Volume 191 - Issue 10
Stop taking warfarin? No way!
Author: James A Fink
Med J Aust 2009; 191 (10): 577-578. || doi: 10.5694/j.1326-5377.2009.tb03324.x
Published online: 16 November 2009
Published online: 16 November 2009
To the Editor: I appreciated Brukner’s perspective on treatment of venous thromboembolism (VTE),1 but I do feel some additional considerations and clarifications are in order.
Quotes from Kearon2 and Kearon and colleagues3 about the duration of therapy are missing an important caveat. The suggestion for longer duration and possibly “indefinite” anticoagulant therapy after a first deep vein thrombosis or pulmonary embolism is in reference to unprovoked VTE. Brukner1 mentions a plane flight from China to Australia 3 days before he experienced a symptomatic pulmonary embolism. According to guidelines issued by the American College of Chest Physicians, such a flight (although I cannot comment with certainty on its duration) is likely to represent a reversible minor risk factor for VTE — “prolonged travel (eg, > 8 h)”.3
Indeed, Kearon2 and the authors of a related research article to which he refers4 make the important distinction between provoked and unprovoked VTE. Kearon comments:
For patients with a minor reversible risk factor, the risk of recurrence is about 5% in the first year after stopping anticoagulant therapy. This is considered low enough to justify stopping anticoagulant therapy at the end of 3 months.2
Additional factors and preferences are also important when considering prolonged anticoagulant therapy for individual patients. For instance, I can empathise with the 25-year-old who wants to discontinue warfarin therapy after 6 months following a first unprovoked VTE — another 50 years of warfarin therapy might seem a disheartening burden. And certainly we must take into account other variables that may increase a patient’s risk of bleeding complications while receiving warfarin therapy, such as older age, the presence of other acute or chronic illnesses and the use of other medications, particularly antiplatelet therapy.3
For someone such as Brukner,1 who claims that his anxiety about a recurrence of VTE is reduced by staying on warfarin therapy, I would probably say, “That’s OK by me, as long as you are aware of the risks and implications of provoked and unprovoked VTE”. For other patients with unprovoked VTE who may not want to continue indefinite anticoagulant therapy, there are other management options worth discussing. First, there is the possibility of further risk stratification for VTE recurrence by testing D-dimer levels. This strategy is receiving considerable study and validation as a useful tool for predicting VTE recurrence.5,6 Second, for patients who refuse to continue warfarin therapy but would consider other therapies for reducing their risk of having a recurrence of VTE, I would suggest taking a daily low dose of vitamin E, which has shown some benefit in reducing VTE.7 Finally, the ASPIRE (Aspirin to Prevent Recurrent Venous Thromboembolism) Trial, which is currently underway, should provide a definitive answer as to whether aspirin is a safe and effective option for secondary VTE prevention. If the trial supports the use of aspirin for this purpose, it would offer another VTE risk-reduction option for those who prefer not to take warfarin indefinitely.8
References
- Brukner PD. Stop taking warfarin? No way! Med J Aust 2009; 190: 704. 0_CHDICBBE
- Kearon C. Stopping anticoagulant therapy after an unprovoked venous thromboembolism. CMAJ 2008; 179: 401-402. 0_i1091878
- Kearon C, Kahn SR, Agnelli G, et al. Antithrombotic therapy for venous thromboembolic disease: American College of Chest Physicians evidence-based clinical practice guidelines. Chest 2008; 133 (6 Suppl): 454S-545S. 0_i1091880
- 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: 417-426. 0_i1091882
- Palareti G, Cosmi B, Legnani C, et al. D-dimer testing to determine the duration of anticoagulation therapy. N Engl J Med 2006; 355: 1780-1789. 0_i1091884
- Verhovsek M, Douketis JD, Yi Q, et al. Systematic review: D-dimer to predict recurrent disease after stopping anticoagulant therapy for unprovoked venous thromboembolism. Ann Intern Med 2008; 149: 481-490. 0_i1091886
- Glynn RJ, Ridker PM, Goldhaber SZ, et al. Effects of random allocation to vitamin E supplementation on the occurrence of venous thromboembolism. Circulation 2007; 116: 1497-1503. 0_i1091890
- National Health and Medical Research Council Clinical Trials Centre. Aspirin to prevent recurrent venous thromboembolism (ASPIRE). http://www.ctc.usyd.edu.au/trials/other_trials/aspire.htm (accessed Sep 2009).