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.

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.

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.

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.

Network meta-analysis and systematic review comparing efficacy and safety between very high power short duration, high power short duration, and conventional radiofrequency ablation of atrial fibrillation.

BACKGROUND: High-power short-duration (HPSD) atrial fibrillation (AF) ablation with a power of 40-50 W was proved to be safe and effective. Very high-power short-duration (vHPSD) AF ablation is a novel method using >50 W to obtain more durable AF ablation. This study aimed to evaluate the efficacy and safety of vHPSD ablation compared with HPSD ablation and conventional power ablation. METHODS: A literature search for studies that reported AF ablation outcomes, including short-term freedom from atrial arrhythmia, first-pass isolation (FPI) rate, procedure time, and major complications, was conducted utilizing MEDLINE, EMBASE, and Cochrane databases. All relevant studies were included in this analysis. A random-effects model of network meta-analysis and surface under cumulative ranking curve (SUCRA) were used to rank the treatment for all outcomes. RESULTS: A total of 29 studies with 9721 patients were included in the analysis. According to the SUCRA analysis, HPSD ablation had the highest probability of maintaining sinus rhythm. Point estimation showed an odds ratio of 1.5 (95% confidence interval [CI]: 1.2-1.9) between HPSD ablation and conventional power ablation and an odds ratio of 1.3 (95% CI: 0.78-2.2) between vHPSD ablation and conventional power ablation. While the odds ratio of FPI between HPSD ablation and conventional power ablation was 3.6 (95% CI: 1.5-8.9), the odds ratio between vHPSD ablation and conventional power ablation was 2.2 (95% CI: 0.61-8.6). The procedure times of vHPSD and HPSD ablations were comparable and, therefore, shorter than that of conventional power ablation. Major complications were low in all techniques. CONCLUSION: vHPSD ablation did not yield higher efficacy than HPSD ablation and conventional power ablation. With the safety concern, vHPSD ablation outcomes were comparable with those of other techniques.

Paroxysmal atrial fibrillation ablation with a novel temperature-controlled CF-sensing catheter: Q-FFICIENCY clinical and healthcare utilization benefits.

INTRODUCTION: The prospective, nonrandomized, multicenter Q-FFICIENCY study demonstrated the safety and 12-month efficacy of paroxysmal atrial fibrillation (AF) ablation with the novel QDOT MICRO temperature-controlled, contact force-sensing, radiofrequency (RF) catheter. Participants underwent pulmonary vein isolation with very high-power short-duration (vHPSD) mode (90 W, ≤4 s) alone or combined with conventional-power temperature-controlled (CPTC) mode (25-50 W). This study aimed to assess quality-of-life (QOL) and healthcare utilization (HCU) benefits experienced by Q-FFICIENCY study participants. METHODS: Besides evaluating procedural efficiency, QOL and HCU were assessed through 12 months postablation via Atrial Fibrillation Effect on Quality-of-Life Tool (AFEQT) score, antiarrhythmic drug (AAD) use, and incidence of cardioversion and cardiovascular hospitalization. RESULTS: Of 191 participants enrolled, 166 were ablated with the new catheter. Compared to baseline, statistically significant, clinically meaningful improvements in composite and subcategories of AFEQT scores were observed at 3 months and sustained through 12 months (12-month increase, 29.3-44.2 points). Class I/III AAD use decreased from 97.6% (162/166) at baseline to 19.6% (31/158) during Months 6-12, representing a significant 79.9% reduction. The cardioversion rate significantly declined by 93.9% from 31.3% (12 months preablation) to 1.9% (evaluation period). One-year Kaplan-Meier estimates of freedom from all-cause and cardiovascular hospitalization were 80.9% (95% confidence interval [CI], 74.8%-86.9%) and 88.8% (95% CI, 84.0%-93.7%), respectively. CONCLUSIONS: Paroxysmal AF ablation with the novel temperature-controlled RF catheter in vHPSD mode, alone or with CPTC mode, led to clinically meaningful improvement in QOL and significant reduction in AAD use, cardioversion, and cardiovascular hospitalization.

Incidence and predictors of stroke and silent cerebral embolism following very high-power short-duration atrial fibrillation ablation.

AIMS: Cerebral thrombo-embolism is a dreaded complication of pulmonary vein isolation (PVI) for atrial fibrillation; its surrogate, silent cerebral embolism (SCE) can be detected by diffusion-weighted brain magnetic resonance imaging (bMRI). Initial investigations have raised a concern that very high-power, short-duration (vHPSD; 90 W/4 s) temperature-controlled PVI with the QDOT Micro catheter may be associated with a higher incidence of SCE compared with low-power long-duration ablation. We aimed to assess the incidence of procedural complications of vHPSD PVI with an emphasis on cerebral safety. METHODS AND RESULTS: We enrolled 328 consecutive patients undergoing their PVI procedure using vHPSD. A subgroup of 61 consecutive patients underwent diffusion-weighted bMRI within 24 h of the procedure, and incidence and predictors of SCE were studied. The mean procedure time and left atrial dwell time for the overall cohort were 69.6 ± 24.1 and 46.5 ± 21.5 min, respectively. First-pass isolation was achieved in 82%. No stroke or transient ischaemic attack occurred. Silent cerebral embolism was identified in 5 of 61 patients (8.2%). Silent cerebral embolism following procedures was significantly associated with lower baseline generator impedance (105.8 vs. 112.6 Ω, P < 0.0001) and with intermittent loss of catheter-tissue contact during ablation (14.1% vs. 6.1%, P < 0.0001). CONCLUSION: Very high-power, short-duration PVI is a safe technique with an excellent acute success rate. Silent cerebral embolism incidence in our cohort was below the previously reported range, with no clinically overt cerebral complications. Lower baseline generator impedance and loss of contact during ablation may contribute to a higher risk of SCEs.

