Relations between monophasic action potential duration and refractoriness after cardioversion of persistent atrial fibrillation: results in wash-out and amiodarone-treated patients.

BACKGROUND: The relation between repolarization and refractoriness has been clinically evaluated both in the atrium and ventricle. However, this relation has not been carefully investigated in the atria of patients with persistent atrial fibrillation after cardioversion. METHODS: We determined the refractoriness and monophasic action potential duration at 90% of repolarization (MAP90), at 5 pacing cycle lengths (300 to 700 ms) and in 5 right atrial sites after internal cardioversion of persistent atrial fibrillation in 27 patients. RESULTS: The effective refractory periods (ERPs) were longer in amiodarone-treated patients (group 1) than in wash-out patients (group 2) (211.3 +/- 26.4 vs 199.1 +/- 24.3 ms, p < 0.002) as well as the MAP90 (243.6 +/- 36.8 vs 223.1 +/- 29.2 ms, p < 0.001). Linear regression analysis showed a direct relation between the MAP90 and ERP changes induced by different pacing cycle lengths (r = 0.77 and r = 0.92 in the amiodarone and wash-out patients, respectively). The ERP/MAP90 ratio was similar at all pacing cycle lengths in both wash-out and amiodarone groups and was always < 1. The mean ERP and MAP90 were shorter in the lateral right atrial sites than in the atrial roof and septum in both group 1 and group 2 patients (p < 0.001). CONCLUSIONS: A linear correlation was found between ERP and MAP90 in response to changes in pacing cycle lengths. Postrepolarization refractoriness was not observed after cardioversion of persistent atrial fibrillation. Pretreatment with oral amiodarone does not affect these electrophysiological features or the dispersion of ERP and MAP90 in the right atrium after sinus rhythm restoration.