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Atrial fibrillation (AF) is a prevalent arrhythmia, while pulmonary vein isolation (PVI) has become a cornerstone in its treatment. The creation of durable lesions is crucial for successful and long-lasting PVI, as inconsistent lesions lead to reconnections and recurrence after ablation. Various approaches have been developed to assess lesion quality and transmurality in vivo, acting as surrogates for improved lesion creation and long-term outcomes utilizing radiofrequency (RF) energy. This review manuscript examines the biophysics of lesion creation and different lesion assessment techniques that can be used daily in the electrophysiology laboratory when utilizing RF energy. These methods provide valuable insights into lesion effectiveness, facilitating optimized ablation procedures and reducing atrial arrhythmia recurrences. However, each approach has its limitations, and a combination of techniques is recommended for comprehensive lesion assessment during AF catheter ablation. Future advancements in imaging techniques, such as magnetic Resonance Imaging (MRI), optical coherence tomography, and photoacoustic imaging, hold promise in further enhancing lesion evaluation and guiding treatment strategies.

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AIMS: Pulsed field ablation (PFA) is a novel, non-thermal, cardiac tissue-selective ablation modality. To date, radiofrequency (RF)-guided high-power short-duration (HPSD) ablation represents the gold standard besides cryo-ablation for pulmonary vein isolation (PVI). This single-centre, retrospective study investigated the efficacy of PFA-PVI vs. HPSD-RF PVI in terms of single-procedure arrhythmia-free outcome and safety in a real-world setting. METHODS AND RESULTS: Consecutive, paroxysmal atrial fibrillation (AF) patients who underwent PVI using PFA or HPSD-RF were enrolled. In group PFA, PVI was performed using a pentaspline PFA catheter. The ablation procedure in group HPSD-RF was performed with RF energy (45 W, ablation index). A total of 410 patients (group PFA, 201; group HPSD-RF, 209) were included. There was no difference between both groups regarding age, gender, and CHA2DS2-VASc score. The procedure time was significantly shorter in group PFA [61 (44-103) vs. 125 (105-143) min; P < 0.001]; fluoroscopy time and dose area product were significantly higher in group PFA [16 (13-20) vs. 4 (2-5) min; P < 0.01 and 412 (270-739) vs. 129 (58-265) µGym2; P < 0.01]. The overall complication rates were 2.9% in group PFA and 6.2% in group HPSD (P = 0.158). There was one fatal stroke in the PFA group. The 1-year Kaplan-Meier estimated freedom from any atrial tachyarrhythmia was 85% with PFA and 79% with HPSD-RF (log-rank P = 0.160). In 56 repeat ablation procedures, the PV reconnection rate was 30% after PFA and 38% after HPSD-RF (P = 0.372). CONCLUSION: Both PFA and HPSD-RF were highly efficient and effective in achieving PVI in paroxysmal AF patients. The arrhythmia-free survival is comparable. The PV reconnection rate was not different.

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BACKGROUND: Personalized radiofrequency (RF) ablation for paroxysmal atrial fibrillation (PAF), adapting the ablation index (AI) to local left atrial wall thickness (LAWT), proved to be highly efficient maintaining high arrhythmia-free survival rates. However, multicentre data are lacking. This multicentre, prospective, non-randomized study was conducted at 5 tertiary hospitals and sought to assess the safety, efficacy, and reproducibility of the LAWT-guided ablation for PAF. METHODS: Consecutive patients referred for first-time PAF were prospectively enrolled. The LAWT maps were obtained from preprocedural multidetector computed tomography and integrated into the navigation system. AI was titrated according to the local LAWT, and the ablation line was personalized to avoid the thickest regions while encircling the pulmonary veins (PVs). RESULTS: A total 109 patients (60.1 ± 9.4 years, 64.2% male) were enrolled. Median procedure time was 61.7 min (48.4-83.8), fluoroscopy time was 1.0 min (0.4-3.3), and RF time was 13.9 min (12.3-16.8). Median AI tailored to the local LAWT was 393 (374-412) for the anterior wall and 340 (315-378) for the posterior wall. Right and left PVs first-pass isolation was achieved in 89% and 91.7% of the patients, respectively. At 12-month follow-up, freedom from any atrial arrhythmia was 93.4% (95% CI 88.7-98.1), without differences across centres (P = 0.169). One patient experienced femoral artery pseudoaneurysm, with no other serious procedural-related complication. CONCLUSION: The Ablate-by-LAWT study proved that LAWT-guided PV isolation for PAF is safe, effective, and efficient in a multicentre setting. Twelve-month recurrence-free survival exceeded 90% (NCT04218604).

