Predictive Value of Preoperative Left Atrial Coupling Indices for Postoperative Atrial Fibrillation After Isolated CABG

<i>Background and Objectives:</i> Postoperative atrial fibrillation (POAF) is the most common arrhythmia after coronary artery bypass grafting (CABG) and is linked to adverse outcomes. This study evaluated the predictive value of the Left Atrial Coupling Index (LACI) for POAF and compared two calculation methods, LACI₁ and the novel LACI₂. <i>Materials and Methods:</i> This prospective study included 130 patients undergoing isolated CABG between January 2022 and June 2023. Preoperative echocardiography was performed to calculate conventional parameters and LACI values: LACI₁ = LAVI/TDI-septal a' and LACI₂ = LAVI/min (TDI-septal a', TDI-lateral a'). Patients were classified into POAF (+) and POAF (-) groups. Clinical, echocardiographic, and outcome data were compared. Logistic regression and receiver operating characteristic (ROC) analyses were performed. <i>Results:</i> POAF occurred in 59 patients (45.4%). Those with POAF were older, had more diabetes mellitus(DM), hypertension(HT), and higher EuroSCORE II values (all <i>p</i> < 0.05). POAF was associated with longer hospitalization and higher in-hospital mortality. Both LACI₁ (4.21 ± 2.62 vs. 2.94 ± 1.02, <i>p</i> < 0.001) and LACI₂ (4.27 ± 2.60 vs. 2.96 ± 1.02, <i>p</i> < 0.001) were significantly higher in the POAF group. In multivariate analysis, LACI₁ (OR 1.45, <i>p</i> = 0.020) and LACI₂ (OR 1.50, <i>p</i> = 0.004) remained independent predictors. ROC analysis showed numerically higher discriminatory performance for LACI₂ (AUC = 0.690, specificity 74.5%) compared with LACI₁ (AUC = 0.677, specificity 67.6%). <i>Conclusions:</i> LACI is an independent predictor of POAF after CABG. The novel LACI₂ demonstrated numerically higher predictive performance compared with LACI₁ and may improve preoperative risk stratification and guide preventive strategies.