Very high-power short-duration ablation for pulmonary vein isolation utilizing a very-close protocol-the FAST AND FURIOUS PVI study

Significance of the local largest bipolar voltage for the optimized ablation strategy using very high-power short duration mode

PURPOSE

Very high-power short-duration (vHPSD) ablation creates shallower lesions, potentially reducing efficacy. This study aims to identify factors leading to insufficient lesions during pulmonary vein antral isolation (PVAI) with vHPSD-ablation and to develop an optimized PVAI strategy using this technology.

METHODS

PVAI was performed on 41 atrial fibrillation patients using vHPSD-ablation (90 W/4 s). Lesion parameters were recorded and analyzed to identify predictors of insufficient lesions. An optimized PVAI strategy, based on these predictors, was tested in subsequent 42 patients.

RESULTS

In total, 3099 RF-applications, including 103(3.3%) insufficient lesions, were analyzed. First-pass PVAI was achieved in 19/40(47.5%) right PVs and 24/41(58.5%) left PVs. Multivariate analysis identified significant predictors of insufficient lesions: local largest bipolar voltage (Bi-V), average contact force, baseline impedance, impedance drop, temperature rise, inter-lesion distance (ILD), and anatomical location (carina or not). An ILD:4-6 mm increased the risk of insufficient lesions 2.2-fold, and lesions at the carina increased it 3.6-fold for both ILD < 4 mm and ILD:4-6 mm. Local largest Bi-V was the strongest predictor for insufficient lesions. The optimized PVAI approach, utilizing vHPSD-ablation with an ILD < 4 mm in non-carinal areas with Bi-V < 4 mV, and high-power ablation-index guided ablation (HPAI, 50 W, ablation-index:450-550) in remaining areas, achieved first-pass PVAI in 92.7% of right PVs and 88.1% of left PVs, using vHPSD-ablation in approximately 65% of total RF-applications. The optimized PVAI achieved significantly higher first-pass PVI rate (p < .0001) with shorter ablation time (p = .04).

CONCLUSION

Appropriate use of vHPSD and HPAI, based on local largest Bi-V and anatomical information, may achieve high first-pass PVAI rates in shorter ablation time with minimal energy delivery.

Feasibility and safety assessment of RF double applications in very high power and short duration ablation

BACKGROUND

Very high power and short duration (vHPSD) ablation is recently used for pulmonary vein isolation. However, low first-pass isolation rates have been reported, possibly because of shallow lesion formation, necessitating deeper lesions to improve treatment outcomes.

OBJECTIVE

This study aimed to confirm the safety and efficacy of double radiofrequency applications of vHPSD ablation in an in vivo beating swine heart model.

METHODS

Eighteen swine were anesthetized and underwent vHPSD ablation using the QDOT-MICRO catheter at 90 W for 4 seconds, targeting a contact force of 10 g. Radiofrequency applications were performed as single application (SA) and double applications (DA) with 4-8 seconds rest intervals. Lesion surface area and volume were measured postablation.

RESULTS

A total of 337 atrial lesions and 74 ventricular lesions were created. Both 4-6 seconds DA and 7-8 seconds DA produced significantly larger and deeper lesions than did SA, with atrial surface lengths averaging 9.0 mm for 4-6 seconds DA, 9.2 mm for 7-8 seconds DA, and 8.0 mm for SA. Transmurality was observed at 100% for 4-6 seconds and 7-8 seconds DAs, while it was 94% for SA (P = .002). Ventricular lesion metrics followed similar trends. Except for 1 event of tiny char formation during 4 seconds DA in the ventricle, neither steam pops nor char formation was observed in either the atrium or the ventricle.

CONCLUSION

In an in vivo swine heart model, DA with 4-6 seconds and 7-8 seconds intervals create deeper and wider lesions than does SA, suggesting its potential for clinical application in areas with thicker myocardial walls. However, DA with very short intervals may still pose a risk of excessive tissue heating.

Underreporting of complications following AF ablation: Comparison of the manufacturer and user facility device experience FDA database and a voluntary invitation-based registry: The POTTER-AF 3 study

BACKGROUND

The Manufacturer and User Facility Device Experience (MAUDE) database houses medical device reports of adverse events involving medical devices marketed in the United States submitted to the U.S. Food and Drug Administration (FDA) by mandatory and voluntary reporters. The MAUDE database is frequently used in clinical studies to report on device-related complications. Data about its efficacy are scarce.

OBJECTIVE

We aimed to compare the mandatory MAUDE database (MAUDE group) with the invitation-based POTTER-AF study (POTTER-AF 1 group) regarding data quality, procedural characteristics, diagnosis, treatment, and survival.

METHODS

The reports of esophageal fistula esophageal fistula following atrial fibrillation (AF) ablation in the MAUDE database were compared with those in the POTTER-AF study between August 1, 2009, and August 31, 2019.

RESULTS

Esophageal fistulas were reported in 47 patients in the MAUDE group and in 81 in the POTTER-AF 1 group. Procedures were performed with radiofrequency, cryoenergy, or laser energy in 66.0%, 31.9%, and 2.1% (MAUDE group) and in 96.3%, 2.5%, and 1.2% (POTTER-AF 1 group). The median time to symptoms was 21 (14, 32.5) days (MAUDE group) and 18.0 (6.8, 22.3) days (POTTER-AF 1 group; P = .031). The diagnostic method was reported in 38.3% of patients in the MAUDE group and in 98.8% in the POTTER-AF 1 group, the treatment in 57.4% and 100%, and the outcome in all patients. In the MAUDE group, treatment was surgical (51.9%), endoscopic (37.0%), combined (3.7%), or conservative (7.4%), compared with 43.2%, 19.8%, 7.4%, and 29.6% in the POTTER-AF 1 group. Overall mortality was 76.6% in the MAUDE group and 61.7% in the POTTER-AF 1 group (P = .118).

CONCLUSION

In the mandatory MAUDE database, fewer esophageal fistula cases were reported compared with an invitation-based study. The data quality in the MAUDE database was significantly poorer.

