New concepts relating to the preexcitation syndrome

Since its original description in 1930, considerable controversy has centered on the basic explanation for the anomalous atrioventricular (AV) conduction seen in the preexcitation or Wolff-Parkinson-White (WPW) syndrome.¹An abnormally short PR interval associated with a prolonged QRS containing a delta wave (an initial slurring or thickening of the first wave of the QRS complex, be this an R or an S) in the presence of sinus rhythm is the classic criteria for its electrocardiographic diagnosis.²The delta wave represents the early excitation of the ventricles. However, in addition to this form of anomalous AV conduction, several variants have come to be recognized.³⁻⁵These include a short PR interval (less than 0.12 seconds) with a normal QRS, ie, a QRS with normal duration and no delta wave and a normal or even prolonged PR interval coupled to a prolonged QRS containing a delta wave. Recent and very