Intravenous sotalol decreases transthoracic cardioversion energy requirement for chronic atrial fibrillation in humans: Assessment of the electrophysiological effects by biatrial basket electrodes

OBJECTIVES This study was undertaken to assess the effects of sotalol on th e transthoracic cardioversion energy requirement for chronic atrial fibrill ation (AF) and on the atrial electrograms during AF recorded by two basket electrodes. BACKGROUND The effects of sotalol infusion on transthoracic electrical card ioversion for chronic atrial fibrillation in humans have not been well inve stigated. METHODS We included 18 patients with persistent AF for more than three mont hs. Atrial electrograms were recorded by two basket electrodes positioned i n each atrium respectively Transthoracic cardioversion was performed before and after sotalol 1.5 mg/kg IV infusion. RESULTS In the 14 patients whose AF could be terminated by cardioversion be fore sotalol infusion, the atrial defibrillation energy was significantly r educed after sotalol infusion (236 +/- 74 jules UI vs. 186 +/- 77 J; p < 0. 01). Atrial fibrillation was refractory to cardioversion in four patients a t baseline and was converted to sinus rhythm by cardioversion after sotalol . infusion in two of them. We further divided the patients into two groups. Group A consisted of 10 patients in whom the energy requirement was decrea sed by sotalol while group B consisted of eight patients in whom the energy requirement was not decreased. The mean A-A (atrial local electrogram) int ervals during AF were significantly increased after sotatol infusion in bot h groups, but the increment of A-A interval was significantly larger in gro up A than it was in group B patients (36 +/- 13 ms vs. 22 +/- 8 ms for the right atrium; 19 +/- 7 ms vs. 9 +/- 7 ms for the left atrium; both p < 0.05 ). The spatial and temporal dispersions of A-A intervals were not significa ntly changed after sotalol infusion in both atria in both groups. CONCLUSIONS Sotalol decreases the atrial defibrillation energy requirement by increasing atrial refractoriness but not by decreasing the dispersion of refractoriness. (C) 2000 by the American College of Cardiology.