High-Power Short-Duration Posterior Wall Isolation in Addition to Pulmonary Vein Isolation in Persistent Atrial Fibrillation Ablation Using the New TactiFlex™ Ablation Catheter

BACKGROUND

The TactiFlex™ ablation catheter, Sensor Enabled™ (Abbott, Minneapolis, MN, USA), is an open-irrigation radiofrequency (RF) ablation catheter with flexible tip technology. This catheter delivers high-power short-duration (HPSD) RF ablations and has been adopted for atrial fibrillation (AF) ablation. HPSD is well-established not only in pulmonary vein isolation (PVI) but also when targeting extra-pulmonary vein (PV) targets. This study aims to determine the safety, effectiveness, and acute outcomes of PVI plus posterior wall isolation (PWI) in patients with persistent atrial fibrillation (Pe-AF) using HPSD and the TactiFlex™ ablation catheter.

METHODS

Consecutive patients who underwent the ablation of Pe-AF in our centre between February 2023 and February 2024 were prospectively enrolled in the study. All patients underwent PVI plus PWI using TactiFlex™ and the HPSD strategy. The RF parameters were 50 W on all the PV segments and the roof, and within the posterior wall (PW). Left atrial mapping was performed with the EnSite X mapping system and the high-density multipolar Advisor HD Grid, Sensor Enabled™ mapping catheter. We compared the procedural data using HPSD with TactiFlex™ (n = 52) vs. a historical cohort of patients who underwent PVI plus PWI using HPSD settings and the TactiCath ablation catheter (n = 84).

RESULTS

Fifty-two consecutive patients were included in the study. PVI and PWI were achieved in all patients in the TactiFlex™ group. First-pass PVI was achieved in 97.9% of PVs (n = 195/199). PWI was obtained in all cases by delivering extensive RF lesions within the PW. There were no significant differences compared to the TactiCath group: first-pass PVI was achieved in 96.3% of PVs (n = 319/331). Adenosine administration revealed PV reconnection in 5.7% of patients, and two reconnections of the PW were documented. Procedure and RF time were significantly shorter in the TactiFlex™ group compared to the TactiCath group, 73.1 ± 12.6 vs. 98.5 ± 16.3 min, and 11.3 ± 1.5 vs. 23.5 ± 3.6 min, respectively, p < 0.001. The fluoroscopy time was comparable between both groups. No intraprocedural and periprocedural complications related to the ablation catheter were observed. Patients had an implantable loop recorder before discharge. At the 6-month follow-up, 76.8% of patients remained free from atrial arrhythmia, with no significant differences between groups.

CONCLUSIONS

HPSD PVI plus PWI using the TactiFlex™ ablation catheter is effective and safe. Compared to a control group, the use of TactiFlex™ to perform HPSD PVI plus PWI is associated with a similar effectiveness but with a significantly shorter procedural and RF time.

Pulsed field vs very high-power short-duration radiofrequency ablation for atrial fibrillation: Results of a multicenter, real-world experience

BACKGROUND

Pulsed field ablation (PFA) and very high-power short-duration (vHPSD) radiofrequency ablation are the most recently introduced technologies for atrial fibrillation (AF) ablation. The procedural performance, safety, and effectiveness of PFA vs vHPSD are currently unknown.

OBJECTIVE

The study aimed to compare PFA with vHPSD for the treatment of paroxysmal or persistent AF.

METHODS

We conducted an observational, multicenter study enrolling 534 consecutive patients (63 ± 9 years; 36% female) with paroxysmal (n = 368 [69%]) or persistent (n = 166 [31%]) AF undergoing ablation by either PFA (Farapulse; n = 192) or vHPSD (90 W/4 seconds; QDOT Micro; n = 342) between 2020 and 2023. Atrial tachyarrhythmia recurrence after a 1-month blanking period was the primary efficacy end point and was assessed both overall and in propensity score-matched patients. The primary safety end point was a composite of procedure-related complications.

RESULTS

Successful pulmonary vein isolation was achieved in all patients, with shorter procedure duration (PFA,70 minutes; vHPSD, 100 minutes; P < .001) but longer fluoroscopy time (PFA, 15 minutes; vHPSD, 7 minutes; P < .001) in the PFA group. PFA was associated with more frequent use of general anesthesia (P < .001). Primary safety outcome events occurred in 19 patients (3.5%), with similar prevalence in both groups (PFA, 4%; vHPSD, 3%; P = .745). After a median follow-up of 12 (9-12) months, survival free from recurrent atrial tachyarrhythmia was similar between the PFA and vHPSD groups, both overall (12-month estimate: PFA, 75%; vHPSD, 76%; log-rank P = .73) and in propensity score-matched patients (n = 342; 12-month estimate: PFA, 75%; vHPSD, 77%; log-rank P = .980).

CONCLUSION

In a large, multicenter experience, PFA was associated with more common use of general anesthesia, shorter procedural times, and longer fluoroscopy exposure compared with vHPSD ablation, with both techniques displaying superimposable safety and efficacy.

Peri-procedural anesthesia and patient pain experience in pulmonary vein isolation by means of very high-power short-duration radiofrequency ablation

BACKGROUND

Very high-power short-duration (vHPSD) temperature-controlled radiofrequency ablation (vHPSD) may reduce ablation times and improve patient tolerability, permitting pulmonary vein (PV) isolation under mild conscious sedation. We evaluated of the anesthetic drugs use and patients' pain experience during vHPSD PV isolation.

METHODS

Fifty-eight patients, with paroxysmal and persistent atrial fibrillation (AF), treated with QDot Micro catheter and vHPSD (90 w for 4 s) (vHPSD group), were compared with the last 33 patients treated with a surround flow contact force-sensing catheter guided by the ablation index (450 anteriorly at 50 W, 330 posteriorly at 40 W) (AI group). Anesthetic drugs use was compared as well as pain experience, measured using a 0-10 scale.

RESULTS

All PVs were acutely isolated. Procedural time (78 ± 10 min vs 84 ± 12 min, p = 0.012), fluoroscopy time (369 ± 139 s vs 441 ± 172 s, p = 0.03), and RF time in the vHPSD group (8.3 ± 2.1 min) were shorter than in the AI group (25 ± 11 min, p < 0.001). Only 4 patients experienced an access site-related vascular complication (groin hematoma). Midazolam was required in 36 (62%) vHPSD group patients vs 31 (94%) AI group patients (p < 0.001). Fentanyl was required in 4 (7%) vHPSD group patients vs 25 (76%) AI group patients (p < 0.001). No patients required general anesthesia. Twenty-two (38%) vHPSD group patients underwent PV isolation without any anesthetic drug. Pain experience was significantly lower in vHPSD group (4.9 ± 2 vs 6.6 ± 1.8, p < 0.001).

