Background: Atrial adverse remodeling drives the maintenance and progression of atrial fibrillation (AF) through electrical and structural myocardial changes, often accompanied by inflammation. Circulating N-glycans are emerging as biomarkers in inflammatory diseases, yet their role in AF remains undefined. Methods: We profiled the serum N-glycome of 138 patients with AF, non-AF arrhythmias, or sinus rhythm (SR) controls from peripheral venous (PV) and coronary sinus (CS) samples using hydrophilic interaction liquid chromatography coupled with high-resolution mass spectrometry. Glycan traits associated with AF were identified via logistic regression adjusted for clinical risk factors. Multivariate glycan scores were derived from PV and CS datasets using LASSO regression. In a subset (N=37), plasma proteome profiling was performed with the Olink Reveal panel. Results: Sixty-two glycan peaks were detected; 27 in PV and 8 in CS serum differed significantly between AF and controls. PV and CS glycan scores accurately classified AF, with the PV score correlating with 11 plasma proteins linked to structural remodeling and thrombo-inflammatory processes. The most abundant glycan, A2G2S2 (peak 30), was associated with higher odds of AF after adjusting for confounders (OR 2.22 [95% CI: 1.40?3.75], P = 0.001). CS A2G2S2 correlated with C-reactive protein (R = 0.432, P = 0.0275) and was elevated in patients with left atrial enlargement (P = 0.0354), but unchanged in those with impaired left ventricular ejection fraction or hypertrophy. Conclusion: Integrated profiling of peripheral and cardiac serum identifies novel N-glycosylation signatures in AF. Specific cardiac and circulating N-glycan signatures, including A2G2S2, are associated with AF and reflect inflammation-driven atrial remodeling, highlighting potential mechanistic pathways and biomarker applications. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work was funded by the British Heart Foundation (BHF) Intermediate (FS/SBSRF/22/31026) and Senior (FS/SBSRF/22/31033) Fellowships (to S.R.), Oxford BHF Centre of Research Excellence (CRE) grants (to S.R.), the British Research Council (BRC4) NIHR Oxford Biomedical Research Centre grant (to S.R. and C.H.K.Y.), the BHF Clinical Research Training Fellowship (FS/CRTF/25/24786; to C.S.M.), the BHF PhD Studentship (FS/20/7/34992; to L.M.M.), the BHF Studentship grant (FS/4yPhD/F/22/34177; to A.M.J.), and The Royal Society University Research Fellowship (URF\R1\221314; to A.B.). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: This study was approved by the South Central-Berkshire B Research Ethics Committee (UK, 18/SC/0404 and 18/SC/0304) at John Radcliffe Hospital, Oxford. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data related to the manuscript is included in the manuscript. The metadata of the patient cohorts that support the findings are available from the first author (C.H.K.Y.) and corresponding author (S.R.) upon request.

Background: Proteins in human plasma serve as critical markers for predicting disease risk and guiding therapeutic development. Current prediction models for atrial fibrillation (AF) largely rely on electronic health records; however, the plasma proteome of patients with AF reflects key biological processes, including inflammation, that are not captured by clinical variables alone. Circulating inflammatory mediators contribute to electrical and structural remodelling in the atria, thereby sustaining the AF phenotype. Identification of plasma proteins associated with AF may therefore improve understanding of the inflammatory and other biological processes underlying AF pathophysiology. Objective: In this study, we profiled the plasma proteome of patients with paroxysmal AF (pxAF), persistent AF (persAF), and non-AF controls using Olink assay technology. Methods: Plasma samples from 30 individuals were analysed with the Olink Reveal panel. Differential expression analysis of normalised protein expression (NPX) values was performed between groups, with differentially expressed proteins (DEPs) defined by P < 0.05. Results: We identified 87 DEPs in pxAF and 107 DEPs in persAF compared with controls. From these, we shortlisted 11 candidate proteins that were upregulated in persAF at baseline and showed reduced expression 12 months after catheter ablation. This subset of proteins is implicated in the regulation of inflammation (CCL23, CXCL10, IL33), metabolism (ALDH3A1, NDUFS6), cell-matrix adhesion (AFAP1L1, LGALS7, SPOCK1), and physiological signalling (NOS1, PROK1, PTH). Conclusion: Collectively, these plasma proteins highlight systemic molecular mechanisms contributing to AF pathogenesis and represent potential AF-specific biomarkers warranting further investigation in larger clinical cohorts and mechanistic studies. ### Competing Interest Statement The authors have declared no competing interest. British Heart Foundation, FS/SBSRF/22/31026, FS/SBSRF/22/31033, FS/CRTF/25/24786 British Heart Foundation Centre of Research Excellence, Oxford, GB NIHR Oxford Biomedical Research Centre

