Electrocardiographic diagnosis of dual AV nodal pathways complicating the Wolff-Parkinson-White syndrome.

he diagnosis of dual AV nodal pathways compliTcating concealed or manifest preexcitation, is usually made at the time of electrophysiologic study in pa tien ts with recurrent paroxysmal supraventriculax tachycardia. In these patients, electrophysiologic studies demonstrate discontinuous antegrade AV nodal conduction curves (dual AV nodal pathways, fast and slow), as well as a unior bidirectionally conducting anomalous pathway. In some of these patients, one or more tachycardias are induced.14 The tachycardias induced can include a fast AV reentrant tachycardia (antegrade fast pathway and retrograde anomalous pathway), a slow AV reentrant tachycardia (antegrade slow and retrograde anomalous pathway ) , and sometimes the usual variety of AV nodal reentrant paroxysmal tachycardia ( antegrade slow pathway and retrograde fast pathway).' In these cases, one then has to retrospectively examine electrocardiograms in an attempt to correlate induced and clinical tachycardias. In the present study, we report a patient with known Wolff -Parkinson-White syndrome, in whom dual pathways were diagnosed from electrocardiographic findings prior to electmphysiologic study. In this patient, the presence of dual pathways was clinically relevant, in that the patient suffered from two different spontaneous paroxysmal tachycardias.