Nonfractionated heparin fails to inhibit arterial thrombosis in a human ex vivo thrombosis model

The effect of nonfractionated heparin on the formation and composition of arterial thrombus is unclear. The purpose of this study in a human ex vivo model was to analyze fibrinoplatelet thrombi and test the inhibitory effect of nonfractionated heparin on arterial thrombus formation. Experiments were carried out in Sakariassen perfusion chambers. Strips coated with either tissue factor (TF) or collagen were exposed to human blood collected from healthy volunteers at an arterial shear stress rate of 2600 s(-1) for 1 to 4 min. Platelet deposition was determined using immunoenzymatic techniques to quantify P-selectine, a platelet membrane receptor, in thrombi. Fibrin deposition was determined by quantifying fibrin degradation products released after application of plasmin (D-dimers). Heparin was injected into the blood flow through a blender port system located between the venous puncture site and perfusion chamber. The results of the study showed that in a human ex vivo model, formation of arterial thrombus on two thrombogenic surfaces (tissue factor and collagen) is not inhibited by nonfractionated heparin.