Temporal analysis of intracardiac electrograms during pulsed-field ablation

Abstract Background Pulsed-field ablation (PFA) aims to treat atrial fibrillation (AF) by the irreversible electrical elimination of the myocardial cells around the pulmonary veins (PV). However, interpretation of the local electrograms (EGMs) from the large 2mm electrodes of the catheter remains challenging. Purpose To characterize the local EGMs recorded by the ablation catheter, assess their changes with PFA applications, and evaluate lesion efficacy. Method We included 32 consecutive patients referred for AF catheter ablation. The pentaspline catheter (Farawave, Boston Scientific) was positioned in basket configuration at the PV ostium. Lesion efficacy was assessed by pacing between the electrodes at three time points: before the first double-pulse application, before the second application following a 30° rotation, and after a 60 sec waiting period (Figure). All EGMs were analyzed for bipolar voltage amplitude and frequency composition using FFT. A frequency cut-off at 50 Hz was applied to calculate the power of the high frequency band (HF50). Results We analyzed 103 applications resulting in 309 epoch and 1545 EGMs. Median voltage and HF50 before first application package were 1.24 mV and 1466 µV^2, respectively, and before second application after rotation of the catheter 0.137 mV and 13 µV^2, respectively (Figure, pink line) with a high interindividual variation. These values remain constant over 60 sec waiting period. Lack of pace-capture can be predicted by a voltage threshold of 0.41mV (accuracy=0.891, sensitivity=0.817, specificity=0.926) and an HF50 threshold of 61.4µV^2 (accuracy=0.883, sensitivity=0.881, specificity=0.884). Conclusion Signal reduction was most pronounced after first application. While the maximal voltage amplitude was comparable to other multipolar diagnostic catheters, the median minimal voltage was >0.1mV. Given the pace-capture threshold of 0.41 mV, a lower scar cutoff between 0.1mV and 0.4mV might be advisable, but this needs further investigation.