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Activation patterns in the left atrium during counterclockwise and clockwise atrial flutter
G Ndrepepa1, B Zrenner, S Weyerbrock
1Deutsches Herzzentrum München, Klinikum rechts der Isar, Technische Universität München, Munich, Germany.
Insights
This study reveals that the left atrium (LA) in patients with atrial flutter (AFL) is activated by two distinct wavefronts originating from the interatrial septum. These activation patterns differ based on whether the atrial flutter is counterclockwise or clockwise.
Area of Science:
- Electrophysiology
- Cardiac Anatomy
- Arrhythmology
Background:
- Left atrial (LA) activation patterns in patients with isthmus-dependent right atrial flutter (AFL) remain understudied.
- Understanding these patterns is crucial for effective ablation strategies.
Purpose of the Study:
- To analyze and compare left atrial activation patterns in patients experiencing counterclockwise and clockwise AFL.
- To elucidate the origin and propagation of electrical wavefronts within the LA during AFL.
Main Methods:
- Utilized a 64-electrode basket catheter for detailed LA mapping in 12 patients with AFL and atrial fibrillation undergoing ablation.
- Mapping was performed via transseptal approach or an open foramen ovale.
- Analyzed activation times and identified earliest electrical breakthroughs.
Main Results:
- In counterclockwise AFL (10 episodes), two distinct breakthroughs from the interatrial septum initiated LA activation, with two wavefronts propagating to anterior and posterior walls.
- In clockwise AFL (5 episodes), breakthroughs occurred in high anteroseptal and low posteroseptal regions, with a dominant superior wavefront from the anterolateral region.
- Mean LA activation times were comparable between counterclockwise (133+/-28 msec) and clockwise (130+/-13 msec) AFL.
Conclusions:
- The left atrium in AFL patients is activated by two wavefronts originating from high anterior and low posterior interatrial septum regions.
- The sequence of interatrial activation and LA conduction properties dictate the observed activation patterns.
- Findings provide insights into the mechanisms underlying AFL and potential targets for catheter ablation.
Introduction:
Activation of the left atrium (LA) in patients with isthmus-dependent right atrial flutter (AFL) has not yet been studied. The aim of this study was to analyze the activation patterns in the LA in patients with counterclockwise and clockwise AFL.
Methods And Results:
The study population consisted of 12 patients (10 men and 2 women; mean age 61+/-13 years) with documented AFL and atrial fibrillation referred for ablation. The LA was mapped with a 64-electrode basket catheter inserted through a transseptal approach (10 patients) or an open foramen ovale (2 patients). In patients with counterclockwise AFL (10 episodes), the LA was activated for a mean of 133+/-28 msec. Two endocardial breakthroughs of earliest activity on the left side of the interatrial septum, separated in time by an interval of 38+/-15 msec, were observed in 9 episodes (90%). Two wavefronts originated from these breakthroughs, which activated the posterior and the anterior LA walls, respectively. In one patient, the entire LA was activated from the inferior breakthrough. In patients with clockwise AFL (five episodes), the LA activation time was 130+/-13 msec. During ongoing episodes, two early electrical breakthroughs, separated in time by an interval of 41+/-15 msec, appeared in the high anteroseptal and low posteroseptal LA regions. The superior wavefront that emerged from the high anterolateral LA region was the dominant activation pathway in 4 (80%) of 5 episodes.
Conclusion:
In patients with AFL, the LA is activated by two wavefronts originating from the high anterior and the low posterior regions of the interatrial septum. The sequence of activation of these interatrial connections in counterclockwise or clockwise AFL and the conductive properties of the LA conduction pathways determine the activation patterns in the LA.