Heart Rate and Cardiovascular Outcomes in Post–Myocardial Infarction Patients Treated by β-Blockers: A Secondary Analysis of the ABYSS Trial

BACKGROUND: Heart rate (HR) is a key prognostic factor after myocardial infarction (MI), but its relevance in the modern reperfusion era is uncertain. We aim to evaluate the association between HR and β-blocker interruption on cardiovascular outcomes. METHODS: A prespecified secondary analysis of the ABYSS trial (Assessment of Beta-Blocker Interruption 1 Year After an Uncomplicted Myocardial Infarction), including 3698 stable post-MI patients (left ventricular ejection fraction ≥40%) randomized to continue or interrupt β-blockers, was conducted. Patients were grouped by prerandomization HR tertiles: <60 bpm (T1), 60 to <68 (T2), and ≥68 (T3). We examined associations between HR, treatment strategy, and the primary endpoint (death, MI, stroke, or cardiovascular rehospitalization), major secondary endpoints, and on-treatment HR. RESULTS: Median age in the study population was 63.5 years (55.9–71.1), and there were 621 women (17.1%). Baseline HR was not associated with the primary endpoint (22.4% versus 21.8% versus 21.6%; P= 0.867). Higher HR was associated with increased risk of death, MI, or stroke (5.5% versus 6.4% versus 9.2%; P <0.001; T3 versus T1 adjusted hazard ratio, 1.55; 95% CI, 1.14–2.12) and death, MI, stroke, or heart failure (6.5% versus 7.1% versus 10.4%; P= 0.007; T3 versus T1 adjusted hazard ratio, 1.47; 95% CI, 1.11–1.97). All-cause mortality rose across tertiles (2.9% versus 3.4% versus 5.9%; P= 0.004; P trend=0.008). β-Blocker interruption produced a dose-dependent HR increase of ≈10–13 bpm during follow-up. The association between interruption and worse outcomes was consistent across HR tertiles (no significant interaction) and LVEF categories (40% to 49% and >50%). CONCLUSIONS: In stabilized post-MI patients with preserved ejection fraction, higher HR remains associated with adverse cardiovascular events and mortality in the reperfusion era. Interrupting β-blockers substantially increases HR and is consistently linked with worse outcomes irrespective of baseline HR, supporting continuation of β-blocker therapy.