Comparison of warfarin versus antiplatelet therapy after surgical bioprosthetic aortic valve replacement

OBJECTIVES: To compare effectiveness of warfarin and antiplatelet exposure regarding both thrombotic and bleeding events, following surgical aortic valve replacement with a biological prosthesis(bioSAVR). METHODS: The study included all patients in Sweden undergoing a bioSAVR during 2008-2014 who were alive at discharge from the index hospital stay. Exposure was analysed and defined as postdischarge dispension of any antithrombotic pharmaceutical, updated at each following dispensions and categorised as single antiplatelet (SAPT), warfarin, warfarin combined with SAPT, dual antiplatelet (DAPT) or no antithrombotic treatment. Exposure to SAPT was used as comparator. Outcome events were all-cause mortality, ischaemic stroke, haemorrhagic stroke, any thromboembolism and major bleedings. We continuously updated adjustments for comorbidities with any indication for antithrombotic treatment by Cox regression analysis. RESULTS: We identified 9539 patients with bioSAVR (36.8% women) at median age of 73 years with a mean follow-up of 3.13 years. As compared with SAPT, warfarin alone was associated with a lower incidence of ischaemic stroke (HR 0.49, 95% CI 0.35 to 0.70) and any thromboembolism (HR 0.75, 95% CI 0.60 to 0.94) but with no difference in mortality (HR 0.94, 95% CI 0.78 to 1.13). The incidence of haemorrhagic stroke (HR 1.94, 95% CI 1.07 to 3.51) and major bleeding (HR 1.67, 95% CI 1.30 to 2.15) was higher during warfarin exposure. As compared with SAPT, DAPT was not associated with any difference in ischaemic stroke or any thromboembolism. Risk-benefit analyses demonstrated that 2.7 (95% CI 1.0 to 11.9) of the ischaemic stroke cases could potentially be avoided per every haemorrhagic stroke caused by warfarin exposure instead of SAPT during the first year. CONCLUSION: In patients discharged after bioSAVR, warfarin exposure as compared with SAPT exposure was associated with lower long-term risk of ischaemic stroke and thromboembolic events, and with a higher incid