BACKGROUND:Patients undergoing catheter ablation (CA) for persistent atrial fibrillation (PsAF) experience high rates of AF recurrence. Direct current cardioversion (DCCV) is often performed prior to CA, with variable post-DCCV duration of sinus rhythm (SR). OBJECTIVE:We aimed to determine whether shorter SR duration after DCCV is associated with AF recurrence after subsequent CA. METHODS:We performed an international multicentre retrospective study of patients undergoing first-time CA for PsAF between 2015 and 2024 with a prior DCCV. SR duration after the last DCCV preceding CA was recorded. The primary outcome was freedom from atrial arrhythmia after CA (after a 56-day postablation blanking period). RESULTS:938 patients undergoing first-time CA for PsAF were identified from six centres and categorised by post-DCCV SR duration: <7 days (group 1, n=212); 7-31 days (group 2, n=236); and >31 days (group 3, n=490). Over median post-CA follow-up of 511 days, 512 patients (55%) experienced atrial arrhythmia recurrence. There was no significant between-group difference in freedom from atrial arrhythmia (log-rank p=0.10). When analysed as a continuous variable in a Cox regression model, there was no association between post-DCCV SR duration and time to first recurrence of atrial arrhythmia (HR per 10-day increment 1.00, 95% CI 1.00 to 1.01, p=0.07). In secondary analyses, there were significantly more blanking period arrhythmias in groups 1 and 2 compared with group 3 (both pairwise p<0.001), and presentation for CA in persistent atrial arrhythmia was associated with a time-dependent increased risk of atrial arrhythmia recurrence compared with presentation in SR. CONCLUSION:In this large multicentre cohort, shorter duration of SR after DCCV was associated with blanking period arrhythmia after subsequent CA, but we did not find evidence of an association with long-term AF recurrence. Clinicians should consider these findings when making decisions regarding suitability for CA or predicting long-term CA success.

Introduction. When using Lesion Size index (LSI) to guide catheter ablation, it is unclear what combination of power, contact force and time would be preferable to use and what LSI target value to aim for. This study aimed at identifying desirable ablation settings and LSI targets by using tissue impedance drop as indicator of lesion formation. Methods. Consecutive patients, undergoing their first left atrial (LA) catheter ablation for atrial fibrillation, with RF powers of 20, 30 and 40 W were enrolled. Tissue impedance, contact force (CF), Force Time Integral (FTI) and LSI values were continuously recorded during ablation and sampled at 100 Hz. Mean CF and Contact Force Variability (CFV) were calculated for every lesion. The effect of RF power, ablation time, CF and CFV on impedance drop and LSI were assessed. Results. A total of 3258 lesions were included in the analysis. For any target LSI value, use of higher RF powers translated into progressively higher impedance drops. The impact of lower CF and higher CFV on impedance drop was more relevant when using lower powers. Target LSI values corresponding to maximum impedance drop were identified depending on RF power, mean CF and CFV used. Conclusions. Even in the context of an LSI-guided ablation strategy, use of lower or higher powers might lead to different lesion sizes. Different LSI targets might be needed depending on the combination of RF power, CF and CFV used for ablation. Incorporating indicators of catheter stability, like CFV, in the LSI formula could improve the predictive value of LSI for lesion size. Studies with clinical outcomes are required to confirm the clinical relevance of these findings.

BACKGROUND:The rate of left ventricular (LV) lead displacement after cardiac resynchronization therapy (CRT) remains high despite improvements in lead technology. In 2017, a novel quadripolar lead with active fixation technology became available in the UK. METHODS:This was a retrospective, observational study analyzing device complications in 476 consecutive patients undergoing successful first-time implantation of a CRT device at a tertiary center from 2017 to 2020. RESULTS:Both active (n = 135) and passive fixation (n = 341) quadripolar leads had similar success rates for implantation (99.3% vs. 98.8%, p = 1.00), although the pacing threshold (0.89 [0.60-1.25] vs. 1.00 [0.70-1.60] V, p = .01) and lead impedance (632 [552-794] vs. 730 [636-862] Ohms, p < .0001) were significantly lower for the active fixation lead. Patients receiving an active fixation lead had a reduced incidence of lead displacement at 6 months (0.74% vs. 4.69%, p = .036). There was no significant difference in the rate of right atrial (RA) and right ventricular (RV) lead displacement between the two groups (RA: 1.48% vs. 1.17%, p = .68; RV: 2.22% vs. 1.76%, p = .72). Reprogramming the LV lead after displacement was unsuccessful in most cases (successful reprogramming: Active fix = 0/1, Passive fix = 1/16) therefore nearly all patients required a repeat procedure. As a result, the rate of intervention within 6 months for lead displacement was significantly lower when patients were implanted with the active fixation lead (0.74% vs. 4.40%, p = .049). CONCLUSION:The novel active fixation lead in our study has a lower incidence of lead displacement and re-intervention compared to conventional quadripolar leads for CRT.

