Po-05-096 prognostic value of near-field electrograms at critical ablation sites during ventricular tachycardia ablation

Electrogram (EGM) annotation during VT is challenging due to complexity of EGMs and difficulty in distinguishing far-field and near-field (NF) EGMs. EGM frequency increases with greater EGM proximity to the recording electrode. The prognostic value of high-frequency EGMs at critical ablation sites during VT ablation is unknown. The utility of recently developed algorithms to annotate local EGM frequency during 3D mapping (Ensite X, Abbott, Inc.) is unknown. The absence of high frequency EGMs at critical sites for VT ablation may suggest that the EGM of interest is deep to or remote from the recording electrode. To investigate the utility of the EGM frequency annotation at critical ablation sites during VT ablation. Consecutive patients with scar-related VT undergoing catheter ablation (RFA) were analyzed. High density substrate maps were created in presenting ventricular rhythm using a High-definition multi-electrode mapping catheter (HD Grid, Abbott, Inc.). Critical sites for induced VT were identified based on pace-mapping, activation mapping, entrainment mapping, or termination of VT with RFA. Substrate maps were retrospectively analyzed with EGM annotation based on NF EGM. The highest frequency EGM within 5mm of the critical ablation site was identified and analyzed. Thirty-four critical sites were identified and ablated in twenty-two patients, 14 (64%) with ischemic cardiomyopathy, age 65±10 years with LVEF was 33±13 %. VT recurred in 9 patients (41%). The peak frequency in the critical site using the NF annotation in patients with recurrence was significantly lower than in patients without recurrence (192 vs 397 Hz; p=0.01). Cox regression analysis shows statistically significant higher risk to have VT recurrence when the frequency is below the median frequency (HR 5.09, 95% C.I 1.05-24.68, p=0.04). Area under the receiver operator characteristic curve for peak EGM frequency at VT critical site as a predictor of VT recurrence was 0.81, with critical site EGM frequency < 286 Hz providing 89% sensitivity and 69% specificity for VT recurrence. Low frequency EGMs at VT critical sites measured by EGM frequency annotation software identify patients at greater risk of VT recurrence. A finding of low frequency EGMs at apparent critical site implies that the successful ablation may require additional mapping, including consideration of epicardial or venous mapping, to localize better the true critical site or ablation techniques to provide deeper ablation.