Differential prognostic impact of acute vs. chronic atrial fibrillation in the cardiovascular ICU: a multivariate analysis of 15,271 admissions

Background In critical care, new-onset (acute) atrial fibrillation (AF) commonly occurs as a stress-related response, whereas chronic AF reflects a fixed atrial substrate and long-standing cardiovascular disease. Their independent prognostic significance in contemporary cardiovascular intensive care remains unclear. Purpose To compare the independent association of acute versus chronic AF with in-hospital mortality in a large real-world cardiovascular ICU cohort. Methods We analysed 15,271 consecutive admissions to a tertiary cardiovascular intensive care unit. Patients were classified into three groups: no AF, acute AF (new-onset during admission), and chronic AF. The primary endpoint was in-hospital mortality. Multivariable logistic regression was used to estimate adjusted associations, controlling for age, left ventricular ejection fraction (LVEF), and chronic renal disease (CRD). A prespecified subgroup analysis was performed in patients admitted with myocardial infarction. Results Chronic AF was present in 9.3% (n=1,424) and acute AF in 4.3% (n=658). Patients with chronic AF were older and had lower LVEF. Crude in-hospital mortality was 14.4% in chronic AF, 6.2% in acute AF, and 6.1% in patients without AF. After multivariable adjustment, chronic AF remained independently associated with higher odds of in-hospital death (OR 1.67; 95% CI 1.36–2.06; p<0.001). In contrast, acute AF was not independently associated with mortality (OR 0.82; p=0.32). In the myocardial infarction subgroup, chronic AF showed the highest adjusted risk (OR 2.16). Conclusion In a large contemporary cardiovascular ICU registry, chronic—but not acute—atrial fibrillation is an independent predictor of in-hospital mortality. This suggests that a chronic atrial substrate identifies a distinct phenotype of cardiac frailty that confers excess risk beyond acute arrhythmic triggers.