Classification of electrophysiological types of atrioventricular nodal re-entrant tachycardia: a reappraisal.

Sequence of retrograde atrial activation is not a reliable criterion for the classification of atrioventricular nodal re-entrant tachycardia (AVNRT) into typical and atypical types. The conventional concept of a lower common pathway is not supported by current evidence and does not represent a reliable or reproducible criterion. The distinction between 'fast-slow' and 'slow-slow' forms is not unanimously defined, and probably of no practical significance. We suggest that AVNRT should be classified as typical or atypical according to the His-atrial interval or, when a His bundle electrogram is not reliably recorded, the ventriculo-atrial interval measured on the His bundle recording electrode.