Background: Little is known about atrial fibrillation (AF) appearing during hospitalization in an Internal Medicine ward.

Purpose: We aimed to investigate characteristics and prognostic significance of in-hospital onset AF.

Methods: We studied 249 consecutive unselected patients admitted to this medical department with paroxysmal or persistent AF (out-of-hospital group) or AF developed following hospitalization (in-hospital group). Demographic, clinical, laboratory, electrocardiographic and echocardiographic data and all-cause mortality following discharge were recorded and compared between the groups.

Results: Diabetes mellitus (p=0.05), renal dysfunction (p<0.001), chronic lung disease (p=0.03) and history of stroke (p=0.01) were found more common in the in-hospital group (56 patients), compared to the out-of-hospital group (193 patients). Patients from the in-hospital group were more likely to have recurrent episodes of AF during hospitalization (p=0.002), were more frequently treated with amiodarone (p<0.001), discharged with sinus rhythm (p=0.04) and with medications for rhythm control (p=0.04). Time from onset to termination of AF (p<0.001) and hospital stay (p<0.001) were longer in the in-hospital group. On a median of 39-months follow-up, survival rate was lower in the in-hospital vs. out-of-hospital group (69.6% vs. 81.3%, p=0.025). Older age was significantly associated with shorter survival in the in-hospital group [odds ratio (OR)=1.87, 95% confidence interval (CI) 1.15−3.03, p=0.009]. In the out-of-hospital group, advanced age (OR=2.17, 95%CI 1.51−3.10, p<0.001), no prior AF episode (OR=3.41, 95%CI 1.56−7.46, p=0.002), diabetes mellitus (OR=2.22, 95%CI 1.12−4.39, p=0.006) and renal dysfunction (OR=2.44, 95%CI 1.10−5.38, p=0.049) were significantly associated with shorter survival. Treatment with statins (OR=0.49, 95%CI 0.22−1.07, p=0.061) predicted better survival.

Conclusion: Patients developing in-hospital AF differed from subjects hospitalized for AF with respect to the severity of the clinical profile and prognosis.