BACKGROUND: Increased resting heart rate is a risk factor for cardiovascular mortality and morbidity. Mineralocorticoid receptor antagonists (MRAs) have been shown to improve cardiac sympathetic nerve activity, reduce heart rate and attenuate left ventricular remodelling. Whether or not the beneficial effects of MRA are affected by heart rate in heart failure patients with reduced ejection fraction (HFREF) is unclear. METHODS: We undertook a secondary analysis of data from the Eplerenone in Mild Patients Hospitalization and Survival Study in Heart Failure study to assess if clinical outcomes, as well as the efficacy of eplerenone, varied according to heart rate at baseline. RESULTS: High resting heart rate of 80 bpm and above predisposed patients to greater risk of all outcomes in the trial, regardless of treatment allocation. The beneficial effects of eplerenone were observed across all categories of heart rate. Eplerenone reduced the risk of primary endpoint, the composite of cardiovascular death and hospitalisation for heart failure, by 30% (aHR 0.70; 95% CI 0.54-0.91) in subjects with heart rate ≥ 80 bpm, and by 48% (aHR 0.52; 95% CI 0.33-0.81) in subjects with heart rate ≤ 60 bpm. Eplerenone also reduced the risks of hospitalisation for heart failure, cardiovascular deaths and all-cause deaths independently of baseline heart rate. CONCLUSIONS: Baseline heart rate appears to be an important predictor of major clinical outcome events in patients with HFREF, as has been previously reported. The benefits of eplerenone were preserved across all categories of baseline heart rate, without observed heterogeneity in the responses.