Mode of initiation of reciprocating tachycardia during programmed ventricular stimulation in the Wolff-Parkinson-White syndrome. With reference to various patterns of ventriculoatrial conduction

The mode of initiation of reciprocating tachycardia in relation to various patterns of ventriculoatrial (V-A) conduction induced by programmed right ventricular stimulation was systematically analyzed in 29 patients with the Wolff-Parkinson-White (WPW) syndrome, type A. His bundle activity and atrial electrograms near the atrial ends of the normal and accessory pathways were simultaneously recorded. V-A conduction time was plotted as a function of premature ventricular coupling intervals. Four groups of patients were observed. In Group I, four patients with absence of V-A conduction, reciprocating tachycardia could not be elicited. In Group II, three patients with persistent retrograde atrial fusion from the normal and accessory pathways, reciprocating tachycardia could not be elicited because of a constant impulse collision at the atrial level. In Group III, seven patients with predominant or exclusive V-A conduction over the normal pathway, concealed retrograde penetration of the accessory pathway might have prevented the initiation of reciprocating tachycardia in all patients. In Group IV, 15 patients with predominant or exclusive V-A conduction over the accessory pathway, reciprocating tachycardia could be elicited only in 7, and its initiation appeared to depend upon the depth of retrograde penetration of the normal pathway; the less the depth of such penetration, the easier it was to elicit a reciprocating tachycardia. Furthermore, with the production of progressively less deep retrograde penetration of the normal pathway, development of repetitive ventricular responses at short ventricular coupling intervals and shortening of the ventricular driving cycle length favored the induction of reciprocating tachycardia in patients in this group. The study demonstrates that the initiation of reciprocating tachycardia during programmed ventricular stimulation in patients with the WPW syndrome is related to various patterns of V-A conduction.