ORIGIN OF JUNCTIONAL RHYTHM DURING RADIOFREQUENCY ABLATION OF ATRIOVENTRICULAR NODAL REENTRANT TACHYCARDIA IN PATIENTS WITHOUT STRUCTURAL HEART-DISEASE

Junctional rhythm is commonly observed during radiofrequency catheter ablation of the fast or slow pathways of atrioventricular nodal reentr ant tachycardia (AVNRT). However, the origin of these beats remains un clear. We analyzed the retrograde atrial activation sequence of 16 pat ients (mean +/- SD: 41.2 +/- 18.9 years old) undergoing catheter ablat ion for typical AVNRT with detailed catheter mapping of the triangle o f Koch. The earliest atrial activations were concordant during tachyca rdia and junctional rhythm in only 5 of 16 patients. The findings sugg est that junctional rhythm is unlikely to represent direct stimulation of the atrioventricular (AV) node via a discrete slow pathway but rat her results from enhanced automaticity from greater than or equal to 1 sites in the AV nodal transitional zone. The ensuing atrial activatio n pattern results from anisotropic spread from these sites. In additio n, these data imply that the original concept of the AV node comprisin g 2 anatomically defined pathways may not be valid, and that a functio nally defined pathway model may be a more accurate representation. (C) 1997 by Excerpta Medica, Inc.