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

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.

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.

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).

LACI-vm independently predicts post-STEMI AF and may identify patients who could benefit from intensified rhythm monitoring after discharge.