Abstract 1786: Translesion Stimulation-Excitation Delay Rapidly Indicates Lesion Completeness and Increased Conduction Path Length Around Ablated Tissue
Variable efficacies of antiarrhythmic ablations suggest a rapid index of lesion completeness during the procedure may improve outcomes by ensuring production of a transmural and continuous lesion and avoiding over-ablation. This study tested translesion stimulus-excitation delay (TED), with stimulation on one side of the lesion and excitation recorded on the opposite side, as an intraoperative index of lesion completeness. We hypothesized that TED corresponds to the minimum path length (MPL) for conduction in viable tissue from one side of the lesion to the other side, and that block by a complete lesion markedly increases TED and MPL. Experiments tested this for linear lesions produced by RF ablation in isolated perfused hearts. Rabbit hearts (n=11) were stained with transmembrane potential-sensitive fluorescent dye. RF ablation (480 kHz, 1800–3600 J/cm2) was performed on ventricular epicardium with a vacuum-enabled probe to produce linear lesions that contained a central gap or were nontransmural (Incomplete), or that were continuous and transmural (Complete). Electrodes were positioned to apply bipolar stimulation on one side of the lesion while recording bipolar electrograms on the other side. The region was optically mapped to observe epicardial block. Completeness of lesions and 3-dimensional MPL were then determined histologically after tetrazolium chloride staining to highlight viable tissue. Results show that the TED increased 3.4 ± 9.0 ms (a 7% increase) after creating Incomplete, and 70 ± 11 ms (a 212% increase) due to block after creating Complete lesions (mean ± SEM, p < 0.05 for Incomplete vs. Complete). The corresponding MPL was 14 ± 0.6 mm for Incomplete and 40 ± 2.4 mm for Complete lesions (p < 0.05). MPL and TED were highly correlated (R = 0.89). Calculated conduction velocities in the shortest viable path for Complete and Incomplete were not different and had nominal values (0.44 ± 0.03 mm/ms), indicating MPL quantitatively accounts for post-ablation TED. TED provides a definitive and immediate index of lesion completeness based on the increase in path length for conduction. As such, TED may be a useful intraoperative measure to guide reablation of incomplete lesions. This may improve outcomes of anti-arrhythmic ablation.