Quantifying Right Atrial Deformation Using Cardiac Imaging

The RA myocardial deformation was quantified using CVI 4.2 Tissue Tracking software (Circle Cardiovascular Imaging, Calgary, Canada). The software then constructed a deformable myocardial model based on the tracing, assuming the myocardium was nearly incompressible. In each of the subsequent frames, the displacement of the myocardial tissue, including the borders, were automatically determined using a gradient-based optical flow method with an incompressible model constraint. The propagated myocardial tissue across the cardiac cycle was verified by the operator to ensure the accuracy of propagation. At end-diastole, endocardial and epicardial borders were manually delineated using a point-and-click approach before the automated tracking algorithm was applied. Atrial endocardial and epicardial border contours were initially traced in the apical four chamber views at end-diastole. Endocardial atrial strain values for each tissue point as well as the global strain values were automatically derived by the software (Fig. 2, Supplementary Video). Feature-tracking techniques for the assessment of atrial phasic strain has been previously described^{5 (link),22 (link)}.Figure 2

Normal RA function stratified according to gender and age. RA booster function gradually increased with age, with a decrease in RA conduit function in order to preserve reservoir function.