Comparison of bivalirudin, enoxaparin, and unfractionated heparin in preventing cardiac catheter thrombosis. Results of an in-vitro study

Bivalirudin, a direct thrombin inhibitor binds specifically and reversibly to both fibrin-bound and unbound thrombin. Bivalirudin is approved for use as an anticoagulant in patients undergoing percutaneous coronary intervention. The OASIS-5 trial presented a significant increase in cardiac catheter thrombosis for the pentasaccharid fondaparinux compared to enoxaparin. Catheter thrombosis has never been reported in any trial using bivalirudin. Our study compared the development of catheter thrombosis for bivalirudin, enoxaparin, and unfractionated heparin in a controlled in-vitro environment. Ten healthy male volunteers were pretreated with aspirin 500 mg 2 hours before venesection of 50 ml of blood. The seven groups of anticoagulant combinations tested were: UFH, UFH + eptifibatide, enoxaparin, enoxaparin + eptifibatide, bivalirudin bolus, bivalirudin + eptifibatide, bivalirudin bolus + continuous infusion. The blood/anticoagulant mix continuously circulated through a cardiac guiding catheter for 60 minutes or until the catheter became blocked with thrombus. Thrombus development was assessed by weighing each catheter before and after the procedure. Electron microscopy was used to quantify the degree of erythrocyte, platelet and fibrin deposition. Following anticoagulation with bolus dose bivalirudin, the catheter was invariably occluded with thrombus after 33 minutes of circulation. However, a continuous infusion of Bivalirudin prevented the development of occlusive catheter thrombosis. In the bolus bivalirudin group the mean thrombus weight was significantly greater than in all other groups (p-value < 0.01 in all analyses). Bivalirudin given as a bolus was not sufficient to prevent cardiac catheter thrombosis in our in-vitro study. However, a continuous infusion of bivalirudin had similar anti-thrombotic efficacy compared to other treatment strategies.