Echocardiographic data acquisition
Echocardiographic images were obtained by three experienced echocardiographers using a Vivid E95 ultrasound scanner (GE Vingmed Ultrasound AS, Horten, Norway). Patients were scanned in the left lateral recumbent position.
A M5Sc-D matrix phased array transducer (1.5-4.6 MHz) was used for two-dimensional echocardiography. A focused examination to evaluate the diastolic function, including 2D and Doppler methods, was performed according to the ASE/EACVI recommendations (9). Three loops were acquired in sinus rhythm and five during atrial fibrillation. Special care was taken to produce an apical 4-chamber and 2-chamber view with a maximized left atria (LA) chamber optimal for endocardial border tracings. Sector width and depth were adjusted to include only the LA. Pulse Wave (PW) Doppler sample volume was aligned with blood flow as accurately as possible according to guidelines (9) in all relevant recordings. 3D images were acquired with a 4V-D volume phased array transducer (1.5-4 MHz). A full-volume dataset of LA consisting of 4-6 wedge-shaped subvolumes was obtained during a single breath hold. Care was taken to avoid stitching artefacts and to include the entire LA by using a nine-slice view, along with three apical views.