CONCLUSIONS

vHPSD radiofrequency ablation for PVI can be performed under conscious sedation using only benzodiazepine in most of patients without compromising patient pain experience.

Evaluation of microembolic signals on carotid ultrasound during pulmonary vein isolation with high-power short-duration and cryoballoon ablations: When and where do bubble and solid emboli arise?

INTRODUCTION

The underlying risks of asymptomatic embolization during high-power short-duration (HPSD) ablation for atrial fibrillation remain unclear. We aimed to evaluate microembolic signals (MESs) during HPSD ablation with power settings of 50 and 90 W in comparison with those during cryoballoon (CB) ablation using a novel carotid ultrasound-Doppler system that classifies solid and air bubble signals using real-time monitoring.

METHODS AND RESULTS

Forty-seven patients underwent HPSD ablation using radiofrequency (RF), and 13 underwent CB ablation. MESs were evaluated using a novel pastable soft ultrasound probe equipped with a carotid ultrasound during pulmonary vein isolation. We compared the detailed MESs and their timing between RF and CB ablations. The number of MESs and solid signals were significantly higher in the RF group than in CB group (209 ± 229 vs. 79 ± 32, p = .047, and 83 ± 89 vs. 28 ± 17, p = .032, respectively). In RF ablation, the number of MESs, solid, and bubble signals per ablation point, or per second, was significantly higher at 90 W than at 50 W ablation. The MESs, solid, and bubble signals were detected more frequently in the bottom and anterior walls of the left pulmonary vein (LPV) ablation. In contrast, many MESs were observed before the first CB application and decreased chronologically as the procedure progressed. Signals were more prevalent during the CB interval rather than during the freezing time. Among the 28 patients, 4 exhibited a high-intensity area on postbrain magnetic resonance imaging (MRI). The MRI-positive group showed a trend of larger signal sizes than did the MRI-negative group.

CONCLUSION

The number of MESs was higher in the HPSD RF group than in the CB group, with this risk being more pronounced in the 90 W ablation group. The primary detection site was the anterior wall of the LPV in RF and the first interval in CB ablation.

Ablation Parameters Predicting Pulmonary Vein Reconnection after Very High-Power Short-Duration Pulmonary Vein Isolation

BACKGROUND

Recurrences due to discontinuity in ablation lines are substantial after pulmonary vein isolation (PVI) with radiofrequency ablation for atrial fibrillation. Data are scarce regarding the durability predictors for very high-power short-duration (vHPSD, 90 W/4 s) ablation.

METHODS

A total of 20 patients were enrolled, who underwent 90 W PVI and a mandatory remapping procedure at 3 months. First-pass isolation (FPI) gaps, and acute pulmonary vein reconnection (PVR) sites were identified at the index procedure; and chronic PVR sites were identified at the repeated procedure. We analyzed parameters of ablation points (n = 1357), and evaluated their roles in predicting a composite endpoint of FPI gaps, acute and chronic PVR.

RESULTS

In total, 45 initial ablation points corresponding to gaps in the ablation lines were analyzed. Parameters associated with gaps were interlesion distance (ILD), baseline generator impedance, mean current, total charge, and loss of catheter-tissue contact. The optimal ILD cut-off for predicting gaps was 3.5 mm anteriorly, and 4 mm posteriorly.

CONCLUSIONS

Biophysical characteristics dependent on generator impedance could affect the efficacy of vHPSD PVI. The use of smaller ILDs is required for effective and durable PVI with vHPSD compared to the consensus targets with lower power ablation, and lower ILDs for anterior applications seem necessary compared to posterior points.

Next-generation atrial fibrillation ablation: clinical performance of pulsed-field ablation and very high-power short-duration radiofrequency

INTRODUCTION

Pulsed-field energy (PFA) and very high-power short-duration radiofrequency (vHPSD-RF) are two novel ablation methods for pulmonary vein isolation (PVI). Both PFA and vHPSD-RF show promise for improving efficacy, safety, and reducing procedure durations. However, direct comparisons between these two techniques are scarce.

METHODS AND RESULTS

Retrospective analysis of 82 patients with symptomatic AF. Of these, 52 patients received PFA and 30 received vHPSD-RF (90 W, 4 s) as index procedure. At the 6-month follow-up, AF recurrence occurred in 4 patients following PFA and 5 patients following vHPSD-RF (p-value = 0.138). Significant improvements in the EHRA and NYHA stages were evident in both PFA (p < 0.001 and p = 0.047, respectively) and vHPSD-RF groups (p = 0.007 and p = 0.012, respectively). The total procedure duration and the left atrial dwell time were significantly shorter in the PFA group (64 ± 19 min vs. 99 ± 32 min, p < 0.001 and 41 ± 12 min vs. 62 ± 29 min, p < 0.001, respectively). The fluoroscopy time and dose area product were significantly higher in PFA (14 ± 6 vs. 9 ± 5 min, p < 0.001 and 14 ± 9 vs. 11 ± 9 Gy cm2, p = 0.046, respectively). One patient in the vHPSD-RF group suffered a stroke, not directly linked to the procedure (0 vs. 1 major complication, p = 0.366).

CONCLUSION

Based on this retrospective single-center study, PFA and vHPSD-RF were associated with similar effectiveness and safety profiles. PFA was linked to shorter procedure times and higher radiation exposure compared to vHPSD-RF.

Posterior wall ablation for persistent atrial fibrillation: Very-high-power short-duration versus standard-power radiofrequency ablation

Background

Posterior wall ablation (PWA) is commonly added to pulmonary vein isolation (PVI) during catheter ablation (CA) of persistent atrial fibrillation (AF).

Objective

The purpose of this study was to compare PVI plus PWA using very-high-power short-duration (vHPSD) vs standard-power (SP) ablation index-guided CA among consecutive patients with persistent AF and to determine the voltage correlation between microbipolar and bipolar mapping in AF.

Methods

We compared 40 patients undergoing PVI plus PWA using vHPSD to 40 controls receiving PVI plus PWA using SP. The primary efficacy endpoint was recurrence of atrial tachyarrhythmias after a 3-month blanking period. The primary safety outcome was a composite of major complications within 30 days after CA. In the vHPSD group, high-density mapping of the posterior wall was performed using both a multipolar catheter and microelectrodes on the tip of the ablation catheter.

