Swedish researchers led by Lund University found that long-term treatment with beta-blockers might not lower the risk of death or myocardial infarction (MI) in patients with MI, a preserved left ventricular ejection fraction (LVEF) of 50% or more, and coronary artery disease.
The results of the REDUCE-AMI study were presented during a Late-Breaking Clinical Trial session at ACC.24—the annual scientific session of the American College of Cardiology (ACC)—and published simultaneously in the New England Journal of Medicine.
As part of the parallel-group, open-label trial, the study team randomly assigned 5,020 patients (median age: 65 years, 22.5% women) with acute MI who had participated in the SWEDEHEART registry, undergone coronary angiography, and had an LVEF ≥50% to long-term treatment with one of two beta-blockers (metoprolol 100 mg and bisoprolol 5 mg) or no beta-blocker treatment. The trial was conducted from September 2017 through May 2023 at 45 centers across Sweden, Estonia, and New Zealand.
The researchers reported that at a median follow-up of 3.5 years, the primary composite endpoint of death from any cause or new MI occurred in 199 (7.9%) patients in the beta-blocker group and 208 (8.3%) patients in the no–beta-blocker group (hazard ratio, 0.96; 95% CI, 0.79-1.16; P = .64). Furthermore, beta-blocker treatment did not lower the incidence of the secondary endpoints, with death from any cause occurring in 97 (3.9%) patients in the beta-blocker group and 103 (4.1%) patients in the control group. Death from cardiovascular causes occurred in 38 (1.5%) and 33 (1.3%) patients, respectively. MI occurred in 112 (4.5%) and 117 (4.7%) patients, hospitalization for atrial fibrillation occurred in 27 (1.1%) and 34 (1.4%) patients, and hospitalization for heart failure occurred in 20 (0.8%) and 22 (0.9%) patients, the study added.
“I think that following this study, many doctors will not find an indication to routinely treat all their patients with beta-blockers following a heart attack,” lead author Troels Yndigegn, MD, said in an ACC press release. “We believe that the evidence still supports beta-blockers for patients with a large myocardial infarction that experience heart failure, but for patients with no signs of heart failure and a normal ejection fraction, this trial establishes that there’s no indication that routine use of beta-blockers is beneficial.”
In terms of safety, the groups had similar outcomes, according to the authors. Hospitalization for bradycardia, second- or third-degree atrioventricular block, hypotension, syncope, or implantation of a pacemaker occurred in 3.4% and 3.2% of the beta-blocker and control groups, respectively, while hospitalization for asthma or chronic obstructive pulmonary disease occurred in 0.6% of each group and hospitalization for stroke occurred in 1.4% and 1.8%.
The report suggested that most trials that have shown a benefit of beta-blocker treatment after MI “included patients with large myocardial infarctions and were conducted in an era before modern biomarker-based diagnosis of myocardial infarction and treatment with percutaneous coronary intervention, antithrombotic agents, high-intensity statins, and renin–angiotensin–aldosterone system antagonists.”
They concluded, “Among patients with acute myocardial infarction who underwent early coronary angiography and had a preserved left ventricular ejection fraction (≥50%), long-term beta-blocker treatment did not lead to a lower risk of the composite primary end point of death from any cause or new myocardial infarction than no beta-blocker use.”
Background information in the articles noted that the efficacy of beta-blockers in patients with heart failure and reduced ejection fraction is “…well documented. Trials have also shown that long-term beta-blocker therapy after myocardial infarction reduces mortality by approximately 20%. However, these results are from trials that mainly involved patients with large myocardial infarctions and left ventricular systolic dysfunction and were conducted primarily in the 1980s.”
The researchers pointed out that this era predates advancements, such as high-sensitivity cardiac troponins, percutaneous coronary interventions, antithrombotic agents, high-intensity statins, and renin-angiotensin-aldosterone system antagonists.
The trial was undertaken because “data on the effect of long-term beta-blocker therapy in patients with acute myocardial infarction and preserved ejection fraction are lacking from contemporary, sufficiently powered, randomized clinical trials,” the researchers explained.
In addition, extensive observational studies and meta-analyses have come up with divergent conclusions on the issue.
“A critical axiom in evidence-based medicine is that absence of evidence is not evidence of absence,” wrote Philippe Gabriel Steg, MD, from Université Paris-Cité in an accompanying editorial commentary. “Given the difficulty of unambiguously showing an absence of benefit with beta-blocker therapy and the limitations of a single, somewhat underpowered, open-label trial, it may be too early to cut beta-blockers from the ‘secondary prevention team’ definitively. While we await the results of the multiple upcoming trials re-evaluating the role of beta-blockers in contemporary care, it may be prudent to place routine beta-blocker therapy after myocardial infarction on ‘injured reserve.’”
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