[Type A Wolff-Parkinson-White syndrome associated with left bundle-branch block. Electrocardiographic, vectorcardiographic, and endocavitary electrophysiological study].

The rate association of a "type A" W.P.W. syndrome with a left bundle branch block gives a characteristic electrocardiographic picture:--the left bundle branch block is partially masked, the delay in the basial region of the left ventricle being in part cancelled by pre-excitation--the features of the W.P.W. syndrome are also modified, since the ventricular axis is corrected by the left bundle branch block. The electrocardiographic tracings taken during the various tachycardias and during treatment for arrhythmia, together with the intra-cavitary recordings allow a precise diagnosis to be made. In this case, vectocardiography was particularly useful as it gave a clear demonstration of the median delay of the ventricular loop, the only pathognomic feature of left bundle branch block, during a period when the left bundle of Kent was functioning.