BACKGROUND:Prior studies show that atrioventricular interval modulation (AVIM) therapy provides immediate, substantial, and sustained clinically meaningful reductions in ambulatory and office systolic blood pressures (SBPs) in hypertensive patients with pacemakers. OBJECTIVES:The goal of this study was to assess the acute and chronic mechanisms by which AVIM therapy reduces blood pressure and assess the impact of lead location on these mechanisms. METHODS:Acute hemodynamic effects were assessed by invasive pressure-volume (PV) analysis in hypertensive subjects (N = 16) with intact atrioventricular (AV) conduction. The impact of standard right ventricular pacing (RVp) vs left bundle branch area pacing (LBBAp) was also evaluated. Chronic effects of AVIM therapy were assessed by using noninvasive PV analysis with data from a subgroup of subjects (n = 32) from the MODERATO II study (NCT02837445). RESULTS:Acutely studied subjects had average office SBP of 144 ± 25 mm Hg despite antihypertensive medications. AVIM therapy significantly reduced end-diastolic volume (-12.6 ± 14.0 mL with RVp [P = 0.003]; -18.6 ± 16.2 mL with LBBAp [P < 0.001]) and effective arterial elastance (-0.23 ± 0.39 mm Hg/mL with RVp [P = 0.032]; -0.31 ± 0.55 mm Hg/mL with LBBAp [P = 0.037]), leading to significant SBP reductions (-17.1 ± 10.1 mm Hg with RVp [P < 0.001]; -19.2 ± 12.6 mm Hg with LBBAp [P < 0.001]). Neither left ventricular (LV) end-systolic nor end-diastolic properties were significantly affected by AVIM therapy at either pacing site. Noninvasive PV analysis showed similar reductions in SBP (-11.7 ± 21.8 mm Hg; P = 0.023) and reductions of end-diastolic volume (-21.5 ± 19.2 mL; P = 0.005 vs control) indicative of reverse remodeling. CONCLUSIONS:AVIM therapy acutely reduces SBP by decreasing preload and effective arterial elastance unrelated to lead location without affecting LV end-systolic or end-diastolic function. Chronic AVIM therapy reduces SBP and end-diastolic volume indicative of favorable reverse LV remodeling.

INTRODUCTION:Concomitant pulmonary vein isolation (PVI) and left atrial appendage (LAA) occlusion (LAAO) have become frequently used therapies. Pulsed-field ablation (PFA), will likely be used for combined PVI plus LAAO procedures. However, there may be concerns regarding the malposition of the LAAO device attributed to the potential tissue edema after PVI. AIM:We aimed to compare the LAA's size before and after PVI performed with the pentaspline catheter, measured intraprocedural by intracardiac echocardiography or transesophageal echocardiography. METHODS:We conducted a multicenter, prospective, observational study investigating PVI using the Farapulse system. The anteroposterior diameter of the left-sided pulmonary vein (LPV), left atrial ridge, and LAA were measured before and after the PFA. RESULTS:We enrolled 91 patients aged 63 ± 10 years, 36% were women, and 47% had paroxysmal AF. The most common comorbidities was hypertension (59%). Procedure time and left atrial dwell time were 65 (52-80) min, and 27 (24-32) min, respectively. The diameter of the LAA was not different before and after the PVI (15 [13-18] and 16 [13-19], respectively; p = 0.756). On the other hand, the diameter of the left atrial ridge (7 [6-8] and 8 [6-8]) and the LPV (13 [10-15] and 13 [11-15]) was smaller before ablation compared to the diameter after PVI (p < 0.0001 for both). No major complications occurred. CONCLUSION:LAA anteroposterior diameter does not change after PVI with PFA. Although there is a significant change in the anteroposterior diameters of the LPV and the left atrial ridge, it does not seem clinically relevant. If significant edema formation is detected in a single case after PVI, postponing the LAAO procedure should be considered.

