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Adding Aspirin to Warfarin Without Indication and Increased Bleeding
Study Questions:
What is the frequency and what are the outcomes of adding aspirin to warfarin for patients without a clear therapeutic indication for combination therapy?
Methods:
The investigators conducted a registry-based cohort study of adults enrolled at six anticoagulation clinics in Michigan (January 1, 2010, to December 31, 2017) who were receiving warfarin therapy for atrial fibrillation (AF) or venous thromboembolism (VTE) without documentation of a recent myocardial infarction or history of valve replacement. Data on aspirin use without therapeutic indication were collected. Rates of any bleeding, major bleeding events, emergency department (ED) visits, hospitalizations, and thrombotic events at 1, 2, and 3 years were the main outcome measures. Survival analysis was used to examine the differences between the two matched groups for each of the endpoints: any bleeding, major bleeding, ED visits and hospitalizations for bleeding, and thrombosis.
Results:
Of the study cohort of 6,539 patients (3,326 men [50.9%]; mean [standard deviation] age, 66.1 [15.5] years), 2,453 patients (37.5%) without a clear therapeutic indication for aspirin were receiving combination warfarin and aspirin therapy. Data from two propensity score–matched cohorts of 1,844 patients were analyzed (warfarin and aspirin vs. warfarin only). At 1 year, patients receiving combination warfarin and aspirin compared with those receiving warfarin only had higher rates of overall bleeding (cumulative incidence, 26.0%; 95% confidence interval [CI], 23.8%-28.3% vs. 20.3%; 95% CI, 18.3%-22.3%; p < 0.001), major bleeding (5.7%; 95% CI, 4.6%-7.1% vs. 3.3%; 95% CI, 2.4%-4.3%; p < 0.001), ED visits for bleeding (13.3%; 95% CI, 11.6%-15.1% vs. 9.8%; 95% CI, 8.4%-11.4%; p = 0.001), and hospitalizations for bleeding (8.1%; 6.8%-9.6% vs. 5.2%; 95% CI, 4.1%-6.4%; p = 0.001). Rates of thrombosis were similar, with a 1-year cumulative incidence of 2.3% (95% CI, 1.6%-3.1%) for those receiving combination warfarin and aspirin therapy compared with 2.7% (95% CI, 2.0%-3.6%) for those receiving warfarin alone (p = 0.40). Similar findings persisted during 3 years of follow-up as well as in sensitivity analyses.
Conclusions:
The authors concluded that compared with warfarin monotherapy, receipt of combination warfarin and aspirin therapy was associated with increased bleeding and similar observed rates of thrombosis.
Perspective:
This registry-based cohort study of patients followed up at anticoagulation clinics while receiving warfarin therapy reports that treatment with combination warfarin and aspirin therapy compared with warfarin monotherapy was associated with a significant increase in bleeding, major bleeding, ED visits, and hospitalizations. Furthermore, these results persisted for at least 3 years of follow-up, without any observed added benefit regarding thrombotic events. There is a need for greater awareness of this issue and efforts to discontinue aspirin therapy in patients without a clear therapeutic indication for receiving aspirin while receiving warfarin therapy. Additional research is indicated to help clinicians determine which patients should receive combination warfarin and aspirin therapy instead of warfarin monotherapy for VTE or AF.
Clinical Topics: Anticoagulation Management, Arrhythmias and Clinical EP, Cardiovascular Care Team, Prevention, Pulmonary Hypertension and Venous Thromboembolism, Anticoagulation Management and Atrial Fibrillation, Anticoagulation Management and Venothromboembolism, Implantable Devices, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias
Keywords: Anticoagulants, Aspirin, Arrhythmias, Cardiac, Atrial Fibrillation, Emergency Service, Hospital, Hemorrhage, Myocardial Infarction, Outcome Assessment, Health Care, Secondary Prevention, Thrombosis, Venous Thromboembolism, Warfarin
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