Grant: Operating Grant -PA: Inst of Circulatory and Respiratory Health - Bridge Funding

Blood clots in leg veins (deep vein thrombosis) or lung arteries (pulmonary embolism) that arise without a clear cause (i.e. unexplained) are collectively called "unprovoked venous thromboembolism"(VTE). There is evidence that some of these patients with first unprovoked VTE are more likely to develop another VTE once oral anticoagulation (blood thinner) is stopped and that they may need longer term to indefinite anticoagulation treatment to prevent recurrences. The REVERSE I study collected 646 first unprovoked VTE patients from 2001 to 2006 and classified these patients as being at low or high risk of recurrence. The present study will follow the REVERSE I study patients for 8 years with the objective of determining the need for indefinite anticoagulation (i.e. life-time) in this population of high risk unprovoked VTE patients. We will also investigate if the predictors of recurrent VTE identified in the REVERSE I study remain predictors for recurrent VTE in the long-term. These findings will assist clinicians to improve stratification of recurrent risk in first unprovoked VTE patients and will facilitate the development of clear guidelines for long-term management of first unprovoked VTE patients at high risk of recurrence.