Early heart rate fluctuation and outcomes in critically ill patients with sepsis: A retrospective cohort study of the MIMIC-IV database

Background: Heart rate (HR) abnormalities are common in critically ill patients, but the significance of HR fluctuation in sepsis remains unclear. We aimed to assess the association of HR fluctuation with intensive care unit (ICU) mortality, hospital mortality, and 28-day mortality in patients with sepsis and identify the cutoff value of HR fluctuation associated with the lowest risk of death.

Methods: We conducted a retrospective cohort study using the medical information mart for the intensive care IV database. HR fluctuation, defined as the difference between maximum and minimum HR within the first 24 h of ICU admission, was analyzed for its association with outcomes using restricted cubic spline and multivariable Cox regression models.

Results: Among 24,419 eligible patients with sepsis, HR fluctuation showed a J-shaped association with ICU mortality, hospital mortality, and 28-day mortality. The high HR fluctuation group (≥ 35 bpm) had a significantly increased risk of ICU mortality ([hazard ratio, 95% confidence interval] 1.12,1.02-1.22, P = 0.013), hospital mortality (1.10,1.02-1.19, P = 0.013), and 28-day mortality (1.11,1.03-1.20, P = 0.007) compared to the control group (HR fluctuation 25-34 bpm). The low HR fluctuation group (< 25 bpm) showed no significant difference in the risk of mortality compared to the control group.

Conclusions: Our large-sample study suggests that early high HR fluctuation is indicative of poor prognosis in critically ill patients with sepsis. Early HR fluctuation may serve as a readily available "high-risk alert system" influencing therapeutic decision-making.