Comparison of the ventricular response during atrial fibrillation in patients with enhanced atrioventricular node conduction and Wolff-Parkinson-White syndrome

Although ventricular fibrillation is a well known sequel to atrial fibrillation in the Wolff-Parkinson-White syndrome, ventricular fibrillation is not generally associated with supraventricular tachycardia in the presence of enhanced atrioventricular (AV) node conduction without pre-excitation. It was hypothesized that the ventricular response during atrial fibrillation may be less in patients with enhanced AV node conduction than in their counterparts with Wolff-Parkinson-White syndrome matched for anterograde effective refractory period. Slower ventricular rates during atrial fibrillation would suggest an increased propensity for concealed conduction in the enhanced AV node conduction group than in the group with an accessory pathway.Three groups of patients aged 16 to 65 years underwent electrophysiologic testing for supraventricular tachycardia or after surgical correction of Wolff-Parkinson-White syndrome. Sixteen patients had enhanced AV node conduction, 16 had Wolff-Parkinson-White syndrome and 16 had normal AV node conduction. Patients with enhanced AV node conduction and Wolff-Parkinson-White syndrome were well matched for anterograde effective refractory period (245 ± 22 versus 258 ± 25 ms) and minimal cycle length, maintaining 1:1 anterograde conduction (261 ± 21 versus 260 ± 40). There was no difference in intervals during atrial fibrillation (average RR interval = 372 ± 37 versus 346 ± 66) or shortest RR interval (266 ± 27 versus 243 ± 51).Thus, patients with Wolff-Parkinson-White syndrome and those with enhanced AV node conduction matched for anterograde refractory period exhibit similar ventricular rates during atrial fibrillation. Because concealed conduction is an important determinant of the ventricular response during atrial fibrillation, the latter suggests that our patients with enhanced AV node conduction did not exhibit a greater propensity for concealed conduction than did patients with an accessory AV pathway matched for refractoriness