Functional Substrate of Macroreentrant Tachycardia　― Similarity of the Atypical Atrial Flutter and Ventricular Tachycardia ―

An 82-year-old woman was referred for catheter ablation of atrial fibrillation and atypical atrial flutter (AFL). After completing pulmonary vein isolation, a substrate map was created using the Octaray catheter and CARTO 3 system (Biosense Webster, Irvine, CA, USA). A scar and low voltage area (LVA) were identified on the left atrial (LA) anterior wall. By setting the cycle length as the LA activation time (176 ms), the Coherent activation map displayed a slow or no conducting (SNO) zone between the right superior pulmonary vein and the center of the anterior LVAs. The Coherent vector revealed a rotational activation pattern (RAP) at the edge of the SNO zone (Figure A; Supplementary Movie). Right atrial extra stimuli (500/280 ms) induced counterclockwise mitral valve isthmus-dependent AFL, which might coexist with a localized AFL around the LA anterior wall. Interestingly, the reversal wavefront was observed in the SNO zone during sinus rhythm, suggesting the area had an anisotropic nature (Figure B; Supplementary Movie). A radiofrequency energy application at the RAP site successfully terminated the AFL.

Figure.

Coherent activation maps during (A) sinus rhythm, and (B) atypical atrial flutter (AFL). PPI, postpacing interval; RAP, rotational activation pattern; SNO, slow or no conducting; TCL, tachycardia cycle length.

The development of macro-re-entrant tachycardia necessitates multiple pathways, unidirectional block, and conduction slowing. The significant conduction slowing creates a line of block and RAP that correlates with the critical isthmus sites of ventricular tachycardia.^1,2 This might also be true in atypical AFL. In the present case, right atrial extra-stimuli might produce a functional block on the LA anterior wall. A subsequent counterclockwise wavefront around the mitral annulus might create a sufficient excitable gap to initiate and sustain the AFL.

Disclosures

None declared.

Supplementary Files

Supplementary Movie. Dynamic images of Coherent activation maps.

Please find supplementary file(s);

https://doi.org/10.1253/circrep.CR-24-0022

References

• 1.   Aziz Z, Shatz D, Raiman M, Upadhyay GA, Beaser AD, Besser SA, et al. Targeted ablation of ventricular tachycardia guided by wavefront discontinuities during sinus rhythm: A new functional substrate mapping strategy. Circulation 2019; 140: 1383–1397.
• 2.   Hattori M, Komatsu Y, Naeemah QJ, Hanaki Y, Ichihara N, Ota C, et al. Rotational activation pattern during functional substrate mapping: Novel target for catheter ablation of scar-related ventricular tachycardia. Circ Arrhythm Electrophysiol 2022; 15: e010308.