Duration of anticoagulation: applying the guidelines and beyond

Despite an improved understanding of the risk factors underlying venous thromboembolism (VTE), extensive clinical investigation, and detailed clinical guidelines, the decision to extend anticoagulation indefinitely for an individual patient with VTE is often problematic. Patients with VTE in association with major surgery, trauma, immobilization, or pregnancy are at relatively low risk of recurrence and generally do not require more than 3 to 6 months of anticoagulant therapy. For patients with a first unprovoked, or idiopathic, episode of VTE, an individualized approach should be taken in deciding on the duration of anticoagulation based on the patient's recurrence and bleeding risk, as well as their personal preference. Although the presence of genetic thrombophilic disorders (factor V Leiden and prothrombin G20210A gene mutations; deficiencies of antithrombin, protein C, and protein S) predispose patients to a first episode of VTE, there is inconsistent data on whether testing for these defects changes patient outcomes or should alter their management. In patients with a single unprovoked VTE, measurement of D-dimer several weeks following the completion of anticoagulant therapy appears useful in stratifying patients with a first unprovoked episode of VTE with regard to recurrence risk. Through a series of clinical vignettes, the utility of the laboratory in risk-stratifying patients with respect to recurrence risk will be discussed, along with decision making regarding the duration of anticoagulation. The potential impact of having a nonremovable inferior vena caval filter will also be addressed.