Objective When reporting coronary CT angiography (CCTA), extracardiac structures are routinely assessed, usually on a wide field-of-view (FOV) reconstruction. We performed a retrospective observational cross-sectional study to investigate the impact of incidental extracardiac abnormalities on resource utilisation and treatment, and cost-effectiveness. Methods All patients undergoing CCTA at a single institution between January 2012 and March 2020 were identified. The indication for CCTA was chest pain or dyspnoea in >90%. Patients with ≥1 significant extracardiac findings were selected. Clinical follow-up, investigations and treatment were documented, and costs were calculated. Results 4340 patients underwent CCTA; 717 extracardiac abnormalities were identified in 687 individuals (15.8%; age 62±12 years; male 336, 49%). The abnormality was already known in 162 (23.6%). Lung nodules and cysts were the most common abnormalities (296, 43.1%). Clinical and/or imaging follow-up was pursued in 292 patients (42.5%). Treatment was required by 14 patients (0.3% of the entire population), including lung resection for adenocarcinoma in six (0.1%). All but two abnormalities (both adenocarcinomas) were identifiable on the limited cardiac FOV. The cost of reporting (£20) and follow-up (£33) of extracardiac abnormalities was £53 per patient. The cost per discounted quality-adjusted life year was £23 930, increasing to £46 674 for reporting the wide FOV rather than the cardiac FOV alone. Conclusions Extracardiac abnormalities are common on CCTA, but identification and follow-up are costly. The few requiring treatment are usually identifiable without review of the wide FOV. The way in which CCTAs are scrutinised for extracardiac abnormalities in a resource-limited healthcare system should be questioned.

AIMS Catheter ablation for atrial fibrillation (AF) has historically required inpatient admission post-procedure, but same-day discharge (SDD) has recently been reported. We aimed to assess the efficacy and safety of SDD compared with overnight stay (OS) post-ablation. METHODS AND RESULTS We performed a systematic search of the PubMed database. Random-effects meta-analysis was performed to assess the efficacy (successful SDD) and safety (24 h complications, 30-day complications, 30-day re-admissions, and 30-day mortality) of a SDD AF ablation strategy. Fourteen non-randomized observational studies met criteria for inclusion, encompassing 26488 patients undergoing AF ablation, of whom 9766 were SDD. The mean age of participants was 61.9 years, and 67.9% were male. Around 61.7% underwent ablation for paroxysmal AF. The pooled success rate of SDD was 83.2% [95% confidence intervals (CIs): 61.5-97.0%, I2 100%]. The risk of bias was severe for all effect estimates due to confounding, as most cohorts were retrospectively identified without appropriately matched comparators. There was no significant difference in 30-day complications [odds ratio (OR): 0.95, 95% CI: 0.65-1.40, I2 53%] or 30-day re-admission (OR 0.96, 95% CI: 0.49-1.89, I2 82%) between groups. There were insufficient data for meta-analysis of 24 h complications and 30-day mortality. Where reported, no re-admissions occurred due to 24 h complications after SDD. Two deaths (0.04%) were reported in both SDD and OS groups. CONCLUSION Same-day discharge after AF ablation appears to be an effective and safe strategy in selected patients. However, the available evidence is of low quality, and more robust prospective studies comparing SDD to OS are needed.

