High heart rate (HR) is associated with increased risks of adverse outcomes in patients with heart failure. This study aimed to evaluate which measures of HR were associated with all-cause mortality in patients with heart failure and reduced ejection fraction (HFrEF). This study involved 741 HFrEF patients (age 65.1 ± 14.7 years, 71% male) who underwent 24 hour Holter electrocardiogram and resting electrocardiogram within 7 days between 2011 and 2015. We examined the associations of resting, 24 hour, and nighttime HRs with all-cause mortality. Nighttime and 24 hour HRs were determined as the mean HRs between 11:00 p.m. and 7:00 a.m. and over 24 hours, respectively. Nighty patients (12.1%) died during the 2-year follow-up. Resting, nighttime, and 24 hour HRs were significantly associated with all-cause mortality, also after adjusting for conventional risk factors. Resting HR did not remain as an independent factor when 24 hour HR (hazard ratio 1.10, 95% confidence interval 1.04-1.18) was included in the model. Including nighttime HR (hazard ratio 1.11, 95% confidence interval 1.05-1.17) in the model also eliminated 24 hour HR as an independent variable. Compared with the lowest quartile of nighttime HR (< 65 beats/minute), the highest quartile of nighttime HR (> 87 beats/minute) was significantly associated with a higher risk of all-cause mortality (hazard ratio 2.89, 95% CI 1.49-5.60). In conclusion, 24 hour HR and nighttime HR were significantly associated with an increased risk of mortality in patients with HFrEF. Nighttime HR appeared to be more strongly associated with all-cause mortality compared with 24 hour HR.
Keywords: Holter ECG; Outcome.