Atrial fibrillation (AF) is the most common supraventricular arrhythmia and a major cause of stroke and systemic embolism. The left arial appendage (LAA) is the predominant site of thrombus formation in AF. According to current guidelines, oral anticoagulant (OAC) therapy is recommended in patients with elevated thromboembolic risk. Non-vitamin K antagonist oral anticoagulants (NOACs) are currently preferred over Vitamin K antagonists (VKAs) due to favorable safety profiles. Nevertheless, a subset of patients develop LAA thrombi despite optimal anticoagulant therapy, a clinical scenario not addressed by current guidelines. Recent retrospective studies, including our own cohort analysis, suggest, that modifying antithrombotic regimen may improve thrombus resolution in these cases. However, no prospective trials have yet defined the optimal strategy. This mini-review summarizes the available evidence, highlights the limitations of current practice, and proposes directions for future research in this underrecognized clinical dilemma.

Pulmonary vein isolation (PVI) is the most effective means of maintaining sinus rhythm in atrial fibrillation (AF); point-by-point radiofrequency (RF) catheter ablation is a widely used approach to PVI. High power short duration (HPSD) and very high power short duration (vHPSD) e.g., 90W and 4 sec) are increasingly popular technologies, featuring higher power and shorter application durations compared to previous methods. In recent years multiple studies assessed the efficacy vHPSD PVI, all of which show similar arrhythmia recurrence rates to the HPSD technology. This, combined with an unprecedented reduction in procedural time, makes vHPSD a popular alternative to lower power modalities. Nevertheless, to date no randomized comparison exists between the HPSD and the vHPSD technology regarding arrhythmia recurrence. In our study we aimed to analyze the data pooled from two single-center randomized trials comparing PVI performed with HPSD ablation using 50W power to vHPSD using 90W power: a) the HPSD-Remap study, conducted to assess PVI durability using mandated invasive remapping at three months after ablation, and b) the HPSD-Esophagus study, aimed at comparing esophageal safety of the two technologies using post-procedural endoscopy. Patients who underwent additional ablation at the three-month remap procedure and those lost to follow-up were excluded. Demographic and procedural data was obtained from the respective trial databases while recurrence data was collected during the regular clinical follow-up visits. Minimal follow-up time was one year. Recurrence was defined as either a) 12-lead ECG recording of atrial fibrillation, b) sustained atrial fibrillation episode registered using an implanted device, or c) the reporting of sustained symptoms which the patient identified as atrial fibrillation. Overall 90 (53%) patients from the vHPSD group and 79 (47%) patients from the HPSD group were analyzed. 107 (63%) patients had paroxysmal atrial fibrillation, mean left ventricular ejection fraction was 57%, and the mean age was 63 ±10 years. Ablation time was shorter in the vHPSD group (27±13 vs. 33±12 minutes, p=0.004) There was a trend towards shorter procedure time in the vHPSD group 65±22 minutes vs. 69±18 minutes, p=0.07. Left atrial dwell time was similar at 48±18 minutes (vHPSD) vs. 52±16 minutes (HPSD), p=0.18. The median follow-up time was 21 (14-30) months. Atrial fibrillation recurrence was observed in 15 (19%) vs. 22 (24%) for the HPSD and the vHPSD group, respectively. Cox regression revealed no significant difference between the two groups, HR: 1.43 (0.75 – 2.74) p=0.277. Analyzing the pooled data from two randomized studies, we found no significant difference between atrial fibrillation recurrence following pulmonary vein isolation using HPSD (50W) and vHPSD (90W) technologies. Ablation time was significantly shorter in the vHPSD group, while the total procedure time was similar.

