Fig. 2

The locations of the leading pacemaker and the patterns of excitation propagation were diverse among preparations but consistent in each SAN preparation. a Schematic diagram of leading pacemaker sites in the SAN. Leading pacemaker sites in 12 different experiments are indicated by dots. b–d Activation maps of pacemaker activity. Excitation propagation initiated near the SVC (b), center (c), and IVC (d) of the SAN. Isochrones were calculated at 2-ms intervals from the leading pacemaker site. IVC Inferior vena cava, SVC superior vena cava, SEP internal septum, RA right atrium, CT crista terminalis, RSARB right sinoatrial ring bundle, LSARB left sinoatrial ring bundle