Sequence and dispersion of repolarization of the right atrium: Implications of repolarization disturbance in atrial fibrillation

Abstract: To explore the global sequence and dispersion of repolarization of the right atrium, monophasic action potentials (MAPs) were sequentially recorded from the right atrium using an electroanatomical mapping (CARTO) system in 10 healthy pigs and in 10 patients with (n=6) and without (n=4) paroxysmal atrial fibrillation (PAF) during sinus rhythm, or using two MAP recording catheters in 30 patients with or without PAF (n=15 each) during sinus rhythm, pacing, and programmed stimulation. The dispersion of activation time (AT), repolarization time (RT) and MAP duration (MAPd) were analyzed. During induced atrial fibrillation (AF), bipolar electrograms were recorded at 4, 10 or 20 right atrial sites and 5 coronary sinus sites in 21 patients with and 12 patients without clinical PAF. The local atrial fibrillation intervals (AFIs) were measured as estimates of the local effective refractory period (ERP). Results: Satisfactory MAPs were obtained from 51 ±14 sites in the 10 pigs and 33±21 sites in the 10 patients using the CARTO system and from 6.6±1.9 sites in the 30 patients using two MAP recording catheters. Bipolar electrograms were obtained from 11±1 sites in the 33 patients. Color-coded, 3-dimensional maps of activation and repolarization sequences were reconstructed using the CARTO system. Gradients of RT were recognizable on all maps, and the sequence of repolarization was mainly following that of activation. A significant correlation was found in all pigs between the RT and AT, but not between the MAPd and AT. The global dispersions of AT, MAPd and RT among all sites were significantly greater than those among 10, 20 or 30 randomly selected sites. The global dispersions were also significantly greater than those calculated from seven different regional areas. No significant regional differences in MAPd or RT were observed. The dispersions of AT, MAPd and RT during sinus rhythm and programmed stimulation, and the estimated dispersions of ERP during AF were significantly greater in patients with PAF than in those without clinical AF. Conclusions: Repolarization gradients exist over the right atrial endocardium in healthy pigs and the temporospatial pattern of activation is an important determinant of the repolarization sequence. MAP mapping using the CARTO system is feasible in evaluating the global repolarization in experimental and clinical settings. The number of recordings could significantly affect the measurement results of the atrial repolarization. The global repolarization could not be estimated by mapping of local areas. Regional heterogeneity of the repolarization is not significant in the in situ right atrium in pigs. Increased dispersion of atrial repolarization contributes to the genesis and/or perpetuation of AF in our patients.