Novel cardiovascular anticoagulation for thromboprophylaxis of mechanical heart valves in a porcine model of heterotopic valve replacement.

摘要

OBJECTIVES: Vitamin K antagonists (VKA) are used to reduce the risk of stroke and thromboembolic complications in patients with mechanical heart valves. Yet, despite frequent blood testing, its poor pharmacokinetic and pharmacodynamic profiles often result in variable therapeutic levels. Rivaroxaban is a direct competitive factor Xa inhibitor that is taken orally. It inhibits the active site of factor Xa without the need for the cofactor antithrombin, and thus, its mechanism of action is differentiated from that of the fractionated heparins and indirect factor Xa inhibitors. No in vivo data exist regarding the effectiveness of rivaroxaban in preventing thromboembolic complications of mechanical heart valves. We tested the hypothesis that rivaroxaban is as effective as low molecular weight heparin for thromboprophylaxis of mechanical valves that use a previously described heterotopic aortic valve porcine model.;METHODS: A modified bileaflet mechanical valved conduit that bypassed the native, ligated descending thoracic aorta was implanted into 30 swine. Postoperatively, the animals were randomly assigned to groups receiving no anticoagulation (n = 10), enoxaparin (LMWH) at 2 mg/kg subcutaneously twice daily (n = 10) or rivaroxaban at 2 mg/kg orally twice daily (n = 10). The amount of valve thrombus was measured on post-implantation day 30 as the primary end point. Quantitative evaluation of radiolabelled platelet deposition on the valve prostheses was done and embolic and hemorrhagic events were measured as secondary end points.;RESULTS: Animals with no anticoagulation had a thrombus mean of 759.9 mg compared with 716.8 mg with LMWH treatment and 209.6 mg with rivaroxaban treatment (P = 0.05 for LMWH vs rivaroxaban). Similarly, the mean number of platelets deposited on the valve prosthesis was lower in the rivaroxaban group (6.13 x 109) than in the LMWH group (3.03 x 10 10) (P = 0.03).;CONCLUSIONS: In this study, rivaroxaban was more effective than LMWH for short-term thromboprophylaxis of mechanical valve prosthetics in the heterotopic aortic position. It reduced valve thrombus and platelet deposition on day 30 following implantation without increased adverse events. Future studies would provide additional support for clinical trials evaluating rivaroxaban as an alternative to VKA for appropriately selected patients with prosthetic aortic valves.