Beta-blockers are not associated with lower risk of myocardial infarction (MI) or stroke in stable outpatients

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Key study points:

1. Beta-blockers are not associated with a significant reduction of cardiovascular death, non-fatal MI, or non-fatal stroke in patients with CAD and distant prior MI, CAD patients without prior MI and patients with CAD risk factors only.

Primer: Beta-blockers have traditionally been used to treat patients post-myocardial infarction (MI), along with a variety of other medications, to prevent future cardiovascular-related events. The widespread use of beta-blockers in cardiac patients, however, are largely based on evidence prior to the advent of stent placement and the use of modern arsenal of therapy that includes aspirin, ACE-inhibitors, and statin therapies. The authors of the study study assess whether beta-blockers in patients with coronary artery disease (CAD) patients continues is indeed beneficial for the following groups: 1) patients with risk factors for CAD, 2) patients with known CAD without history of MI, and 3) patients with known prior MI.

Background reading:

1. World Heart Federation and the Preventive Cardiovascular Nurses Association.  AHA/ACCF Secondary Prevention and Risk Reduction Therapy for Patients With Coronary and Other Atherosclerotic Vascular Disease: 2011 update: a guideline from the American Heart Association and American College of Cardiology Foundation.  Circulation. 2011;124(22):2458-2473.
2. “Beta blockers in the management of acute coronary syndrome.” UpToDate. 4 October 2012.
3. “Beta blockers in the management of stable angina pectoris.” UpToDate. 4 October 2012.

This [prospective cohort] study: The Reduction of Atherothrombosis for Continued Health (REACH) registry is used to analyze whether or not beta-blocker use was associated with reduction of cardiovascular events. For the purpose of this study, patients with documented use of beta-blockers were stratified into 3 groups: known prior MI, CAD without known MI, and CAD risk factors. A total of 44,078 patients met study criteria and 21,860 were included in a propensity score-matched analysis. Controlling variables such as region, NSAID use, co-morbidities such as diabetes, and other pharmaceutical therapies (hypertensive medications, lipid-lowering agents), beta-blockers did not significantly reduce adverse cardiovascular outcomes in CAD patients with prior MI (16.93% vs. 18.60%, p = .14), without prior MI (12.94% vs. 13.55%, p =.31), and patients with CAD risk factors alone (14.22% vs. 12.11%, p = .02). The median follow-up period was 44 months.

In sum: Findings from the analysis of the REACH registry data demonstrate that there is no significantly reduced risk of MI, stroke, or cardiovascular-related death in CAD patients or patients with CAD risk factors using beta-blocker therapy. For patients with prior MI, beta-blockers have been shown to have mortality benefit, but their long-term use is not as well established. Accordingly, the American Heart Association recently downgraded the strength of evidence supporting the use of beta-blocker therapy beyond 3 years after a MI.

For patients without prior MI, the use of beta-blocker as a means of primary prevention has never been well supported by prior studies. Hence beta-blocker usage seems to have greatest mortality benefit in its use in the acute and subacute period following MI as well as established utility in patients with congestive heart failure.

In terms of limitations, the specifics of beta-blocker therapy for the patients were not known, and the study findings are primarily applicable to populations that would fit into the inclusion criteria for the REACH registry (see paper). Further assessment of different types of beta-blockers and their effects on different subgroups (such as differences based on ethnicity) are warranted.

Click to read the study in JAMA

By [SK] and [RR]

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