Abstract
Venous thromboembolism is the third leading cause of vascular death,1 with a high incidence, especially among older persons. Incidence rates increase from 1 per 10,000 annually among persons less than 40 years of age to nearly 1% annually among persons 80 years of age or older2; more than one third of cases occur in persons older than 60 years of age.3 The mainstay of treatment for more than a generation of physician experience involves bridging anticoagulation therapy from a parenteral heparin-type anticoagulant to a vitamin K antagonist such as warfarin, which requires laboratory monitoring. Given the rapid expansion of . . .