RADIOFREQUENCY ABLATION THERAPY IN CONCEALED LEFT FREE-WALL ACCESSORYPATHWAY WITH DECREMENTAL CONDUCTION

An electrophysiologic study followed by transcatheter radiofrequency a blation therapy was performed in two adult patients with a permanent f orm of junctional tachycardia. Both patients had no structural heart d isease and exhibited a normal resting EGG. The P wave during tachycard ia was negative in leads 1, 3, and aVF, biphasic over V-6, and positiv e in V-1 and aVL in both patients, while the P-R/R-P interval ratio du ring tachycardia was 0.82 and 0.36, respectively, in both patients. Bo th patients displayed an eccentric atrial activation sequence with the earliest atrial activation occurring at the distal coronary sinus and a decremental retrograde conduction property during incremental ventr icular pacing, suggesting the presence of a concealed slowly conductin g left free wall accessory pathway. The tachycardia used the normal at rioventricular pathway for anterograde conduction and the concealed sl ow left accessory pathway for retrograde conduction. It was terminated following adenosine administration in both patients; termination of t achycardia was due to a block in the retrograde accessory pathway in o ne patient and due to a block in the atrioventricular node in the othe r patient. Radiofrequency ablation was performed by the retrograde tra nsaortic approach. The radiofrequency current was delivered to the sit e of the earliest atrial activation during tachycardia at the ventricu lar aspect of the mitral annulus. The successful ablation site had a v entriculoatrial (VA) interval of 120 and 130 ms, respectively, and was located at the posterolateral and lateral aspects of the mitral annul us. Following ablation, there was no VA conduction; however, conductio n through the normal atrioventricular pathway was noted during isoprot erenol infusion in both patients. There was no induction of tachycardi a. This study demonstrates that the permanent form of junctional tachy cardia in adults can incorporate a concealed left free wall accessory pathway with a decremental property. Radiofrequency ablation therapy i s effective and safe in this form of arrhythmia.