Abstract 4112: Lesion Transumurality for Surgical Epicardial Linear Atrial Ablation can be Predicted by Electrogram Amplitude Reduction and Double Potentials
The purpose of this study was to determine, for epicardial bipolar linear radiofrequency (RF) ablation, if electrograms (Eg) over the lesion can differentiate between transmural and non-transmural linear atrial lesions. Six dogs were studied open chest. Surgical ablation probe (Cool Rails, AtriCure) with 2 parallel 30 mm copper tubes (internally irrigated 30 ml/min) for bipolar RF ablation. The probe was modified with 3 unipolar recording electrodes (1.5 mm spacing) between the copper tubes and 2 pacing electrodes lateral to the copper tube (Fig⇓). The probe was placed on the epicardium of RA and LA. To create transmural and non-transmural lesions, epicardial RF (30W) was applied between the copper tubes for 10, 20, 30 and 40 sec in RA and LA of each dog (8 lesions/dog). 3 Unipolar Eg (1–500 Hz) were recorded during atrial pacing lateral to the copper tubes (perpendicular atrial wavefront) before and after ablation. Dogs were sacrificed at 2 hours and lesions were examined (TTC stain) for transmurality along its length. Of 48 lesions, 7 were transmural along entire length (TNS), 7 were non-transmural along the entire length (Non-TNS) and 34 were partially transmural. Unipolar Eg amplitude (3 per lesion) was significantly smaller for the 7 TNS lesions than the 7 Non-TNS lesions (<0.4 mV in 21/21 vs. 3/21, p<0.01, Fig⇓). Double potentials were recorded in all TNS (21/21 Eg) but none of Non-TNS (0/21 Eg). Atrial myocardium thickness was 3.1 ± 0.8 mm in TNS and 3.5 ± 0.9 mm in Non-TNS (p=NS). For epicardial linear atrial ablation, lesion transmurality can be identified by marked decrease (<0.4 mV) of unipolar Eg and development of double potentials over the ablation site.