Letter to the Editor Heparin Cofactor II Levels Do Not Predict the Development of Coronary Heart Disease: The Atherosclerosis Risk in Communities (ARIC) Study

To the Editor: Heparin cofactor II (HCII) is a plasma glycoprotein that inactivates thrombin rapidly in the presence of dermatan sulfate or heparin.1 Although the presence of thrombin–HCII complexes in normal human plasma indicates that HCII inhibits thrombin in vivo,2 the physiological function of HCII remains unknown. Homozygous HCII-deficient mice develop thrombotic occlusion of the carotid artery faster than wild-type mice after photochemically-induced damage to the endothelium,3 suggesting that HCII might play a role in inhibiting thrombosis after arterial injury. Numerous clinical studies, however, have failed to demonstrate a convincing association between HCII deficiency and arterial or venous thrombosis.4 More recent studies suggest that individuals with higher than average HCII levels are less likely to develop …