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Background: The concept of ablation index (AI) was introduced to evaluate radiofrequency (RF) ablation lesions. It is calculated from power, contact force (CF), and RF duration. However, other factors may also affect the quality of ablation lesions. To examine the difference in RF lesions made during sinus rhythm (SR) and atrial fibrillation (AF). Methods: Sixty patients underwent index pulmonary vein isolation during SR (n = 30, SR group) or AF (n = 30, AF group). All ablations were performed with a power of 50 W, a targeted CF of 5-15 g, and AI of 400-450 using Thermocool Smarttouch SF. The CF, AI, RF duration, temperature rise (Δtemp), impedance drop (Δimp), and the CF stability of each ablation point quantified as the standard deviation of the CF (CF-SD) were compared between the two groups. Results: A total of 3579 ablation points were analyzed, which included 1618 and 1961 points in the SR and the AF groups, respectively. Power, average CF, RF duration per point, and the resultant AI (389 ± 59 vs. 388 ± 57) were similar for the two rhythms. However, differences were seen in the CF-SD (3.5 ± 2.2 vs. 3.8 ± 2.1 g, p < .01), Δtemp (3.8 ± 1.3 vs. 4.0 ± 1.3°C, p < .005), and Δimp (10.3 ± 5.8 vs. 9.4 ± 5.4 Ω, p < .005). Conclusions: Despite similar AI, various RF parameters differed according to the underlying atrial rhythm. Ablation delivered during SR demonstrated less CF variability and temperature increase and greater impedance drop than during AF.

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INTRODUCTION: The optimized ablation index (AI) value for catheter ablation of atrial fibrillation (AF) remains to be defined. We aimed to compare the efficacy and safety of CLOSE protocol and lower AI protocol in paroxysmal AF. METHODS AND RESULTS: Patients with symptomatic, drug-resistant paroxysmal AF for first ablation were prospectively enrolled from September 2020 to January 2022. The patients were randomly divided into CLOSE group (AI ≥ 550 for anterior/roof segments and ≥400 for posterior/inferior segments) and lower AI group (AI ≥ 450 for anterior/roof segments and ≥350 for posterior/inferior segments). First-pass isolation, acute pulmonary vein (PV) reconnections, 1-year arrhythmia recurrence, and major complications were assessed. Of the 270 enrolled patients, 238 completed 1-year follow-up (118 in CLOSE group and 120 in lower AI group). First-pass isolation in left PVs was higher in CLOSE group (71.2% vs. 53.3%, p = .005). Acute PV reconnections were comparable between groups (9.3% vs. 14.2%, p = .246). At 1 year, 86.4% in CLOSE group versus 81.7% in lower AI group were free from atrial arrhythmia (log rank p = .334). The proportion difference was -4.8% (95% CI: -14.1% to 4.6%), and p = .475 for noninferiority. Stroke occurred in four patients of lower AI group, and no cardiac tamponade, atrioesophageal fistula, major bleeding or death occurred post procedure. CONCLUSION: For patients with paroxysmal AF and treated by AI-guided PV ablation, lower AI is not noninferior to CLOSE protocol.

