Stephan Moll, MD writes… For patients stopping blood thinning therapy (anticoagulation) whose deep vein thrombosis (DVT) or pulmonary embolism (PE) was considered unprovoked (i.e. out of the blue and with no obvious triggering, transient cause, such as surgery, hormone use, immobility), aspirin is beneficial in some patients in preventing further clots. A new publication in the journal Circulation re-confirms findings from two previous studies, showing that aspirin reduces the risk of recurrent DVT/PE by more than a third without significantly increasing the risk of bleeding [ref 1,2,3].
Methods and results
The present publication combined the analysis of two previous studies (called WARFASA and ASPIRE trials) in which patients with an unprovoked clot who had been treated with blood thinners for at least 3 months, received 100 mg of aspirin a day and were monitored for at least two years. Researchers found that aspirin reduced the risk of recurring blood clots by up to 42 percent. Rates of major bleeding were low.
Key points for patients
- This analysis provides additional evidence that aspirin reduces the risk of recurrent DVT/PE.
- However, aspirin is clearly less effective than prescription blood thinners (anticoagulants). While aspirin was found to reduce the risk of recurrent clot by up to 42% (for the scientifically interested person: 32 % risk reduction in the intention-to-treat analysis; 42 % reduction in the on-treatment analysis), this is still much less than what can be achieved with warfarin (Coumadin®, Jantoven®) or the new oral anticoagulants (Eliquis®, Pradaxa®, Xarelto®) which reduce the risk for future clots by around 80%. Thus, aspirin is NOT a replacement for prescription anticoagulants.
- However, aspirin can be considered in the patient with unprovoked DVT/PE in whom anticoagulation is not given long-term.
- Although the study yielded clear results, researchers advise patients to talk to their doctor about taking aspirin after stopping treatment with prescription blood thinners (anticoagulants).
The authors add an interesting calculation: Globally, many patients with unexplained clots are not routinely treated with long-term blood thinning therapy. A conservative estimate is that over a million patients worldwide have unprovoked clots each year and an even greater number have a past history. Less than half of these patients remain on long-term blood thinning therapy. If a million patients worldwide could be treated with aspirin each year, 100,000 new clotting events might be prevented with a minimal increase in bleeding. The authors also note that aspirin in an inexpensive treatment.
- Simes J et al. Aspirin for the Prevention of Recurrent Venous Thromboembolism: The INSPIRE Collaboration. Circulation 2014 Aug 25 [Epub ahead of print].
- Becattini C et al. WARFASA Investigators. Aspirin for preventing the recurrence of venous thromboembolism. N Engl J Med. 2012;366:1959-1967.
- Brighton TA et al. ASPIRE Investigators. Low-dose aspirin for preventing recurrent venous thromboembolism. N Engl J Med. 2012;367:1979-1987.
Disclosure: I have consulted for Janssen, Daiichi, Boehringer Ingelheim.
Last updated: Sept 9th, 2014