Fig. 1: Electromechanical assessment in the healthy atria of pigs.

a Schematic experimental flow-chart. b Two-dimensional and tissue Doppler imaging (TDI) snapshots (during acquisition and segmentation) of the posterior left atrial wall (PLA) during transesophageal echocardiography imaging in a pig. c Representative simultaneous TDI- and lead II-derived atrial signals during programmed atrial stimulation at 300, 250 and 200 ms cycle length. Their respective power spectral density and dominant frequency (DF) peaks are also shown. d Quantification of electromechanical dissociation (EMD = DF of atrial ECG signal – DF of atrial TDI signal) in all animals undergoing programmed atrial stimulation. e Representative TDI- and lead II-derived atrial signals during short-lasting atrial fibrillation (AF) after burst pacing. f Quantification of EMD during short-lasting AF episodes in control animals with healthy atria (‘n’ indicates the number of movies for analysis). g, h Regional analysis of EMD using TDI signals from the PLA and the left atrial free wall (LAFW). Based on the spectral resolution of atrial ECG and TDI signals, the EMD threshold was set at 0.32 Hz, which ensures proper distinction of the two DF peaks (See Suppl. Material for details). The Fisher’s exact test was used to assess differences. Light red tracings (in c, e, g) show the original tracings before subtracting QRS-T complexes from lead II and the intrinsic mode functions from TDI signals (See Methods for details). AVN atrio-ventricular node, CS coronary sinus, LA left atrium, LV left ventricle, PV pulmonary vein. Source data are provided as a Source Data file.