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INTRODUCTION: The utility of ablation index (AI) to guide ventricular tachycardia (VT) ablation in patients with structural heart disease is unknown. The aim of this study was to assess procedural characteristics and clinical outcomes achieved using AI-guided strategy (target value 550) or conventional non-AI-guided parameters in patients undergoing scar-related VT ablation. METHODS: Consecutive patients (n = 103) undergoing initial VT ablation at a single center from 2017 to 2022 were evaluated. Patient groups were 1:1 propensity-matched for baseline characteristics. Single lesion characteristics for all 4707 lesions in the matched cohort (n = 74) were analyzed. The impact of ablation characteristics was assessed by linear regression and clinical outcomes were evaluated by Cox proportional hazard model. RESULTS: After propensity-matching, baseline characteristics were well-balanced between AI (n = 37) and non-AI (n = 37) groups. Lesion sets were similar (scar homogenization [41% vs. 27%; p = .34], scar dechanneling [19% vs. 8%; p = .18], core isolation [5% vs. 11%; p = .4], linear and elimination late potentials/local abnormal ventricular activities [35% vs. 44%; p = .48], epicardial mapping/ablation [11% vs. 14%; p = .73]). AI-guided strategy had 21% lower procedure duration (-47.27 min, 95% confidence interval [CI] [-81.613, -12.928]; p = .008), 49% lower radiofrequency time per lesion (-13.707 s, 95% CI [-17.86, -9.555]; p < .001), 21% lower volume of fluid administered (1664 cc [1127, 2209] vs. 2126 cc [1750, 2593]; p = .005). Total radiofrequency duration (-339 s [-24%], 95%CI [-776, 62]; p = .09) and steam pops (-155.6%, 95% CI [19.8%, -330.9%]; p = .08) were nonsignificantly lower in the AI group. Acute procedural success (95% vs. 89%; p = .7) and VT recurrence (0.97, 95% CI [0.42-2.2]; p = .93) were similar for both groups. Lesion analysis (n = 4707) demonstrated a plateau in the magnitude of impedance drops once reaching an AI of 550-600. CONCLUSION: In this pilot study, an AI-guided ablation strategy for scar-related VT resulted in shorter procedure time and average radiofrequency time per lesion with similar acute procedural and intermediate-term clinical outcomes to a non-AI-guided approach utilizing traditional ablation parameters.

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Aim: To evaluate the costs and consequences of two front-line atrial fibrillation (AF) treatments from Chinese healthcare system perspective: radiofrequency catheter ablation (RFCA) using ThermoCool SmartTouch Catheter guided by Ablation Index (STAI), in comparison to antiarrhythmic drugs (AADs). Patients & methods: We simulated clinical and economic consequences for AF patients initially receiving STAI or AADs using a short-term decision tree model leading to a 10-year long-term Markov model. The model projected both clinical consequences and costs associated with, among others, AF, heart failure (HF), strokes, and deaths due to AF or AF related complications. Data informing the models included combination of a local real-world study and published clinical studies. Results: STAI was advantageous versus AADs on all 4 main clinical outcomes evaluated; AF: 25.83% lower (12.84% vs 38.67%), HF: 2.22% lower (1.33% vs 3.55%), stroke or post stroke: 1.82% lower (10.00% vs 11.82%) and deaths due to AF or AF related complications: 0.64% lower (4.11% vs 4.75%). The average total cost per patient in STAI group was ¥16,682 lower (¥123,124 vs ¥139,806). The one-way sensitivity analysis indicated that the difference in total cost was most sensitive to annual AF recurrence probability in AADs-treated patients. Probabilistic sensitivity analysis indicated a 98.5% probability that RFCA treatment would result in cost savings by the end of the 10th year. Conclusion: Radiofrequency catheter ablation using SmartTouch catheter guided by Ablation Index was superior to AADs as the first-line AF treatment in Chinese setting with better clinical outcomes and at lower costs over a 10-year time horizon.

