Prolonged elevated heart rate and 28-day in-hospital mortality in patients with asthma-related critical illness: a multicenter retrospective cohort study.

BACKGROUND

Prolonged elevated heart rate (PeHR) has been reported to be associated with adverse outcomes in several critical illnesses, but its prognostic significance in patients with asthma-related critical illness remains unclear. This study aimed to evaluate the association between PeHR and 28-day in-hospital mortality in this population.

METHODS

We conducted a retrospective cohort study using two large intensive care unit (ICU) databases, the Medical Information Mart for Intensive Care IV (MIMIC-IV) and the eICU Collaborative Research Database (eICU-CRD). The MIMIC-IV cohort included 2,355 ICU patients with a recorded diagnosis of asthma or status asthmaticus, and the eICU-CRD cohort included 1,575 patients as an external validation cohort. PeHR was defined as an hourly mean heart rate >100 beats per minute (bpm) for at least 11 hours within any consecutive 12-hour window. Cox proportional hazards models were used to evaluate the association between PeHR and 28-day in-hospital mortality. A 24-hour landmark analysis, subgroup analyses, and multiple sensitivity analyses were further performed. As an exploratory supplementary analysis, elastic-net models based on routinely available variables from the first 24 hours after ICU admission were developed to stratify the risk of 28-day in-hospital mortality after the 24-hour landmark and to assess the incremental predictive value of PeHR.

RESULTS

In the MIMIC-IV cohort, 589 patients (25.0%) met the PeHR definition. The 28-day in-hospital mortality rate was higher in the PeHR group than in the no-PeHR group (11.4% vs. 2.2%). In the fully adjusted Cox model, PeHR was independently associated with increased 28-day in-hospital mortality [hazard ratio (HR), 2.75; 95% confidence interval (CI): 1.76-4.28; P<0.001]. This association was also observed in the eICU-CRD external validation cohort (HR, 1.70; 95% CI: 1.10-2.90; P=0.041). In the 24-hour landmark analysis, the association was attenuated but remained statistically significant in both cohorts (MIMIC-IV: HR, 1.46; 95% CI: 1.11-1.93; P=0.009; eICU-CRD: HR, 1.34; 95% CI: 1.05-1.71; P=0.02). Sensitivity analyses generally supported the main findings. Exploratory elastic-net models showed good risk-stratification performance in both internal and external validation, but adding PeHR did not materially improve discrimination, precision-recall performance, or calibration.

CONCLUSIONS

Among patients with asthma-related critical illness, PeHR was independently associated with higher 28-day in-hospital mortality, with a similar direction of association observed in the external validation cohort and in the 24-hour landmark analysis. PeHR may serve as an easily obtainable and interpretable marker of short-term mortality risk; however, its incremental predictive value in multivariable prediction models appears limited and requires further prospective validation.