Background: Although lesion transmurality is required for durable pulmonary vein isolation, excess ablation is associated with increased risk of complications.
Objective: To understand the impact of different RF delivery conditions on lesion transmurality in the atrial free wall.
Methods: Thirty-three (11 LA, 22 RA) RF ablation lesions were created in the atria of 6 swine using power control mode (25W, target contact force 15g) with one of three conditions: (1) 15s ablation, (2) 30s ablation, or (3) two 15s ablations at the same site separated by a 2-min interruption (15s x2).
Results: Thirty of 33 lesion were transmural. Rates of transmurality (p=0.45) and endocardial lesion width (p=0.70) were similar between conditions (Table). Mean tissue thickness was 1.71±0.77mm for transmural lesions. Wide variability in bipolar and unipolar electrogram attenuation was observed across and within conditions and there were no significant between group differences. Although impedance reductions were numerically greater in the 30s and 15s x 2 conditions compared to the 15s condition, variability was large, and differences were not statistically significant. Despite similar lesion sizes across the groups, Force-time integral (FTI) predicted larger lesions for the 30s and 15s x 2 conditions.
Conclusion: A 15s ablation at 25W (contact force 15.7±3.5g) with good stability produced lesions of similar size compared to 30s ablations and two 15s ablation at the same site in atrial free wall tissue. These data suggest over ablation in the atria is common and some clinically available parameters of lesion size may be unreliable on the atrial free wall.