Effect of adenosine triphosphate on the accessory pathways.

To determine the site of the anterograde and retrograde conduction in the Wolff-Parkinson-White syndrome (WPW), 40 mg of adenosine triphosphate (ATP) was injected during electrophysiological studies in 53 patients with ventricular preexcitation. In 40 cases, the accessory pathway was evident (group 1) and in 13 cases it was concealed (group 2). In 10 cases in group 1, anterograde conduction was abolished with disappearance of the features of preexcitation. In 7 patients of group 1 and in 4 patients of group 2, retrograde conduction in the accessory pathway was prolonged or abolished. These effects were unexpected because ATP is a parasympathomimetic drug. There was a correlation between the Kent effective refractory period (ERP) and the action of ATP. When the drug did not change the anterograde and retrograde conduction in the Kent bundle, the anterograde accessory pathway ERP was always less than 230 ms. When ATP only decreased retrograde conduction in the Kent bundle, anterograde accessory pathway ERP was always more than 280 ms.