Misguided Aspirin Use in 1 in 10 Low-Risk Heart-Clinic Patients: Study

Marlene Busko

January 12, 2015

HOUSTON, TX — More than 10% of patients in a representative sample of US cardiology clinics were "inappropriately" taking aspirin for primary prevention of CVD; that is, their 10-year risk for CVD was less than 6%, according to a new study[1].

The study, published in the January 20, 2015 issue of the Journal of the American College of Cardiology, also found that inappropriate aspirin use in different cardiology practices varied from 0% to 70%.

Because aspirin is widely available over the counter, not all inappropriate aspirin use was due to prescribed aspirin; in some cases, patients likely decided to take it on their own, senior author Dr Salim S Virani (Michael E DeBakey Veterans Affairs Medical Center, Houston, TX) told heartwire .

For cardiologists, the take-away message is that "for any patient for whom we prescribe aspirin [for primary prevention] or who is using aspirin on their own, [we] should get into the habit of calculating 10-year CVD risk and then having a discussion with the patient as to what is the risk vs benefit," he said.

This research identifies an important area for quality improvement, which could have widespread ramifications, since aspirin is used by an estimated 36% of the US population, he added. "Using aspirin in a more scientific manner has the potential to improve CV outcomes and avoid harm caused by use of the medication in every patient who comes to our office."

Further study is needed to investigate the widespread practice variation in inappropriate aspirin use for primary prevention in low-risk patients and to evaluate the benefit of aspirin in patients concurrently receiving statins, first author Dr Ravi S Hira (Baylor College of Medicine, Houston, TX) and colleagues conclude.

Cardiologists and Aspirin for Primary Prevention

The researchers identified 254 339 outpatients who were seen in 119 US cardiology practices that were part of the National Cardiovascular Disease Registry Practice Innovation and Clinical Excellence (PINNACLE) registry and were taking aspirin between January 2008 and June 2013. This sample excluded patients taking aspirin for secondary prevention for CVD and those taking warfarin, clopidogrel, ticlopidine, or an aspirin/extended-release dipyridamole combination.

Hira and colleagues used the Framingham risk calculator (based on age, sex, hypertension, diabetes, smoking, total and HDL cholesterol, systolic blood pressure, and hypertension medications) to calculate the patients' 10-year risk of CVD.

Almost three-quarters of the patients (72.9%) had missing variables, mainly missing cholesterol values, leaving 68 808 patients for which a risk score could be calculated.

The researchers used a "conservative" 10-year CVD risk of less than 6% as indicating "inappropriate" use of aspirin for primary CVD prevention, although according to some guidelines, inappropriate use is a risk that is below 10%, Virani noted.

They found that 11.6% of the patients taking aspirin had a 10-year CVD risk of less than 6%.

The patients who were taking aspirin inappropriately vs appropriately were younger (mean age 49.9 vs 65.9) and were more likely to be women (79.7% vs 52.6%).

The adjusted median rate ratio (MRR) for inappropriate aspirin use in different clinical practices was 1.63, meaning that there was a 63% likelihood that if two "identical" patients were seen in two different practices, one patient would have inappropriate aspirin use.

After researchers excluded older women and patients with diabetes (who are more likely to benefit from aspirin) and excluded statin use—which increased during the study period—inappropriate use and MRR remained relatively unchanged.

Study Emphasizes Need to Calculate Underlying Risk

Asked to comment, Dr Francisco Lopez-Jimenez (Mayo Clinic, Rochester, MN) said that "the most important message is to recognize that there are people [who take] aspirin believing that they are protecting themselves from having heart attacks when they are actually exposing themselves to the [bleeding] risks of taking aspirin and likely having no benefit at all." This likely represents millions of people, given the widespread use of aspirin, he noted.

According to Lopez, the paper does a good job of emphasizing that clinicians need to determine a patient's underlying risk for cardiovascular events. "Perhaps one way to assess risk now is to use the AHA pooled-cohort calculator," which also takes into account race as well as Framingham risk markers, he suggested.

In an accompanying editorial[2], Dr Freek WA Verheugt (Radboud University, Amsterdam, the Netherlands) notes that the work of Hira et al is "unique and important," since most of the clinical trials that have looked at the use of aspirin for primary prevention of CVD were done in a general-practice setting.

Although "cardiologists mainly see patients with symptomatic heart disease, who are beyond primary prevention . . . there may be patients without coronary disease who see a cardiologist for other reasons, such as atypical chest pain, arrhythmia, or heart failure and who are at risk for coronary events," he notes.

"Thus, there is a clear role for the practicing cardiologists in that risk factors should be collected and appropriate prophylactic therapy instituted," he adds, in agreement with the study authors and Lopez.

Excess extracranial bleeding risk associated with aspirin "may be due to other preventive strategies [including statins] currently applied and used extensively in cardiology practice," according to Verheugt. "Thus, inappropriate use of aspirin should be avoided, especially in the younger patient population, as demonstrated in the present study."

Virani has received grant/research support from the Department of Veterans Affairs, the American Diabetes Association, and the American Heart Association that was paid to his institution. Disclosures for the coauthors are listed in the article. Verheugt has received educational and research grants and honoraria for consultancies/presentations from Bayer Healthcare.

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