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BACKGROUND: Ninety-watt applications are more sensitive to catheter instability and produce lesions that are shallower and smaller in diameter than 50-W applications. These characteristics were considered for the development of a combined (90-50 W) pulmonary vein isolation (PVI) strategy which was prospectively compared to a 50 W-only ablation index (AI)-guided PVI strategy. METHODS: One hundred fifty consecutive paroxysmal AF patients underwent PVI under general anesthesia using CARTO. In the first 75 patients, PVI was performed with a combined (90-50 W) strategy using the QDOT-MICRO catheter in a temperature-controlled mode. This strategy consisted of 90 W-4 s applications on the posterior LA wall (at sites of catheter stability and expectedly thin atrial tissue) with an interlesion distance (ILD) ≤ 4 mm and 50-W applications elsewhere (at sites of catheter instability or expectedly thick atrial tissue) with ILD < 6 mm. In the subsequent 75 patients, PVI was performed with a 50 W-only AI-guided strategy using the SmartTouch-SF catheter in a power-controlled mode. RESULTS: Both groups of patients had similar clinical characteristics and LA dimensions (123.1 ± 24.9 ml vs 119 ± 26.8 ml, P = 0.33). Total procedural times (61 [56-70] vs 65 [60-75] min, P = 0.12), first-pass PVI (82.6 vs 80%, P = 0.81), acute PV reconnection (0 vs 6.6%, P = 0.05), and 1-year SR maintenance (93.3 vs 90.6%, P = 0.57) rates were also similar in both groups of patients. There were no complications in the combined (90-50 W) group while only 2 groin hematomas were reported in the 50 W group. CONCLUSIONS: In paroxysmal AF patients, a combined (90-50 W) strategy for PVI did not improve safety, efficiency, or effectiveness compared to a 50 W-only AI-guided strategy.

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BACKGROUND: Real-time monitoring of generator impedance drop is not considered in CLOSE protocol pulmonary vein (PV) isolation (PVI) in patients with atrial fibrillation (AF). We verified whether additional information of impedance drop could minimize ablation index required for PVI using modified CLOSE protocol (target ablation index ≥ 500 on anterior wall and ≥400 on posterior wall along with inter-lesion distance of 3-6 mm and maximum power of 35 W) without any adverse effect of procedural data and efficacy. METHODS: Sixty consecutive Japanese AF patients [paroxysmal AF: 43 (72 %) patients] underwent first-time PVI with modified CLOSE protocol with real-time monitoring of impedance drop (impedance-guided modified CLOSE protocol). Ablation tags were colored according to impedance drop and ablation was immediately terminated before reaching target ablation index if impedance drop of ≥10â€¯Ω was confirmed. Ablation index needed for PVI, first-pass PVI rate, other procedural data, and atrial tachyarrhythmia recurrence were evaluated. RESULTS: Mean ablation index and impedance drop on anterior and posterior walls were 437.6 ±â€¯43.5â€¯Ω and 10.2 ±â€¯2.6â€¯Ω and 393.3 ±â€¯27.4â€¯Ω and 9.3 ±â€¯2.2 Ω, respectively. First-pass PVI per PV pair was accomplished in 90/120 (75 %). No complications occurred. PV gaps after first-pass ablation were locationally most often found on right posterior wall than on the other parts (p < 0.001). There were no differences in mean contact force, impedance drop, and ablation index between walls with and without PV gaps after first-pass PV ablation. During a mean follow-up of 24 ±â€¯9 months, survival from atrial tachyarrhythmia recurrence was 51/60 (85 %) patients. CONCLUSIONS: Using additional generator impedance drop information may be useful to minimize radiofrequency current application to accomplish PVI with modified CLOSE protocol while maintaining efficacy and safety in Japanese AF population.

