LAUSR

© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial License (https://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact [email protected] A 58-year-old man was referred for ablation of paroxysmal atrial fibrillation. He underwent surgical closure of an atrial septal defect at age 20 and ablations for atrial flutter and incisional atrial re-entry. A single-chamber pacemaker had been inserted shortly after surgery for the occurrence of sick sinus syndrome. A screw-in-atrial lead had been inserted 7 years ago at the right appendage (original lead abandoned at the same position), with a chronic stable pacing threshold around 1 V. Pulsed field ablation (PFA) of the four pulmonary veins was performed under general anaesthesia. Because of fractionated potentials just below the superior vena cava and repeated induction of Afib after mechanical contact in this area, an application of PFA energy was decided at this spot. The 35 mm Farawave TM catheter (Boston Sc) was positioned just below the opening of the superior vena cava (SVC) in a basket-like conformation. Immediately after the first application (1.8 KV), loss of atrial capture happened. This application was automatically interrupted after one second by the generator, probably because of the restricted opening of the catheter and too close position of some splines as seen on fluoroscopy although direct contact to the pacing lead with shortcut cannot be ruled out (but not visually evident and without artefact on intracardiac recordings). Immediate control revealed an elevated threshold (2.5 V) which slowly recovered (1.8 V at 10 min in uni and bipolar configurations and normalized < 1 V at 4 h and the day after). Impedance was normal (380 Ohms in uni and bipolar configurations). No further ablation was performed. The pacemaker was programmed with high-output amplitude (4 V), and the patient was discharged without any relevant event over the following weeks.