Combined Aspirin Study for Mechanical Prosthetic Valve in Kyushu and Ryukyu by Inter-University Hospital Network (ASPIRIN-Trial)

BACKGROUND: The benefits of adding aspirin to warfarin and warfarin treatment intensity for Japanese patients with mechanical valve replacement (MeVR) are unclear. METHODS AND RESULTS: This multicenter non-randomized observational study recruited 158 Japanese patients who underwent MeVR in 11 university hospitals in Kyushu and Okinawa; 74 patients were allocated to the warfarin (W) group and 84 were allocated to the warfarin plus aspirin (W+A) group. Patients were followed for a mean (±SD) of 5.0±1.9 years. The primary and secondary endpoints were mainly atherosclerotic/thrombotic and bleeding events, respectively. There was no difference in the incidence of the primary endpoint between the W and W+A groups (14% vs. 22%, respectively; P=0.13). Univariate analysis revealed a higher incidence of the secondary endpoint in the W+A than W group (35% vs. 22%; P=0.032), but the difference was not significant in multivariate analysis. For the entire cohort, the postoperative mean international normalized ratio of prothrombin time (PT-INR) was relatively low (2.1±0.3). There were no differences in the incidence of events between PT-INR