Abstract 134: Postoperative Atrial Fibrillation and the Short-term Risk of Ischemic Stroke

Abstract

Introduction: We have recently shown an association between new-onset postoperative atrial fibrillation (AF) and the long-term risk of ischemic stroke after noncardiac surgery. However, the degree of stroke risk with AF in the postoperative setting remains unclear. Hypothesis: New-onset postoperative AF is associated with an increased risk of ischemic stroke in the 30 days after surgery. Methods: Administrative claims data from all discharges at nonfederal acute care hospitals in California, New York, and Florida were used to identify patients who underwent inpatient surgery in 2007-2012. Our predictor variable was new-onset AF, defined using validated ICD-9-CM diagnosis and present-on-admission codes. Patients with prior stroke or AF were excluded. The outcome was postoperative stroke, defined as ischemic stroke occurring within 30 days of surgery. Cox proportional hazards analysis was used to examine the association between postoperative AF and stroke while adjusting for demographics and vascular risk factors. In sensitivity analyses, we limited the outcome to stroke occurring after discharge but within 30 days of surgery. Cardiac and noncardiac surgeries were analyzed separately. Results: Among 7,139,472 patients with inpatient surgery, 102,831 (1.44%) developed postoperative AF and 17,117 (0.24%) developed a postoperative stroke. After noncardiac surgery, the 30-day cumulative risk of stroke was significantly higher in those with postoperative AF (2.07%) than those without AF (0.18%). This difference was significant after adjustment for demographics and potential confounders (hazard ratio [HR], 4.3; 95% CI, 4.1-4.6). After cardiac surgery, postoperative AF was also associated with an increased cumulative risk of stroke (2.27%) compared to those without AF (1.17%), but the strength of association (HR, 1.8; 95% CI, 1.6-1.9) was less marked than in the setting of noncardiac surgery ( P value for interaction <0.001). Postoperative AF was associated with stroke occurring after discharge and within 30 days of noncardiac surgery (HR, 1.9; 95% CI, 1.6-2.3), but not cardiac surgery (HR, 1.1; 95% CI, 0.9-1.3). Conclusions: Postoperative AF is associated with an increased short-term risk of stroke after noncardiac surgery.