Preliminary data in human suggest that both Intracardiac echocardiography (ICE) and Intravascular ultrasound (IVUS) can be used for real-time information on the left atrial (LA) wall thickness and on the acute tissue changes produced by energy delivery. This pilot study was conducted to compare ICE and IVUS for real-time LA wall imaging and assessment of acute tissue changes produced by radiofrequency (RF), cryo and laser catheter ablation. Patients scheduled for RF, cryoballoon or laser balloon Pulmonary Vein Isolation (PVI) catheter ablation were enrolled. Each pulmonary vein (PV) was imaged before and immediately after ablation with either ICE or IVUS. The performance of ICE and IVUS for imaging were compared. Pre- and post-ablation measurements (lumen and vessel diameters, areas and sphericity indexes, wall thickness and muscular sleeve thickness) were taken at the level of each PV ostium. A total of 48 PVs in 12 patients were imaged before and after ablation. Both ICE and IVUS showed acute tissue changes. Compared to IVUS, ICE showed higher imaging quality and inter-observer reproducibility of the PV measurements obtained. Acute wall thickening suggestive of oedema was observed after RF treatment (p = 0.003) and laser treatment (p = 0.003) but not after cryoablation (p = 0.69). Our pilot study suggests that ICE might be preferable to IVUS for LA wall thickness imaging at the LA-PV junctions during ablation. Ablation causes acute wall thickening when using RF or laser energy, but not cryoenergy delivery. Larger studies are needed to confirm these preliminary findings.

Aims Systemic inflammation and increased activity of atrial NOX2-containing NADPH oxidases have been associated with the new onset of atrial fibrillation (AF) after cardiac surgery. In addition to lowering LDL-cholesterol, statins exert rapid anti-inflammatory and antioxidant effects, the clinical significance of which remains controversial. Methods and results We first assessed the impact of cardiac surgery and cardiopulmonary bypass (CPB) on atrial nitroso-redox balance by measuring NO synthase (NOS) and GTP cyclohydrolase-1 (GCH-1) activity, biopterin content, and superoxide production in paired samples of the right atrial appendage obtained before (PRE) and after CPB and reperfusion (POST) in 116 patients. The effect of perioperative treatment with atorvastatin (80 mg once daily) on these parameters, blood biomarkers, and the post-operative atrial effective refractory period (AERP) was then evaluated in a randomized, double-blind, placebo-controlled study in 80 patients undergoing cardiac surgery on CPB. CPB and reperfusion led to a significant increase in atrial superoxide production (74% CI 71-76%, n = 46 paired samples, P < 0.0001) and a reduction in atrial tetrahydrobiopterin (BH4) (34% CI 33-35%, n = 36 paired samples, P < 0.01), and in GCH-1 (56% CI 55-58%, n = 26 paired samples, P < 0.001) and NOS activity (58% CI 52-67%, n = 20 paired samples, P < 0.001). Perioperative atorvastatin treatment prevented the effect of CPB and reperfusion on all parameters but had no significant effect on the postoperative right AERP, troponin release, or NT-proBNP after cardiac surgery. Conclusion Perioperative statin therapy prevents post-reperfusion atrial nitroso-redox imbalance in patients undergoing on-pump cardiac surgery but has no significant impact on postoperative atrial refractoriness, perioperative myocardial injury, or markers of postoperative LV function.

Expanding use of pacemakers and implantable cardioverter defibrillators (ICDs) has made it common for patients with devices to present for elective or emergency surgery and other interventional procedures. The key issue in perioperative management is the potential for electromagnetic interference (EMI) altering performance of devices, possibly leading to malfunction and/or adverse clinical consequences. This chapter covers the American College of Cardiology, American Heart Association, and UK Medicines and Healthcare Products Regulatory Agency guidelines for perioperative management of pacemakers or ICDs. Assessment, intra-operative management, and post-operative management are all described.

Background Atrial fibrillation ( AF ) is associated with myocardial infarction, and patients with AF and no obstructive coronary artery disease can present with symptoms and evidence of cardiac ischemia. We hypothesized that microvascular coronary dysfunction underlies these observations. Methods and Results Myocardial blood flow ( MBF ) at baseline and during adenosine stress and left ventricular and left atrial function were evaluated by magnetic resonance in 49 patients with AF (25 paroxysmal, 24 persistent) with no history of epicardial coronary artery disease or diabetes mellitus, before and 6 to 9 months after ablation. Findings were compared with those obtained in matched controls in sinus rhythm (n=25). Before ablation, patients with AF had impaired left atrial function and left ventricular ejection fraction and strain indices (all P <0.05 versus controls). MBF was impaired in patients both under baseline conditions (1.21±0.24 mL/min per g·[mm Hg·bpm/10 4 ] −1 versus 1.34±0.28 mL/min per g·[mm Hg·bpm/10 4 ] −1 in controls, P =0.044) and during adenosine stress (2.29±0.48 mL/min per g versus 2.73±0.37 mL/min per g in controls, P <0.001). Under baseline conditions, MBF correlated with left ventricular strain and left atrial function (all P ≤0.001), so that cardiac function was most impaired in patients with the lowest MBF . Baseline and stress MBF remained unchanged postablation (both P =ns), and baseline MBF showed similar correlations with functional indices to those present preablation (all P ≤0.001). Conclusions Baseline and stress MBF are significantly impaired in patients with AF but no epicardial coronary artery disease. Reduction in MBF is proportional to severity of left ventricular and left atrial dysfunction, even after successful ablation. Coronary microvascular dysfunction may be a relevant pathophysiological mechanism in patients with a history of AF .

