Concealed Wolff-Parkinson-White syndrome.

Sixty-nine patients, 23 of whom had documented attacks of paroxysmal supraventricular tachycardia (PSVT), were studied electrophysiologically and the following results were obtained: (1) Antegrade concealed Wolff-Parkinson-White syndrom (AC WPW) was demonstrated in 7 out of 69 patients by atrial stimulation including extrastimulus. Six of these 7 patients presented an accessory pathway (AP) conduction of the Kent type, 5 of which showed Type A and another, Type B. The remaining one of these 7 patients showed an AP conduction of the Mahaim type. One of the 7 patients showed a combination with the James and Kent types AP conduction. (2) Retrograde concealed Wolff-Parkinson-White syndrome (RC WPW) was demonstrated in 8 out of 49 patients in whom the presence of V-A conduction was revealed by ventricular stimulation, while PSVT was documented in 7 of these 8 patients. An AP of the Kent type was identified in the left side of the heart in 5 out of 7 patients with documented PSVT, the right side in one and in the septal region in one. (3) The presence of bilateral or two APs were demonstrated in 3 patients. In another one with documented PSVT, the presence of a branched AP from a left-sided Kent bundle was assumed. In conclusion, our study demonstrated that concealed APs may be more frequent than realized. For example, the frequency of RC WPW in patients with PSVT was 30.4% (7/23) in our series. Accordingly, it is postulated that RC WPW may also be indicated for surgical therapy and that detailed electrophysiologic examination by the physician should be carried out for the sake of determining the indication.