Left atrial appendage (LAA) thrombus is the primary cause of stroke and systemic embolism in atrial fibrillation (AF). Non-vitamin-K oral anticoagulants (NOACs) effectively reduce LAA thrombus prevalence and stroke risk. However, the optimal treatment of a NOAC-resistant thrombus remains unclear. We aimed to evaluate therapeutic strategies for resolving LAA thrombus in patients on optimal NOAC therapy. We retrospectively analyzed patients scheduled for cardioversion or catheter ablation of AF between 2014 and 2023 with LAA thrombus on transesophageal echocardiography (TEE) despite being on optimal NOAC therapy. We assessed how the applied management strategy affected thrombus resolution. Among the analyzed 120 patients, a change to a different NOAC occurred in 41

Aims:We hypothesize that sinus rhythm (SR) maintenance in persistent atrial fibrillation (AF) patients taking anti-arrhythmic drugs (AADs) after pre-procedural electrical cardioversion (ECV) could predict outcomes after catheter ablation procedures. Methods and results:219 persistent AF patients on AADs underwent ECV 1-6 months before ablation. Patients were categorized into two groups according to their response to ECV: patients in whom SR was restored and maintained until the ablation procedure (ECV-SR group), and patients with AF recurrence before the procedure (ECV-AF group). Then, 1:1 propensity score matching was used to create study groups (94-94 patients). The efficacy outcomes of the present study were freedom from atrial tachyarrhythmia on/off AADs following a single ablation procedure and recurrence of persistent AF. The median follow-up duration was 42 (20-73) months. Freedom from atrial tachyarrhythmia at 36 months was lower in the ECV-AF group compared to ECV-SR patients (31.4% vs. 51.2%, respectively; crude HR = 2.58, 95% CI = 1.58-3.70, P < 0.001). The most frequent pattern of atrial arrhythmia recurrence was persistent AF in the ECV-AF group and paroxysmal AF in the ECV-SR group. Freedom from persistent AF at 36 months was 54% and 84.3%, respectively (crude HR = 3.72, 95% CI = 1.94-7.14, P < 0.001). Differences in the risk of the efficacy outcomes were similar after multi-variable adjustment and in all analysed subgroups, including pulmonary vein isolation (PVI)-only procedures. Conclusion:Our findings indicate that the positive response to pre-procedural ECV may be a valuable marker for identifying persistent AF patients in whom a PVI-only strategy is sufficient.

Background:Catheter ablation using pulsed-field energy may penetrate deeper into scarred tissue than thermal energies; however, evidence regarding its role in treating ventricular arrhythmias (VAs) is limited. In this prospective study, we report our current experience on pulsed field ablation (PFA) with pentaspline catheter for the treatment of premature ventricular contractions (PVCs) originating from the right ventricular outflow tract (RVOT) and scar-related ventricular tachycardias (VTs). Methods:Consecutive VA patients who underwent PFA with Farapulse system were enrolled. Seven patients underwent ablation for idiopathic RVOT PVCs, and five patients with structural heart disease underwent ablation for scar-related VTs. The recurrence of arrhythmias was assessed by 24-hour Holter electrocardiography monitoring or implantable cardioverter defibrillator interrogation. Results:Twelve patients were enrolled, age 51 ± 9 years, nine were men, four had previously failed radiofrequency ablation. Procedural and fluoroscopy times were 53 (41-105) minutes and 8 (4-20) minutes, respectively. The median number of PFA applications was 20 ± 13 in the VT group and 8 (7-8) in the PVC group. Acute procedural success was achieved in 92% (CI 62%-100%) of patients. During a mean follow-up of 100 (97-140) days, freedom from VT was 80% (CI 28%-99%), and a PVC burden <1% was achieved in 71% (CI 29%-96%) of patients. Conclusion:The ablation of idiopathic RVOT PVCs and scar-related VTs with the pentaspline PFA catheter is feasible, with good acute and mid-term efficacy observed in our cohort. Further research involving larger cohorts and longer follow-up periods is needed to analyze the safety and define the role of PFA in VAs.

