Clinical and electrophysiologic observations in patients with concealed accessory atrioventricular bypass tracts

Abstract

In 12 of 46 consecutive patients with paroxysmal supraventricular tachycardia or atrial flutter-fibrillation, without electrocardiographic evidence of ventricular preexcitation, electrophysiologic studies suggested the presence of accessory atrioventricular (A-V) pathways capable only of retrograde conduction (concealed Wolff-Parkinson-White syndrome). The ages of these patients ranged from 29 days to 71 years (mean 39.2 years). Most patients were clinically symptomatic with palpitations, dizziness, weakness or congestive heart failure. One patient had “cardiac dysrhythmia” described by an obstetrician during intrauterine life. Eleven patients manifested A-V reciprocating tachycardia involving the normal pathway for anterograde conduction and the accessory pathway for retrograde conduction. The remaining patient manifested recurrent paroxysms of atrial flutter-fibrillation as a result of rapid ventriculoatrial activation through the accessory pathway during the atrial vulnerable phase. The electrophysiologic observations were analyzed with regard to clinical and electrocardiographic characteristics in these patients. The presence of concealed accessory pathways should be suspected in patients presenting with (1) an “incessant” form of tachycardia, (2) spontaneous onset of A-V reciprocal rhythms or reciprocating tachycardias after acceleration of the sinus rate without antecedent atrial extrasystoles or P-R interval prolongation, (3) slowing of the tachycardia rate consequent to the development of functional bundle branch block, (4) retrograde P waves (negative in leads II, III and aVF) discernible after the QRS complexes, with the R-P interval being shorter than the P-R interval during both A-V reciprocal rhythm and reciprocating tachycardia, and (5) oc-currence of atrial flutter-fibrillation in association with A-V reciprocal rhythms. It is suggested that medical treatment in patients having concealed accessory pathways should be aimed at increasing the refractoriness of either the A-V node or the accessory pathway for reciprocating tachycardia, while increasing the refractoriness of the atrium and the accessory pathway in cases with atrial flutter-fibrillation. Pacemaker therapy and surgical intervention may be indicated in selected patients refractory to antiarrhythmic agents.