Abstract 14754: Peak Frequency Mapping in Low Voltage Zones Can Identify the Critical Isthmus in Atypical Atrial Flutters

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Introduction: Atypical atrial flutters (AFL) are a heterogeneous group of reentrant arrhythmias and can be challenging to map. Peak frequency (PF) mapping is a novel method of identifying local conductivity and may help identify critical portions of myocardial substrate supporting reentry. Hypothesis: The critical isthmuses of left atrial (LA) AFLs demonstrate a combination of low-voltage and high PF. Methods: LA omnipolar voltage and PF maps were generated using the EnSite Precision Mapping System and HD-Grid catheter in 13 patients undergoing AFL ablation. For the purpose of this study, mapping was performed during AFL and normal voltage was defined as ≥ 0.5 mV, low-voltage (LV) 0.1 - 0.5 mV, and scar < 0.1 mV. PF distributions were analyzed in each tissue type. Conduction velocity (CV) was characterized across PF with correlational analysis. The 1-cm radius from sites of arrhythmia termination with ablation were analyzed to characterize mean PF and voltage in nearby myocardial tissue. Results: Mean age was 65.8 ± 9.3 years and 54% were female. A total of 37,331 points were analyzed. Sites of slow conduction included the mitral isthmus (46%), LA roof (23%), pulmonary vein antra (15%), posterior wall (8%), and anterior wall (8%). In normal voltage tissue, mean PF was 337.7 ± 115.4 Hz. LV and scar tissue had left-skewed PF distributions and lower mean PF ( p < 0.0001). While CV had no trend across PF in tissue with normal voltage ( R 2 , 0.0002 to 0.1), there was moderate conduction slowing at higher PF in LV tissue ( R 2 , 0.07 to 0.30). In PF-LV overlay maps, all termination sites resided in regions of LV and high PF ( Figure ). Of the 1-cm areas neighboring termination, 77% had significantly higher PF than the global LA ( p < 0.05), of which 80% had significantly lower mean voltage ( p < 0.01) or mean voltage < 0.5 mV. Conclusions: Sites of arrhythmia termination can be identified in LV tissue at higher PF. Low-voltage, high-PF areas may be critical targets during catheter ablation of atypical AFL.