Author + information
- Received April 6, 2018
- Revision received May 11, 2018
- Accepted May 17, 2018
- Published online August 20, 2018.
- Charlene Pius, MBChB∗ (, )
- Maille Baptiste, MBBS,
- Dhiraj Gupta, MD, DM and
- Simon Modi, MBBS
- ↵∗Address for correspondence:
Dr. Charlene Pius, Department of Cardiology, Liverpool Heart & Chest Hospital, Thomas Drive, Liverpool, Merseyside L14 3PE, United Kingdom.
Radiofrequency ablation of the cavotricuspid isthmus (CTI) is recognized as a highly successful technique in the treatment of typical atrial flutter. Transmural CTI ablation with the achievement of bidirectional conduction block is a recognized marker for success. The “muscle bundle hypotheses” postulates that the conduction in atrial flutter occurs over discrete muscle bundles rather than over a uniform sheet of CTI and that these muscle bundles have varied courses (1,2).
The use of maximum voltage–gated ablation involving a single ablation site with the largest atrial electrogram along the CTI demonstrated success in achieving bidirectional block supporting the muscle bundle hypothesis (3). These high-voltage areas may indicate sites of superficial or endocardial passage of the muscle bundles.
The use of 3-dimensional mapping software such as Rhythmia mapping (Boston Scientific, Marlborough, Massachusetts) has provided evidence of epicardial-endocardial breakthrough in stable atrial macro–re-entry (4).
Our Rhythmia map (caudal, left anterior oblique view) was taken during a redo-ablation of counterclockwise tricuspid isthmus–dependent atrial flutter that had been confirmed with favorable post-pacing intervals during entrainment around the tricuspid annulus. The 40-ms wave front (the burgundy area in Figure 1, Online Video 1) in flutter is seen to propagate around the tricuspid annulus in a counterclockwise direction and halts superficially at the previously ablated CTI. The wave front then reappears, again superficially and medial to the CTI line with both continued counterclockwise propagation around the tricuspid annulus as well as clockwise propagation for a short distance back to the CTI line. This activation pattern demonstrates the superficial breakout point of a deep CTI muscle bundle, remote from the previous CTI ablation. Ablation at this site cleanly terminated atrial flutter. The voltage map (with schematic) highlights a possible course of the deep muscle bundle. The alternative hypothesis of a focal or micro–re-entrant atrial tachycardia medial to a blocked triscupid isthmus is refuted due to favorable tricuspid annular entrainment.
Dr. Gupta has received a research grant from Biosense Webster. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
All authors attest they are in compliance with human studies committees and animal welfare regulations of the authors’ institutions and Food and Drug Administration guidelines, including patient consent where appropriate. For more information, visit the JACC: Clinical Electrophysiology author instructions page.
- Received April 6, 2018.
- Revision received May 11, 2018.
- Accepted May 17, 2018.
- 2018 American College of Cardiology Foundation
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