Abstract Body (Do not enter title and authors here): Background: Ventricular tachycardia (VT) substrate characterization in patients with ischemic cardiomyopathy (ICM) utilizing conventional peak-to-peak bipolar voltage mapping is limited by preferential automatic annotation of large amplitude far-field electrograms (EGMs).

Objective: To investigate the role of a novel peak frequency (PF) software that prioritizes annotation of the near-field high-frequency component of bipolar EGMs as compared to standard bipolar voltage mapping (Std-Bip) for postinfarction substrate characterization.

Methods: We studied 23 patients (age 67.2±9.4 years, 95.7% male, LVEF 37.4±14.6%) undergoing catheter ablation of postinfarction VT (34.8% anterior infarction, 73.9% inferior infarction). High-density endocardial substrate maps were created in sinus rhythm (43.5%) or right ventricular pacing (56.5%) using a 16-electrode mapping catheter (HD grid, Abbott, IL). The peak-to-peak bipolar voltage of collected EGMs was analyzed in Std-Bip configuration and after applying the PF software.

Results: A total of 105,815 Std-Bip and PF EGMs were analyzed. Overall, 30.6% Std-Bip EGMs had a voltage 0.5-1.5 mV and 39% a voltage <0.5 mV. After applying the PF software, 26.3% PF EGMs had a voltage 0.5-1.5 mV and 48.4% a voltage <0.5 mV (p<0.01 for comparison, Figure). The PF software reclassified an average of 8.9% (range 3.1% to 21.9%) Std-Bip EGMs to a voltage <0.5 mV and an average 3.5% (range -7.9% to 13.5%) Std-Bip EGMs to a voltage 0.5-1.5 mV. This resulted in an average increase in LV surface area subtending low voltage (<1.5 mV) EGMs of 3.9±0.03%.

Conclusions: Postinfarction substrate mapping with a PF annotation algorithm significantly improves identification of low voltage bipolar EGMs compared to Std-Bip mapping.