Fig. 1.

Left atrial (LA) strain and strain rate measurement in 4- and 2-chamber views. Left figures show an example of LA feature tracking and strain and strain rate profiles (Endo GLS: endocardial global longitudinal strain). Right figures show the fast long-axis strain and strain rates. White squares denote the three anatomical reference points that were tracked automatically throughout the cardiac cycle. D is the distance between the left atrioventricular junction and the user-defined point at the mid posterior LA wall on standard CMR 4-chamber (denoted as D_septal and D_lateral) and 2-chamber (denoted as D_anterior and D_inferior) views. Fast strain was derived from time variation of distance D. Strain rate was then obtained by taking the first-order derivative of the strain curve. The fast strain and strain rate curves on the right side are based on averaging the results from septal and lateral walls for 4-chamber view and from anterior and inferior walls for 2-chamber view, respectively. Reservoir strain (ε_s) and strain rate (SR_s) correspond to reservoir function. Conduit strain (ε_e) and strain rate (SR_e) correspond to conduit function. Booster strain (ε_a) and strain rate (SR_a) correspond to booster pump function. Details see text