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Abstract

Introduction: New-onset atrial fibrillation (AF) has been associated with increased morbidity and mortality in surgical populations. Outcomes of patients with new-onset AF in the medical intensive care unit (ICU) are largely unknown. Hypothesis: To characterize morbidity and mortality in patients with new-onset, chronic, and no prior history of AF to better determine the effect of AF in a medical ICU population. Methods: Retrospective database review at University of Chicago Medical Center, a 596-bed university-affiliated teaching hospital with a 16-bed medical ICU. Patients were included if they were admitted to the ICU for >24 hours and were >18 years of age between June 1, 2008 and June 30, 2010. Exclusions included history of cardiothoracic surgery 90 days prior to admission or incomplete patient data. Primary outcome was 60-day mortality. Secondary outcomes included in-hospital mortality, ICU and hospital length of stay, and ICU and hospital costs. Chi-square and Fischer’s exact test for nominal data and student’s t-test for continuous variables were used for data analysis. Cox regression was utilized for multivariate analysis and Kaplan-Meier survival curves for time to mortality. Forward, step-wise logistic regression was used to evaluate confounding variables. Results: Of the 870 patients included in analysis, 701 had no AF, 53 experienced new-onset AF, and 116 had pre-existing AF. Pre-existing AF patients were separated into rapid ventricular response (RVR) (n=20) or no RVR (n=96). Patients with new-onset and pre-existing AF with RVR had significantly higher mortality than those who did not (50.9% vs. 65% vs. 25.2%, respectively; p<0.001 for all). In-hospital mortality was also significantly higher in new-onset and pre-existing AF with RVR compared to those with no history (45.3% vs. 35% vs. 18.1%; p<0.001 for all). Total hospital costs were higher and both ICU and hospital length of stay were significantly increased for patients with new-onset and pre-existing AF with RVR (p<0.001 for all). Conclusions: Medical ICU patients who develop new-onset AF or have pre-existing AF with an episode of RVR during ICU admission may experience higher mortality and morbidity than those with no prior history of AF.