These guidelines relate to discontinuing anticoagulants in patients who have had just a single unprovoked venous thromboembolic event (VTE).

Venous thromboembolism is a common, potentially fatal but treatable condition. Whether to continue oral anticoagulant therapy beyond 6 months after unprovoked venous thromboembolism still remains a matter of debate.

McRae's 2007 article was a meta-analysis to assess whether men and women have the same risk of recurrent venous thromboembolism after stopping anticoagulant treatment. 15 studies (nine randomized controlled trials and six prospective observational studies) enrolling 5416 patients (2729 men), of whom 816 (523 men) had recurrent venous thromboembolism after stopping treatment, were included. The authors concluded that men have a 50% higher risk than women of recurrent venous thromboembolism after stopping anticoagulant treatment

Douketis's 2007 article studied the risk for fatal pulmonary embolism after discontinuing anticoagulant therapy for venous thromboembolism. They concluded that the risk for fatal PE is 0.19 to 0.49 events per 100 person-years for patients who have finished a course of anticoagulant therapy for a first episode of symptomatic VTE. The case-fatality rate for death from recurrent PE was 4-9%.

Rodger's 2008 article determined clinical predictors to identify patients who are at low risk of recurrent venous thromboembolism who could safely discontinue anticoagulants. Interestingly, no clinical predictors could identify low risk men who could be recommended to stop their anticoagulants.

Women with <2 of the following features were felt to be at low risk of recurrent venous thromboembolism, and were felt safe to discontinue therapy (after 5-7 months of oral anticoagulants):

• Post thrombotic signs (hyperpigmentation, edema or redness in either leg)
• D-Dimer level >=250 mcg/L
• Body mass index >=30 kg/m2
• Age >=65 years

Details of Rodger's 2008 Study: This study identified patients who could safely discontinue anticoagulants after an unprovoked VTE. In this multicenter prospective cohort study, 646 participants with a first, unprovoked major venous thromboembolism were enrolled over a period of 4 years. The authors collected data for 69 potential predictors of recurrent venous thromboembolism while patients were taking oral anticoagulation therapy (5-7) months after initiation. Recurrences after stopping the therapy were also recorded over a mean 18 month follow up.

Results: There were 91 confirmed episodes of recurrent venous thromboembolism after discontinuing oral anticoagulants contributing to an annual risk of 9.3%. In women, the annual risk was 1.6% for those with <2 of the following; Hyperpigmentation, edema or redness of either leg; D-dimer >=250 mcg/L on warfarin; BMI >=30 kg/m2; age >=65. The risk increased to 14.1% for women having two or more findings of the above listed predictors. No clinical predictors could identify a group of low risk men who can safely discontinue oral anti coagulants.

References:

1. Douketis JD, Gu CS, Schulman S et al. The risk for fatal pulmonary embolism after discontinuing anticoagulant therapy for venous thromboembolism. Ann Intern Med . 2007 Dec 4;147(11):766-74.
2. McRae S, Tran H, Schulman S et al. Effect of patient's sex on risk of recurrent venous thromboembolism: a meta-analysis. Lancet . 2006 Jul 29;368(9533):371-8.
3. Rodger MA, Kahn SR, Wells PS, et al. Identifying unprovoked thromboembolism patients at low risk for recurrence who can discontinue anticoagulant therapy. CMAJ . 2008;179(5): 417-26.