Structural enlargement and functional impairment: distinct but complementary dimensions of atrial myopathy

Introduction Left atrial (LA) enlargement and impaired deformation are both established markers of atrial remodeling and predictors of atrial fibrillation (AF), heart failure (HF) and other cardiac pathologies. While LA volume index (LAVI) is widely used as a structural indicator of chronic hemodynamic burden, speckle-tracking strain parameters may detect earlier functional impairment. Whether structural enlargement adequately reflects functional deterioration remains uncertain. Purpose To examine the relationship between LA volume and functional indices and to determine whether structural and functional parameters represent interchangeable expressions or distinct dimensions of atrial myopathy. Methods In 1000 patients presenting various pathologies, LA diameters and LAVI were measured alongside LA emptying fraction (LAEF) and strain-derived parameters (peak atrial longitudinal strain - PALS), left atrial conduit strain – LACDS, peak atrial contraction strain - PACS). Correlation analyses explored associations between structural and functional indices. Multivariable linear regression models assessed independent determinants of impaired LAEF and PALS, incorporating demographic variables, LV mass index, LV size and diastolic parameters. Logistic regression evaluated the independent contribution of LAVI and PALS to AF history. Results LAVI demonstrated modest inverse correlations with LAEF and PALS, indicating partial but limited structural and functional coupling. Multiple regression models explained only up to 32.7% of LAEF variability and approximately one quarter of PALS variability, even after adjustment for multiple clinical and echocardiographic covariates, such as age, sex, diagnosis, LV mass index and diastolic indices (FIGURE 1). Structural indices showed moderate diagnostic performance for identifying impaired LA function, underscoring limited interchangeability. Notably, after controlling for LAVI, each 1% reduction in PALS independently increased the odds of AF by 11%, highlighting the incremental prognostic contribution of functional impairment beyond structural enlargement. Furthermore, a substantial proportion of patients demonstrated discordance between volume and strain abnormalities, reinforcing the concept of heterogeneous atrial remodeling phenotypes. Conclusions LA volume and deformation reflect biologically distinct aspects of atrial myopathy. Enlargement represents cumulative structural remodeling, often occurring later in disease evolution, whereas strain abnormalities may indicate earlier or mechanistically different dysfunction. These parameters are complementary rather than interchangeable and should be integrated to achieve comprehensive evaluation of atrial remodeling, diastolic dysfunction and AF risk.