The ABYSS trial, presented at the ESC Congress 2024, found that interrupting beta-blocker treatment in patients with a history of myocardial infarction (MI) did not demonstrate cardiovascular safety compared to continuing the medication.

In this trial, 3,698 patients were randomly assigned to either continue or interrupt their beta-blocker therapy, with a follow-up period of at least one year.

All participants had a left ventricular ejection fraction of at least 40% and had not experienced any cardiovascular events in the previous six months.

The primary outcome, which included death, non-fatal MI, non-fatal stroke, or hospitalization for cardiovascular reasons, occurred in 23.8% of the interruption group compared to 21.1% in the continuation group.

This resulted in a risk difference of 2.8 percentage points and a hazard ratio of 1.16, indicating that non-inferiority was not achieved.

Patients who stopped taking beta-blockers had higher rates of cardiovascular hospitalization, with 18.9% in the interruption group versus 16.6% in the continuation group.

Death rates were similar between the two groups, at 4.1% in the interruption group and 4.0% in the continuation group, with myocardial infarction rates also comparable.

Discontinuation of beta-blockers was associated with increases in blood pressure and heart rate after six months, suggesting negative cardiovascular effects.

Contrary to expectations, there was no improvement in quality of life for patients who interrupted beta-blockers, as measured by the European Quality of Life-5 Dimensions questionnaire.

Professor Johanne Silvain, the trial's lead investigator, emphasized that the findings do not support the interruption of chronic beta-blocker treatment in post-MI patients.

Further trials are ongoing to provide additional data on the safety and efficacy of discontinuing beta-blocker therapy in this patient population.

These findings challenge existing guidelines that suggest beta-blockers can be safely discontinued after one year in certain patient populations.