Does the isolation of the pulmonary veins with pulsed field ablation affect the right atrium?

Abstract Background Pulsed Field Ablation (PFA) of atrial fibrillation (AF) is a non-thermal novel ablative modality in which high-voltage electric pulses are delivered to generate a high myocardial tissue-specific cellular death, with negligible consequences on surrounding structures. Lesion depth seems to increase significantly with increasing number of PFA deliveries, contact and contact force. Lesion depth can be crucial to know in case of hypertrophic septum or thicker different cardiac substrate to ablate. Purpose Little data are available on the effect of PFA lesion depth in the real-world clinical setting. The aim of this study is to investigate whether PFA ablation can also affect the right atrium/right septum or superior vena cava in a case series of conventional PVI in AF ablation in relation to septum thickness as well. Methods We included consecutive patients undergoing AF ablation with biphasic, 2k Volts, bipolar PFA using a 12-F over-the-wire PFA catheter containing 5 splines (Farawave). All patients performed a routine computed tomography angiography (CTA) and 2 repeated measures of thickness were performed at 3 different levels (upper, middle and inferior) of the interatrial septum in correspondence of right pulmonary veins antra. At the end of the procedure, upon completion of PFA deliveries to every pulmonary veins, left and right atrium were mapped with conventional electroanatomical mapping system (Carto v7 or Ensite X EP system). Conventional 0.05-0,5 mV voltage cut-off was used to discriminate dense scar, border zone and healthy myocardium. Results 17 consecutive PFA patients were analysed, median age 65 yo (IQR 59-73), all paroxysmal AF, median LVEF 58% (IQR 56-61%) (Fig. 1). At the CTA the median thickness at 3 different level was, from the upper to the inferior level (Fig. 2), 4,6 mm (IQR 3.5-5.3), 3,4 mm (IQR 2.6-4.4) and 2.9 mm (IQR 2.6-3.7) respectively. All patients were successfully treated with a protocol previously clinically validated with 4+4 deliveries (4 in the so called "basket" configuration and 4 in the "flower" configuration) per vein and at remap all 68/68 veins remained isolated. At the bipolar voltage mapping in the right atrium no area of border zone (<0.5 mv) or dense scar (<0.05 mV) were evident in any patients, even in correspondence of the right PVs isolated antra. Conclusions PFA does not affect voltage in the right atrium or in the septum in acute. As median septum thickness is included between 2.9 and 4.6 mm we aspect that actual PFA protocol deliveries do not create lesions that overcome this measure.