Clinical significance of the mitral annulus-left atrium coupling index for predicting left atrial appendage thrombogenic milieu in patients with non-valvular atrial fibrillation

Left atrial appendage (LAA) function is governed by the structure and function of the left atrium (LA) and left ventricle (LV). The mitral annular–left atrial coupling index (MALACI) may provide incremental value for thrombogenic milieu risk stratification in non-valvular atrial fibrillation (NVAF), but current data are limited. This is a cross-sectional study. Consecutive patients with NVAF undergoing transesophageal echocardiography (TEE) prior to cardioversion or catheter ablation were enrolled. The LAA thrombogenic milieu defined as the presence of LAA thrombus, severe spontaneous echo contrast, or sludge, served as a surrogate endpoint for cardioembolic risk. The MALACI was calculated as the ratio of the left atrial minimum volume index to mitral annular plane systolic excursion (MAPSE). A decision tree model incorporating MALACI aimed to stratify the risk of the LAA thrombogenic milieu. A total of 605 NVAF patients were enrolled. Among them, 196 (32.4%) were identified as having the LAA thrombogenic milieu. Compared with those without the thrombogenic milieu, patients with the milieu exhibited significantly higher MALACI values. MALACI showed a strong linear negative correlation with LAA emptying velocity. It also exhibited superior discriminatory ability for detecting LAA thrombogenic milieu (AUC 0.932), outperforming conventional echocardiographic parameters and the CHA₂DS₂-VASc score (AUC 0.626). Across ten separate multivariate logistic regression models, MAPSE, LVEDD, LVESD, LVEF, LAVImax, LAVImin, LAEF, LASr, and MALACI were each independently associated with the LAA thrombogenic milieu. Moreover, MALACI provided incremental predictive value beyond conventional echocardiographic parameters and performed comparably to LAEF and LASr. The decision tree model, incorporating MALACI, LASr, and LAEF, predicted the LAA thrombogenic milieu with good accuracy (accuracy 89.93%, sensitivity 82.14%, specificity 93.78%), including patients with low CHA2DS2-VASc score (0–2) (accuracy 90.29%,sensitivity 77.78%, specificity 94.62%). MALACI and the decision tree algorithm exhibited favorable discrimination across persistent and paroxysmal AF subgroups. In the exploratory analysis of definite LAA thrombu, all 8 subjects with LAA thrombus were categorized as moderate- to high-risk by the algorithm, with none in the low-risk group. MALACI is associated with the LAA thrombogenic milieu and may provide incremental value beyond conventional echocardiographic parameters for risk stratification in NVAF patients. MALACI: mitral annulus-left atrium coupling index; NVAF: non-valvular atrial fibrillation; LASr: left atrial reservoir strain; LAEF: left atrial emptying fraction; TEE: transesophageal echocardiography