Park JJ, et al. - In 5,625 patients hospitalized for acute heart failure, identified from the Korean Acute Heart Failure registry, researchers assessed the variability in the impacts of β-blockers on clinical outcomes, based on the discharge heart rate, in patients hospitalized with heart failure and reduced ejection fraction (HFrEF). Patients with HFrEF (left ventricular ejection fraction ≤40%) were included. A slow heart rate was reported in 840 (29%) of patients and 56% got β-blockers at discharge, among overall 2,932 patients with HFrEF. Older age and lower 1-year mortality was seen in patients with slow heart rates vs those with high heart rates. Discharge heart rate and β-blocker had significant interaction. Higher 1-year mortality was seen only in patients without a β-blocker prescription and with a high heart rate, on stratification. In patients with high heart rates a 24% reduced risk for 1-year mortality was observed in relation to β-blocker prescription at discharge, but not in those with slow heart rates.