High Nighttime Heart Rate is Associated with Increased Risk of All-Cause Mortality in Patients with Heart Failure and Reduced Ejection Fraction

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.