Electrophysiological diagnosis of participation of accessory pathway in patients with paroxysmal supraventricular tachycardia.

Electrophysiological studies were performed on 34 patients whose reentrant circuit of paroxysmal supraventricular tachycardia (PSVT) involved normal atrioventricular (AV) conduction system as the antegrade limb and either overt (25 patients) or concealed (9 patients) accessory AV pathway as the retrograde limb. The diagnosis of this mechanism was made by one or more of the following: 1) eccentric retrograde atrial activation sequence; 2) effect of bundle branch block on ventriculoatrial (VA) conduction time; 3) paradoxically premature atrial capture; 4) atrial capture by premature ventricular stimulation of VA conduction time with retrograde during PSVT; 5) no significant prolongation of VA conduction time with retrograde atrial activation sequence to that of PSVT during incremental and premature ventricular stimulation; 6) shortening of cycle length with constant H-V and V-A intervals after atropine administration. The participation of accessory pathway in PSVT circuit should be decided by as many of the above-mentioned findings or procedures as possible for optimal therapy. Electrophysiological studies have led to the recognition that accessory pathway, functionally silent during antegrade conduction, is responsible for some patients with PSVT. If the mechanisms of PSVT were more carefully analyzed, the recognition of PSVT cases involving accessory pathway would increase.