Association of adding antiplatelet therapy to warfarin for management of venous thromboembolism with bleeding and other adverse events

Document Type

Conference Proceeding

Publication Date


Publication Title

Research and Practice in Thrombosis and Haemostasis


Background : Historically, guidelines regarding anticoagulation and antiplatelet treatment regimens have focused on patients with coronary artery disease (CAD) and atrial fibrillation. Few studies have examined the use of anticoagulation and antiplatelet therapy in patients with venous thromboembolism (VTE) and other comorbidities, including CAD. Aims : To evaluate the frequency and outcomes of antiplatelet therapy in addition to warfarin for patients with VTE. Methods : Using a registry-based cohort study of adults enrolled at six anticoagulation clinics in Michigan, USA from 2009 to 2020, we evaluated patients started on warfarin for VTE without comorbid atrial fibrillation/ flutter, antiphospholipid syndrome, or history of valve replacement. Adverse event rates were calculated via Kaplan-Meier survival analysis. Adjusted associations between number of antiplatelets and outcomes of thrombosis and bleeding were assessed using Cox proportional hazards. Results : Of the study cohort of 2918 patients (1333 men [45.7%]; mean [SD] age, 61.0 [16.4] years), 820 patients (28.1%) received warfarin plus one or more antiplatelet medication. Incidence of CAD was greater among those on combination warfarin and antiplatelet therapy versus warfarin alone (74.6% vs. 13.4%, P < 0.001). Incidence of bleeding events was also greater in patients on combination warfarin and antiplatelet therapy versus warfarin alone (28.8% vs. 21.9%, P < 0.001). In unadjusted analysis, an increase in number of antiplatelet medications was associated with increased rates of bleeding. After controlling for age, gender, race, provoked status of VTE, and RIETE score for risk of major bleeding, use of one antiplatelet medication (hazard ratio, 1.21; 95% CI, 1.02-1.43) and use of two antiplatelet medications (hazard ratio, 2.37; 95% CI, 1.65-3.39) remained significantly associated with increased bleeding. Conclusions : Among patients with VTE, combination warfarin and antiplatelet therapy was associated with increased bleeding and similar rates of thrombosis, compared to warfarin monotherapy. Further research is needed to evaluate bleeding risk among patients with VTE compared to similarly matched patients with atrial fibrillation.

PubMed ID

Not assigned.