Left Atrial Voltage Attenuation Beyond Ablation Sites After Unipolar Pulsed-Field Ablation for Atrial Fibrillation.

INTRODUCTION: Unlike most pulsed-field ablation (PFA) systems, Affera (Medtronic) delivers unipolar energy between a lattice-tip catheter and a cutaneous return patch, potentially generating a broader electric field. We hypothesized that this may attenuate voltage beyond ablated regions and tested this using spatially matched pre- and post-ablation maps. METHODS AND RESULTS: We retrospectively studied five consecutive patients undergoing primary atrial fibrillation ablation with the Affera system. Pre- and immediate post-ablation voltage maps were generated using CARTO 3 and OCTARAY (Biosense Webster) with identical settings during right atrial pacing. Because Affera lacks point-level 3D coordinates for spatial matching, coordinates (x, y, z) and bipolar voltages were extracted from CARTO 3. Pre- and post-ablation points-outside energy delivery sites, excluding the annulus and left atrial appendage-were spatially matched using a 2 mm mutual nearest-neighbor criterion. This yielded 3772 pairs. Bipolar voltages were averaged by case. Mean bipolar voltage decreased in all cases from 1.01 ± 0.61 to 0.56 ± 0.29 mV, representing a 40.2% reduction (95% CI, 24.6%-55.8%; p = 0.044). In a distance-stratified analysis, residual bipolar voltage (post/pre × 100) was lowest just beyond the ablated zone and increased progressively with distance from the nearest application tag center (16.5% at 10-15 mm to 57.8% at 25-30 mm; all p < 0.001), becoming numerically comparable to baseline beyond approximately 30 mm. CONCLUSIONS: Affera-based unipolar ablation produced acute bipolar voltage attenuation that extended into non-ablated myocardium adjacent to the lesion set but diminished with distance and was largely confined within approximately 30 mm of the application sites.