Document Detail

The response of atrioventricular junctional tissue to temperature.
MedLine Citation:
PMID:  8022050     Owner:  NLM     Status:  MEDLINE    
To determine the optimal temperature for catheter heat mapping without damaging cardiac tissue, we studied the electrophysiologic and histologic responses of the atrioventricular (AV) conduction system exposed to a specific range of temperatures. In 18 closed-chest dogs, an electrode catheter with a thermistor, tip was positioned transvenously at the AV junction. Radiofrequency current (RFC) was applied in incremental temperature steps until transient 2nd-degree AV block was induced. Catheter tip temperature (CTT) was measured at each step. RFC was immediately discontinued when AV block occurred. AV conduction was evaluated before and 4 weeks after the procedure. Acute transient 2nd-degree AV block was induced in 45 applications, during which the average CTT was 48.7 +/- 2.7 degrees C. In another 40 applications in which 2nd degree AV block was not induced, the average CTT was significantly lower [46.3 +/- 2.5 degrees C] (p < 0.001). Eleven of 16 dogs showed acute 2nd-degree AV block, but had normal AV conduction at 4 weeks (Group A). In the other 5 dogs, 1st-degree AV block was seen at 4 weeks (Group B). The lowest CTTs in Groups A and B were 45 and 49 degrees C, respectively. Histologic findings in 2 dogs from Group A revealed that 10-15% (by area) of the AV node was fibrotic. These findings suggest that the induction of fully reversible AV block can be achieved by titration of RFC, during the application of RFC to the AV junction. In conclusion, RF energy was used to produce a tip temperature of between 45 degrees C and 49 degrees C, which induced reversible and significant interruption of conduction of in tissue in the AV junction, and presumably also in target sites in clinical RF ablation.
K Hirao; T Sato; K Otomo; N Yamamoto; H Nawara; N Doshida; F Suzuki; T Kawara; K Hiejima; M Tanaka
Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Japanese circulation journal     Volume:  58     ISSN:  0047-1828     ISO Abbreviation:  Jpn. Circ. J.     Publication Date:  1994 May 
Date Detail:
Created Date:  1994-08-03     Completed Date:  1994-08-03     Revised Date:  2003-11-14    
Medline Journal Info:
Nlm Unique ID:  7806868     Medline TA:  Jpn Circ J     Country:  JAPAN    
Other Details:
Languages:  eng     Pagination:  351-61     Citation Subset:  IM    
First Department of Internal Medicine, School of Medicine, Tokyo Medical and Dental University, Japan.
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MeSH Terms
Atrioventricular Node / physiology*,  surgery
Catheter Ablation
Heart Block / pathology,  physiopathology
Heart Catheterization
Monitoring, Physiologic*
Myocardium / pathology

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