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INTRODUCTION: Carina breakthrough (CB) at the right pulmonary vein (RPV) can occur after circumferential pulmonary vein isolation (PVI) due to epicardial bridging or transient tissue edema. High-power short-duration (HPSD) ablation may increase the incidence of RPV CB. Currently, the surrogate of ablation parameters to predict RPV CB is not well established. This study investigated predictors of RPV CB in patients undergoing ablation index (AI)-guided PVI with HPSD. METHODS: The study included 62 patients with symptomatic atrial fibrillation (AF) who underwent AI-guided PVI using HPSD. Patients were categorized into two groups based on the presence or absence of RPV CB. Lesions adjacent to the RPV carina were assessed, and CB was confirmed through residual voltage, low voltage along the ablation lesions, and activation wavefront propagation. RESULTS: Out of the 62 patients, 21 (33.87%) experienced RPV CB (Group 1), while 41 (66.13%) achieved first-pass RPV isolation (Group 2). Despite similar AI and HPSD, patients with RPV CB had lower contact force (CF) at lesions adjacent to the RPV carina. Receiver operating characteristic (ROC) curve analysis identified CF < 10.5 g as a predictor of RPV CB, with 75.7% sensitivity and 56.2% specificity (area under the curve: 0.714). CONCLUSION: In patients undergoing AI-guided PVI with HPSD, lower CF adjacent to the carina was associated with a higher risk of RPV CB. These findings suggest that maintaining higher CF during ablation in this region may reduce the occurrence of RPV CB.

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INTRODUCTION: Pulmonary vein isolations (PVI) are being performed using a high-power, short-duration (HPSD) strategy. The purpose of this study was to compare the clinical efficacy and safety outcomes of an HPSD versus low-power, long-duration (LPLD) approach to PVI in patients with paroxysmal atrial fibrillation (AF). METHODS: Patients were grouped according to a HPSD (≥40 W) or LPLD (≤35 W) strategy. The primary endpoint was the 1-year recurrence of any atrial arrhythmia lasting ≥30 s, detected using three 14-day ambulatory continuous ECG monitoring. Procedural and safety endpoints were also evaluated. The primary analysis were regression models incorporating propensity scores yielding adjusted relative risk (RRa ) and mean difference (MDa ) estimates. RESULTS: Of the 398 patients included in the AWARE Trial, 173 (43%) underwent HPSD and 225 (57%) LPLD ablation. The distribution of power was 50 W in 75%, 45 W in 20%, and 40 W in 5% in the HPSD group, and 35 W with 25 W on the posterior wall in the LPLD group. The primary outcome was not statistically significant at 30.1% versus 22.2% in HPSD and LPLD groups with RRa 0.77 (95% confidence interval [CI]) 0.55-1.10; p = .165). The secondary outcome of repeat catheter ablation was not statistically significant at 6.9% and 9.8% (RRa 1.59 [95% CI 0.77-3.30]; p = .208) respectively, nor was the incidence of any ECG documented AF during the blanking period: 1.7% versus 8.0% (RRa 3.95 [95% CI 1.00-15.61; p = .049) in the HPSD versus LPLD group respectively. The total procedure time was significantly shorter in the HPSD group (MDa 97.5 min [95% CI 84.8-110.4)]; p < .0001) with no difference in adjudicated serious adverse events. CONCLUSIONS: An HPSD strategy was associated with significantly shorter procedural times with similar efficacy in terms of clinical arrhythmia recurrence. Importantly, there was no signal for increased harm with a HPSD strategy.

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We compared the efficacy and complication rates of quantitative radiofrequency ablation guided by ablation index (RFCA-AI) with those of second-generation cryoballoon ablation (CBA-2). Consecutive patients (n = 230) with symptomatic atrial fibrillation (AF) undergoing a first ablation CBA-2 (92 patients) or RFCA-AI (138 patients) procedure were enrolled in this study. The late recurrence rate in the CBA-2 group was higher than that in the RFCA-AI group (P = .012). Subgroup analysis showed the same result in patients with paroxysmal AF (PAF) (P = .039), but no difference was found in patients with persistent AF (P = .21). The average operation duration in the CBA-2 group (85 [75-99.5] minutes) was shorter than that in the RFCA-AI group (100 [84.5-120] minutes) (P < .0001), but the average exposure time (17.36(13.87-22.49) vs 5.49(4.00-8.24) minutes) in the CBA-2 group and X-ray dose (223.25(149.15-336.95) vs 109.15(80.75-168.7) mGym) were significantly longer than those in RFCA-AI group (P < .0001). Multivariate logistic regression analysis showed that left atrial diameter (LAD), early recurrence, and methods of ablation (cryoballoon ablation) were independent risk factors for late recurrence after AF ablation. Early recurrence of AF and LAD were independent risk factors for predicting late recurrence after AF ablation.

