Heart rate and cardiovascular outcomes with and without beta-blocker in post-mi patients: a pre-specified analysis of the ABYSS trial

Abstract Importance The importance of heart rate control in post-myocardial infarction (MI) patients hasn’t been explored in the era of reperfusion. Objective To evaluate the impact of heart rate (HR) control on cardiovascular outcomes and quality of life. Methods Prespecified analysis of the ABYSS randomized trial were stable post-MI patients with left ventricular ejection fraction ≥40% were randomized to beta-blocker interruption or continuation. Patients were divided into 3 groups according the tertiles of pre-randomization HR: 60 bpm (T1), 60-68 bpm (T2), and ≥68 bpm (T3). The primary endpoint was a composite of death, MI, stroke, or hospitalization for cardiovascular reasons. Secondary outcomes included MACE (death, MI, stroke) and MACE with hospitalization for heart failure. Results Among the 3623 randomized patients of the study, n= 1,220 patients had a HR measured in consultation below 60 BPM (median 55), n= 1,149 patients between 60 to 67 BPM (median 63), and n=1,254 above 68 BPM (median 75). While there were no differences in the rate of the primary endpoint between the three groups, patients with lower heart rate at baseline had a lower rate of MACE with heart failure (6.5% vs 7.1% vs 10.4% p0.001); MACE (5.5% vs 6.4% vs 9.2% p0.001); all-cause mortality (2.9% vs 3.4% vs 5.9% p0.001); cardiovascular death (0.7% vs 1.2% vs. 2.1% p=0.014) and MI 1.8% vs 2.3% vs. 3.3% p0.001). Beta-blocker interruption led to a significant increase in HR with a dose-dependent rebound effect and higher risk of cardiovascular events consistent across tertiles, although more pronounced in patients with elevated baseline HR (figure). There was no association between HR control and quality of life. Conclusions Heart rate control in post-myocardial infarction (MI) patients is a major determinant of outcomes in post MI patients. Beta-blocker interruption was associated with a significant rebound in HR and worst cardiovascular outcomes.