Background: Autonomic denervation is an ancillary phenomenon during thermal ablation of atrial fibrillation (AF), that may have synergistic effects on symptomatic improvement and long-term freedom from AF. Pulsed field ablation (PFA), a nonthermal ablation modality, was noninferior to thermal ablation in treating AF; however, PFA's relative myocardial selectivity may minimize autonomic effects., Objectives: This study sought to compare heart rate (HR) and heart rate variability (HRV) metrics as markers of autonomic function after ablation using PFA vs thermal ablation., Methods: ADVENT (FARAPULSE ADVENT PIVOTAL Trial PFA System vs SOC Ablation for Paroxysmal Atrial Fibrillation) was a randomized pivotal study comparing PFA (pentaspline catheter) with thermal ablation (radiofrequency [RF] or cryoballoon [CB]) for treating paroxysmal AF. Baseline HR was acquired from a pre-ablation 12-lead electrocardiogram, whereas follow-up HRs, as well as HRV (standard deviation of all normal to normal RR intervals, standard deviation of 5-minute average RR intervals) metrics, were derived from 72-hour Holter monitors at 6 and 12 months., Results: This study included 379 paroxysmal AF patients undergoing PFA (n = 194) or thermal ablation (n = 185; n = 102 RF, n = 83 CB) completing 6- and 12-month Holter monitoring. Compared with PFA, thermal patients had significantly greater increases in HR from baseline to 6 months (ΔHR; 10.1 vs 5.9 beats/min; P = 0.02) and 12 months (ΔHR; 8.8 vs 5.2 beats/min; P = 0.03). This increase in HR at 6 and 12 months was similar between CB and RF (P = 0.94 and 0.83, respectively). HRV, both standard deviation of all normal to normal RR intervals and standard deviation of 5-minute average RR intervals, were significantly lower at both 6 and 12 months after thermal ablation compared with PFA (P < 0.01)., Conclusions: PFA's effect on the autonomic nervous system was attenuated compared with thermal ablation. Whether this affects long-term freedom from AF or symptomatic bradycardia/pauses after AF ablation requires further study., Competing Interests: Funding Support and Author Disclosures The ADVENT study was funded by Boston Scientific, Inc. Dr Gerstenfeld has served on an advisory board (unpaid) for Boston Scientific; serves as a consultant for Abbott, Adagio Medical and Biosense Webster, unrelated to this work; has received lecture honoraria from Medtronic, Abbott, Boston Scientific, and Biosense Webster; and has received research funding from Abbott, Biosense Webster, and Adagio Medical. Dr Mansour has been a consultant for Boston Scientific, Biosense Webster, Abbott, Medtronic, Siemens Novartis, Janssen, Boehringer Ingelheim, Pfizer, and SentreHEART/AtriCure; and has equity in EPD-Philips (divested), and NewPace Ltd. Dr Ellis has received research grants (to VUMC), from Boston Scientific, AtriCure, and Medtronic; and has served on advisory boards or received consulting fees from Abbott Medical, Boston Scientific, AtriCure, and Medtronic. Dr Osorio has been a consultant for Boston Scientific, Biosense Webster, Medtronic, Volta, and Abbott Medical; and has served on advisory boards for Boston Scientific, Biosense Webster, and Volta. Dr DeLurgio has been a consultant and speaker for Boston Scientific. Dr McElderry has served as a consultant for Boston Scientific (formerly Farapulse), Abbott, Medtronic, Heamonetics, and Biosense Webster. Ms Richards, Dr Albrecht, Mr Schneider, and Dr Sutton are salaried employees of Boston Scientific. Dr Reddy has equity in Farapulse Inc (now divested), Ablacon, Acutus Medical, Affera-Medtronic, Anumana, Apama Medical-Boston Scientific, APN Health, AquaHeart, Atacor, Autonomix, Axon Therapies, Backbeat, BioSig, CardiaCare, CardioFocus, CardioNXT/AFTx, Circa Scientific, CoRISMA, Corvia Medical, Dinova-Hangzhou DiNovA EP Technology, East End Medical, EPD-Philips, EP Frontiers, Epix Therapeutics-Medtronic, EpiEP, Eximo, Field Medical, Focused Therapeutics, HRT, Intershunt, Javelin, Kardium, Keystone Heart, Laminar Medical, LuxMed, Medlumics, Middlepeak, Neutrace, Nuvera-Biosense Webster, Oracle Health, Restore Medical, Sirona Medical, SoundCath, and Valcare, and unrelated to this work, in Atraverse, DRS Vascular, Manual Surgical Sciences, Newpace, Nyra Medical, Soundcath, Surecor, and Vizaramed; has served as a consultant for Boston Scientific Inc and Farapulse Inc, and unrelated to this work, Abbott, Adagio Medical, Append Medical, AtriAN, Biosense-Webster, BioTel Heart, Biotronik, Cairdac, Cardionomic, CoreMap, Fire1, Gore & Associates, Impulse Dynamics, Medtronic, Novartis, Novo Nordisk, Philips, Ablacon, Acutus Medical, Affera-Medtronic, Anumana, Apama Medical-Boston Scientific, APN Health, AquaHeart, Atacor, Autonomix, Axon Therapies, Backbeat, BioSig, CardiaCare, CardioFocus, CardioNXT/AFTx, Circa Scientific, CoRISMA, Corvia Medical, Dinova-Hangzhou DiNovA EP Technology, East End Medical, EPD-Philips, EP Frontiers, Epix Therapeutics-Medtronic, EpiEP, Eximo, Field Medical, Focused Therapeutics, HRT, Intershunt, Javelin, Kardium, Keystone Heart, Laminar Medical, LuxMed, Medlumics, Middlepeak, Neutrace, Nuvera-Biosense Webster, Oracle Health, Restore Medical, Sirona Medical, SoundCath, Valcare, and Pulse Biosciences. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2024 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)