August 27, 2014
News Review From Harvard Medical School -- Aspirin May Cut Risk of 2nd Deep-Vein Clot
Aspirin may offer some long-term protection for people who have had blood clots in the legs or lungs, a new study suggests. The study combined the results of two similar, smaller studies. They included 1,224 people who had a previous deep-vein thrombosis or pulmonary embolism, a blood clot in the legs or lungs. In each case, there was no likely cause, such as recent surgery. They were treated with heparin to dissolve the clot. In this situation, the risk of another clot is about 10% in the next year. To reduce the risk, people take warfarin or another blood thinner for 6 months to a year. But then most people stop taking the drugs because they increase the risk of bleeding. Everyone in these studies had completed initial treatment. They were randomly assigned to further treatment with daily low-dose aspirin or placebo (fake) pills. Researchers kept track of them for about 2½ years. In that time, 7.5% of the placebo group and 5.1% of the aspirin group had another clot. That was a 42% reduction in risk for the aspirin group compared with the placebo group. The journal Circulation published the study. HealthDay News wrote about it August 26.
By Howard LeWine, M.D.
Harvard Medical School
What Is the Doctor's Reaction?
Blood clots in the legs can happen after surgery, major injury or a long bed rest. But often doctors don't find a reason why a blood clot forms in a leg vein. Doctors call them unprovoked deep-vein thromboses (DVTs).
Someone with an unprovoked DVT has a lifelong risk that it will happen again. But taking one of the usual medicines to prevent another clot brings its own problems and risks, especially the risk of major bleeding. The results of this study suggest a safer option after the first year -- daily low-dose aspirin.
A DVT causes pain and swelling. It can limit movement. But the greatest danger is the risk that part of the clot will break away from the leg and travel to the lungs. That's called a pulmonary embolism (PE). The symptoms are shortness of breath, chest pain and lightheadedness. And if the embolism is large, it can cause sudden death.
The usual treatment for an unprovoked DVT or PE is an anticoagulant ("blood thinner"), such as heparin. Injections are given for a few days. Then people take either warfarin (Coumadin) by mouth or one of the newer anticoagulant pills for at least 6 months. Most doctors recommend 12 months.
But after this treatment is done, you still have a high risk of another DVT or PE. The risk is 10% in the first year and 5% per year after that.
Taking a blood thinner for the rest of your life provides the greatest protection against having a second DVT or PE. But most often patients and their doctors opt to stop the drug after one year. That's because over a lifetime the risk of major bleeding caused by the blood thinner is actually higher than the risk of another DVT or PE.
Low-dose aspirin is not as good, but it is much safer. It's only half as effective as warfarin or one of the newer blood thinners. But the lifetime bleeding risk is much lower. And aspirin also protects against heart attacks, strokes and potentially some cancers.
What Changes Can I Make Now?
If you have had a DVT or PE in the past and currently do not take warfarin or another blood thinner, talk with your doctor about low-dose aspirin to help prevent another clot.
You also can take other steps to help prevent a DVT from ever happening or happening again:
- Stay active.
- Get up from your desk often and take short walks.
- When sitting, move your feet up and down often to squeeze your calf muscles.
- Maintain a healthy weight.
- Don't smoke.
- Drink plenty of liquids, especially when travelling long distances. Avoid alcohol during the trip, as it can dehydrate you.
- If you are admitted to the hospital or have surgery, ask your doctor about preventive treatment with blood thinners or leg "compressors."
What Can I Expect Looking to the Future?
Aspirin will likely become standard treatment for people with unprovoked DVT or PE once they stop their anticoagulant drug. Many people who have had a DVT related to surgery, injury or long-term bed rest may also decide to take daily low-dose aspirin.
But aspirin should not be considered a replacement for a full course of anticoagulant drug therapy.