Oral anticoagulation among atrial fibrillation patients with anaemia: an observational cohort study

Abstract

Aims To investigate the risk of stroke/thromboembolism (TE) and major bleeding associated with anaemia among patients with atrial fibrillation (AF). Also, to assess the effects of oral anticoagulation (OAC) and time in therapeutic range (TTR) with vitamin K antagonists according to level of haemoglobin (Hb). Methods and results Through administrative registry databases, we identified all Danish patients diagnosed with AF from 1997 to 2012. We included 18 734 AF patients with recent available data on Hb. Multiple Cox regression analyses were used to estimate hazard ratios and to compute standardized absolute 1-year risks of stroke/TE and major bleeding. Among included patients, 3796 (20%) had mild anaemia (Hb 6.83–7.45 mmol/L for women and Hb 6.83–8.03 mmol/L for men) and 2562 (14%) had moderate/severe anaemia (Hb <6.83 mmol/L). Moderate/severe anaemia was associated with increased risk of major bleeding and 9.1% lower median TTR compared with no anaemia. Use of OAC was associated with reduced risk of stroke/TE among patients without anaemia [standardized absolute 1-year difference −2.5%, 95% confidence interval (CI) −3.8 to −1.7%] or with mild anaemia (−2.3%, 95% CI −2.8 to −1.8%), but not with moderate/severe anaemia, (0.03%, −1.8 to +2.8%, interaction P = 0.01). Oral anticoagulation was associated with a 5.3% (95% CI 2.1–8.7%) increased standardized absolute risk of major bleeding among AF patients with moderate/severe anaemia. Conclusion Anaemia was common in patients with AF and associated with major bleeding and lower TTR. Oral anticoagulation was associated with more major bleeding, but no reduction in risk of stroke/TE among AF patients with moderate/severe anaemia.

Impact of anemia on clinical outcomes of patients with atrial fibrillation: The COOL‐AF registry

“…Anemia could affect physician or patient decision regarding whether or not to use OAC 7 . It may also influence the choice of OAC, and when patients were on warfarin, anemia influenced the level of anticoagulation control leading to a poor TTR 7 . The TTR among patients who were on warfarin in our study was also lower in patients with anemia compared to those without.…”

“…Most patients with NVAF need OAC for stroke prevention 2‐4 . Anemia could affect physician or patient decision regarding whether or not to use OAC 7 . It may also influence the choice of OAC, and when patients were on warfarin, anemia influenced the level of anticoagulation control leading to a poor TTR 7 .…”

“…Anemia is detected in approximately 21% of subjects older than 65 years, and in 31% of those older than 80 years 5 . Among patients with NVAF, anemia was detected in 13–34% 6,7 . OAC treatment in patients with anemia may increase the risk of bleeding since some patients may have a hidden site of bleeding 6,8 .…”

“…Compared to the decision whether or not to use OAC in non‐anemic NVAF, the decision to prescribe OAC in NVAF patients with anemia will depend on the cause and severity of anemia 7 . Moreover, when using OAC, anemia may affect the choice of OAC 6,8,9 .…”

“…Moreover, when using OAC, anemia may affect the choice of OAC 6,8,9 . When warfarin is used, physicians tend to maintain a low international normalized ratio (INR) target, which often leads to a suboptimal time in therapeutic range (TTR) 7 …”