Effect of beta blocker withholding or withdrawal after myocardial infarction without reduced ejection fraction on ischaemic events: a post hoc analysis from the REBOOT trial.

Background: Current guidelines recommend beta blockers after myocardial infarction (MI) regardless of left ventricular ejection fraction (LVEF), aiming to reduce reinfarction and ventricular arrhythmias. However, recent trials have challenged this practice in patients without reduced LVEF. Whether beta blocker withdrawal in these patients increases short-term or recurrent ischaemic events remains uncertain.

Aims: We aimed to evaluate the short-term ischaemic safety of beta blocker withholding or withdrawal at hospital discharge in patients with MI and LVEF >40% and to determine the effect of beta blocker therapy on a broad composite ischaemic endpoint.

Methods: This is a post hoc analysis of the REBOOT trial, in which patients with MI and LVEF >40% were randomised to beta blocker therapy or no beta blocker at discharge. The incidence of short-term (3-month) and recurrent ischaemic events (a composite of cardiac death, reinfarction, sustained ventricular tachycardia/fibrillation, resuscitated cardiac arrest, or unplanned revascularisation) was assessed overall and according to prior beta blocker use.

Results: From the 8,438 patients in the intention-to-treat population of the trial, information regarding beta blocker history was available for 8,401. Of these, 12.1% were on chronic beta blocker therapy before MI. Overall, withholding or withdrawing beta blockers was not associated with increased short-term ischaemic risk (hazard ratio [HR] 1.13, 95% confidence interval [CI]: 0.74-1.72). Over a median follow-up of 3.7 years, there were no differences in recurrent ischaemic events between groups (HR 0.98, 95% CI: 0.82-1.16), nor significant interactions with prior beta blocker therapy. In patients who were on a beta blocker before the index MI, randomisation to no beta blocker (withdrawal) was not associated with an increased risk of ischaemic events during trial follow-up (composite ischaemic endpoint HR 0.93, 95% CI: 0.64-1.34).

Conclusions: In patients with MI and LVEF >40%, beta blocker withholding or withdrawal at discharge was not associated with increased short-term or recurrent ischaemic events, supporting the safety of this strategy in contemporary clinical practice.