An Aspirin a Day After Blood Clots

Aspirin after a blood clot may reduce risk of heart attack and stroke

/ Author:  / Reviewed by: Joseph V. Madia, MD

(RxWiki News) A common treatment after having a blood clot is taking blood thinner medication. But many doctors will eventually take patients off medication when it's no longer necessary. Then what?

Some doctors will then recommend that patients take a daily aspirin. Will that prevent another clot?

A recent study shows that taking daily aspirin may not prevent another clot. But it might lower a patient's risk of having a heart attack or stroke or dying from a heart condition.

"Ask your doctor about aspirin."

The study, led by Timothy A. Brighton, MB, BS, in the Department of Hematology at Prince of Wales Hospital in Sydney, Australia, aimed to find out whether aspirin might help prevent a reoccurrence of blood clots in a person's veins. The study was funded partly by Bayer, which manufactures aspirin.

The researchers were focused on "venous thromboembolism," blood clots that occur in the deep veins of a person's legs or lungs (not clots in the heart or brain).

The study involved 822 patients who had finished taking blood thinners after having had a blood clot without any apparent risk factors for blood clotting ahead of time.

For up to four years, half the patients (411) took 100 mg of aspirin each day and the other half took a placebo (fake pill) daily. During the course of the study, 73 of the patients (6.5%) taking the placebo had another blood clot, compared to 47 (4.8%)of those taking aspirin.

However, mathematically, these rates are not different enough from each other to determine that the aspirin reduced the likelihood of getting another clot. The higher number among placebo patients could have been due to chance.

Yet those taking aspirin did have a more significant reduction in the number of heart attacks, strokes or deaths from a heart-related problem.

While 8 percent of those taking the placebo had a heart attack or stroke or died from a cardiovascular condition, only 5.2 percent of those taking aspirin suffered one of these outcomes. This difference was statistically not due to chance.

"Also, the investigators reported that many of the people assigned to take aspirin stopped taking it, so the study probably underestimated the potential benefits of aspirin," Sarah Samaan, MD, told dailyRx News. Dr. Samaan is a cardiologist at Legacy Heart Center in Plano, Texas, and co-director of the Women's Cardiovascular Institute at The Baylor Heart Hospital.

"Aspirin is inexpensive, relatively safe (as long as there are no underlying gastrointestinal or bleeding issues), and remarkably effective in reducing heart attacks and strokes in people at risk," Dr. Samaan said.

The two groups had similar rates of other conditions and did not show any side effects from the aspirin or placebo. However, there are possible side effects, Dr. Samaan pointed out.

"It can cause gastrointestinal side effects, including ulcers and bleeding, so it's not for everyone," she said. "Gastrointestinal side effects were one of the main reasons that people stopped taking aspirin in this study."

Even though this study showed that daily aspirin did not significantly reduce the risk of another blood clot, it did appear to reduce the risk of a heart attack, stroke or cardiovascular death.

The study was published November 4 in the New England Journal of Medicine. The research was funded by the National Health and Medical Research Council (Australia), the Health Research Council (New Zealand), the Australasian Society of Thrombosis and Hemostasis, the National Heart Foundation of Australia and Bayer HealthCare.

Five authors reporting receiving research, consulting or lecture fees from a range of pharmaceutical companies.

Reviewed by: 
Review Date: 
November 19, 2012
Last Updated:
November 26, 2012