The aim of the present study was to assess whether elevated B-type natriuretic peptide (BNP) levels, as an objective marker of heart failure, is a predictor of subsequent thromboembolic events in patients with atrial fibrillation (AF) during oral anticoagulant therapy. This was a post hoc analysis of a single-center, prospective, observational study. Consecutive patients with AF (261 patients, 74 ± 9 years old, 153 paroxysmal AF) treated with warfarin were included for the analysis. BNP level at baseline examination was measured to assess the relationship of this parameter with subsequent thromboembolic events. BNP levels at the time of entry were 161 ± 188 (5-1,500, median 105) pg/ml. During an average follow-up time of 762 ± 220 (median 742) days, nine (1.8%/year) thromboembolic events occurred. Receiver operating characteristic curve showed that an optimal cut-off value for BNP to predict thromboembolic events was 218 pg/ml. There were six thromboembolic events observed among patients with a baseline BNP levels ≥200 pg/ml (n = 73) as compared to three such events in those with baseline BNP levels <200 pg/ml (n = 188). Kaplan-Meier curves for BNP level showed that elevated BNP level (≥200 pg/ml) was significantly associated with thromboembolic events (p < 0.01). Cox-proportional hazard analysis also revealed that a high BNP level (≥200 pg/ml) was a significant predictor of subsequent thromboembolic events (hazard ratio 5.32, p = 0.018). Elevated BNP levels (≥200 pg/ml) could be a useful marker of subsequent thromboembolic events in patients with AF during oral anticoagulant therapy. However, the number of patients and events in this study was small and drawing a definite conclusion was not possible with this small sample size. Therefore, further larger-scale, multicenter studies are needed to confirm these findings.
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