Global Repolarization Sequence of the Right Atrium: Monophasic Action Potential Mapping in Healthy Pigs

The aim of the study was to explore the global sequence of atrial repolarization and its correlation to that of activation. Endocardial monophasic action potentials (MAPs) were sequentially recorded from51 ± 14sites in the right atrium of ten healthy pigs using the CARTO electroanatomic mapping system. Local activation time (AT), MAP duration, and 90% repolarization time (RT) were obtained, and from these data, color coded three-dimensional maps of AT and RT sequences and spatial distribution of MAP duration were reconstructed. The results of the study were: (1) An activation sequence was recognizable in all maps, starting from the posterosuperior wall and ending in the posteroinferior wall near the tricuspid annulus. (2) The repolarization sequence was also recognizable in all maps, and mainly followed the sequence of activation. (3) A significant positive correlation between the RT and AT was observed in all maps with an average r value being0.571 ± 0.159 (P < 0.01 – 0.0001), suggesting that progressively later AT associates with progressively longer RT. (4) No consistent correlation between the MAP duration and AT was found. In conclusion, repolarization gradients exist over the atrial endocardium in healthy pigs. The repolarization sequence follows the same sequence as the activation, suggesting that the spatiotemporal pattern of activation is an important determinant of the characteristics of the repolarization sequence. (PACE 2003; 26:1803–1808)