Aspirin for Primary Prevention of Cardiovascular Disease? Still a Very Close Call.

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Aspirin for Primary Prevention of Cardiovascular Disease? Still a Very

Close Call.Individual risk assessment might be the best approach.In patients with established cardiovascular disease, daily aspirin clearly lowers the incidence of adverse cardiovascular events. But do at-risk patients without histories of cardiovascular events also benefit? Several guidelines recommend daily aspirin for primary prevention in subgroups of such patients, but evidence of benefit has been sparse. In 2008 and 2009, two new randomized

trials, three new meta-analyses, and a new guideline from the U.S. Preventive Services Task Force (USPSTF) added new information.In one randomized trial, ish investigators assigned 1276 adults with diabetes and asymptomatic peripheral arterial disease (PAD) to receive daily aspirin or placebo for a median 7 years (JW Gen Med Nov 13 2008); in the other, Japanese investigators randomized 2539 patients with type 2 diabetes to receive daily aspirin or placebo for a median 4 years (JW Gen Med Nov 13 2008). In both studies, aspirin and placebo groups had similar incidences of composite cardiovascular endpoints.In a meta-analysis of 18 trials in which 5269 patients with PAD of any severity were randomized to receive aspirin (with or without dipyridamole) or placebo for 10 days to 7 years, 12% fewer adverse cardiovascular events (a composite endpoint assessment) in the aspirin group than in the placebo group failed to reach significance. A meta-analysis of six randomized trials, in which 10,117 patients with diabetes but no preexisting cardiovascular disease were enrolled, showed no significant difference in any cardiovascular endpoint. In each of these analyses, whether aspirin was ineffective or whether statistical power was insufficient to detect a difference was unclear (JW Gen Med May 19 2009).In the most definitive meta-analysis to date, researchers pooled patient-level data from six trials in which 95,000 patients without preexisting cardiovascular disease were randomized to aspirin or no aspirin for at least 2 years. In this analysis, the 12% proportional reduction in risk for serious vascular events didreach significance, and the aspirin benefit was similar regardless of preexisting risk factors, such as diabetes, hypertension, or high cholesterol level. But the absolute difference in serious vascular events conferred

by aspirin was only 0.06% annually in these relatively low-risk patients, and aspirin patients experienced significantly more major extracranial bleeds than did placebo patients. Because most participants did not have access to statins and other minimal-risk therapies that now are used routinely to prevent adverse cardiovascular events, the authors concluded that evidence of net benefit is insufficient to recommend routine aspirin for primary cardiovascular prevention in any patient subgroup (JW Gen Med Jun 18 2009).The new USPSTF guidelines implicitly embrace this view; they recommend that middle-aged and older men (age range, 45–79) and women (age range, 55–79) take aspirin only if an individualized quantitative risk assessment shows that risk for adverse cardiovascular events exceeds risk for serious bleeding (JW Gen Med Apr 14 2009). This recommendation requirescalculations for each patient, but it might be the best approach to a question that remains very close to clinical equipoise.— Bruce Soloway, MDPublished in Journal Watch General Medicine December 31, 2009 Regards, Vergelpowerusa dot org