Are beta-blockers always beneficial after a myocardial infarction?

Prescribing beta-blocker therapy to a patient after a myocardial infarction (MI) is thought to reduce recurrent MI and mortality and has been a reportable quality measure for decades. A 2000 American Family Physician article on this topic, “Optimizing beta-blocker use after myocardial infarction,” implied that this intervention was settled science. However, the benefits of beta-blockers were established in studies mostly conducted in the 1980s, when most diagnosed MIs caused significant left ventricular systolic dysfunction, and prior to the use of high-sensitivity cardiac troponin tests, percutaneous coronary interventions (PCI), thrombolytics, high intensity statins, and renin-angiotensin-aldosterone system antagonists.

A 2014 meta-analysis of 12 randomized trials performed in the “reperfusion era” reexamined the benefits and harms of adding beta-blockers to modern interventions in patients after MI. Beta-blockers did not improve mortality, and their benefits were limited to the first 30 days. An AFP POEM synopsis reported that while beta-blockers reduced the risk of recurrent MI (number needed to treat = 209) and angina symptoms (NNT = 26), they also increased rates of heart failure (number needed to harm = 79) and cardiogenic shock (NNH=90).

On the other hand, a 2020 Cochrane for Clinicians on beta-blockers after suspected or diagnosed acute MI, while noting that “most trials were conducted before the introduction of what is now considered standard reperfusion therapy,” found reduced risks of MI, cardiovascular and all-cause mortality even in patients who had not received PCI, thrombolytics, or coronary artery bypass grafting. Consequently, the authors recommended, “family physicians should continue to incorporate beta-blocker therapy in the care of patients with a history of MI.” The current American College of Cardiology / American Heart Association guideline for management of patients with chronic coronary disease splits the difference. As stated in a POEM in the March 2024 issue, “Long-term beta blockers are no longer routinely recommended and should be limited to patients with heart failure, myocardial infarction in the past year, or another indication.”

To clarify the effects of beta-blocker therapy post-MI, a randomized, open-label trial published earlier this month assigned more than 5,000 patients with an acute MI and preserved left ventricular ejection fraction (LVEF) of at least 50% to long-term therapy with metoprolol or bisoprolol or no treatment. After a median of 3.5 years, there was no difference between the groups in the primary composite outcome of death from any cause or new MI. Other potential benefits and harms, including hospitalization for atrial fibrillation or heart failure and hospitalization for bradycardia, hypotension, or syncope, were also statistically similar between the groups. Although these findings suggest that beta-blockers have no effects in post-MI patients without heart failure, an accompanying editorial observed that several more trials addressing this important clinical question will be completed in the next few years.

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This post first appeared on the AFP Community Blog.