Abstract Background/Introduction The ability to classify and differentiate between near field and far-field components of intracardiac signals is a key element in identifying critical arrhythmogenic substrate during ventricular tachycardia (VT) ablation. Near Field algorithms based on omnipolar electrograms enable detection and automation of true localised signals providing unique insights into substrate characteristics. This novel feature identifies localised signal peak frequency (PF) which can be displayed across different voltage ranges. Purpose/Aims The significance of PF mapping in the context of VT ablation is limited and its utility in the identification of the critical diastolic isthmus zone (IZ) is not known. The aim of this study is to explore the utilisation of PF mapping during VT ablation and evaluate whether significant differences in PF occur within areas of interest and critical components of the VT circuit during substrate mapping. Methods All patients underwent VT ablation using the EnSite™ X mapping system with the HDGrid omnipolar mapping catheter. Only cases with both high density sinus rhythm (SR) substrate maps and VT activation maps with clear identification of the IZ were included. VT activation and propagation maps were generated and the diastolic IZ was superimposed onto the SR substrate map. PF analysis was performed retrospectively. Surface area, omnipolar voltage and PF of the maps were measured in the SR substrate maps and co-localised with the critical IZ of the VT circuit as identified in the VT activation maps. Analysis of PF was conducted across different voltage ranges: healthy myocardium (>1.5mV), scar (1.5-0.5mV) and dense scar (0.5-0.1mV). Sensitivity and specificity measurements were made within segments of the IZ and non-isthmus zones and depicted as ROC curves. Results 55 patients underwent VT ablation over a 12-month period, with a total of 18 fulfilling the inclusion criteria. Mean age was 70 (±12.5years) with an average ejection fraction of 36%. The overall PF of the SR substrate maps was 121.85±26.85 Hz, compared to 162.22±46.22Hz within the IZ (p=0.002). Within the low voltage scar region, the overall PF was 120.86±33.24Hz compared to 188.32±81.36Hz within the IZ (p=0.003). No significant difference in PF was observed within healthy myocardium (112.70±52.06 Hz) compared to components of the IZ within the >1.5mV range (157.61±136.11Hz), p=0.207. The AUC for PF within the overall substrate map and co-localisation with the IZ was 0.67, and 0.73 within low voltage zones (<1.5mV). Conclusions PF mapping may identify critical components of the VT circuit during SR substrate mapping and its utilisation may compliment established substrate mapping approaches. PF guided ablation strategies require further evaluation in future prospective studies.