Lactate and atrial fibrillation risk in ICU patients
I Moseley, A CorreaAbstract
Background/Introduction
Atrial fibrillation (AF) is highly prevalent among critically ill patients and frequently coexists with systemic hypoperfusion, shock states, and metabolic derangements. Lactate is a widely available biomarker of global tissue stress, yet its ability to refine early risk stratification in ICU patients with AF remains underexplored. Understanding how lactate integrates into early prognostication may improve triage decisions, rhythm-management strategies, and the identification of patients at highest mortality risk.
Purpose
To quantify the relationship between early lactate levels and in-hospital mortality, and to describe how AF prevalence varies across lactate strata in a large, real-world ICU population.
Methods
Using MIMIC-IV, we identified 94,458 adult ICU admissions with a blood lactate measured within the first 24 hours of ICU arrival. For each admission, we captured the first lactate and 24-hour maximum lactate and restricted analyses to each patient’s first ICU stay. AF was identified using validated ICD-9/10 codes (ICD-9 42731/42732; ICD-10 I48*). Lactate values were grouped into clinically relevant bins (≤1.0, 1.01–2.0, 2.01–3.0, 3.01–5.0, 5.01–10.0, >10.0 mmol/L). The primary outcome was in-hospital mortality, assessed overall and across lactate subgroups. Crude AF prevalence was evaluated within each lactate bin to characterize arrhythmia burden relative to physiologic stress.
Results
The final cohort included 94,458 ICU admissions, of which 18,492 (19.6%) had AF. Overall in-hospital mortality was 11.2% (10,543 deaths). Median first lactate was 1.8 mmol/L (IQR 1.2–3.1), and median 24-hour maximum was 2.4 mmol/L (IQR 1.6–4.5). Mortality increased stepwise across lactate bins, from 4.2% (≤1.0 mmol/L) to 38.9% (>10 mmol/L). AF prevalence was substantial across all strata, ranging from 15.7% in the lowest lactate bin to 28.4% at lactate >10 mmol/L. Similar monotonic patterns were observed when using 24-hour maximum lactate. Together, these findings demonstrate that even modest lactate elevations meaningfully stratify mortality risk and identify a physiologic phenotype in which AF is common.
Conclusion
Among ICU patients with early lactate measurement, rising lactate values were strongly associated with increasing in-hospital mortality and higher AF prevalence. These results suggest that early lactate provides immediate, clinically actionable prognostic information that may enhance rhythm-specific management and early risk stratification. Incorporating lactate into AF-focused ICU decision pathways and evaluating its incremental value over established scores represent important next steps.Mortality Across Lactate CategoriesAF Prevalence Across Lactate Categories