Low-Normal Peri-Procedural Potassium as a Prognostic Marker of Atrial Fibrillation and Stroke After CABG

Background Postoperative atrial fibrillation (POAF) and stroke are major complications following coronary artery bypass grafting (CABG). The clinical significance of peri-procedural potassium levels within the normal range remains unclear. Objective To evaluate whether low-normal peri-procedural mean potassium identifies patients at increased risk of POAF and 30-day stroke after isolated CABG. Methods We included 5,794 patients undergoing isolated CABG in an international multicenter cohort. Peri-procedural mean potassium (average of measurements 24 hours before and after surgery) was stratified into three groups: 3.5–3.9, 4.0–4.4 (reference), and 4.5–5.0 mmol/L. Primary and secondary outcomes were 30-day POAF and stroke, respectively. We used adjusted Cox proportional hazards and linear spline models. Results POAF occurred in 1,156 patients (20.0%) and 30-day stroke in 105 (1.8%). Compared with the reference group, low-normal potassium (3.5–3.9 mmol/L) was associated with a higher risk of POAF (adjusted HR 1.40, 95% CI 1.21–1.63, p<0.001) and stroke (adjusted HR 2.13, 95% CI 1.31–3.44, p=0.002). These associations remained materially unchanged in sensitivity analyses additionally adjusting for diabetes-related, potassium-modifying, and postoperative antithrombotic medications. Higher potassium (4.5–5.0 mmol/L) was not significantly associated with either outcome. A linear spline model showed an inverse association between potassium levels and POAF risk (p<0.001), without significant slope change at 4.0 mmol/L. Conclusion Low-normal peri-procedural potassium was associated with increased risks of POAF and 30-day stroke after CABG. These findings suggest that low-normal potassium may serve as a marker of increased perioperative vulnerability rather than evidence supporting routine aggressive potassium supplementation.