Monday, March 23, 2015

Stop beta-blockers 30 days after acute MI?

- Jennifer Middleton, MD, MPH

Although prescribing a beta-blocker for patients with acute myocardial infarction (AMI) has been dogma for decades, a recent meta-analysis raises serious questions about the benefit - and harms - of continued use afterwards. The March 15 AFP reviews this study that found the benefits of beta-blockade may be limited to 30 days after AMI, and the harms may be greater than previously realized.

The authors of this large meta-analysis identified 60 studies that met their inclusion criteria (randomized controlled trials examining beta-blocker use in patients with AMI); they divided studies into pre-reperfusion-era ("early," before stents, thrombolytics, etc) and reperfusion-era ("modern era"). They found that, while in the early studies, beta-blockers conferred significant survival benefit (incident rate ratio [IRR] 0.86; 95% confidence interval [CI], 0.79-0.94), in the modern era they did not (IRR 0.98; 95% CI, 0.92-1.05). In the modern era, beta-blockers did reduce angina and reinfarction rates, but only in the first 30 days, and they increased the rates of heart failure and cardiogenic shock. The authors hypothesized that reperfusion technologies are so effective nowadays that any added benefit from beta-blockers is minimal.

COMMIT (ClOpidogrel and Metoprolol in Myocardial Infarction Trial) was by far the largest study in the modern era group; published in 2005, it had 45,000+ participants and found that metoprolol did not reduce the risk of death, reinfarction, or cardiac arrest even in the first few days after AMI. The COMMIT authors did not seem to seek to change practice widely, however, stating only that "it might generally be prudent to consider starting β-blocker therapy in hospital only when the haemodynamic condition after MI has stabilised."

Beta-blocker use following AMI is a Joint Commission Core Measure, and hospitals receive performance incentives for demonstrating that patients admitted with AMI are discharged with a beta-blocker. The American College of Cardiology and the American Heart Association's (ACC/AHA) 2013 Guideline for the Management of ST-Elevation Myocardial Infarction also recommends beta-blocker use after AMI. (The AFP By Topic on Coronary Artery Disease/Coronary Heart Disease includes many additional resources if you'd like to read more.)

The COMMIT trial sought to explore appropriate beta-blocker use immediately after AMI; the Joint Commission and ACC/AHA, similarly, describe recommended practice immediately after AMI. While this new meta-analysis potentially raises questions about beta-blocker use immediately after AMI, the bigger issue is what happens 30 days after AMI, when the risk of harm and lack of benefit are clear. The greatest challenge for family physicians managing patients following up after an AMI admission may be the decision to stop a beta-blocker. Discontinuing therapies may be difficult for physicians; many physicians continue clopidogrel (Plavix) past its recommended 12 months following drug-eluting stent placement, and many patients with asthma remain on controller treatment regimens past the 3 month time when physicians and patients should investigate stepping down that regimen. Inertia can be difficult to overcome, especially when other colleagues and specialities follow other practices. 

Will this meta-analysis change how you care for patients when they follow-up after AMI?

1 comment:

  1. This sobering study brings to mind the Mayo Clinic article by Prasad et al (Mayo Clin Proc: 88(8):790-798, 2013) in which the authors reviewed all original studies (some 2,000+ articles) published in the New England Journal of Medicine over a 10-year period (from 2001-2010). Of the 363 articles that tested standard of care - 40% were "reversals" of practice (ie, what was thought to be dogma just a few years earlier was no longer even being recommended ... ). This is truly humbling stuff! The changing indications for beta-blockers post-MI is but another such example ...

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