Sorbonne Université researchers and colleagues point out that the appropriate duration of treatment with beta-blocker drugs after a myocardial infarction is unknown. With results published in the New England Journal of Medicine, they sought to better understand the safety and efficacy of the interruption of long-term beta-blocker treatment to reduce side effects and improve quality of life in patients with a history of uncomplicated myocardial infarction.
“In our trial, we tested the hypothesis that the interruption of beta-blocker therapy would be noninferior to the continuation of such therapy over a 3-year follow-up period among patients with a history of myocardial infarction. However, the noninferiority of this strategy was not shown with respect to the risk of death, nonfatal myocardial infarction, nonfatal stroke, or hospitalization for cardiovascular reasons (the composite primary outcome),” the authors pointed out. “In addition, interruption of beta-blocker therapy did not result in an improvement in patient-reported quality of life. Beta-blocker interruption was associated with a numerical increase in the risk of recurrent angina and other coronary-related conditions leading to hospitalization and coronary procedures, although hypothesis testing was not performed for these end points.”
The multicenter, open-label, randomized, noninferiority trial was conducted at 49 sites in France. The researchers randomly assigned patients with a history of myocardial infarction, in a 1:1 ratio, to interruption or continuation of beta-blocker treatment. All the patients, who had no history of a cardiovascular event in the last 6 months, had a left ventricular ejection fraction of at least 40% while receiving long-term beta-blocker treatment.
The primary endpoint was defined as a composite of death, nonfatal myocardial infarction, nonfatal stroke, or hospitalization for cardiovascular reasons at the longest follow-up (minimum, 1 year), according to an analysis of noninferiority (defined as a between-group difference of <3 percentage points for the upper boundary of the two-sided 95% CI). The main secondary endpoint was the change in quality of life as measured by the European Quality of Life–5 Dimensions questionnaire.
Of the 3,698 patients who underwent randomization, 1,846 were in the interruption group and 1852 were in the continuation group. Their median time between the last myocardial infarction and randomization was 2.9 years (interquartile range [IQR], 1.2 to 6.4), and the median follow-up was 3.0 years (IQR, 2.0-4.0).
The researchers reported that a primary-outcome event occurred in 432 of 1,812 patients (23.8%) in the interruption group and in 384 of 1,821 patients (21.1%) in the continuation group (risk difference, 2.8 percentage points; 95% CI, <0.1-5.5), for a hazard ratio of 1.16 (95% CI, 1.01-1.33; P = .44 for noninferiority).
“Beta-blocker interruption did not seem to improve the patients’ quality of life,” the authors advised.
The study team concluded that “In patients with a history of myocardial infarction, interruption of long-term beta-blocker treatment was not found to be noninferior to a strategy of beta-blocker continuation.”
An estimated 2 million people in the United States and Europe have an acute myocardial infarction every year. “The lack of contemporary large-scale randomized trials and of consensus recommendation on the duration of beta-blocker therapy after myocardial infarction has resulted in lifelong therapy in many patients, making this class of drugs one of the most prescribed worldwide,” the researchers explained. “Beta-blocker therapy is not only a standard of care for patients after myocardial infarction but also a quality indicator of secondary prevention, with a prescription rate that has reached over 90% in most Western registries.”
The trials demonstrating the benefit of beta-blocker therapy in patients with myocardial infarction were carried out before the modern era of myocardial reperfusion and pharmacotherapy, according to the report, which added, “Early coronary reperfusion therapy has led to a sharp decrease in the risks of heart failure and death after myocardial infarction and has led to questions about the add-on benefits of lifelong beta-blocker treatment in patients with a preserved left ventricular ejection fraction and no other primary indication for beta-blocker therapy. Contemporary large nationwide registries have often suggested an absence of long-term benefit of beta-blocker therapy in such patients, although data have been inconsistent.”
The ABYSS (Assessment of Beta-Blocker Interruption 1 Year after an Uncomplicated Myocardial Infarction on Safety and Symptomatic Cardiac Events Requiring Hospitalization) trial was designed to evaluate beta-blocker continuation or interruption among patients with a history of myocardial infarction who had a left ventricular ejection fraction of at least 40%. “We hypothesized that beta-blocker interruption would be clinically safe and that the patients’ quality of life would improve,” the authors said, but the results did not show that.
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