[Effects of oral sotalol on the conduction of accessory atrioventricular pathways]

The effects of oral Sotalol were assessed by electrophysiological investigations in 6 patients with ventricular preexcitation (Wolff-Parkinson-White syndrome) and a short anterograde refractory period (less than or equal to 280 ms) of the accessory pathway. After 27 to 80 days (mean 41 +/- 19 days) of oral Sotalol (160 mg daily in 5 patients, 320 mg daily in 1 patient). The effective anterograde refractory period of the accessory pathway increased from 268 +/- 13 ms to 318 +/- 33 ms (less than 0.05); the shortest QR interval with appearances of preexcitation increased either during rapid atrial pacing (272 +/- 19 ms to 374 +/- 74 ms: p less than 0.05) or during induced atrial fibrillation (258 +/- 61 to 335 +/- 56 ms: p less than 0.01). The effective refractory period could only be measured in 4 cases during Sotalol therapy and increased by 10 ms, 130 ms and by at least 220 and 300 ms. During the repeat electrophysiological investigation the plasma concentrations of Sotalol ranged from 0.33 to 2.3 g/ml. These results show that oral Sotalol significantly increases the effective refractory periods of accessory pathways even when they are short under basal conditions. This product could therefore be effective in preventing the rapid ventricular response to atrial fibrillation in patients with the WPW syndrome and also in the prevention of reciprocating tachycardias.