Localization of critical isthmus in left atrial macroreentrant tachycardias: insights from peak frequency mapping during sinus rhythm and coronary sinus pacing
Authors: Handayani A , Yamaguchi T , Kim S , Martinez Cossiani M , Relan J , Sanroman-Junquera M , Castrejon-Castrejon S , Jauregui Abularach M , Guido Lopez L , Merino D , Carton Sanchez A J , Martinez Maldonado M E , De La Vieja Alarcon J J , Sanchez Somonte P , Merino Llorens J L 
Published: May 2024

Abstract

Background
Successful ablation of left atrium macroreentrant tachycardia (LAMRT) has advanced significantly, benefiting from an enhanced understanding of reentrant mechanisms and technological innovations. However, challenges like difficult inductions and the presence of multiple coexistent LAMRTs can complicate tachycardia mapping, potentially resulting in recurrences during follow-up. Consequently, there is a growing need for strategies that focus on pinpointing the critical isthmus of conduction (CIC) in LAMRT circuits outside of tachycardia episodes. Peak frequency (PF) mapping, with its ability to discern near-field (NF) from far-field (FF) electrograms (EGMs) in low voltage areas, emerges as a valuable tool for precisely identifying these critical isthmuses.

Purpose
This study aims to investigate whether the accurate identification of the CIC in LAMRT circuits is achievable through PF mapping during sinus rhythm or coronary sinus pacing.

Methods
Patients with sustained LAMRT undergoing radiofrequency (RF) ablation were enrolled. Utilizing a 16-pole grid catheter (HD-Grid), bipolar voltage and activation maps were generated during LAMRT. PF maps were retrospectively computed. Voltage, activation, and PF maps were also created during sinus rhythm and coronary sinus pacing (500 ms). Potential CICs (P-CICs) were defined as areas with low voltage (&lt;0.2 mV) and high PF (&gt;250 Hz), covering a surface area of &lt;2 cm2 by adjusting the PF threshold above 250 Hz. Only instances of LAMRT terminated by focal RF lesions (boundary &lt;1.5 cm diameter) were included. Confirmed CICs (C-CICs) were identified at sites where LAMRT termination occurred due to RF application. The localization of P-CICs found during LAMRT, sinus rhythm (SR), and coronary sinus pacing (CSP) mapping, in relation to that of CIC, was analyzed, considering them matching if separated by &lt;10 mm.

Results
Twenty-four consecutive patients with 26 atrial tachycardias (ATs) were prospectively enrolled, including 18 LAMRTs (270±63 ms) terminated by 2.2±2.9 focal RF lesions after 9.4±8.2 sec of energy delivery. A P-CIC was consistently identified at the tachycardia termination site during LAMRT mapping, with a visual cutoffs discrimination score (1-5) of 4.1±0.7, a mean P-P voltage cutoff &lt;0.22±0.09 mV, and a mean PF cutoff &gt;330±67 Hz in all patients. Importantly, P-CICs found during SR and CSP mapping matched those found during LAMRT mapping in all patients (figure).

Conclusion
PF mapping demonstrates precision in identifying the critical isthmus in LAMRT circuits during actual tachycardia episodes. Notably, the consistent identification of the CIC through PF mapping during sinus rhythm or coronary sinus pacing exhibits a high correlation with findings during LAMRT mapping. This approach holds promising potential for reducing arrhythmia recurrences, especially in scenarios involving multiple or unmappable LAMRTs.