Dispersion of repolarization in paroxysmal atrial fibrillation

Widened dispersion of refractoriness has been considered to lead to an increase in atrial vulnerability. In this study, we obtained simultaneous monophasic action potential recordings by 2 special catheters from 2 different loci in the right atrium in 9 normal subjects (Group 1) and in 7 patients with paroxysmal atrial fibrillation (Group 2). We measured action potential duration at 50% (APD50) and 90% (APD90) repolarization from both loci in the right atrium during steady-state through one of the two catheters. The differences between APD50 and APD90 recorded by the two catheters were designated as dispersion of APD50 and dispersion of APD90, respectively. While, the mean APD50 and APD90 were 149.7+/-16.9 and 228.3+/-44.7 ms respectively in Group 1, the corresponding values for Group 2 were 145.7+/-33.5 and 213.5+/-53.1 ms. The difference between the 2 groups was not statistically significant. However, the dispersion of APD50 and APD90 were 13.8+/-13.8 and 10.0+/-9.7 ms in Group 1 and 42.8+/-19.6 and 57.1+/-32.4 in Group 2, respectively and the difference between the 2 groups for both measurements was statistically significant (P<0.01). Another finding was a high correlation between age and dispersion of APD90 in the whole population studied (r=0.82, P<0.001). With these findings, although one can not derive the conclusion that patients with paroxysmal atrial fibrillation have a greater dispersion of repolarization, our finding of increasing dispersion of repolarization with age could be an explanatory factor for the increased prevalence of atrial fibrillation with advanced age.