title: Endothelial cell damage in heparin-induced thrombocytopenia.
abstract: Heparin-induced thrombocytopenia type II is a severe complication of heparin treatment that may result in thrombosis. When thrombosis occurs it carries a 50% mortality rate. The exact pathophysiology is not fully understood but in the majority of cases it is associated with the production of heparin/platelet factor 4 antibodies. The endothelium provides a protective anticoagulant surface over which blood flows. Perturbation of the endothelial cells causes a reversal of the anticoagulant properties of the cells to that of a procoagulant surface. This is often due to release or down-regulation of the anticoagulant membrane proteins such as thrombomodulin and up-regulation of procoagulant factors such as tissue factor. We studied 10 patients in our cardiothoracic institute with clinically and laboratory-confirmed heparin-induced thrombocytopenia type II for evidence of endothelial cell damage. There was a statistically significant rise in the concentrations of von Willebrand factor (P < 0.0001) and soluble thrombomodulin (P = 0.004) when patients with heparin-induced thrombocytopenia type II were compared with healthy laboratory controls and patients having had cardiopulmonary bypass surgery (von Willebrand factor 324 versus 103 versus 108 U/dl and soluble thrombomodulin 9.5 versus 2.3 versus 1.2 ng/ml, respectively). Our findings suggest that endothelial cell damage is a major factor in the pathophysiology of heparin-induced thrombocytopenia.
authors.affiliation: Department of Haematology, Royal Brompton Hospital, Sydney Street, London, UK. s.davidson@rbh.nthames.nhs.uk
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Davidson
authors.forename: Paul
authors.initials: P
authors.lastname: Wadham
authors.forename: Louise
authors.initials: L
authors.lastname: Rogers
authors.forename: John F
authors.initials: JF
authors.lastname: Burman
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D005260:Female; D005343:Fibrinolytic Agents / Q000009:adverse effects*; D006493:Heparin / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D013921:Thrombocytopenia / Q000139:chemically induced* / Q000503:physiopathology; D018180:Thrombomodulin / Q000378:metabolism*; D014841:von Willebrand Factor / Q000378:metabolism*
chemical_list: D005343:Fibrinolytic Agents; D018180:Thrombomodulin; D014841:von Willebrand Factor; D006493:Heparin