Nonfractionated heparin fails to inhibit arterial thrombosis in a human exvivo thrombosis model

The effect of nonfractionated heparin on the formation and composition of a rterial thrombus is unclear. The purpose of this study in a human ex vivo m odel 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 t issue factor (TF) or collagen were exposed to human blood collected from he althy 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 dep osition was determined by quantifying fibrin degradation products released after application of plasmin (D-dimers). Heparin was injected into the bloo d flow through a blender port system located between the venous puncture si te and perfusion chamber. The results of the study showed that in a human e x vivo model, formation of arterial thrombus on two thrombogenic surfaces ( tissue factor and collagen) is not inhibited by nonfractionated heparin.