Atrial fibrillation (AF) often leads to structural remodeling of the heart, increasing the risk of heart failure, stroke and death. The primary challenges remain the progression of atrial cardiomyopathy and AF recurrence after ablation. Pulsed-field ablation (PFA) is a novel, tissue-selective modality of catheter ablation of AF. Data regarding the effect of PFA beyond PVI is limited. Extensive radiofrequency ablation carries the risk of stiff left atrium (LA) syndrome, associated with pulmonary hypertension and symptoms of heart failure. Our goal was to investigate the effect of extensive PFA on LA function and development of stiff LA syndrome. The aim of the study was to measure left atrial strain and fibrosis after AF ablation in two patient groups: PVI only and PVI plus additional ablation. Patients with symptomatic AF who underwent PFA as an initial ablation between March 2023 and April 2024 were enrolled. The study groups consisted of patients who underwent pulmonary vein isolation only (PVI only) and those who had additional ablation of either two including the roof, mitral isthmus, posterior wall or anterior wall (PVI plus). The ablation strategy was left to the operating physician’s discretion. All patients were scheduled for speckle-tracking echocardiography, laboratory tests including fibrosis marker analysis and completion of a quality of life questionnaire. Seventy-eight patients were enrolled with a median age of 63 (55-70) years, 50 (64%) were male. The scheduled tests were carried out a median 144 (97-171) days after the procedure. Patients in the PVI plus group (n=27; 35%) had significantly larger LA volume (p=0.042), lower LA reservoir strain (LArS, p=0.003), but higher LA contractile strain (p=0.007). LA stiffness measured by medial and lateral e/E' – to - LArS ratio showed reduced LA compliance (p<0.001 and 0.005, respectively). However, there was no difference in pulmonary artery systolic pressure (32.5 [28.5-39.8] vs. 30 [27.5-38.5], p=0.42) between the two groups. Quality of life measured by the AFEQT questionnaire was similar among the groups (p=0.55). The 12-month follow-up for AF freedom and fibrosis marker analyses are still ongoing. Patients who underwent an extensive initial PFA had significantly higher LA reservoir strain and reduced LA compliance compared to the PVI only group with similar patient reported outcomes. Although LA stiffness was increased in PVI plus group, no clinical signs of stiff LA syndrome was observed.

Atrial fibrillation (AF) is a prevalent cardiac arrhythmia associated with increased morbidity and mortality. Pulmonary vein isolation (PVI) is an effective treatment for AF; however, recurrence after ablation remains a significant clinical challenge. Identifying predictors of AF recurrence is essential for optimising post-ablation patient management. Holter monitoring provides continuous electrocardiographic data and may reveal patterns predictive of recurrence. To identify predictors of AF recurrence after ablation by analyzing post-operative Holter monitoring data. We conducted a retrospective study involving patients who underwent PVI for AF. The dataset included intervention details, clinical history, and echocardiographic parameters collected from 2020 to 2024. We excluded those Holter recordings, where a recurrence of AF was observed. We analyzed Holter measurements during two 4-hour segments during daytime ("peri-noon", 10:00–14:00) and night time ("peri-midnight", 22:00–02:00). From these segments, we calculated heart rate variability (HRV) and P-wave, PR-interval duration distribution. A total of 92 patients had Holter monitoring within the three-year follow-up period. AF recurrence was observed in 30 patients. P-wave duration during the night significantly predicted AF recurrence, with a univariate Cox regression hazard ratio (HR) of 1.60 (95% confidence interval [CI]: 1.09–2.34; p = 0.017). A longer PR interval during both day and night periods predicted recurrence (day: HR 1.87 [95% CI: 1.33–2.63], night: HR 1.80 [95% CI: 1.25–2.60]; p < 0.001). From the HRV data, the 80th percentile of normal-to-normal (NN) intervals was the most important predictor (HR 1.76 [95% CI: 1.19–2.61]; p = 0.004). Easily obtainable parameters from Holter ECG recordings may significantly contribute to the prediction of atrial fibrillation recurrence after pulmonary vein isolation. Furthermore, analyzing samples from different time periods of the day may have distinct predictive power. In particular,a longer P-wave duration during the peri-midnight period and a longer PR interval in both the peri-midnight and the peri-noon samples showed a correlation with AF recurrence.

