Interruption of beta-blocker treatment in patients with a history of myocardial infarction (MI) did not reduce risk of cardiovascular events or death, nor did it appear to improve quality of life compared with continuation of treatment, based on findings from the ABYSS trial presented at ESC Congress 2024 in London and simultaneously published in The New England Journal of Medicine (NEJM).

The trial conducted at 49 sites in France, randomized 3,698 patients to either interruption of beta-blocker therapy (n=1846) or continuation (n=1852). All patients had a left ventricular ejection fraction of at least 40% and were receiving long-term beta-blocker treatment, with no history of a cardiovascular event in the six months prior to enrollment. The primary endpoint was a composite of death, nonfatal MI, nonfatal stroke, or hospitalization for cardiovascular reasons at a minimum of one year (median time between randomization and last MI was 2.9 years).

Results showed a primary-outcome event occurred in 432 (23.8%) of patients in the interruption group compared with 384 patients (21.1%) in the continuation group (p=0.44 for noninferiority). Additionally, researchers said that interruption of beta-blocker treatment did not seem to improve quality of life.

"Improvements in MI management and data from observational studies have led physicians to question whether continuing beta-blockers after one-year post-MI is needed since unnecessary treatment may result in side effects," said Principal Investigator Johanne Silvain, MD, of the Sorbonne University, Paris, France. "We conducted the ABYSS trial to provide conclusive randomized data on the effects of beta-blocker interruption vs. continuation on cardiovascular events and quality of life, but we were unable to show safety preservation in terms of clinical events nor any benefit on quality of life with beta-blocker interruption."

Silvain and colleagues highlighted several limitations of the trial, including the fact that it was not blinded and conducted in a single country, which could have influenced outcomes. Given the limitations and the overall results, Silvain cautions that the ABYSS findings "do not support interruption of a chronic beta-blocker treatment in post-MI patients" and "must be put into context with recent findings from the open-label REDUCE-MI trial and ongoing trials to provide additional evidence on the optimal use of beta-blockers after MI."

In a related editorial comment, published in NEJM, Tomas Jernberg, MD, PhD, agrees, writing that "it is prudent to wait for the results of additional ongoing trials of beta-blockers involving patients with [MI] and a preserved left ventricular ejection fraction before definitively updating guidelines. He adds: "Taken together, the results of the ABYSS, REDUCE-AMI, and ongoing trials will most likely provide firm evidence regarding beta-blocker treatment in this patient population."