Thromboembolism and
bleeding after mechanical heart valve replacement are still unsolved problems, particularly for patients requiring anticoagulative bridging
therapy. The aim of this study was to investigate whether
rivaroxaban, a new oral selective and direct
coagulation factor Xa inhibitor, is as effective as
enoxaparin and
unfractionated heparin (UFH) in preventing
thrombus formation on mechanical heart valves using an in vitro system. Blood from healthy male donors was anticoagulated with either UFH,
enoxaparin,
rivaroxaban at 300 ng/ml, (n = 10 each), or
rivaroxaban at 30 ng/ml (n = 3). Mechanical aortic valve
prostheses were placed into the in vitro testing system THIA II and exposed to the
anticoagulant blood mixtures at a pulsatile flow for 60 min. Overall
thrombus weight, coagulation parameters, and electron microscopic features of
thrombus formation on the valve surface were quantified as endpoints. The mean
thrombus weights were 163 ± 64 mg for group 1 (UFH), 341 ± 63 mg for the group 2 (
enoxaparin), 238 ± 83 mg for group 3 (
rivaroxaban 300 ng/ml) and 1.739 ± 16 mg for group 4 (
rivaroxaban 30 ng/ml). Whereas high-dosed
rivaroxaban showed no significant differences compared to UFH or
enoxaparin, low-dosed
rivaroxaban generated a massive
thrombus generation, thus differing significantly from all other treatment groups regarding the
thrombus weight. We hypothesize that high-dose
rivaroxaban is a competitive oral available alternative to UFH and
LMWH's, that might be a worthwhile alternative for patients in need of anticoagulative bridging
therapy. Prospective studies have to evaluate if
rivaroxaban might even overcome the limitations of OAC in patients after implantation of
artificial heart valves.