The role of the right and left ventricles in the ventricular pre-excitation (WPW) syndrome: An experimental study in man

In three patients with Wolff-Parkinson-White syndrome, right bundle branch block was induced during right cardiac catheterization. Electrocardiograms and vectorcardiograms were obtained before and after the production of right bundle branch block. In cases with WPW type A it was possible to obtain simultaneous features of pre-excitation syndrome and an advanced degree of right bundle branch block in the electrocardiogram and vectorcardiogram. This suggests that the muscular segment prematurely activated is located in the left ventricle and that the right bundle branch block delays the right ventricular activation. Right bundle branch block did not modify the end of the ventricular activation in the case with WPW type B. It is postulated that in this type of WPW syndrome the pre-excitation takes place in the right ventricle, and therefore depolarization of this ventricle is mainly dependent on the pre-excitation phenomenon. The different topographic situations of the pre-excitation area, as has been shown by the experimental production of right bundle branch block, are in agreement with the characteristic features of the two varieties of WPW syndrome.