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Long-term use of beta blocker in patients with acute myocardial infarction (MI) with a preserved left ventricular ejection fraction (LVEF) of ≥50% did not lower the risk of deaths or a second heart attack, study results have suggested.
The prospective, randomised, open-label, parallel-group study, published in the New England Journal of Medicine on 7 April 2024, included 5,020 participants who had an acute MI confirmed with coronary angiography across 45 centres in Sweden, Estonia and New Zealand from September 2019 to May 2023.
Participants were randomly assigned to receive either long-term treatment with a beta-blocker (metoprolol or bisoprolol) or no beta-blocker treatment and were followed up for a median duration of 3.5 years (ranging from 2.2–4.7 years).
The primary end point for the study was a composite of death from any cause or new MI. Secondary end points included death from any cause, death from cardiovascular disease, new MI and hospitalisation from atrial fibrillation or heart failure.
In the study, researchers found that death or another MI occurred in 199 (7.9%) in the beta-blocker group and 208 (8.3%) in the no beta-blocker group (hazard ratio [HR]: 0.96 (95% confidence interval [CI]); P=0.64).
The researchers also reported that beta-blockers did not appear to lower cumulative incidence of secondary end points with similar safety end points among the two groups — 3.4% in the beta-blocker group and 3.2% in the no beta-blocker group.
Commenting on the study, Paul Wright, lead cardiac pharmacist at Barts Health NHS Trust, said: “This is an interesting study and addressed a long-term question of the benefits of beta blockers for all patients post-acute MI.
“We have to be mindful that the original beta blocker data comes in the era pre-primary percutaneous coronary intervention (PPCI), with many patients being managed medically or with fibrinolysis with many suffering left ventricular dysfunction hence supporting betablocker use,” he added.
“In the absence of heart failure following acute MI and PPCI, we are seeing an absence of effects of our established gold standard therapies.
“It is likely that guidelines are going to have to reflect a more tailored patient approach and recommending therapies for comorbidities not just the index event of AMI — i.e. tailoring according to heart failure status, diabetes, etc.”
Current guidance on acute coronary syndrome by the National Institute for Health and Care Excellence states that beta-blockers should be currently offered for at least 12 months after an MI to people without a reduced LVEF.
However, it does not recommend a definite time for stopping treatment owing to absence of direct evidence on the optimal duration of beta-blockers.
Commenting on the study results, Anna Man, lead pharmacists for clinical and cardiothoracic services at Mid and South Essex NHS Foundation Trust, said: “This study show that patients with preserved EF might not need beta-blockers, as the mortality benefit is not the same with those at higher risk/impaired EF.
“This means reducing drug cost, and the medicine burden in patients who are already taking other secondary preventative medicines,” she added.
“However, it is worth noting that the author states doses used in the study were ‘lower than those in previous trials’, aiming for at least 100mg metoprolol and 5mg for bisoprolol.
“This suggests to me that maximal doses were not used. Although the study didn’t show a significant mortality benefit with beta-blockers, this shouldn’t automatically rule out beta-blockers,” Man advised.
