[Prevalence and electrocardiographic forms of the Wolff-Parkinson-White syndrome].

In a routine electrocardiographic study of 133929 subjects aged from 20 to 73, 136 cases of the Wolff-Parkinson-White syndrome were detected, 6 with intermittent pre-excitation. In this study, the prevelance of WPW was about 1 in a 1000, the highest incidence being in the 20-40 year age group with an equal sex ratio. The ECG analysis of the 136 cases consisted in determining the orientation of the delta wave in the precordial leads to establish the right or left ventricular origin of the pre-excitation, calculating the direction of the delta wave vector in the frontal plane to find out the anterior, lateral or posterior origin of the pre-excitation and analyse the position of the QRS axis to assess the appearances of the latest ventricular activity. The 136 ECGs were then classified according to electrophysiological criteria and the results of mapping: 1. Left ventricular pre-excitation; 74 cases characterised by a dominant delta wave in the right precordial leads. These cases were subdivided into: - 30 cases with posterior paraseptal pre-excitation, axis of the delta wave deviated superiorly and to the left, between -30 degrees and -60 degrees; - 20 cases of lateral pre-excitation with the vector of the delta wave deviated inferiorly and to the right between +100 degrees and +120 degrees; - 24 cases of anterior paraseptal pre-excitation with high amplitude delta and QRS deflections in all precordial leads and a delta wave axis between +50 degrees and +80 degrees. 2. Right ventricular pre-excitation; 62 cases characterised by a negative or isoelectric delta wave in the right precordial leads, including: - 14 posterior paraseptal pre-excitation with significant delta wave axis deviation between -30 degrees and -60 degrees; - 33 lateral pre-excitation with the delta and QRS axis pointing directly to the left at about 0 degrees; - 15 cases of anterior paraseptal pre-excitation with the delta wave axis between +50 degrees and +80 degrees. The cases with terminal forces of left ventricular activation in the same direction as the delta wave, superiorly and to the left at -60 degrees or inferiorly and to the right at +120 degrees, forming a single deflection of over 0,12 seconds' duration, are the result of delayed activation of the anterior or posterior fascicle of the left bundle after a long delay. On the other hand, the cases in which the direction of the pre-excitation is the same but the final part of ventricular activation moves away from the delta are probably the result of tension between the activation of the normal and accessory pathways.