Background and aims
The evidence for beta-blocker therapy after myocardial infarction (MI) is randomized trials conducted more than 30 years ago, and the continued efficacy has been questioned.

Design and methods
The ongoing Danish (DANBLOCK) and Norwegian (BETAMI) randomized beta-blocker trials are joined to evaluate the effectiveness and risks of long-term beta-blocker therapy after MI. Patients with normal or mildly reduced left ventricular ejection fraction (LVEF ≥ 40%) will be randomized to open-label treatment with beta-blockers or no such therapy. The event-driven trial will randomize ∼5700 patients and continue until 950 primary endpoints have occurred. As of July 2023, 5228 patients have been randomized. Of the first 4000 patients randomized, median age was 62 years, 79% were men, 48% had a ST-segment elevation myocardial infarction (STEMI), and 84% had a normal LVEF. The primary endpoint is a composite of adjudicated recurrent MI, incident heart failure (HF), coronary revascularization, ischaemic stroke, all-cause mortality, malignant ventricular arrhythmia, or resuscitated cardiac arrest. The primary safety endpoint includes a composite of recurrent MI, HF, all-cause mortality, malignant ventricular arrhythmia, or resuscitated cardiac arrest 30 days after randomization. Secondary endpoints include each of the components of the primary endpoint, patient-reported outcomes, and other clinical outcomes linked to beta-blocker therapy. The primary analysis will be conducted according to the intention-to-treat principle using a Cox proportional hazards regression model. End of follow-up is expected in December 2024.

Conclusion
The combined BETAMI–DANBLOCK trial will have the potential to affect current clinical practice for beta-blocker therapy in patients with normal or mildly reduced LVEF after MI.