An Aspirin a Day Keeps the MI Away - For Some - myocardial infarctions

Author: William F. Miser
Date: May 15, 2002

One of the latest recommendations by the third U.S. Preventive Services Task Force (USPSTF) appears in this issue of American Family Physician.(1) In this review, the USPSTF found good evidence that the potential benefit of daily aspirin therapy in persons at high risk for a cardiovascular event, defined as a 10-year risk of at least 6 percent, outweighs the potential harm. For every 1,000 high-risk patients taking aspirin daily for five years, four to 12 nonfatal and fatal myocardial infarctions (MIs) will be avoided, while two to four major gastrointestinal bleeding events and zero to two hemorrhagic strokes will be caused. Although this therapy has no net effect on all-cause mortality, the USPSTF strongly recommends that we discuss the potential benefits and harms of aspirin chemoprophylaxis with adult patients who are at increased risk for coronary heart disease.

Complementing these recommendations is recent evidence from a large meta-analysis.2 According to evidence-based medicine guidelines, meta-analyses, if done correctly, provide the strongest evidence for therapeutic interventions.(3) The authors of this meta-analysis(2) reviewed data on more than 100,000 patients at high risk for a cardiovascular event, representing more than 250,000 patient-years of follow-up. Overall, antiplatelet therapy (including aspirin) reduced the risk of nonfatal MIs, nonfatal strokes, and vascular death by about 25 percent. The authors also reviewed the optimal dosage of aspirin therapy and concluded that 75 to 150 mg daily was effective for long-term use. Higher dosages were no more effective but increased the risk of an adverse event. There were few data to support the use of aspirin in dosages of less than 75 mg per day.

The findings of another study(4) may be useful in patients who decide to use aspirin chemoprophylaxis. The authors in this disease-oriented study found that the antiplatelet effects of aspirin were blocked when a single daily 400-mg dosage of ibuprofen was taken two hours before the aspirin (81 mg), or when ibuprofen was taken several times during the day, regardless of when the aspirin was taken. Acetaminophen, rofecoxib, and diclofenac did not have this effect. The authors made a bold conclusion that ibuprofen may limit the cardioprotective effects of aspirin. It is important to realize that the authors did not study the patient-oriented outcomes that physicians are most concerned about (e.g., cardiovascular mortality), and thus made a leap of faith, albeit a logical one. However, until further studies are done, it may be wise to counsel patients to avoid taking ibuprofen, especially on a regular basis, if they are also taking aspirin to prevent a cardiovascular event.

So what do these three studies have to do with family physicians? We, in alliance with our patients, are on the battlefront in the war against cardiovascular disease that, despite modern medical technology, continues to be the most common cause of death and disability in the United States.(5,6) Although some cardiac risk factors cannot be modified (e.g., age, gender, family history), offering patients advice about aspirin therapy is a viable intervention, along with counseling on sedentary lifestyle, tobacco use, poor nutrition, hyperlipidemia, and hypertension.(7) Despite the evidence that such advice is effective,(8) many opportunities to provide this counseling are missed in our daily practice.(9-13) For the busy family physician, time is always a critical issue. For this, we can use technology to our advantage by referring patients to Internet resources. A good patient education handout that describes the benefits and risks of aspirin therapy is available online at www.annals. org/issues/v136n2/fpdf/200201150-00005. pdf, and an online Cardiac Risk Assessment Tool to help patients decide if aspirin chemoprophylaxis may benefit them may be found at www.med-decisions.com. A similar risk assessment tool with a personal digital assistant (PDA) application is available at www. statcoder.com.

In summary, the evidence is in--aspirin chemoprophylaxis for certain high-risk persons may be beneficial. However, aspirin is not a panacea and, as with all therapies, physicians are obligated to spend time with patients discussing the advantages and disadvantages of this treatment, and to assist them in making wise decisions. The burden is now ours to implement these findings into daily practice.

REFERENCES

(1.) Berg A. Aspirin for the primary prevention of cardiovascular events: Recommendations and rationale. Am Fam Physician 2002;65:2107-10.

(2.) Antithrombotic Trialists' Collaboration. Collaborative meta-analysis of randomised trials of antiplatelet therapy for prevention of death, myocardial infarction, and stroke in high-risk patients. BMJ 2002;324:71-86.

(3.) Miser WF. Applying a meta-analysis to daily clinical practice. J Am Board Fam Pract 2000;13:201-10.

(4.) Catella-Lawson F, Reilly MP, Kapoor SC, Cucchiara AJ, DeMarco S, Tournier B, et al. Cyclooxygenase inhibitors and the antiplatelet effects of aspirin. N Engl J Med 2001;345:1809-17.

(5.) Minino AM, Smith BL. Deaths: preliminary data for 2000. Natl Vital Stat Rep 2001;49(12):1-40.

(6.) Pollard TJ. The acute myocardial infarction. Prim Care 2000;27:631-49.

(7.) Hixon AL, Chapman RW. Healthy People 2010: the role of family physicians in addressing health disparities. Am Fam Physician 2000;62:1971-8.

(8.) Kreuter MW, Chheda G, Bull FC. How does physician advice influence patient behavior? Evidence for a priming effect. Arch Fam Med 2000;9:426-33.

(9.) Stange KC, Flocke SA, Goodwin MA, Kelly RB, Zyzanski SJ. Direct observation of rates of preventive service delivery in community family practice. Prev Med 2000;31(2 Pt 1):167-76.

(10.) Parnes B, Main DS, Holcomb S, Pace W. Tobacco cessation counseling among underserved patients: A report from CaReNet. J Fam Pract 2002;51:65-9.

(11.) Goodwin MA, Flocke SA, Borawski EA, Zyzanski SJ, Stange KC. Direct observation of health-habit counseling of adolescents. Arch Pediatr Adolesc Med 1999;153:367-73.

(12.) Thorndike AN, Rigotti NA, Stafford RS, Singer DE. National patterns in the treatment of smokers by physicians. JAMA 1998;279:604-8.

(13.) Jaen CR, McIlvain H, Pol L, Phillips RL Jr, Flocke S, Crabtree BF. Tailoring tobacco counseling to the competing demands in the clinical encounter. J Fam Pract 2001;50:859-63. n

William F. Miser, M.D., is an associate professor and residency director in the Department of Family Medicine at The Ohio State University College of Medicine and Public Health, Columbus.

Address correspondence to William F. Miser, M.D., Department of Family Medicine, 2231 N. High St., Columbus, OH 43201.

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