Unplanned 30-day readmission, comorbidity, and impact on mortality after incident atrial fibrillation hospitalisation in Western Australia, 2001-2015

Background
The healthcare burden of atrial fibrillation (AF) is dominated by hospitalisations, but data on 30-day unplanned readmissions after AF hospitalisation and impact on mortality are limited.
Objective
To assess causes and trends of 30-day unplanned readmission in incident (first-ever) hospitalised AF patients, and the risk of readmission for subsequent all-cause mortality.
Methods
Patients aged 25-94 years, with an incident AF hospitalisation (principal diagnosis) between 2001-2015, and surviving 30-days post-discharge, were identified from linked Western Australian hospitalisation and mortality data. Unplanned 30-day readmissions were categorised by principal diagnosis. Multivariable logistic and Cox regression analyses determined the independent predictors of readmission and the hazard ratio (HR) with 95% confidence intervals (CI) of readmission for subsequent 1-year mortality.
Results
Of 22,814 patients, 57.7% male, mean age 67.8±13.8 (SD) years, 9.5% experienced one or more 30-day unplanned readmission, with standardised rates increasing 2.0% annually (95% CI, 1.0-3.1). Among all readmissions, 64.8% were cardiovascular-related, with AF (31.7%), coronary events (12.2%), and heart failure (8.5%) being the most frequent. In 30-day survivors, 4.3% died within 1-year. Patients with any cardiovascular or non-cardiovascular readmission (versus none) had a multivariable-adjusted mortality HR of 2.12 (95% CI, 1.82-2.45). Coexistent comorbidities were independently associated with 30-day unplanned readmission and 1-year mortality.
Conclusion
Following incident AF hospitalisation, 30-day unplanned readmissions were common, mostly cardiovascular-related, but any readmission regardless of cause, was associated with a twofold higher adjusted mortality risk. Our findings also support the importance of comorbidity optimisation within an integrated care pathway to reduce adverse outcomes in AF patients.