Lower Survival After Coronary Artery Bypass in Patients Who Had Atrial Fibrillation Missed by Widely Used Definitions

OBJECTIVE: To investigate the impact of limiting the definition of post-coronary artery bypass graft (CABG) atrial fibrillation (AF) to AF/flutter requiring treatment—as in the Society of Thoracic Surgeons' (STS) database— on the association with survival. PATIENTS AND METHODS: We assessed in-hospital incidence of post-CABG AF in 7110 consecutive isolated patients with CABG without preoperative AF at 4 hospitals (January 1, 2004 to December 31, 2010). Patients with ≥1 episode of post-CABG AF detected via continuous in-hospital electrocardiogram (ECG)/telemetry monitoring documented by physicians were assigned to the following: Group 1, identified as having post-CABG AF in STS data and Group 2, not identified as having post-CABG AF in STS data. Patients without documented post-CABG AF constituted Group 3. Survival was compared via a Cox model, adjusted for STS risk of mortality and accounting for site differences. RESULTS: Over 7 years’ follow-up, 16.0% (295 of 1841) of Group 1, 18.7% (79 of 422) of Group 2, and 7.9% (382 of 4847) of Group 3 died. Group 2 had a significantly greater adjusted risk of death than both Group 1 (hazard ratio [HR]: 1.16; 95% confidence interval [CI], 1.02 to 1.33) and Group 3 (HR: 1.94; 95% CI, 1.69 to 2.22). CONCLUSIONS: The statistically significant 16% higher risk of death for patients with AF post-CABG missed vs captured in STS data suggests treatment and postdischarge management should be investigated for differences. The historical misclassification of “missed” patients as experiencing no AF in the STS data weakens the ability to observe differences in risk between patients with and without post-CABG AF. Therefore, STS data should not be used for research examining post-CABG AF.