Aspirin's Benefits Unclear in PAD Patients

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Updated: 6/24 11:59 am

May 12, 2009 -- A new analysis raises more questions about the benefits of aspirin therapy in patients with peripheral artery disease, a condition characterized by restricted blood flow to the arms and legs that is common among people with diabetes.

Like coronary artery disease (CAD), peripheral artery disease (PAD) is associated with an increased risk for heart attack and stroke.

But unlike coronary artery disease, it is not clear whether aspirin therapy helps reduce this risk.

In the new analysis of combined data from 18 randomized trials with more than 5,000 patients, daily aspirin therapy was not associated with a significant decrease in heart attacks and death from heart attack or stroke.

The research appears in the May 13 issue of the Journal of the American Medical Association.

Millions With PAD May Not Benefit From Aspirin

Between 8 million and 12 million Americans have PAD, according to the American Heart Association.

Study co-author William R. Hiatt, MD, of the University of Colorado, Denver, tells WebMD that about half of these patients also have known coronary artery disease and should definitely be on aspirin therapy.

But he adds that it is far from clear if the benefits of aspirin outweigh the risks in the roughly 4 million to 6 million patients with PAD who don’t have documented coronary artery disease.

“My interpretation is that there is really no compelling reason to prescribe aspirin to these patients, but I suspect that is going to be a bit controversial,” he says. “Others may beg to differ.”

In PAD, fatty deposits build up in the inner linings of the arteries that send blood to all parts of the body except the heart and brain. Just as CAD restricts blood flow to the heart, PAD restricts blood flow to the arms, legs, feet, and other major organs.

Many patients with PAD experience cramping in their legs during strenuous activity, but others have no symptoms at all.

The American Heart Association and the American College of Cardiology recommend aspirin therapy for patients with PAD, and the American Diabetes Association recommends aspirin for diabetic people at high risk of having a heart attack or stroke.

But negative findings from several recent studies have raised doubts the benefits of aspirin therapy in patients with PAD and diabetes.

Aspirin for PAD: More Study Needed

In the newly published analysis, Hiatt and colleagues combined data from trials comparing outcomes among patients with PAD who took aspirin therapy to those of patients who did not.

They found that:

  • Aspirin therapy was associated with a 12% reduction in cardiovascular events, which was not statistically significant.
  • A statistically significant (34%) reduction in nonfatal strokes was seen in the aspirin group.
  • Most of the studies did not assess the incidence of major bleeding, which is the biggest risk associated with aspirin therapy.

The study authors were careful to point out that the current evidence was insufficient to rule out small but important benefits of aspirin (as suggested by the point estimate of a 12% risk reduction).

Cardiologist and study co-author Mori J. Krantz, MD, of the Colorado Prevention Center, tells WebMD that a large, randomized study is needed to fully understand the risks versus benefits of aspirin therapy in patients with PAD.

“The benefits of aspirin therapy in coronary artery disease are unequivocal, but we can’t say the same for patients with peripheral artery disease,” he says. “In this era of evidence-based medicine, we owe it to ourselves to adequately study this drug regimen in this population.”

Internist and PAD researcher Mary McGrae McDermott, MD, of Northwestern University’s Feinberg School of Medicine, agrees.

“This analysis gives a more complete picture of the benefits of aspirin in patients with peripheral artery disease, but we need more data,” McDermott tells WebMD.

She points out that of the 18 studies included in the analysis, 15 were published more than a decade ago. In addition, some of the studies involved small numbers of patients and were of short duration, potentially skewing the results.

“To best inform evidence-based clinical practice guidelines, more high-quality clinical trials are needed,” she writes in an editorial published with the study. But McDermott concludes that “based on the limitations of data available, the findings [of the present study] should not alter recommendations for aspirin as an important therapeutic tool for secondary prevention in patients with PAD.”

Hiatt tells WebMD that a trial now under way in the United Kingdom could help clarify the role of aspirin in patients with peripheral artery disease.

Although the value of aspirin therapy in patients with PAD remains a subject of debate, Hiatt says there is no debate about the benefits of other preventive therapies like cholesterol -- and blood pressure-lowering drugs for lowering cardiovascular risk in this patient population.

“The real downside is that patients will ignore these other risk factors because they think aspirin alone will keep them from having a heart attack or stroke,” he says.  “It is much more important that they stay on the drugs that have been proven to reduce their risk.”

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