Pseudoblock and pseudoconduction across the cavotricuspid isthmus

Abstract

Ablation of typical atrial flutter is dependent on creating a line of block in the inferior vena cava-tricuspid annulus isthmus (CTI), a critical part of the macroreentrant circuit. 1 Saoudi N. Atallah G. Kirkorian G. Touboul P. Catheter ablation of the atrial myocardium in human type I atrial flutter. Circulation. 1990; 81: 762-771 Crossref PubMed Google Scholar , 2 Cosio F.G. Lopez G.M. Goicolea A. Arribas F. Barrosa J.L. Radiofrequency ablation of the inferior vena cava-tricuspid valve isthmus in common atrial flutter. Am J Cardiol. 1993; 71: 705-709 Abstract Full Text PDF PubMed Scopus (511) Google Scholar Success of the linear lesion is confirmed by the presence of bidirectional block during pacing maneuvers from the low lateral right atrium and proximal coronary sinus (CS). 3 Poty H. Saoudi N. Nair M. Radiofrequency catheter ablation of atrial flutter: Further insights into the various types of isthmus block. Application to ablation during sinus rhythm. Circulation. 1996; 94: 3204-3213 Crossref PubMed Scopus (282) Google Scholar , 4 Cauchemez B. Haissaguerre M. Fischer B. Electrophysiological effects of catheter ablation of inferior vena cava-tricuspid annulus isthmus in common atrial flutter. Circulation. 1996; 93: 284-294 Crossref PubMed Scopus (307) Google Scholar The ability to accurately assess CTI block during CS pacing is dependent on at least two critical assumptions: (1) when pacing from the CS, the impulse does not propagate across the crista terminalis, and (2) clockwise activation of the CTI during CS pacing occurs via circumferential muscle fibers surrounding the CS rather than by superior transseptal propagation across Bachmann’s bundle.