Aims We aimed to externally validate the SEMMELWEIS-CRT score for predicting 1-year all-cause mortality in the European Cardiac Resynchronization Therapy (CRT) Survey I dataset-a large multi-centre cohort of patients undergoing CRT implantation. Methods and results The SEMMELWEIS-CRT score is a machine learning-based tool trained for predicting all-cause mortality in patients undergoing CRT implantation. This tool demonstrated impressive performance during internal validation but has not yet been validated externally. To this end, we applied it to the data of 1367 patients from the European CRT Survey I dataset. The SEMMELWEIS-CRT predicted 1-year mortality with an area under the receiver operating characteristic curve (AUC) of 0.729 (0.682-0.776), which concurred with the performance measured during internal validation [AUC: 0.768 (0.674-0.861), P = 0.466]. Moreover, the SEMMELWEIS-CRT score outperformed multiple conventional statistics-based risk scores, and we demonstrated that a higher predicted probability is not only associated with a higher risk of death [odds ratio (OR): 1.081 (1.061-1.101), P < 0.001] but also with an increased risk of hospitalizations for any cause [OR: 1.013 (1.002-1.025), P = 0.020] or for heart failure [OR: 1.033 (1.015-1.052), P < 0.001], a less than 5% improvement in left ventricular ejection fraction [OR: 1.033 (1.021-1.047), P < 0.001], and lack of improvement in New York Heart Association functional class compared with baseline [OR: 1.018 (1.006-1.029), P = 0.003]. Conclusion In the European CRT Survey I dataset, the SEMMELWEIS-CRT score predicted 1-year all-cause mortality with good discriminatory power, which confirms the generalizability and demonstrates the potential clinical utility of this machine learning-based risk stratification tool.

BackgroundWe aimed to correlate left atrial appendage (LAA) structure and function with the history of stroke/transient ischemic attack (TIA) in patients with atrial fibrillation (AF).MethodsWe analyzed data of 649 patients with AF who were scheduled for catheter ablation. Patients underwent cardiac CT and transesophageal echocardiography prior to ablation. LAA morphologies depicted by cardiac CT were categorized into four groups: cauliflower, chicken wing, swan and windsock shapes. ResultsMean age was 61.3±10.5 years, 33.9% were female. Prevalence of stroke/TIA was 7.1%. After adjustment for the main risk factors, LAA flow velocity ≤35.3 cm/sec (OR=2.18; 95%CI=1.09-4.61; p=0.033) and swan LAA shape (OR=2.69; 95%CI=0.96-6.86; p=0.047) independently associated with higher, while windsock LAA morphology with lower risk of stroke/TIA (OR=0.32; 95%CI=0.12-0.77; p=0.017) as compared to cauliflower LAA shape. When comparing the differences between LAA morphology groups, we measured significantly smaller LAA orifice area (389.3±137.7 mm2 in windsock vs 428.3±158.9 ml in cauliflower, p=0.021) and LAA volume (7.4±3.0 mm2 in windsock vs 8.5±4.8 mm2 in cauliflower, p=0.012) in patients with windsock LAA morphology, while LAA flow velocity did not differ significantly. ConclusionReduced LAA function and swan LAA morphology were independently associated with higher, while windsock LAA shape with lower prevalence of stroke/TIA. When comparing the differences between the various LAA morphology types, significantly lower LAA volume and LAA orifice area were measured in windsock LAA shape as compared to cauliflower LAA shape.