Results

PVI was more commonly obtained with vHPSD compared to SP ablation (98%vs 75%; P = .007), despite shorter procedural and fluoroscopy times (P <.001). Survival free from recurrent atrial tachyarrhythmias at 18 months was 68% and 47% in the vHPSD and SP groups, respectively (log-rank P = .071), without major adverse events. The vHPSD approach was significantly associated with reduced risk of recurrent AF at multivariable analysis (hazard ratio 0.39; P = .030). Microbipolar voltage cutoffs of 0.71 and 1.69 mV predicted minimum bipolar values of 0.16 and 0.31 mV in AF, respectively, with accuracies of 0.67 and 0.88.

Conclusion

vHPSD PWA plus PVI may be faster and as safe as SP CA among patients with persistent AF, with a trend for superior efficacy. Adapted voltage cutoffs should be used for identifying atrial low-voltage areas with microbipolar mapping.

Lesion metrics and 12-month outcomes of very-high power short duration radiofrequency ablation (90W/4 s) under mild conscious sedation

INTRODUCTION

Pulmonary vein isolation (PVI) is often performed under general anaesthesia (GA) or deep sedation. Anaesthetic availability is limited in many centers, and deep sedation is prohibited in some countries without anaesthetic support. Very high-power short duration (vHPSD-90W/4 s) PVI using the Q-Dot catheter is generally well tolerated under mild conscious sedation (MCS) though an understanding of catheter stability and long-term effectiveness is lacking. We analyzed lesion metrics and 12-month freedom from atrial arrythmia with this approach.

METHODS

Our approach to radiofrequency (RF) PVI under MCS is standardized and includes a single catheter approach with a steerable sheath. We identified patients undergoing Q-Dot RF PVI between March 2021 and December 2022 in our center, comparing those undergoing vHPSD ablation under MCS (90W/MCS) against those undergoing 50 W ablation under GA (50 W/GA) up to 12 months of follow-up. Data were extracted from clinical records and the CARTO system.

RESULTS

Eighty-three patients met our inclusion criteria (51 90W/MCS; 32 50 W/GA). Despite shorter ablation times (353 vs. 886 s; p < .001), the 90 W/MCS group received more lesions (median 87 vs. 58, p < .001), resulting in similar procedure times (149.3 vs. 149.1 min; p = .981). PVI was achieved in all cases, and first pass isolation rates were similar (left wide antral circumferential ablation [WACA] 82.4% vs. 87.5%, p = .758; right WACA 74.5% vs. 78.1%, p = .796; 90 W/MCS vs. 50 W/GA respectively). Analysis of 6647 ablation lesions found similar mean impedance drops (10.0 ± 1.9 Ω vs. 10.0 ± 2.2 Ω; p = .989) and mean contact force (14.6 ± 2.0 g vs. 15.1 ± 1.6 g; p = .248). Only median 2.5% of lesions in the 90 W/MCS cohort failed to achieve ≥ 5 Ω drop. In the 90 W/MCS group, there were no procedural related complications, and 12-month freedom from atrial arrhythmia was observed in 78.4%.

CONCLUSION

vHPSD PVI is feasible under MCS, with encouraging acute and long-term procedural outcomes. This provides a compelling option for centers with limited anaesthetic support.

Long-term outcome of high-power ablation guided by ablation index in the treatment of atrial fibrillation

Objective

High-power ablation has been widely used in atrial fibrillation (AF). However, there were many studies observed the outcomes of the short-term follow-up. This study aims to the long-term results of high-power ablation guided by ablation index (AI) in patients with AF.

Methods

Analysis of patients with AF, who first received high-power (40-50 W) ablation, to pulmonary vein isolation (PVI) in the Second Hospital of Shanxi Medical University from May 2020 to March 2022. All patients were managed perioperatively according to the routine treatment procedures. High-power ablation was conducted under the guidance of our conventional power AI and baseline data, first-pass PVI rate, ablation time, operative time, and long-term surgical success rate were analyzed.

Results

A total of 83 patients with atrial fibrillation were enrolled in the study, with an average age of 61.62 ± 9.04 years, 47 male patients, and 49 paroxysmal atrial fibrillation. All patients achieved PVI, and the rate of first pass was 82%. The ablation time of the left atrial was 28.54 ± 9.11 min. There were no serious complications related to ablation, and only a small amount of pericardial effusion was found in 4 patients. During the follow-up period of 26.36 ± 6.11 months, 8 patients were lost to follow-up and the overall success rate was 84%, including 91% for paroxysmal AF and 71% for persistent AF.

Conclusion

High-power ablation long-term results appear a high freedom atrial arrhythmia, but further expanded samples are needed for controlled studies.

Pulsed Field Energy in Atrial Fibrillation Ablation: From Physical Principles to Clinical Applications

Atrial fibrillation, representing the most prevalent sustained cardiac arrhythmia, significantly impacts stroke risk and cardiovascular mortality. Historically managed with antiarrhythmic drugs with limited efficacy, and more recently, catheter ablation, the interventional approach field is still evolving with technological advances. This review highlights pulsed field ablation (PFA), a revolutionary technique gaining prominence in interventional electrophysiology because of its efficacy and safety. PFA employs non-thermal electric fields to create irreversible electroporation, disrupting cell membranes selectively within myocardial tissue, thus preventing the non-selective damage associated with traditional thermal ablation methods like radiofrequency or cryoablation. Clinical studies have consistently shown PFA's ability to achieve pulmonary vein isolation-a cornerstone of AF treatment-rapidly and with minimal complications. Notably, PFA reduces procedure times and has shown a lower incidence of esophageal and phrenic nerve damage, two common concerns with thermal techniques. Emerging from oncological applications, the principles of electroporation provide a unique tissue-selective ablation method that minimizes collateral damage. This review synthesizes findings from foundational animal studies through to recent clinical trials, such as the MANIFEST-PF and ADVENT trials, demonstrating PFA's effectiveness and safety. Future perspectives point towards expanding indications and refinement of techniques that promise to improve AF management outcomes further. PFA represents a paradigm shift in AF ablation, offering a safer, faster, and equally effective alternative to conventional methods. This synthesis of its development and clinical application outlines its potential to become the new standard in AF treatment protocols.

