Abstract 3239: Risk of Stroke after New-Onset Atrial Fibrillation versus Chronic AF in Patients Undergoing Coronary Artery Bypass Surgery
Background: Among patients undergoing isolated coronary artery bypass graft surgery (CABG), the risk of post-operative stroke has not been compared between patients with chronic atrial fibrillation (AF) versus patients with hospital-acquired new-onset AF (new-AF).
Methods: Using linked hospital discharge data together with comprehensive clinical data from the California CABG outcomes reporting program, we conducted a retrospective cohort study of all patients undergoing isolated CABG in California between years 2003–2006. Using hospital discharge data, chronic AF was defined as ICD-9-CM =427.31 present at time of admission and during a previous hospitalization. New-AF was defined as a first-ever code for AF that was not present at the time of admission. The risk of stroke < 30 days after surgery, defined using specific ICD-9-CM codes, was analyzed using logistic regression, with adjustment for 15 clinically important stroke risk factors. As a sensitivity analysis, we developed a propensity model for new-AF, and analyzed the risk of stroke after hospital discharge but within 30 days of surgery.
Results: Among 61,031 cases, 2081 (3.4%) had chronic AF; 9858 (17%) had new-AF; the 30-day incidence of stroke was 1222 (2.0%). Compared to patients with no-AF, the adjusted risk of stroke in patients with chronic AF was odds ratio (OR) = 1.2 (CI: 0.9 –1.5), whereas for new-AF, it was OR= 1.7 (CI: 1.5–1.9), c-statistic = 0.73. Using the propensity analysis, the risk of stroke after hospital discharge associated with new-AF versus no-AF was similar across quintiles of the risk score (OR range=1.7–1.8).
Conclusion: After adjusting for stroke risk factors, patients who developed AF during hospitalization for CABG had an approximately 70% higher risk of stroke within 30 days compared to patients without AF, whereas the risk of stroke in patients with chronic AF was not significantly increased. Interventions that reduce the incidence of new-AF after CABG surgery may reduce the incidence of subsequent stroke.