Peak Frequency for Characterizing and Predicting Critical Isthmus and Termination Sites in Macro-Re-Entrant Atrial Tachycardia.

Background: Identifying critical isthmuses in macro-re-entrant atrial tachycardia (MRAT) is challenging. Omnipolar Technology Near Field mapping with the Peak Frequency (PF) tool holds promise for identifying critical regions sustaining re-entry, though PF signal characteristics and the algorithm's clinical value need further exploration.

Objectives: This study sought to analyze properties of PF in MRAT critical isthmuses and evaluate the value of Omnipolar Technology Near Field PF mapping in guiding ablation.

Methods: Consecutive patients undergoing MRAT ablation procedures with fully mapped circuits (using EnSite-X and HD-Grid) and termination during ablation were included. PF values were analyzed globally across the atrium and compared to the ablation termination site (within 5-mm diameter). The absolute maximum PF at and the number of ablation lesions required for termination were recorded.

Results: The study involved 21 MRATs (12 left, 9 right atrial) from 17 patients (age 63.9 ± 18.3 years). Termination typically required a median of 1 (Q1-Q3: 1-7) ablation lesion, with 48% terminating after the initial lesion. Maximum PF values at termination sites were significantly higher (615.2 ± 85.7 Hz) than global PF values (317.6 ± 45.4 Hz; P < 0.01) and PF within the 5-mm termination diameter (499.6 ± 115.4 Hz; P < 0.01). Voltage at termination sites (0.39 ± 0.56) was significantly lower than the global average (0.73 ± 0.57; P < 0.01). PF values above 363 Hz differentiated isthmus regions from global atrial PF, with values >530 Hz indicating maximum PF at termination sites.

Conclusions: Peak frequencies at MRAT termination sites are substantially higher than global atrial PFs, supporting the potential of PF mapping as an effective tool for identifying critical isthmuses in MRAT ablation procedures.