Relationship between minimum heart rate and mortality in ICU patients with traumatic brain injury (TBI): a retrospective analysis based on the MIMIC-IV database.

Background: The association between minimum heart rate (MinHR) within 24 h of ICU admission and 1-month mortality in traumatic brain injury (TBI) patients remains unclear. Methods: This retrospective cohort study analyzed 2267 TBI patients from the MIMIC-IV v3.1 database. Multivariable Cox regression, restricted cubic spline (RCS) analysis, and subgroup analyses evaluated relationships between 24-hour MinHR and mortality. Results: The cohort (median age 67 [IQR 51-80] years; 62.6% female) had a median MinHR of 59 [52-68] bpm, with 248 deaths (10.94%). RCS analysis revealed a U-shaped association (P for nonlinear =0.001) with 59 bpm as the inflection point. MinHR ≥59 bpm independently predicted higher mortality after full adjustment (HR=1.84, 95%CI:1.31-2.60; P < 0.001). This association was pronounced in non-hypertensive patients (HR=1.50, 95%CI:1.08-2.08; P = 0.015). Conclusions: A U-shaped association exists between 24-hour MinHR and 1-month mortality in TBI patients, with 59 bpm as the critical threshold. MinHR ≥59 bpm independently predicts increased mortality. These findings support using 59 bpm as an alert threshold for early intervention.