Heparin-induced thrombocytopenia: a historical perspective.

Heparin was discovered 90 years ago,1 and within 2 decades it was being widely used as an anticoagulant.2 The numerous advantages of heparin lend to its broad use including its immediate onset of action, relatively short half-life ( 60 minutes), simple laboratory monitoring (aPTT), ability to be reversed (using protamine), and low cost. Despite a long experience of using heparin, the counterintuitive notion that an anticoagulant could be intensely prothrombotic took almost 4 decades to become recognized. Our understanding of heparin-induced thrombocytopenia (HIT) has increased considerably and to a large measure exemplifies the best of translational research. Sometimes, basic studies investigating the pathophysiology of HIT lead to clinical insights. In other instances, clinical observations prompted basic studies. Together, these basic and applied investigations have dramatically enhanced our understanding of the pathogenesis and treatment of HIT.