BACKGROUND:Radiofrequency catheter ablation (RFCA) is a well-established treatment for atrial fibrillation (AF). Fluoroscopy, a widely used imaging method for RFCA, has significant implications for human health. Although no fluoroscopy or near-zero fluoroscopy strategies have gained popularity, they have limitations, such as long procedure times, additional equipment, and expertise. A simple and cost-effective radiation reduction method is needed for treating AF and is compatible with the daily workflow. We aimed to compare the efficacy and safety of fluoroscopy-free and lead apron-free (LAF) after transseptal puncture AF ablation with conventional ablation (CON). METHODS:This retrospective study included all patients who underwent RF catheter AF ablation. The lead apron used for protection was removed immediately before 3D reconstruction of the left atrium (LA) after transseptal puncture (TSP), while fluoroscopy was performed on stand-by and locked-in. The pulmonary vein isolation (PVI) was performed using a 3D mapping system, a multielectrode catheter, and a Smart Touch contact force (CF) sensing catheter, via the lead-apron-free (LAF) method, which is similar to the conventional ablation (CON) method. RESULTS:This study enrolled 152 consecutive patients, with 72 and 80 patients in the LAF and CON groups, respectively. The LAF group demonstrated significantly lower values in total fluoroscopy time (6.9 vs. 14 min, P<0.001) and dose area product (DAP) values (15.4±12.1 vs. 31.5±17.4 G/m2, P<0.001) than the CON group. However, there was no significant difference in the total procedure time (83.6±21.1 vs. 77.2±11.4 min, P=0.12) between the two groups. Only four procedures (5.5%) required repositioning of the apron, and no complications were observed with the LAF method. Pulmonary vein isolation was achieved in all patients. CONCLUSIONS:The LAF method reduced fluoroscopy use compared with CON, with no change in procedure time or efficacy.

Abstract Introduction The BUDAPEST CRT Upgrade trial has established the strong clinical benefit of upgrading heart failure patients with a reduced left ventricular (LV) ejection fraction (HFrEF) and a high right ventricular pacing (RVP) burden to cardiac resynchronization therapy with defibrillator (CRT-D). Importantly, however, the CRT upgrade response is not homogeneous regarding LV reverse remodeling and associated clinical outcomes. The presence of mechanical dyssynchrony (MD) assessed by echocardiography has been linked to more CRT benefits; still, its change in response to CRT and added prognostic value in HFrEF patients with high RVP are scarcely investigated. Purpose Accordingly, we aimed to assess the prevalence, clinical characteristics, CRT response rate, and prognostic value of RVP-induced MD in the BUDAPEST CRT Upgrade cohort. Methods The multicentre, randomized, controlled trial enrolled 360 HFrEF patients with a pacemaker or implantable cardioverter defibrillator (ICD) and significant RVP (≥ 20%) who were randomly assigned to receive CRT-D upgrade or ICD in a 3:2 ratio. Protocol echocardiography was performed at baseline and at 12-month follow-up visits and was evaluated at a central core lab. Beyond LV end-diastolic (EDV) and end-systolic volumes (ESV), longitudinal strain-derived septal deformation patterns by speckle tracking were assessed to determine the presence of RVP-induced MD. The endpoints were volumetric non-response (defined by a relative decrease in LV ESV <15%) and the composite of volumetric non-response or HF hospitalization. Results The echocardiographic assessment was feasible in 325 patients at baseline; 133 (41%) patients presented with MD. Females were more likely to present with MD (female vs. male, 65% vs. 38%, p=0.003). MD patients had higher LV EDV (MD vs. no-MD, 248±78 vs. 219±78 mL, p=0.001) and LV ESV (190±67 vs. 165±64 mL, p<0.001) at baseline. In the CRT-D group, 126 (75%) patients were volumetric responders, and 41 (25%) were non-responders at 12 months. CRT patients with baseline MD were less likely to experience volumetric non-response (OR 0.35 [95% CI 0.15-0.82], p=0.015) or the composite endpoint (OR 0.37 [95% CI 0.17-0.77], p=0.008). Out of 57 CRT patients with baseline MD who had follow-up assessment available, 52 (91%) patients had a favorable change: the MD pattern disappeared. Patients with MD resolution at 12 months were less likely to experience volumetric non-response or the composite endpoint (OR 0.39 [95% CI 0.17-0.93], p=0.034; OR 0.38 [95% CI 0.16-0.86], p=0.021, respectively). CRT patients with resolved MD were less likely of ischemic etiology and had 100% posterior or lateral LV lead location. Conclusions The presence of RVP-induced MD and its resolution is associated with better clinical response in HFrEF patients undergoing CRT-D upgrade. MD assessment can refine patient selection algorithms of CRT.Figure 1