Venous vascular closure system vs. figure-of-eight suture following atrial fibrillation ablation: the STYLE-AF Study

AIMS

Simplified ablation technologies for pulmonary vein isolation (PVI) are increasingly performed worldwide. One of the most common complications following PVI are vascular access-related complications. Lately, venous closure systems (VCSs) were introduced into clinical practice, aiming to reduce the time of bed rest, to increase the patients' comfort, and to reduce vascular access-related complications. The aim of the present study is to compare the safety and efficacy of using a VCS to achieve haemostasis following single-shot PVI to the actual standard of care [figure-of-eight suture and manual compression (MC)].

METHODS AND RESULTS

This is a prospective, multicentre, randomized, controlled, open-label trial performed at three German centres. Patients were randomized 1:1 to undergo haemostasis either by means of VCS (VCS group) or of a figure-of-eight suture and MC (F8 group). The primary efficacy endpoint was the time to ambulation, while the primary safety endpoint was the incidence of major periprocedural adverse events until hospital discharge. A total of 125 patients were randomized. The baseline characteristics were similar between the groups. The VCS group showed a shorter time to ambulation [109.0 (82.0, 160.0) vs. 269.0 (243.8, 340.5) min; P < 0.001], shorter time to haemostasis [1 (1, 2) vs. 5 (2, 10) min; P < 0.001], and shorter time to discharge eligibility [270 (270, 270) vs. 340 (300, 458) min; P < 0.001]. No major vascular access-related complication was reported in either group. A trend towards a lower incidence of minor vascular access-related complications on the day of procedure was observed in the VCS group [7 (11.1%) vs. 15 (24.2%); P = 0.063] as compared to the control group.

CONCLUSION

Following AF ablation, the use of a VCS results in a significantly shorter time to ambulation, time to haemostasis, and time to discharge eligibility. No major vascular access-related complications were identified. The use of MC and a figure-of-eight suture showed a trend towards a higher incidence of minor vascular access-related complications.

Durable pulmonary vein isolation with optimized high-power and very high-power short-duration temperature-controlled ablation: A step-by-step guide

INTRODUCTION

Through systematic scientific rigor, the CLOSE guided workflow was developed and has been shown to improve pulmonary vein isolation durability. However, this technique was developed at a time when using power-controlled ablation catheters with conventional power ranges was the norm. There has been increased adoption of a high-power and very high-power short-duration ablation practice propelled by the availability of the temperature-controlled radiofrequency QDOT MICRO catheter.

METHODS

There are fundamental differences in biophysics between very high-powered temperature guided ablation and conventional ablation strategy that may impact patient outcomes. The catheter's design and ablation modes offer flexibility in technique while accommodating the individual operator's clinical discretion and preference to deliver a durable, transmural, and contiguous lesion set.

RESULTS

Here, we provide recommendations for 3 different workflows using the QDOT MICRO catheter in a step-by-step manner for pulmonary vein isolation based on our cumulative experience as early adopters of the technology and the data available in the scientific literature.

CONCLUSIONS

With standardization, temperature-controlled ablation with the QDOT MICRO catheter provides operators the flexibility of implementing different ablation strategies to ensure durable contiguous pulmonary vein isolation depending on patient characteristics.

Initial experience, safety, and feasibility using remote access or onsite technical support for complex ablation procedures: results of the REMOTE study

Aims

Electroanatomical mapping (EAM) systems are essential for the treatment of cardiac arrhythmias. The EAM system is usually operated by qualified staff or field technical engineers from the control room. Novel remote support technology allows for remote access of EAM via online services. Remote access increases the flexibility of the electrophysiological lab, reduces travel time, and overcomes hospital access limitations especially during the COVID-19 pandemic. Here, we report on the feasibility and safety of EAM remote access for cardiac ablation procedures.

Methods and results

Mapping and ablation were achieved by combining the EnsiteX™ EAM system and the integrated Ensite™ Connect Remote Support software, together with an integrated audiovisual solution system for remote support (Medinbox). Communication between the operator and the remote support was achieved using an incorporated internet-based common communication platform (Zoom™), headphones, and high-resolution cameras. We investigated 50 remote access-assisted consecutive electrophysiological procedures from September 2022 to February 2023 (remote group). The data were compared with matched patients (n = 50) with onsite support from the control room (control group). The median procedure time was 100 min (76, 120; remote) vs. 86 min (60, 110; control), P = 0.090. The procedural success (both groups 100%, P = 0.999) and complication rate (remote: 2%, control: 0%, P = 0.553) were comparable between the groups. Travel burden could be reduced by 11 280 km.

Conclusion

Remote access for EAM was feasible and safe in this single-centre study. Procedural data were comparable to procedures with onsite support. In the future, this new solution might have a great impact on facilitating electrophysiological procedures.

Impedance-guided modified CLOSE protocol ablation can reduce ablation index necessary for pulmonary vein isolation in patients with atrial fibrillation

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 ≥10 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 ± 43.5 Ω and 10.2 ± 2.6 Ω and 393.3 ± 27.4 Ω and 9.3 ± 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 ± 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.

Where is the gap after a 90 W/4 s very-high-power short-duration ablation of atrial fibrillation?: Association with the left atrial-pulmonary vein voltage and wall thickness

Background

Although pulmonary vein isolation (PVI) for atrial fibrillation (AF) utilizing radiofrequency (RF) applications with a very high-power and short-duration (vHPSD) has shortened the procedure time, the determinants of pulmonary vein (PV) gaps in the first-pass PVI and acute PV reconnections are unclear.

Methods

An extensive encircling PVI was performed with the QDOT MICRO catheter with a vHPSD (90 W-4 s) in 30 patients with AF (19 men, 64 ± 10 years). The association of the PV gap sites (first-pass PVI failure, acute PV reconnections [spontaneous reconnections or dormant conduction provoked by adenosine triphosphate] or both) with the left atrial (LA) wall thickness and LA bipolar voltage on the PVI line and ablation-related parameters were assessed.

