Abstract 5872: Argatroban And Bivalirudin Compared To Unfractionated Heparin In Preventing Thrombus Formation On Mechanical Heart Valves, Results Of An In Vitro Study
Introduction Argatroban and bivalirudin both selectively inhibit thrombin at its active site. In patients with heparin-induced thrombocytopenia, and HIT complicated by thrombosis (HIT II), argatroban and bivalirudin are recommended due to their ability to significantly decrease the risk of thrombembolic complications in comparison to other treatments. The aim of the present study was to investigate the efficacy of argatroban and bivalirudin in comparison to unfractionated heparin (UFH) in preventing thrombus formation on mechanical heart valves using an in vitro system.
Materials and Methods Blood (220 ml) from young and healthy male volunteers was anticoagulated either by UFH, argatroban bolus, argatroban bolus + continuous infusion, bivalirudin bolus, or bivalirudin bolus + continuous infusion. St. Jude Medical 27 mm prosthesis were placed in a newly constructed in vitro thrombosis tester, and exposed to a continuous circulation rate of 80 beats per minute to anticoagulated blood samples. The total exposure time was 60 minutes. To quantify the thrombi that developed, electron microscopy was performed. Using a Data Acquisition Unit (DAQ), flow- and pressure differences, before and after the heart valve, could be measured and compared between the five groups. And finally each valve was weighed before and after the experiment.
Results The mean thrombus weight in group 1 (UFH) was 117 ± 93 mg, in group 2 (argatroban bolus) 722 ± 428 mg, in group 3 (argatroban bolus + continuous infusion) 162 ± 98 mg, in group 4 (bivalirudin bolus) 758 ± 323 mg, and in group 5 (bivalirudin bolus + continuous) 166 ± 141 mg (p-value: <0,00 for comparison between groups 2 and 4 to the other 3 groups). Electron microscopy showed higher rates of thrombus formation in groups 2 and 4.
Conclusion Argatroban and bivalirudin were as efficient as UFH in preventing thrombus formation on mechanical heart valves in our in vitro experiments, when they were administered continuously. We hypothesize that either the continuous infusion of argatroban or bivalirudin are an optimal treatment option for patients with HIT after mechanical heart valve replacement for adapting oral to parenteral anticoagulation or vice versa.