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BACKGROUND: Pulmonary vein isolation (PVI) is an effective treatment option for patients with symptomatic atrial fibrillation (AF). However, the electrical recovery of pulmonary veins (PVs) is the main trigger for AF recurrences. This study investigates the characteristics of patients admitted for redo AF ablation, the PV reconnection rates depending on previous ablation modalities and the impact of different ablation strategies for redo procedures. METHODS: Consecutive patients undergoing first redo AF ablation were included. Patients were grouped according to the electrical recovery of at least one PV. The impacts of the technique for first AF ablation on PV reconnection rates and patients with and without PV reconnection were compared. Different ablation strategies for redo procedures were compared and its recurrence rates after a mean follow-up of 25 ± 20 months were investigated. RESULTS: A total of 389 patients (68 ± 10 years; 57% male; 39% paroxysmal AF) underwent a first redo. The median time between the first and redo procedure was 40 ± 39 months. Radiofrequency was used in 278 patients, cryoballoon was used in 85 patients and surgical AF ablation was performed on 26 patients. In total, 325 patients (84%) had at least one PV reconnected, and the mean number of reconnected PVs was 2.0 ± 1.3, with significant differences between ablation approaches (p for all = 0.002); this was mainly due to differences in the left inferior PV and right superior PV reconnections. The presence of PV reconnection during redo was not associated with better long-term success compared to completely isolated PVs (67% vs. 67%; log-rank p = 0.997). Overall, the different ablation strategies for redos were comparable regarding AF recurrences during follow-up (p = 0.079), with the ablation approach having no impact in the case of left atrial low voltage or without. CONCLUSIONS: PV reconnections after initial successful PVI are common among all techniques of AF ablation. Long-term rhythm control off antiarrhythmic drugs was possible in 2/3 of all patients after the redo procedure; however, different ablation strategies with extra-PV trigger ablation did not improve long-term success. Patients with recurrent AF after PVI constitute a challenging group of patients.

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INTRODUCTION: Although left atrial wall thickness (LAWT) is known to be varied, a fixed target Ablation Index (AI) based pulmonary vein isolation (PVI) has been suggested in catheter ablation for atrial fibrillation (AF). We aimed to evaluate the efficacy and safety of PVI applying tailored AI based on LAWT assessed by cardiac computed tomography (CT). METHODS: The thick segment was defined as the segment including ≥LAWT grade 3 (≥1.5 mm). The fixed AI strategy was defined as AI targets were 450 on the anterior/roof segments and 350 on the posterior/inferior/carina segments regardless of LAWT. The tailored AI strategy consisted of AI increasing the targets to 500 on the anterior/roof segments and to 400 on the posterior/inferior/carina segments when ablating the thick segment. After PVI, acute pulmonary vein (PV) reconnection, defined by the composite of residual potential and early reconnection, was evaluated. RESULTS: A total of 156 patients (paroxysmal AF 72%) were consecutively included (86 for the fixed AI group and 70 for the tailored AI group). The tailored AI group showed a significantly lower rate of segments with acute PV reconnection than the fixed AI group (8% vs. 5%, p = .007). The tailored AI group showed a trend for shorter ablation time for PVI. One-year AF/atrial tachycardia free survival rate was similar in two groups (87.2% in the fixed AI group and 90.0% in the tailored AI group, p = .606). CONCLUSION: Applying tailored AI based on the LAWT was a feasible and effective strategy to reduce acute PV reconnection after PVI.

