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The electrocardiographic characteristics of spontaneous escape rhythm during complete heart block induced by transcatheter ablation of the atrioventricular junction was prospectively studied in 21 patients by periodically interrupting temporary pacing. The data derived from 13 of these 21 patients, in whom conduction recurred after the procedure, were analyzed. An escape rhythm was present In 12 patients 8.2 ± 5.8 minutes after shock delivery at a cycle length of 1985 ± 974 ms. The escape QRS had a configuration of right bundle branch block with left axis deviation in 9 patients, of right bundle branch block with normal axis in 1, of left bundle branch block with left axis deviation in 1, and 2 distinct morphologies in the remaining patient. After resumption of conduction, the conducted complexes were identical to the escape complexes in six patients, different only in axis in four patients, and different in morphology in two patients. This suggests that in the majority of patients the escape rhythm seen during transient heart block, induced by transcatheter ablation of the atrioventricular junction, presents a right bundle branch morphology with or without a left axis deviation, and most likely originates from an area above, or close to, the site of the anatomical damage. [ABSTRACT FROM AUTHOR]

We report on two patients out of a series of 22 who underwent transcatheter ablation of the atrioventricular (AV) junction. The procedure failed to induce permanent complete heart block in 15 patients, 12 of whom were in sinus rhythm with 1:1 AV conduction before hospital discharge. Of the 12 patients, two (16.6%) were found to be in high degree heart block, one month later. We discuss the mechanism of late occurrence of high degree heart block and we emphasize the need for systematic implantation of permanent ventricular or dual chamber pacemakers, despite failure transcatheter ablation of the AV junction. [ABSTRACT FROM AUTHOR]

Although pacing-induced ventriculo-atrial (VA) Wenckebach conduction has been previously described, the occurrence of this phenomenon during ventricular tachycardia has received little attention. The latter is defined as 2:2 VA block in which the conducted beats show progressive lengthening of VA conduction until the sequence is terminated by two or three blocked ventricular beats. This phenomenon was observed in a 16-year-old boy who underwent electrophysiologic study for ventricular tachycardia as a late complication of surgical correction of tetralogy of Fallot. During pacing-induced ventricular tachycardia with a morphology similar to that of the spontaneous tachycardia, 8:4 alternating VA block was observed. This sequence suggested that the AV node was the site of block, the 2:2 block being located at the upper level, and the VA Wenckebach block at the lower level. Alternate VA Wenckeboch conduction appears as a possible cause of variation in atrial depolarization intervals during ventricular tachycardias with short cycle lengths. [ABSTRACT FROM AUTHOR]