BackgroundAcute respiratory distress syndrome (ARDS) is associated with high mortality. Atrial fibrillation (AF) is a common arrhythmia seen in critically ill patients. The impact of AF on the outcomes in patients with ARDS is less understood. In this analysis we attempt to evaluate the association of concurrent AF and various clinical outcomes in patients with ARDS. MethodsWe conducted a retrospective analysis of adult discharges from the National Inpatient Sample (NIS) between 2004 and 2014. International Classification of Disease codes were used to identify those with ARDS and AF. ResultsWe found 1,200,737 hospitalizations with ARDS, out of which 238,455 had concomitant diagnosis of AF. Hospitalizations with AF had higher prevalence of comorbidities including chronic pulmonary disease, diabetes mellitus, hypertension, obesity, congestive heart failure and renal failure. On adjusted analysis, AF was associated with increased odds of acute myocardial infarction, cardiogenic shock, pressor use, acute kidney injury, permanent pacemaker implantation, cardiac arrest, mechanical circulatory support use and higher length of stay and inflation-adjusted cost in hospitalizations with ARDS. However, there was no significant difference in adjusted all-cause mortality in ARDS with and without AF (25.42% vs 20.23%, p=0.53). ConclusionsAF is associated with worse clinical outcomes, higher length of stay and cost in ARDS hospitalizations as compared to those without AF.