Results

PV gaps were observed in 29 (6%) of 480 segments (16 segments per patient) in 17 patients (56%). The PV gaps were associated with the LA wall thickness, bipolar voltage, and the number of RF points (LA wall thickness, 2.5 ± 0.5 vs. 1.9 ± 0.4 mm, p < .001; bipolar voltage, 2.59 ± 1.62 vs. 1.34 ± 1.14 mV, p < .001; RF points, 6 ± 2 vs. 4 ± 2, p = .008) but were not with the other ablation-related parameters. Receiver operating characteristic curves yielded that an LA wall thickness ≥2.3 mm and bipolar voltage ≥2.40 mV were determinants of PV gaps with an area under the curve of 0.82 and 0.73, respectively.

Conclusions

The LA voltage and wall thickness on the PV-encircling ablation line were highly associated with PV gaps using the 90 W/4 s-vHPSD ablation.

Personalized pulmonary vein isolation with very high-power short-duration lesions guided by left atrial wall thickness: the QDOT-by-LAWT randomized trial

AIMS

Pulmonary vein isolation (PVI) for paroxysmal atrial fibrillation (PAF) using very high-power short-duration (vHPSD) radiofrequency (RF) ablation proved to be safe and effective. However, vHPSD applications result in shallower lesions that might not be always transmural. Multidetector computed tomography-derived left atrial wall thickness (LAWT) maps could enable a thickness-guided switching from vHPSD to the standard-power ablation mode. The aim of this randomized trial was to compare the safety, the efficacy, and the efficiency of a LAWT-guided vHPSD PVI approach with those of the CLOSE protocol for PAF ablation (NCT04298177).

METHODS AND RESULTS

Consecutive patients referred for first-time PAF ablation were randomized on a 1:1 basis. In the QDOT-by-LAWT arm, for LAWT ≤2.5 mm, vHPSD ablation was performed; for points with LAWT > 2.5 mm, standard-power RF ablation titrating ablation index (AI) according to the local LAWT was performed. In the CLOSE arm, LAWT information was not available to the operator; ablation was performed according to the CLOSE study settings: AI ≥400 at the posterior wall and ≥550 at the anterior wall. A total of 162 patients were included. In the QDOT-by-LAWT group, a significant reduction in procedure time (40 vs. 70 min; P < 0.001) and RF time (6.6 vs. 25.7 min; P < 0.001) was observed. No difference was observed between the groups regarding complication rate (P = 0.99) and first-pass isolation (P = 0.99). At 12-month follow-up, no significant differences occurred in atrial arrhythmia-free survival between groups (P = 0.88).

CONCLUSION

LAWT-guided PVI combining vHPSD and standard-power ablation is not inferior to the CLOSE protocol in terms of 1-year atrial arrhythmia-free survival and demonstrated a reduction in procedural and RF times.

Cryoablation versus hybrid radiofrequency with high- and very-high-power short-duration catheter ablation for the treatment of paroxysmal atrial fibrillation

BACKGROUND

High-power short-duration (HPSD) and very-high-power short-duration (vHPSD-90 W/4 s) radiofrequency (RF) technology has reduced the procedure time of pulmonary vein isolation (PVI) using RF without compromising the efficacy of the technique. The current study compares the novel technology of HPSD/vHPSD with cryoablation (CRYO) in terms of efficacy, safety, and procedure time in a cohort of symptomatic patients with paroxysmal atrial fibrillation (pAF).

METHODS

This is a prospective, non-randomized trial. Patients with pAF received either CRYO or HPSD/vHPSD RF PVI. The primary endpoint of the study was arrhythmia recurrence in a 12 month follow-up period. Secondary endpoints included procedure time, fluoroscopy time, and safety.

RESULTS

104 patients were included (45 in HPSD/vHPSD and 59 in CRYO), with comparable characteristics between groups. The follow-up was 12.4 ± 0.5 months. There was no significant difference regarding arrhythmia recurrences during the early post-procedural period of the first 3 months (8.9% recurrences in HPSD/vHPSD versus 5.1% in CRYO-p 0.463) and in the mid-term follow-up of 12 months (17.8% recurrences in HPSD/vHPSD versus 10.2% in CRYO-p 0.385). Safety was excellent for both procedures. CRYO was a procedure of significantly shorter duration (64.64 ± 8.94 min versus 75.29 ± 18.30 min, p = 0.0001) at the expense of longer fluoroscopy time (HPSD/vHPSD 5.34 ± 1.83 versus 7.89 ± 3.70 min CRYO, p 0.001).

CONCLUSIONS

HPSD/vHPSD and CRYO in pAF were comparable regarding the arrhythmia recurrence rates in a 12-month follow-up with excellent safety. The hybrid approach of HPSD/vHPSD has accelerated RF-PVI compared to conventional RF, but CRYO remains a procedure of significantly shorter duration at the expense of longer fluoroscopy time.

Atrial fibrillation ablation workflow optimization facilitated by high-power short-duration ablation and high-resolution mapping

AIMS

Pulmonary vein isolation (PVI) for catheter ablation of atrial fibrillation (AF) is a time-demanding procedure. High-power short-duration (HPSD) ablation protocols and high-density mapping catheters have recently been introduced to clinical practice. We investigated the impact of high-density mapping and HPSD ablation protocols on procedural timing, efficacy, and safety by comparing different standardized set-ups.

METHODS AND RESULTS

Three electrophysiology (EP) laboratory set-ups were analysed: (i) circular catheter for mapping and HPSD ablation with 30/35 W guided by an ablation index (AI); (ii) pentaspline catheter for mapping an HPSD ablation with 50 W guided by an AI; and (iii) pentaspline catheter for mapping and HPSD ablation with 90 W over 4 s using a novel ablation catheter. All patients underwent PVI without additional left atrial ablation strategies. Procedural data and operating intervals in the EP laboratory were systematically analysed. Three hundred seven patients were analysed (30/35 W AI: n = 102, 50 W AI: n = 102, 90 W/4 s: n = 103). Skin-to-skin times [105.3 ± 22.7 (30/35 W AI) vs. 81.4 ± 21.3 (50 W AI) vs. 69.5 ± 12.2 (90 W/4 s) min, P ≤ 0.001] and total laboratory times (132.8 ± 42.1 vs. 107.4 ± 25.7 vs. 95.2 ± 14.0 min, P < 0.001) significantly differed among the study groups. Laboratory interval analysis revealed significant shortening of mapping and ablation times. Arrhythmia-free survival after 12 months was not different among the study groups (log-rank P = 0.96).

