The role of an accessory atrioventricular pathway in reciprocal tachycardia

Abstract

To study the pathway of tachycardia in patients with the Wolff-Parkinson-White (WPW) syndrome and reciprocal tachycardias, results from intracavitary recordings and atrial and ventricular stimulation were reviewed in 71 patients with the WPW syndrome and 54 patients without pre-excitation. In all patients a reproducible tachycardia could be initiated and terminated by appropriately timed electrical stimuli. The following findings were accepted as suggesting the participation of an accessory pathway in the tachycardia circuit: (1) no increase in ventriculo-atrial conduction (V-A C) time following ventricular stimuli given with increasing prematurity; (2) activation of right or left atrium (depending upon the location of the atrial end of the accessory pathway) prior to activation of atrium in the His bundle lead; (3) slowing of tachycardia following bundle branch block to the ventricle in which the accessory pathway inserts; (4) V-A C time of early stimuli on the ventricle during tachycardia equal to or less than the V-A C time following QRS complexes during tachycardia; (5) inability to initiate tachycardia or slowing of tachycardia following the administration of drugs affecting the accessory pathway. Accepted as suggestive for atrioventricular (A-V) nodal re-entry were the following factors: (1) activation of atrium following initiation of tachycardia by a single atrial premature beat after activation of the bundle of His but before or simultaneous with ventricular activation in first and subsequent beats of tachycardia; (2) initiation of tachycardia following a gradual increase in V-A C time with the appearance of a His bundle electrogram in between the premature beat and retrograde atrial activation; (3) gradual increase in V-A C time with the appearance of a His bundle electrogram following ventricular premature beats given with increasing prematurity; (4) two-to-one block distal to the A-V node or His bundle with persistence of tachycardia.