Document Detail

Electrophysiology of the right anterior approach to the atrioventricular node: studies in vivo and in the isolated perfused dog heart.
MedLine Citation:
PMID:  9116968     Owner:  NLM     Status:  MEDLINE    
INTRODUCTION: Previous reports have described electrophysiologic properties and rate-dependent responses in the transitional cell zone of the posterior AV nodal input (slow pathway). The purpose of this study was to investigate the electrophysiology of the anterior transitional cell zone (fast pathway) in vivo and in a Langendorff preparation perfused with a nonblood solution containing butanedionemonoxime to inhibit contraction. METHODS AND RESULTS: In five anesthetized dogs, the His-bundle electrogram recorded from the aortic root included atrial activity in close proximity to the anterior limbus of the fossa ovalis. During decremental atrial pacing, the atrial potential exhibited amplitude alternans at a pacing cycle length (CL) of 135 +/- 14 msec. In ten isolated perfused canine hearts, a bipolar electrode catheter was positioned with its tip against the right anterior interatrial septum just superior to the tendon of Todaro. The AV Wenckebach CL (WCL) averaged 262 +/- 21 msec. During further decreases in pacing CL, the bipolar atrial potential developed a 2:1 amplitude alternans (9/10 dogs) at CL = 168 +/- 15 msec and then split into two components with subsequent 2:1 block between these components (10/10 dogs) at CL = 152 +/- 19 msec. Radiofrequency ablation at this site in six dogs prolonged the stimulus to HB interval from 113 +/- 19 to 151 +/- 30 msec (P < 0.01) without changing the WCL, consistent with ablation of the fast AV nodal pathway. In six other isolated perfused canine hearts, an octapolar catheter (2-mm spacing) was positioned along the anterior limbus of the fossa ovalis with the tip electrode located over the anterior portion (apex) of the triangle of Koch. The aforementioned 2:1 amplitude alternans occurred at a longer CL in the distal electrodes located at the tendon of Todaro than in the proximal electrodes at farther distances from the tendon of Todaro (185 +/- 25 vs 171 +/- 20 msec, P < 0.05), as did the 2:1 block between the two components (161 +/- 18 vs 150 +/- 18 msec, P < 0.05). Microelectrode recordings obtained adjacent to the catheter demonstrated 2:1 alternans and block patterns in the action potentials of transitional cells but not in atrial cells, which exhibited 1:1 conduction at all CL. CONCLUSIONS: The transitional cell zone in the anterior interatrial septum exhibits a specific rate-dependent, spatial gradient of conduction block, which can be recorded in bipolar electrograms as well as microelectrode recordings. Electrophysiologic changes induced by radiofrequency ablation of this anterior atrial/transitional cell zone (corroborated by histology) provide strong presumptive evidence that this area constitutes all or a major part of the fast AV nodal pathway.
M Antz; B J Scherlag; E Patterson; K Otomo; C Tondo; J Pitha; M D Gonzalez; W M Jackman; R Lazzara
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of cardiovascular electrophysiology     Volume:  8     ISSN:  1045-3873     ISO Abbreviation:  J. Cardiovasc. Electrophysiol.     Publication Date:  1997 Jan 
Date Detail:
Created Date:  1997-04-22     Completed Date:  1997-04-22     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9010756     Medline TA:  J Cardiovasc Electrophysiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  47-61     Citation Subset:  IM    
Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, USA.
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MeSH Terms
Atrioventricular Node / physiology*
Heart Conduction System / physiology*

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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