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Risks and Benefits of Anticoagulation in Atrial Fibrillation: Insights From the Outcomes Registry for Better Informed Treatment of Atrial Fibrillation (ORBIT-AF) Registry
Study Questions:
What is the association between stroke and bleeding risk on rates of oral anticoagulation (OAC)?
Methods:
The investigators analyzed OAC use among 10,098 patients with AF from 174 community-based outpatient practices enrolled in 2010–2011 in the Outcomes Registry for Better Informed Treatment of Atrial Fibrillation (ORBIT-AF). OAC was defined as warfarin or dabigatran use at study enrollment. Stroke and bleeding risk were calculated using congestive heart failure, hypertension, age, diabetes mellitus, prior stroke (CHADS2), and anticoagulation and risk factors in AF (ATRIA) scores, respectively. Logistic regression tested the interaction between stroke risk (i.e., CHADS2 score) and bleeding risk (i.e., ATRIA score) on rates of OAC in both the primary and secondary sensitivity analyses.
Results:
The mean subject age was 73 years; 58% were men. Overall, 76% of patients received OAC (71% warfarin and 5% dabigatran). The use of OAC increased among those with higher CHADS2 scores, from 53% for CHADS2 = 0 to 80% for CHADS2 ≥2 (p < 0.001). OAC use fell slightly with increasing ATRIA bleeding risk score, from 81% for ATRIA = 3 to 73% for ATRIA ≥5 (p < 0.001). A significant interaction existed between ATRIA and CHADS2 scores (p = 0.021). Among those with low bleeding risk, use of OAC increased significantly with increasing stroke risk. Among those with high bleeding risk, CHADS2 stroke risk had a smaller impact on use of OAC.
Conclusions:
The authors concluded that in community-based outpatients with AF, use of OAC was high and driven by not only predominantly stroke, but also bleeding risk.
Perspective:
This study suggests that rates of OAC increased with increasing stroke risk in patients with both high and low bleeding risks. In this population of stable outpatients, the risk-treatment paradox does not appear to exist, and stroke risk primarily drives decisions on use of OAC. Furthermore, stroke risk significantly affects OAC use among those with low bleeding risk, whereas those with high bleeding risk demonstrate consistently lower use of OAC regardless of stroke risk. Despite improvements in appropriate use of OAC, continuous quality initiatives are indicated to improve overall stroke prevention treatment in patients with AF. Future studies need to test the benefit of a combined bleeding and stroke score approach to anticoagulation to optimize care.
Keywords: Stroke, Warfarin, Heart Failure, Atrial Fibrillation, Risk Factors, Hypertension
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