Introduction Cardiac Resynchronisation Therapy (CRT) is an effective therapy for selected patients with heart failure, but is limited in some patients by inability to place the left ventricular (LV) lead via the coronary sinus. We have developed an alternative technique, placing the LV lead endocardially through an interventricular septal puncture. We now report the results of a pilot study assessing this technique, and in addition assessing the optimal endocardial pacing site. Methods All patients were anticoagulated with INR 2.5–3.5. A superior approach ventricular transseptal puncture using RF energy was performed. We undertook endocardial LV electrical activation mapping. Acute haemodynamic response (AHR) to CRT was assessed at the site of latest electrical activation (LEA), at the site of latest mechanical activation (LMA) as assessed on pre-procedure speckle-tracking echocardiography, and at an empirical lateral position. An active-fixation pacing lead was delivered through the septum to the site with optimal haemodynamics. Patients were followed up at 6 months with the Packer Clinical Composite Score (CCS) which categorises HF patients as clinically improved or worsened. AHR results were compared with generalised mixed-effects multi-level linear modelling. Results 18 patients were recruited, 13 with failed transvenous LV lead placement and 5 non-responders to standard CRT with poor LV lead position. Age was 66 ± 12, 83% male, QRSD 156 ± 14 ms, ischaemic 44%, NYHA class 2.9 ± 0.6, EF 28 ± 7%, CHADS-VASc score 3.6 ± 1.4 (all mean+/-SD). AHR could be assessed in 17 patients; the optimal site was at the LEA in 8, at the LMA in 6 and lateral in 2. Overall there was no significant difference in AHR between the LEA and LMA. Electrical delay >100ms was a significant multivariate predictor of AHR, but placement at the LMA site was not.Abstract 56 Figure 1 Acute haemodynamic response to biventricular pacing at the sites of latest electrical and mechanical activation The procedure was successful in all and safe with no serious complications, and two wound haematomas. Packer clinical composite score improved at 6 months in 57%, and was worse in 43%. LV ejection fraction improved >5% in 71%, from 28+/-7% to 39+/-9%. 6 min walking distance improved >10% in 75%, from 256+/-128m to 314+/-111m.Abstract 56 Figure 2 Response to CRT as assessed by LVEF One patient suffered a lacunar ischaemic stroke after 5 months with partial neurological recovery, associated with labile INRs. Another died of pneumonia after 3 months. Conclusions LV endocardial pacing via interventricular septal puncture in patients in whom standard CRT is not possible is similarly effective and durable, with reasonable risks. Optimal pacing sites may need personalisation to the patient, but a lateral position with a long electrical delay is a reasonable empirical site.

Aims:Endocardial left ventricular (LV) pacing for Cardiac Resynchronization Therapy has been proposed as an alternative to conventional LV lead placement via the coronary sinus. In order to assess the relative benefits and risks of this technique, we have performed a meta-analysis of published reports. Methods and results:A systemic search was performed using online databases to identify studies of lead-based endocardial pacing. A random-effects meta-analysis was performed, to assess the rate of complications and clinical response (defined as ≥1 decrease in NYHA class). We selected 23 studies, including 384 patients. The trans-atrial septal technique was used in 20 studies, 1 used the trans-ventricular apical technique, and 2 used the trans-ventricular septal technique. Mean age was 66 years, male 66%, EF 26%, NYHA class 3.0. Procedural success rates were over 95% in all studies. Clinical response was reported by 16 studies for 262 patients, giving a response estimate of 82% (95% CI 71-89%). There was significant heterogeneity, and response in the only large study was 59%. Thromboembolic (TE) complications were reported by all studies, over 22 ±32 months follow up. The rate of stroke was 2.5 events per 100 patient years (95% CI 1.5-4.3), and TIA 2.6 (1.1-6.1). The mortality rate was 4.5 (1.5-13.6) per 100 patient years. Conclusion:LV endocardial pacing appears to be a viable technique when conventional lead placement is not possible. Response rates were heterogeneous but comparable with conventional CRT. There is likely to be a small increase over expected rates of stroke, although included patients were high risk.

