MedWire News: High-dose rivaroxaban may offer an alternative to standard anticoagulation with oral vitamin K antagonists for patients with mechanical heart valves, in vitro study data show.
"Lifelong oral anticoagulation (OAC) is mandatory after mechanical heart valve replacement to prevent thromboembolic events," explain Axel Schlitt (Martin Luther-University Halle-Wittenberg, Germany) and colleagues in the Journal of Thrombosis and Thrombolysis.
"However, several situations necessitate interruption of OAC, for example, in preparation for surgical procedures or nonsurgical interventions such as cardiac catheterization," they add.
Since interrupting anticoagulation can be associated with bleeding or thromboembolic events, novel oral anticoagulants may be promising alternatives for bridging therapy in patients after mechanical heart valve replacement.
In the present study, Schlitt and team used an in vitro system to investigate whether rivaroxaban, a novel oral selective and direct factor Xa inhibitor, is as effective as enoxaparin and unfractionated heparin (UFH) in preventing thrombus formation on mechanical heart valves.
Blood from healthy male donors was anticoagulated with UFH 0.8 IU/ml, enoxaparin 0.7 IU/ml, rivaroxaban 300 ng/ml, (n=10 each), or rivaroxaban 30 ng/ml (n=3).
Mechanical aortic valve prostheses were then placed into an in vitro testing system (Thrombosis Tester Helholtz Institute Aachen II) and exposed to the anticoagulant blood mixtures at a pulsatile flow of 60 bpm for 60 minutes.
At the end of the experimental period the mean thrombus weights did not differ significantly among the UFH, enoxaparin, and high-dose rivaroxaban groups, at 163, 341, and 238 mg respectively. In contrast the thrombus weight was significantly higher in the low-dose rivaroxaban group than in the other groups, at 1739 mg.
Electron microscopy confirmed these findings by demonstrating no significant differences in erythrocyte, thrombocyte, and fibrin deposition among the UFH, enoxaparin, and high-dose rivaroxaban groups, and a significant increase in these parameters in low-dose rivaroxaban group.
Schlitt and co-authors conclude: "High-dose rivaroxaban might be effective in preventing thromboembolic events after mechanical heart valve replacement and would therefore be an attractive alternative to UFH and low molecular weight heparin in bridging therapy."
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