Beta-blockers did not reduce the risk of death in patients with myocardial infarction
An open clinical trial by Australian, Swedish and Estonian scientists has shown that among patients with acute myocardial infarction who underwent coronarography and with preserved left ventricular ejection fraction (more than 50 per cent), long-term treatment with beta-adrenoblockers did not reduce the risk of death from any cause or new myocardial infarction. As reported in The New England Journal of Medicine, the study's total sample size was more than five thousand people.
The efficacy of beta-adrenoblockers in patients with heart failure and reduced left ventricular ejection fraction is well known: long-term therapy with beta-adrenoblockers after a myocardial infarction reduces mortality by about 20 per cent. However, these data come from studies that mainly involved patients with massive myocardial infarctions and left ventricular systolic dysfunction conducted in the 1980s. At that time, the determination of highly sensitive cardiac troponins, which can be used to monitor the biochemical processes of myocardial damage, was not used in clinical practice. Percutaneous coronary interventions, antithrombotic drugs, high-intensity statins, and renin-angiotensin-aldosterone system antagonists were also not used.
Meta-analyses have shown that in the era of modern reperfusion strategies, beta-adrenoblockers did not significantly reduce mortality in myocardial infarction. However, there is some uncertainty in the definitive understanding of the efficacy of beta-blockers in myocardial infarction. That said, despite the lack of clear evidence of benefit for this class of drugs, current protocols widely recommend the use of beta-adrenoblockers after myocardial infarction.
A research team led by Tomas Jernberg from Karolinska Institute investigated the effectiveness of long-term beta-adrenoblockers with early initiation in patients with acute myocardial infarction and preserved left ventricular ejection fraction (greater than 50 per cent) in reducing the risk of death or new myocardial infarction. To do this, they enrolled patients with myocardial infarction from New Zealand, Sweden and Estonia who underwent coronary angiography. According to its data, the stenosis of the coronary arteries had to be at least 50 per cent. Treating physicians were advised to aim for a dose of metoprolol of at least 100 milligrams per day or bisoprolol of at least five milligrams per day when prescribing medication.
A total of 5,020 patients with a mean age of 65 years were included in the study. Of the 2,508 patients in the treatment group, 1,560 (62.2 per cent) received metoprolol and 948 (37.8 per cent) received bisoprolol. For metoprolol, the mean starting dose was 50 milligrams, and for bisoprolol, the mean starting dose was 2.5 milligrams. The vast majority of patients took beta-blockers for at least six weeks, with about 15 per cent taking them for 11 to 13 months. The median follow-up in each study group was 3.5 years.
Death from any cause or new myocardial infarction (primary endpoint) occurred in 199 of 2,508 patients (7.9 per cent) in the beta-adrenoblocker group and in 208 of 2,512 patients (8.3 per cent)in the group not taking beta-adrenoblockers (risk ratio 0.96; p = 0.64). In addition, treatment with beta-adrenoblockers did not appear to reduce the cumulative incidence of secondary endpoints - death from cardiovascular causes, myocardial infarction, hospitalisation for atrial fibrillation and heart failure.
Researchers conclude that beta-adrenoblocker therapy initiated early in patients with myocardial infarction and preserved left ventricular ejection fraction does not reduce the cumulative incidence of death or new myocardial infarction. These results contradict the generally accepted protocol for the treatment of patients with myocardial infarction, and additional larger studies will be required.