Aims Oesophageal temperature monitoring is currently used during atrial fibrillation (AF) ablation to prevent atrio-oesophageal fistula. The aim of our study was to investigate if oesophageal temperature alerts, leading to early termination of radiofrequency (RF) energy and/or reduction in power during pulmonary vein isolation, can promote pulmonary vein reconnection (PVR). Methods and results Patients undergone two consecutive AF ablation procedures with a three-dimensional electro-anatomical mapping system and oesophageal temperature monitoring were studied. Any lesions causing oesophageal temperature rises >39°C during the index procedure, leading to premature cessation of RF and/or reduction in power, were labelled on the left atrial geometry in a different colour from standard uninterrupted RF lesions. Acute (at the time of the index procedure) and chronic (at the time of there-do procedure) PVR and the site of subsequent re-isolation were compared with the lesion markers for temperature alerts from the index procedure. Fifty-four patients were included (36 male, mean age 68 ± 8, 59% persistent AF). Forty-six PVs (21% of the total) in 30 patients (56%) had been subject to at least one temperature alert during the index procedure. In 12 patients, 23 PVs had acute PVR requiring further ablation. At the re-do procedure, 103 PVs were found to be reconnected in 44 patients. No correlation was found between the occurrence of temperature alerts at the index procedure and acute or chronic PVR in the associated PV. Conclusion Just over half of patients undergoing PV isolation will have an oesophageal temperature alert, however, precautionary oesophageal temperature monitoring does not compromise ablation efficacy.

Introduction: Atrial fibrillation (AF) is associated with non-ST elevation myocardial infarction independently of atherosclerotic risk factors, and patients with AF can present with evidence of cardiac ischemia in the absence of epicardial coronary artery disease (CAD). Hypothesis: We hypothesised that absolute myocardial perfusion would be impaired and related to left ventricular (LV) dysfunction in patients with “lone” AF and no significant comorbidities or CAD, even after catheter ablation. Methods: Patients with lone paroxysmal or persistent AF underwent cardiac magnetic resonance (1.5 Tesla) for the evaluation of LV strain, and myocardial perfusion with absolute quantification of myocardial blood flow (MBF) both at baseline and during adenosine stress, before (n=49) and 6-9 months after (n=40) catheter ablation. Analyses were blinded, and results compared with those from matched controls in sinus rhythm (n=25). Results: Patients with AF had LV dysfunction compared to controls (P<0.001 for peak systol...

Background: Low radiofrequency powers are commonly used on the posterior wall of the left atrium for atrial fibrillation ablation to prevent esophageal damage. Compared with higher powers, they require longer ablation durations to achieve a target lesion size index (LSI). Esophageal heating during ablation is the result of a time-dependent process of conductive heating produced by nearby radiofrequency delivery. This randomized study was conducted to compare risk of esophageal heating and acute procedure success of different LSI-guided ablation protocols combining higher or lower radiofrequency power and different target LSI values. Methods: Eighty consecutive patients were prospectively enrolled and randomized to one of 4 combinations of radiofrequency power and target LSI for ablation on the left atrium posterior wall (20 W/LSI 4, 20 W/LSI 5, 40 W/LSI 4, and 40 W/LSI 5). The primary end point of the study was the occurrence and number of esophageal temperature alerts per patient during ablation. Acute indicators of procedure success were considered as secondary end points. Long-term follow-up data were also collected for all patients. Results: Esophageal temperature alerts occurred in a similar proportion of patients in all groups. Significantly, shorter radiofrequency durations were required to achieve the target LSI in the 40 W groups. Less than 50% of the radiofrequency lesions reached the target LSI of 5 when using 20 W despite a longer radiofrequency duration. A lower rate of first-pass pulmonary vein isolation and a higher rate of acute pulmonary vein reconnection were recorded in the group 20 W/LSI 5. A lower atrial fibrillation recurrence rate was observed in the 40 W groups compared with the 20 W groups at 29 months follow-up. Conclusions: When guided by LSI, posterior wall ablation with 40 W is associated with a similar rate of esophageal temperature alerts and a lower atrial fibrillation recurrence rate at follow-up if compared with 20 W. These data will provide a basis to plan future randomized trials. Registration: URL: https://www.clinicaltrials.gov . Unique identifier: NCT02619396.