Clinical significance of the atrial fibrillation threshold in patients with paroxysmal atrial fibrillation

AF threshold and the other electrophysiological parameters were measured to quantify atrial vulnerability in patients with paroxysmal atrial fibrillat ion (PAF, n = 47), and those M without AF (non-PAF, n = 25). Stimulations w ere delivered at the right atrial appendage with a basic cycle length of 50 0 ms. The PAF group had a significantly larger percentage of maximum atrial fragmentation (%MAF, non-PAF: mean +/- SD = 149 +/- 29%, PAF: 166 +/- 26%, P = 0.009), fragmented atrial activity zone (FAZ, non-PAF: median 0 ms, in terquartile range 0-20 ms, PAF: 20 ms, 10-40 ms, P = 0.008). Atrial fibrill ation threshold (AF threshold, non-PAF: median 11 mA, interquartile range 6 -21 mA, PAF: 5 mA, 3-6; mA, P < 0.001) was smaller in the PAF group than in the non-PAF group. Sensitivity, specificity, and positive predictive value of electrophysiological parameters were as follows, respectively: %MAF (cu t off at 150%, 78%, 52%, 76%), FAZ (cut off at 20 ms, 47%, 84%, 85%), AF th reshold (cut off at 10 mA, 94%, 60%, 81 %). There were no statistically sig nificant differences between the non-PAF and PAF groups in the other parame ters (effective refractory period, interatrial conduction time, maximum con duction delay, conduction delay zone, repetitive atrial firing zone, wavele ngth index), that were not specific for PAF. In conclusion, the AF threshol d could be a useful indicator to evaluate atrial vulnerability in patients with AF.