Radiofrequency catheter ablation of septal accessory pathways within the triangle of Koch: Importance of energy titration testing other than the local electrogram characteristics for identifying the successful target site

Jiunn Lee Lin, Shoei K.Stephen Huang, Ling Ping Lai, Ting Fu Cheng, Yung Zu Tseng, Wen Pin Lien

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Radiofrequency (RF) catheter ablation of accessory atrioventricular (AV) connections in the proximity of His bundle or AV node is at high risk of developing complete heart block. A safe and effective protocol has not been well established. Nineteen consecutive patients with 19 septal accessory pathways within the triangle of Koch underwent a protocol with power-titrated RF energy testing to identify the target site for successful catheter ablation. At every potential target site preselected by local electrogram characteristics, RF energy was started at 5 W for 10 seconds, with an increment of 5 W (duration remained at 10 s) until maximally 30 W or the observation of transient interruption of accessory pathway conduction. By this stepwise RF energy testing, we successfully localized and ablated 18 (94.7%) of the 19 septal accessory pathways, 10 close to His bundle (zone I) and 8 away from it (zone II). The test-effective RF power was 20 W or less in 9 of all 11 septal accessory pathways in zone I, and 5 of the 8 in zone II (P = 0.68). Meanwhile, the final RF power for successful ablation was 30 W or less in 9 of the 10 zone 1 and 6 of the 8 zone II septal accessory pathways (P = 0.83). One patient with an accessory pathway in zone I was complicated with complete AV block after final ablation at 30 W. None of the local electrogram characteristics except continuous electrical activity during retrograde mapping was helpful in the prediction of ablation outcome. Careful RF energy titration testing could effectively help identify the target site for successful RF catheter ablation of septal accessory pathways within the triangle of Koch. The dependence on local electrogram manifestations could be frustrated by a low probability of success.

Original languageEnglish
Pages (from-to)1909-1917
Number of pages9
JournalPACE - Pacing and Clinical Electrophysiology
Issue number10
Publication statusPublished - Oct 15 1998
Externally publishedYes



  • Complete heart block
  • Radiofrequency catheter ablation
  • Septal accessory pathway
  • Triangle of Koch

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine

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