Value of the ajmaline-procainamide test to predict the effect of long-term oral amiodarone on the anterograde effective refractory period of the accessory pathway in the Wolff-Parkinson-White Syndrome

In patients with the Wolff-Parkinson-White syndrome, intravenous ajmaline (50 mg administered over 3 minutes) or procainamide (10 mg/kg body weight administered over 10 minutes) is helpful in defining the duration of the anterograde effective refractory period of the accessory pathway. In this study the value of the ajmaline-procainamide test to predict the effects on the anterograde effective refractory period of the accessory pathway of long-term oral amiodarone were assessed. Thirty-six patients with the Wolff-Parkinson-White syndrome were studied. Twenty-four (Group A) had a negative result of the ajmaline-procainamide test and a mean duration of the anterograde effective refractory period of the accessory pathway of 237 ± 24 ms. Twelve (Group B) had a positive result in the ajmaline-procainamide test (disappearance of preexcitation during sinus rhythm after administration of ajmaline and procainamide) and a duration of the anterograde effective refractory period of the accessory pathway of 284 ± 25 ms (p < 0.05 versus values in Group A). Amiodarone prolonged the anterograde effective refractory period of the accessory pathway by 53 ± 35 ms in patients in Group A to 290 ± 37 ms (p < 0.001) and by 100 ± 85 ms in patients in Group B to 384 ± 94 ms (p < 0.001). The difference in mean increase between both groups was not significant. In most patients (83%) in Group A amiodarone prolonged the anterograde effective refractory period of the accessory pathway to 260 to 330 ms. However, in most patients (83%) in Group B, amiodarone prolonged the anterograde effective refractory period of the accessory pathway to ≥ 330 ms (p < 0.01). Thus, an ajmaline-procainamide test is of value in predicting the results of oral amiodarone on the anterograde effective refractory period of the accessory pathway.