Abstract Background The beneficial effects of mineralocorticoid receptor antagonists (MRAs) regarding sudden cardiac death (SCD) risk and cardiac remodeling are well known, moreover, they also reduce episodes of ventricular tachycardia (VT). However, superiority in effectiveness between receptor selective eplerenone and conventional spironolactone is unknown. Purpose Our aim was to assess the effect of eplerenone and spironolactone on ventricular tachycardia (VT) recurrence in patients with ischemic heart disease (IHD). Methods We collected data of 563 patients with IHD following hospitalization due to a sustained VT episode in a structured registry. Propensity score matching was performed based on age, hypertension, diabetes, history of acute myocardial infarction, left ventricular ejection fraction (LVEF) and presentation with incessant VT. The matched population consisted of 188 patients and was further analyzed. Predictors were assessed using univariate and multivariate Cox regression models. Kaplan-Meier curves were used for time-to-event analyses. Results The median age was 70 years with 81% being male. One third of the patients had an ICD implanted, while 43 (23%) had CRT. The median LVEF was 30%. Twenty-five (13%) patients presented with an electrical storm and 19 (10%) had incessant VT. In 86 cases (46%), the VT caused hemodynamic instability. Ablation was performed in 66 patients (35%), while 4 required mechanical circulatory support. During the median follow-up of 856 [399-1624] days, 69 patients had VT recurrence and 118 patients died. Eplerenone use significantly reduced the risk of VT recurrence compared to spironolactone (HR: 0.48 [0.29-0.78], log-rank p=0.003). This effect was consistent in the multivariate model as well (p=0.006). Conclusions Eplerenone use may be more beneficial in terms of VT recurrence in patients with IHD who present with a sustained VT. Further analysis is required to confirm these findings.

Background: Atrial fibrillation (AF) recurrence after pulmonary vein isolation (PVI) is predominantly attributed to pulmonary vein reconnection (PVR). Predictors of AF recurrence have been widely studied; however, data are scarce on procedural parameters that predict chronic PVR. We aimed to study PVR rates and predictors of PVR. Methods: We retrospectively included 100 patients who underwent repeated ablation due to AF recurrence after initial PVI with the CARTO system. PVR was determined during the repeated procedure by electrophysiological evaluation, and initial procedural characteristics predicting PVR were studied, including adherence to the CLOSE protocol, use of high power, first-pass isolation (FPI), and baseline generator impedance (BGI). Results: Thirty-eight patients underwent initial CLOSE-guided PVI, and sixty-two underwent initial non-CLOSE PVI. A repeat procedure was performed 23 ± 16 months after the initial procedure. In total, PVR was found in 192 of 373 PVs (51.5%), and all PVs were isolated in 17/100 (17%) patients. Factors associated with all PVs being isolated were adherence to the CLOSE protocol, a higher power setting, the presence of bilateral FPI, and lower BGI (88% vs. 28%, p < 0.0001; 37.5 W vs. 30 W, p = 0.0276; 88.2% vs. 40.4%, p = 0.0007; and 127.6 Ω vs. 136.6 Ω, p = 0.0027, respectively). In initial procedures with adherence to the CLOSE protocol, the FPI rate was significantly higher (73.7% vs. 25%, p < 0.0001), while there were no significant differences in terms of procedure time and left atrial dwell time (81 vs. 85 min, p = 0.83; and 60 vs. 58 min, p = 0.08, respectively). BGI ≥ 130 Ω (AUC = 0.7403, sensitivity: 77.1%, specificity: 68.8%, p = 0.0032) was associated with a significantly higher probability of PVR (OR = 6.757; p < 0.0001). In multivariable analysis, independent predictors for PVR were non-adherence to the CLOSE protocol and BGI ≥ 130 Ω. Conclusions: Our findings indicate that adherence to the CLOSE protocol and baseline generator impedance < 130 Ω during AF ablation are independent predictors of PVI durability.