CONCLUSION

The integration of high-density mapping and HPSD protocols into an institutional AF ablation process resulted in reduced procedure times without compromising safety or efficacy.

Very high-power short-duration catheter ablation for treatment of cardiac arrhythmias: Insights from the FAST and FURIOUS study series

The QDOT MICRO™ Catheter is a novel open-irrigated contact force-sensing radiofrequency ablation catheter. It offers very high-power short-duration (vHPSD) ablation with 90 W for 4 s to improve safety and efficacy of catheter ablation procedures. Although the QDOT MICRO™ Catheter was mainly designed for pulmonary vein isolation (PVI) its versatility to treat atrial fibrillation (AF) and other types of arrhythmias was recently evaluated by the FAST and FURIOUS study series and other studies and will be presented in this article. Available study and registry data as well as case reports concerning utilization of the QDOT MICRO™ Catheter for the treatment of cardiac arrhythmias including AF, focal and macroreentry atrial tachycardia, typical atrial flutter by cavotricuspid isthmus block, premature ventricular contractions, and accessory pathways were reviewed and summarized. In summary, the QDOT MICRO™ Catheter showed safety and efficacy for PVI and is able to treat also other types of arrhythmias as is was recently evaluated by case reports and the FAST and FURIOUS studies.

Pulmonary vein isolation durability after very high-power short-duration ablation utilizing a very-close protocol - The FAST AND FURIOUS redo study

Background

Very high-power short-duration (vHP-SD) radiofrequency (RF) ablation of atrial fibrillation (AF) treatment by pulmonary vein isolation (PVI) aims for safer, more effective and faster procedures. Although acute efficacy and safety for PVI was recently shown data on chronic PVI durability is limited. Here chronic PVI durability was evaluated during repeat electrophysiological procedures in patients after initial vHP-SD and conventional RF based PVI.

Methods

A total of 25 consecutive patients with repeat left atrial procedures after initial vHP-SD based PVI were included in this study. Twenty-five patients with previous conventional RF based PVI and repeat left atrial procedures served as control (control group).

Results

For index procedures the median RF time was 328 (277, 392) seconds (vHP-SD) and 1470 (1310, 1742) seconds (control); p < 0.001, the median procedure time was 55 (53, 68) minutes (vHP-SD) and 110 (94, 119) (control); p < 0.001). First pass isolation rate was 84 % (vHP-SD) and 88 % (control, p = 0.888). No differences for severe adverse events (vHP-SD: 1/25, 4 % vs. control: 0/25, 0 %; p = 0.676 were detected.Chronic durability of all PVs was assessed in vHP-SD: 16/25 (64 %) and control: 8/25 (32 %) patients (p = 0.023) and vHP-SD: 81 % and control: 62 % of PVs were found to be isolated (p = 0.003). For right PVs vHP-SD: 84 % vs. control: 60 % of PVs (p < 0.001) and for left PVs vHP-SD: 78 % vs. control: 64 % (p = 0.123) were found to be isolated.

Conclusions

PVI solely utilizing vHP-SD via a very close-protocol provides fast, safe and effective acute PVI. High rates of chronically isolated pulmonary veins have been detected.

Very-high-power Short-duration Ablation versus Conventional Ablation for Pulmonary Vein Isolation in Atrial Fibrillation: Systematic Review and Meta-analysis

The aim of this study was to compare the effectiveness and safety of very-high-power short-duration (VHPSD) ablation (70-90 W/4-7 s) with conventional ablation (30-40 W/>20 s, 50 W/7-11 s) for pulmonary vein isolation (PVI) in patients with AF. A total of 13 studies were included in this analysis (1,527 patients). AF recurrence occurred in 14% (95% CI [11-18%]) of the VHPSD group. VHPSD was associated with lower AF recurrence (OR 0.65; 95% CI [0.48-0.89]; p=0.006) compared with the conventional ablation group. Subgroup analysis showed that additional ablation beyond PVI had a similar rate of AF recurrence (16% versus 10%) compared with PVI alone. Procedure and ablation durations were significantly shorter in the VHPSD group with a mean differences of -14.4 minutes (p=0.017) and -14.1 minutes (p<0.001), respectively. Complications occurred in 6% (95% CI [3-9%]) of the VHPSD group, and the rate was similar between the two groups (OR 1.03; 95% CI [0.60-1.80]; p=0.498). VHPSD ablation resulted in less AF recurrence and a shorter procedure time. Additional ablation beyond PVI alone in VHPSD may not provide additional benefits.

Comparison of very high-power short-duration, high-power short-duration, and low-power long-duration radiofrequency ablation for atrial fibrillation: A systematic review and network meta-analysis

BACKGROUND

The optimal power and duration settings for radiofrequency (RF) atrial fibrillation (AF) ablation to improve efficacy and safety is unclear. We compared low-power long-duration (LPLD), high-power short-duration (HPSD), and very HPSD (vHPSD) RF settings for AF ablation.

METHODS

This network meta-analysis (NMA) was structured according to the Preferred Reporting Items for Systematic Review and Meta-Analyses guidelines. Medline, Scopus and Cochrane Central Register of Controlled Trials were systematically searched to identify relevant studies. Observational and randomized studies were included. Eligible studies compared outcomes in AF patients who underwent first-time RF ablation with the following settings: vHPSD (70-90 W, 3-10 s), HPSD (45-60 W, 5-10 s), or LPLD (20-40 W, 20-60 s).

RESULTS

Thirty-six studies comprising 10,375 patients were included (33% female). Frequentist NMA showed LPLD tended toward a lower odds of freedom from arrhythmia (FFA) versus HPSD (OR 0.93, 95% CI 0.86-1.00). There was no difference in FFA between vHPSD versus HPSD. Splitwise interval estimates showed a lower odds of FFA in LPLD versus vHPSD on direct (OR 0.78, 95% CI 0.65-0.93) and network estimates (OR 0.85, 95% CI 0.73-0.98). Frequentist NMA showed less total procedural (TP) time with HPSD versus LPLD (generic variance 1.06, 95% CI 0.83 to 1.29) and no difference between HPSD versus vHPSD.

CONCLUSION

This NMA shows improved procedural times in HPSD and vHPSD versus LPLD. Although HPSD tended toward improved odds of FFA compared to LPLD, the overall result was not statistically significant. The odds of FFA in LPLD was lower versus vHPSD on direct and network estimates on splitwise interval analysis. Large prospective head-to-head randomized trials are needed to validate HPSD and vHPSD settings.

