Impact of mitral versus aortic bioprosthetic valve position on thromboembolism and bleeding risk in patients with atrial fibrillation

Background: The impact of valve position on thromboembolic and bleeding events in patients with atrial fibrillation (AF) and bioprosthetic valves is uncertain.

Methods: We analyzed 159 patients with AF after surgical single-valve replacement from the BPV-AF registry (Retro) (UMIN000034198), which was a multicenter, retrospective, observational registry that enrolled 214 patients with AF and bioprosthetic valves to assess differences in bioprosthetic valve position. Baseline characteristics and clinical outcomes were compared on the basis of the position of aortic or mitral bioprosthetic valves. The primary efficacy endpoint was stroke or systemic embolism, and the primary safety endpoint was major bleeding.

Results: There were 85 patients (53.5%) in the aortic valve (AV) group and 74 patients (46.5%) in the mitral valve (MV) group. The MV group had a lower body weight and a higher prevalence of prior major bleeding compared with the AV group. Thromboembolic and bleeding risk scores and the administration of antithrombotic agents were not significantly different between the groups. The primary efficacy endpoint was not significantly different [AV group: 8.2%; 2.25/100 person-years (PY); MV group: 4.1%; 1.01/100 PY] (log-rank, p = 0.23). The primary safety endpoint was significantly higher in the MV group (17.6%; 4.54/100 PY) compared with the AV group (5.9%; 1.59/100 PY) (log-rank, p = 0.049). The adjusted hazard ratio of the primary safety endpoint in the MV group relative to the AV group was 2.71 (95% confidence interval 0.86-8.54, p = 0.09).

Conclusions: In Japanese patients with AF and bioprosthetic valves, thromboembolic risk does not differ on the basis of valve position. Bleeding risk is higher in patients with MV bioprostheses, although valve position itself might not be an independent predictor for bleeding.