Characterization of left atrioventricular coupling in severe aortic stenosis: CMR-derived LACI

Abstract Background Aortic stenosis (AS) imposes a pressure overload to the left ventricle that in the advanced stages is transmitted to the left atrium and pulmonary vasculature. The Left Atrial Coupling Index (LACI), an integrated measure of left atrioventricular coupling, has emerged as an independent predictor of adverse outcomes across various cardiovascular conditions. Objective to assess the distribution and clinical associations of cardiac magnetic resonance (CMR) -derived LACI in patients with severe aortic stenosis. Methods A total of 95 patients (mean age: 74 years; 63% male) with severe AS diagnosed by echocardiography who underwent CMR were analyzed. Comprehensive evaluation of cardiac chamber size and function was performed, including quantification of LACI and myocardial strain parameters. The presence of left ventricular late gadolinium enhancement (LGE) was also assessed. Symptomatic status was recorded at the time of CMR. Results At the moment of CMR scanning, 21 patients were symptomatic and the remainders were asymptomatic. Patients were stratified into LACI tertiles (first tertile LACI 20.45 17.8 - 23.5, best left atrioventricular coupling, 2nd tertile LACI 34.3 29.5 - 35.7 and third tertile LACI 50.2 43.8 - 73.7, the worst left atrioventricular coupling). Higher LACI values were associated with more advanced left heart remodeling. Significant differences were observed across tertiles of LACI for NT-proBNP (p 0.001), LA functional parameters including reservoir strain, conduit strain and booster strain (LARS, LACS and LABS; all p 0.001), and CMR-derived metrics of right ventricular strain (p = 0.01–0.02). While conventional markers of aortic stenosis severity (e.g., AVA, gradients) did not significantly differ across tertiles, indexed LVEDV (p = 0.017) and RVEDV (p = 0.02) were lower in patients with higher LACI. These findings support a progressive impairment in biatrial and biventricular function in patients with elevated LACI. Conclusions In patients with severe aortic stenosis, higher LACI values were associated with more advanced cardiac remodeling and elevated NT-proBNP levels, suggesting that LACI may serve as a sensitive imaging biomarker of early global cardiac remodeling, beyond traditional measures of AS severity.