The Association Between Atrial Fibrillation Burden and All‐Cause Mortality in Critically Ill Survivors: A Retrospective Study From the MIMIC ‐ IV Database

Background Atrial fibrillation (AF) is a common condition among critically ill patients, and AF burden serves as a quantitative measure of its occurrence. However, no studies have investigated the impact of in‐hospital AF burden on the prognosis of critically ill patients. Aim To explore the impact of AF burden during intensive care unit (ICU) on all‐cause mortality. Study Design This retrospective observational study utilised population data from the Medical Information Mart for Intensive Care‐IV Database. Patients who experienced episodes of AF during their ICU stay and were discharged from the hospital were included, and AF burden was calculated on the basis of nurse‐documented hourly cardiac rhythm. We classified patients into three groups based on the tertile of AF burden: low (T1, < 9.58%), medium (T2, 9.58%–62.42%) and high (T3, ≥ 62.43%). The multivariate Cox regression models and restricted cubic spline analyses were used to estimate hazard ratios and 95% CIs and explore linear and nonlinear relationships of AF burden and all‐cause mortality, respectively. Results A total of 6215 critically ill survivors with the episode of AF during the ICU stay were included. The mean age was 72.46 ± 11.86 years. High AF burden was associated with an increased risk of 1‐year all‐cause mortality (adjusted hazard ratio: 1.28, 95% CI: 1.13–1.45, p < 0.001), and restricted cubic spline analyses showed a linear relationship of AF burden with 1‐year all‐cause mortality. Additionally, there were no significant associations of AF burden and 30‐day all‐cause mortality. Conclusion In critically ill survivors, high AF burden during the ICU stay was associated with increased 1‐year all‐cause mortality, but not with 30‐day all‐cause mortality. Relevance to Clinical Practice This finding underscores the value of nurse‐documented AF burden in long‐term risk stratification of discharged critically ill patients with AF, facilitating individual management to improve the prognosis.