Coronary sinus lactate at reperfusion: A predictor of atrial fibrillation after coronary artery bypass grafting

Objective Postoperative atrial fibrillation (POAF) is the most common complication after coronary artery bypass grafting (CABG). This study explored the association of coronary sinus (CS) lactate levels with POAF following CABG. Methods This was a single-center prospective cohort study of patients without a history of atrial fibrillation undergoing isolated CABG (12/2024-2/2026). CS lactate was sampled before initiation of cardiopulmonary bypass (pre-CPB), prior to cross-clamp removal (pre-XC), and after cross-clamp removal (post-XC). POAF was defined as electrocardiogram documented atrial fibrillation treated with amiodarone during the index hospitalization. Restricted cubic splines were used to define a binary cutoff of post-XC CS lactate at >3 mmol/L. Multivariable logistic regression was performed to assess the association between CS lactate elevation and POAF. Results Of the 94 patients included, POAF occurred in 24 patients (26%). Patients with POAF were older and more commonly male but had similar median cardiopulmonary bypass time and cross-clamp duration. Patients with a post-XC lactate >3mmol/L (n=13/94, 14%) had significantly greater rates of POAF compared to those without lactate elevation (62% vs 20%, p=0.001). Following risk-adjustment, post-XC lactate >3 mmol/L was associated with a 11.7-fold increase in odds of POAF (p=0.010). Increasing age was also linked to greater likelihood of POAF. There was no significant association of POAF with CPB time, XC duration, pre-CPB CS lactate, or pre-XC CS lactate. Conclusions Elevated CS lactate after cardiac reperfusion was associated with increased likelihood of POAF. Our findings suggest that CS lactate may be used to guide POAF prophylaxis.