Abstract Body (Do not enter title and authors here): Background: Delirium and atrial fibrillation (AF) are two common complications after cardiac surgery. Each of them has been associated with several other adverse outcomes including mortality and prolonged hospital stay. We sought to determine the frequency of the co-incidence of postoperative delirium (POD) and postoperative atrial fibrillation (POAF) and its association with risk of one-year mortality following cardiac surgery compared to POD or POAF alone.

Methods: We established a retrospective observational cohort of adult patients who underwent cardiac surgery within our healthcare system between 2014 and 2022. POD was defined as a postoperative positive CAM-ICU test in a patient with a Richmond Agitation-Sedation Scale (RASS) >= -3. POAF was defined as a documented AF event within 30 days after surgery. Patients were stratified into four distinct groups: Co-incidence of POD and POAF, POD only, POAF only, and None (i.e., neither complication).

Results: Among 6136 patients, there were 256 (4.2%) patients experienced both POD and POAF, 221 (3.6%) had POD only, 2127 (34.7%) had POAF only, and 3532 (57.6%) had neither complication. The overall one-year mortality rate was 5.8%, with mortality rates of 21.9% for the co-occurrence group, 14.0% for the POD only group, 6.8% for the POAF only group, and 3.5% for the group with neither complication. The differences in one-year survival among the four groups are shown in Figure 1. Multivariable logistic regression analysis identified the top predictors for one-year mortality as co-incidence of POD and POAF (adjusted odds ratio (OR)=3.98, 95% CI=2.69-5.85, p<0.001), POD only (OR=2.95, 95% CI=1.84-4.61, p<0.001), higher Charlson comorbidity index (OR=2.18, 95% CI=1.00-4.46, p=0.040), longer surgery duration per hour (OR=1.62, 95% CI=1.46-1.79, p<0.001), and POAF only (OR=1.50, 95% CI=1.15-1.97, p=0.003).

Conclusions: More than half of the cardiac surgery patients with POD also developed POAF. The co-incidence of POD and POAF was associated with elevated risk of one-year mortality compared to either complication alone. Further research to explore the underlying mechanisms connecting POD and POAF and to identify risk factors specific to their co-incidence is warranted.