Echocardiographic Left Atrial Volumetric–mechanical Coupling Index for Prediction of Atrial Fibrillation after STEMI

BACKGROUND Atrial fibrillation (AF) commonly complicates ST-segment elevation myocardial infarction (STEMI). Conventional echocardiographic measures may incompletely capture left atrial remodeling. The left atrial volumetric-mechanical coupling index (LACI-vm), integrating left atrial volume index (LAVI) and mitral annular a' velocity, emerges as a novel predictor of cardiovascular outcomes. This study evaluated the association between LACI-vm measured during index hospitalization and incident AF after STEMI and its incremental predictive value beyond clinical and echocardiographic variables. METHODS Consecutive STEMI patients undergoing primary coronary angiography from 2017-2023 were retrospectively analyzed. LACI-vm was calculated as LAVI/a'. Patients with prior AF/flutter, non-sinus rhythm during echocardiography, or significant structural heart disease were excluded. Multivariable Cox regression, receiver operating characteristic (ROC) analysis, and net reclassification improvement (NRI) were performed. RESULTS Among 469 patients (64.5 ± 12.5 years, 24.9% female), median LACI-vm was 3.4 (IQR 2.6-4.9). During a median 56-month follow-up (2,193 person-years), 66 patients (14.1%) developed AF, with an incidence rate of 30.1 per 1,000 person-years. AF incidence was higher with LACI-vm >3.4 than ≤3.4 (23.9% vs. 4.3%, 58.0 vs. 8.1 per 1,000 person-years). LACI-vm independently predicted AF (HR 2.73, 95% CI 1.33-5.64, p=0.006). ROC analysis showed an AUC of 0.857; a cutoff of 4.27 yielded 81% sensitivity and 91% specificity. LACI-vm was not independently associated with mortality. NRI demonstrated improved AF prediction (0.170-0.175, all p<0.001). CONCLUSIONS LACI-vm independently predicts post-STEMI AF and may identify patients who could benefit from intensified rhythm monitoring after discharge.