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INTRODUCTION: To investigate the optimal range of quantitative ablation index (AI) value during superior vena cava (SVC) electrical isolation by radiofrequency catheter ablation (RFCA). METHODS: First, in a development cohort of patients with atrial fibrillation (AF), the RFCA with 40 W was performed to complete SVC isolation guided by the conduction breakthrough point from the right atrium to SVC. Then, the range of AI value was calculated by offline analysis on different segments of SVC. Lastly, for the validation of AF patients, the safety and effectiveness of SVC isolation with the optimized target range of AI value were evaluated with an additional adenosine test. RESULTS: A total of 101 patients with AF were included in the study (44 patients in the development cohort/57 in the validation cohort). The segmental ablation strategy was applied in 70% of the patients. According to the offline analysis of the AI values in the development cohort, the target AI value range was set as 350-400. The success rate of SVC isolation in the validation cohort was significantly higher than that in the exploration cohort (100% vs. 90.9%, p = .02), and no complications occurred in the exploration cohort. During the adenosine test, the recovery rate of electrical conduction in SVC was significantly lower than that in the pulmonary vein (3.5% vs. 17.5%). CONCLUSION: The target AI value with a range from 350 to 400 is safe and effective for high-power RFCA to complete SVC isolation.

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AIMS: The effectiveness of pulmonary vein isolation (PVI) guided by VISITAG SURPOINT (VS) has been demonstrated in Western populations. However, data for Asian populations are limited. VS settings may differ for Asians, given their smaller body size. This study aimed to describe outcomes of radiofrequency atrial fibrillation (AF) ablation guided by VS in a large Asian population. METHODS AND RESULTS: The prospective, observational, multicentre MIYABI registry collected real-world data from patients undergoing VS-guided AF ablation using ThermoCool SmartTouch and ThermoCool SmartTouch SF catheters from 50 Japanese centres. All patients had paroxysmal AF or persistent AF for <6 months. Primary adverse events (PAEs) were evaluated for safety. The primary efficacy endpoint was the proportion of patients with PVI at the end of the procedure. Mid-term effectiveness (up to 12 months) was evaluated by freedom from documented atrial arrhythmias. Of the 1011 patients enrolled, 1002 completed AF ablation. The mean number of VS values per procedure was 428.8 on the anterior wall and 400.4 on the posterior wall. Nine patients (0.9%) experienced PAEs. Upon procedure completion, 99.7% of patients had PVI. Twelve-month freedom from atrial arrhythmia recurrence was 88.5%; 5.7% of patients were re-ablated. At repeat ablation, 54% of RSPV, 73% of RIPV, 70% of LSPV, and 86% of LIPV evaluated remained durably isolated. CONCLUSION: Despite lower anterior wall VS values compared with the CLOSE protocol (≥550), the present study demonstrated comparable efficacy outcomes, indicating that a VS of ≥550 for the anterior wall may not be necessary for Asian patients.

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AIMS: Pulmonary vein isolation (PVI) guided by the Ablation Index (AI) has shown high acute and mid-term efficacy in the treatment of paroxysmal atrial fibrillation (AF). Previous data before the AI-era had suggested that wide-area circumferential ablation (WACA) was preferable to ostial ablation. However, with the use of AI, we hypothesize that ostial circumferential ablation is non-inferior to WACA and can improve outcomes in paroxysmal AF. METHODS AND RESULTS: Prospective, multicentre, non-randomized, non-inferiority study of consecutive patients were referred for paroxysmal AF ablation from January 2020 to September 2021. All procedures were performed using the AI software, and patients were separated into two different groups: WACA vs. ostial circumferential ablation. Acute reconnection, procedural data, and 1-year arrhythmia recurrence were assessed. During the enrolment period, 162 patients (64% males, mean age of 60 ± 11 years) fulfilled the study inclusion criteria-81 patients [304 pulmonary vein (PV)] in the WACA group and 81 patients (301 PV) in the ostial group. Acute PV reconnection was identified in 7.9% [95% confidence interval (CI), 4.9-11.1%] of PVs in the WACA group compared with 3.3% (95% CI, 1.8-6.1%) of PVs in the ostial group [P < 0.001 for non-inferiority; adjusted odds ratio 0.51 (95% CI, 0.23-0.83), P = 0.05]. Patients in the WACA group had longer ablation (35 vs. 29 min, P = 0.001) and procedure (121 vs. 102 min, P < 0.001) times. No significant difference in arrhythmia recurrence was seen at 1-year of follow-up [11.1% in WACA vs. 9.9% in ostial, hazard ratio 1.13 (95% CI, 0.44-1.94), P = 0.80 for superiority]. CONCLUSION: In paroxysmal AF patients treated with tailored AI-guided PVI, ostial circumferential ablation is not inferior to WACA with regard to acute PV reconnection, while allowing quicker procedures with less ablation time.

