however, the serologic confirmation of the presence of HPF4 antibodies is also necessary part of the evaluation. Assays are based on the immunodetection of HPF4 antibodies and/ or their functional ability to activate cells. Currently, there are several assays in use and a few newer/ rapid immunoassays are becoming available. Recent studies have confirmed that HPF4 antibody generation ( seroconversion) is common after cardiac surgery and suggest that patients receiving bovine heparin are more likely to generate functional ( pathogenic) HPF4 antibodies of the IgG subclass. Thus, the use of bovine heparin in cardiovascular surgery should be avoided. A brief account of the currently available options for the management of HIT patients with non- heparin anticoagulants is provided.