Safety verification of a novel irrigation catheter with flexible tip of laser-cut kerfs and contact force sensor

BACKGROUND AND AIMS

The safety evaluation of TactiFlex, a novel contact-force sensing catheter with a flexible 4-mm tip irrigated through laser-cut kerfs, has been ongoing. This study aimed to verify the safety of this type of catheter.

METHODS

Study 1: Radiofrequency (RF) applications at a range of powers (30-50 W), contact forces (10-20 g), and durations (10-60 s) using perpendicular/parallel catheter orientation with half-normal (HNS) or normal saline irrigation were compared between TactiFlex (4-mm tip) and TactiCath (3.5-mm tip) with temperature-controlled mode in excised porcine hearts. Study 2: The relation between RF applications using TactiFlex and the incidence of steam-pops in the real clinical cases were examined.

RESULTS

Study-1: 576 RF lesions were examined. TactiFlex demonstrated a significantly lower risk of steam-pops (5[1.7%] vs. 59[20.5%], p < .0001). Compared to 3.5-mm-tip catheter (TactiCath), 4-mm-tip catheter (TactiFlex) produced smaller lesion volume at perpendicular (193[98-554]mm3 vs. 263[139-436]mm3 , p < .0001), but relatively similar lesion volume at parallel contact (243[105-443]mm3 vs. 278[180-440]mm3 , p = .06). HNS-irrigation tended to increase the lesion volume in both catheters and to increase the incidence of steam-pops with TactiCath, but not with TactiFlex. The cut-off value of %impedance-drop ( = absolute impedance-drop/initial impedance) of 20% predicted steam-pops with a sensitivity = 100% and specificity = 89.6% in TactiFlex. Study-2: 5496 RF applications in 84 patients (51AFs/8ATs/3AVNRTs/4AVRTs/17PVCs/4VTs) using TactiFlex were analyzed. Four steam-pops (0.07%) in three patients with pericardial effusion were observed (%impedance-drop = 24%/26%/29%/35%, respectively). The cut-off value of %impedance-drop = 20%, derived from ex-vivo study, showed sensitivity = 100% and specificity = 90.1% in detecting steam-pops.

CONCLUSION

TactiFlex reduced the risk of steam-pops than TactiCath. %impedance-drop ≤ 20% may be reasonable for safely use with a sufficient safety margin. For 4-mm-tip catheter, parallel-contact may be recommended for larger lesion creation.

50-W vs 40-W During High-Power Short-Duration Ablation for Paroxysmal Atrial Fibrillation: A Multicenter Prospective Study

BACKGROUND

High-power short-duration (HPSD) radiofrequency ablation of atrial fibrillation (AF) increases first-pass pulmonary vein isolation (PVI) and freedom from atrial arrhythmias while decreasing procedural time. However, the optimal power setting in terms of safety and efficacy has not been determined.

OBJECTIVES

This study compared the procedural characteristics and clinical outcomes of 50-W vs 40-W during HPSD ablation of paroxysmal AF.

METHODS

Patients from the REAL-AF prospective multicenter registry (Real-World Experience of Catheter Ablation for Treatment of Symptomatic Paroxysmal and Persistent Atrial Fibrillation) undergoing HPSD ablation of paroxysmal AF, either using 50-W or 40-W, were included. The primary efficacy outcome was freedom from all-atrial arrhythmias. The primary safety outcome was the occurrence of any procedural complication at 12 months. Secondary outcomes included procedural characteristics, AF-related symptoms, and the occurrence of transient ischemic attack or stroke at 12 months.

RESULTS

A total of 383 patients were included. Freedom from all-atrial arrhythmias at 12 months was 80.7% in the 50-W group and 77.3% in the 40-W group (Log-rank P = 0.387). The primary safety outcome occurred in 3.7% of patients in the 50-W group vs 2.8% in the 40-W group (P = 0.646). The 50-W group had a higher rate of first-pass PVI (82.3% vs 76.2%; P = 0.040) as well as shorter procedural (67 minutes [IQR: 54-87.5 minutes] vs 93 minutes [IQR: 80.5-111 minutes]; P < 0.001) and radiofrequency ablation times (15 minutes [IQR: 11.4-20 minutes] vs 27 minutes [IQR: 21.5-34.6 minutes]; P < 0.001) than the 40-W group.

CONCLUSIONS

There was no significant difference in freedom from all-atrial arrhythmias or procedural safety outcomes between 50-W and 40-W during HPSD ablation of paroxysmal AF. The use of 50-W was associated with a higher rate of first-pass PVI as well as shorter procedural times.

Optimal interlesion distance for 90 and 50 watt radiofrequency applications with low ablation index values: experimental findings in a chronic ovine model

AIMS

The optimal interlesion distance (ILD) for 90 and 50 W radiofrequency applications with low ablation index (AI) values in the atria has not been established. Excessive ILDs can predispose to interlesion gaps, whereas restrictive ILDs can predispose to procedural complications. The present study sought, therefore, to experimentally determine the optimal ILD for 90 W-4 s and 50 W applications with low AI values to optimize catheter ablation outcomes in humans.

METHODS AND RESULTS

Posterior intercaval lines were created in eight adult sheep using CARTO and the QDOT-MICRO catheter in a temperature-controlled mode. In four animals, the lines were created with 50 W applications, a target AI value ≥350, and ILDs of 6, 5, 4, and 3 mm, respectively. In the other four animals, the lines were created with 90 W-4 s applications and ILDs of 6, 5, 4, and 3 mm, respectively. Activation maps were created immediately after ablation and at 21 days to assess linear block prior to gross and histological analyses. All eight lines appeared transmural and continuous on histology. However, for 50 W-only applications with an ILD of 3 mm resulted in durable linear electrical block, whereas for 90 W applications, only the lines with ILDs of 4 and 3 mm were blocked. No complications were detected during ablation procedures, but all power and ILD combinations except 50 W-6 mm resulted in asymptomatic shallow lung lesions.

CONCLUSION

In the intercaval region in sheep, for 50 W applications with an AI value of ∼370, the optimal ILD is 3 mm, whereas for 90 W-4 s applications, the optimal ILD is 3-4 mm.