Atrial reciprocal rhythm and reciprocating tachycardia in Wolff-Parkinson-White syndrome.

In an infant with type A Wolff-Parkinson-White syndrome, atrial reciprocal beats and attacks of reciprocating tachycardia were repeatedly recorded. Their dependence on a prolongation of the P-R interval could be well demonstrated during Wenckebach periods. Because of the normal aspect of the QRS complex during arrhythmia, the short ventriculo-atrial conduction time (0.08 sec), and the vectorial orientation of the secondary P wave, it was concluded that retrograde reactivation of the atria probably took place via the anomalous bundle. The versatility of the conduction through the accessory bundle is shown by the fact that its direction may change from antegrade in one beat to retrograde in the next. The importance of a circus movement in the genesis of some types of tachycardia in the WPW syndrome is discussed.