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Background: The optimal ablation index (AI) value for cavotricuspid isthmus (CTI) ablation is unknow. Objective: This study investigated the optimal AI value and whether preassessment of local electrogram voltage of CTI could predict first-pass success of ablation. Methods: Voltage maps of CTI were created before ablation. In the preliminary group, the procedure was performed in 50 patients targeting an AI ≥450 on the anterior side (two-thirds segment of CTI) and AI ≥400 on the posterior side (one-third segment of CTI). The modified group also included 50 patients, but the target AI for the anterior side was modified to ≥500. Results: In the modified group, the first-pass rate of success was higher (88% vs 62%; P < .01) than in the preliminary group, and there were no differences in the average bipolar and unipolar voltages at the CTI line. Multivariate logistic regression analysis revealed that ablation with an AI ≥500 on the anterior side was the only independent predictor (odds ratio 4.17; 95% confidence interval 1.44-12.05; P < .01). The bipolar and unipolar voltages were higher at sites without conduction block than at sites with conduction block (both P < .01). The cutoff values for predicting conduction gap were ≥1.94 mV and ≥2.33 mV with areas under the curve of 0.655 and 0.679, respectively. Conclusions: CTI ablation with a target AI >500 on the anterior side was shown to be more effective than an AI >450, and local voltage at a conduction gap was higher than without a conduction gap.

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BACKGROUND: Ablation index (AI) is used for guiding therapy during pulmonary vein isolation. However, its potential utility in ventricular myocardium is unknown. OBJECTIVES: This study sought to examine the correlation between AI and lesion dimensions in healthy and infarcted ventricles. METHODS: In ex vivo experiments using healthy swine ventricles, the correlation between AI (400-1,200) and lesion dimensions was examined at fixed power (30 W) and contact force (CF) (15 g). To examine the accuracy of AI in predicting lesion dimensions created by different combinations of ablation parameters, applications with a similar prespecified AI value created using different power (30 vs 40 W), CF (15 vs 25 g) or impedance (130-170 Ω) were created. In in vivo experiments, the correlation between AI and lesion dimensions was examined in healthy and infarcted myocardium. RESULTS: Ex vivo experiments (247 lesions, 36 hearts) showed good correlation between AI and lesion depth (R = 0.93; P < 0.001). However, in vivo experiments (9 healthy swine and 10 infarcted swine) showed moderate correlation in healthy myocardium (R = 0.64; P < 0.01) and poor correlation in infarcted myocardium (R = 0.23; P = 0.61). AI values achieved using different combinations of power, CF, and baseline impedance resulted in different lesion depths: Ablation at 30 W produced deeper lesions compared with 40 W, ablation with CF of 15 g produced deeper lesions compared with CF of 25 g, and ablation at lower impedance produced larger lesions at similar prespecified AI values (P < 0.01 for all). CONCLUSIONS: AI has limited value for guiding ablation in ventricular myocardium, particularly scar. This may be related to small proportional significance of application duration and complex tissue architecture.

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