4D ultrasound reveals regional left atrial strain remodelling in a murine model of reversible pressure overload

As a marker of atrial mechanics, left atrial (LA) strain offers unique insight into the functional impact of heart failure treatments. However, given its complex geometry and contractile pattern, the evolution of global and regional LA biomechanics during pressure overload and subsequent release remains unclear. We performed four-dimensional (4D) ultrasound in mice (n = 8) to evaluate global and regional LA kinematics at baseline, 3 weeks after transverse aortic constriction (TAC), and 1 and 4 weeks after aortic debanding (deTAC). LA maximum volume increased from 11.8 ± 0.8 µL at baseline to 30.4 ± 9.4 µL after TAC (P = 0.0024), returning to baseline after deTAC. LA ejection fraction declined from 68.0 ± 5.8 to 29.1 ± 9.2% after TAC (P < 0.0001), partially recovering after deTAC. Global longitudinal strain dropped from 24.8 ± 3.6% at baseline to 10.2 ± 3.7% after TAC (P < 0.0001), improving to 18.9 ± 3.5% by 4 weeks after deTAC (P = 0.0073 vs baseline). Despite partial functional recovery, fibrosis remained elevated after pressure release. Notably, regional strain recovery was heterogeneous, with anterior strain measurements showing stronger correlations with delayed ventricular functional improvement than global LA strain, highlighting the superior predictive value of regional analysis. This approach reveals incomplete and region-specific atrial recovery following pressure overload reversal, offering new perspectives on reverse remodelling and potential prognostic value in heart failure management. KEY POINTS: Advanced 4D ultrasound enables precise assessment of regional left atrial strain dynamics throughout cardiac remodelling. Left atrial strain reveals region-specific remodelling patterns during both pressure overload and its reversal. Functional changes in the atrium, particularly in the anterior wall, serve as early predictors of subsequent ventricular remodelling.