How an innovative catheter with temperature control and very high-power, short-duration ablation changed our approach to the treatment of persistent atrial fibrillation.

Ablation targets of persistent atrial fibrillation remain poorly understood nowadays: due to structural alterations of the left atrium, isolation of the pulmonary veins alone has proved ineffective. New ablation targets such as the posterior wall, coronary sinus, and left atrial appendage were then sought. A new catheter (QDOT Micro™) has recently been released, which has the potential to increase the safety and efficacy of the procedure: it is connected to a new radiofrequency generator that allows for temperature-controlled ablation by reducing power and increasing irrigation with the increase in tissue temperature and allows to deliver power up to 90 W for few seconds (very high-power short-duration).

Radiofrequency ablation of atrial fibrillation-50 W or 90 W?

BACKGROUND: This study sought to evaluate the short and midterm efficacy and safety of the novel very high power very short duration (vHPvSD) 90 W approach compared to HPSD 50 W for atrial fibrillation (AF) ablation as well as reconnection patterns of 90 W ablations. METHODS AND RESULTS: Consecutive patients undergoing first AF ablation with vHPvSD (90 W; predefined ablation time of 3 s for posterior wall ablation and 4 s for anterior wall ablation) were compared to patients using HPSD (50 W; ablation index-guided; AI 350 for posterior wall ablation, AI 450 for anterior wall ablation) retrospectively. A total of 84 patients (67.1 ± 9.8 years; 58% male; 47% paroxysmal AF) were included (42 with 90 W, 42 with 50 W) out of a propensity score-matched cohort. 90 W ablations revealed shorter ablation times (10.5 ± 6.7 min vs. 17.4 ± 9.9 min; p = .001). No major complication occurred. 90 W ablations revealed lower first pass PVI rates (40% vs. 62%; p = .049) and higher AF recurrences during blanking period (38% vs. 12%; p = .007). After 12 months, both ablation approaches revealed comparable midterm outcomes (62% vs. 70%; log-rank p = .452). In a multivariable Cox regression model, persistent AF (hazard ratio [HR]: 1.442, 95% confidence interval [CI]: 1.035-2.010, p = .031) and increased procedural duration (HR: 1.011, 95% CI: 1.005-1.017, p = .001) were identified as independent predictors of AF recurrence during follow-up. CONCLUSIONS: AF ablation using 90 W vHPvSD reveals a similar safety profile compared to 50 W ablation with shorter ablation times. However, vHPvSD ablation was associated with lower rates of first-pass isolations and increased AF recurrences during the blanking period. After 12 months, 90 W revealed comparable efficacy results to 50 W ablations in a nonrandomized, propensity-matched comparison.

Safety of very high-power short-duration radiofrequency ablation for pulmonary vein isolation: a two-centre report with emphasis on silent oesophageal injury.

AIMS: Very high-power short-duration (vHPSD) via temperature-controlled ablation (TCA) is a new modality to perform radiofrequency pulmonary vein isolation (PVI), conceivably at the cost of a narrower safety margin towards the oesophagus. In this two-centre trial, we aimed to determine the safety of vHPSD-based PVI with specific emphasis on silent oesophageal injury. METHODS AND RESULTS: Ninety consecutive patients with atrial fibrillation (AF) underwent vHPSD-PVI (90 W, 3-4 s, TCA) using the QDOT MICRO catheter, in conjunction with the nGEN (Bad Neustadt, n = 45) or nMARQ generator (Bruges, n = 45). All patients underwent post-ablation oesophageal endoscopy. Procedural parameters and complications were recorded. A subgroup of 21 patients from Bad Neustadt underwent cerebral magnetic resonance imaging (cMRI) to detect silent cerebral events (SCEs). Mean age was 67 ± 9 years, 59% patients were male, and 66% patients had paroxysmal AF. Pulmonary vein isolation was obtained in all cases after 96 ± 29 min. No steam pop, cardiac tamponade, stroke, or fistula was reported. None of the 90 patients demonstrated oesophageal ulceration (0%). Charring was not observed in the nMARQ cohort (0% vs. 11% in the nGEN group). In 5 out of 21 patients (24%), cMRI demonstrated SCE (exclusively nGEN cohort). CONCLUSION: Temperature-controlled vHPSD catheter ablation allows straightforward PVI without evidence of oesophageal ulcerations or symptomatic complications. Catheter tip charring and silent cerebral lesions when using the nGEN generator have led to further modification.

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.

Optimized workflow for pulmonary vein isolation using 90-W radiofrequency applications: a comparative study.

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.

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.

The Feasibility, Safety and Outcome of Very High-Power Short Duration Radiofrequency Ablation in Pulmonary Vein Isolation: A Real-World Observation Study.

Background: Pulmonary vein isolation (PVI) ablation is the established gold standard therapy for patients with symptomatic drug refractory atrial fibrillation (AF). Advancements in radiofrequency (RF) ablation, have led to the development of the novel contact force-sensing temperature-controlled very high-power short-duration (vHPSD) RF ablation. This setting delivers 90 W for up to 4 seconds with a constant irrigation flow rate of 8 mL/min. The aim of this study was to compare procedural outcomes and safety with conventional radiofrequency ablation. Methods: An observational study was conducted with patients who underwent first time PVI ablation between August 2020 and January 2022. The cohort was divided into: (1) vHPSD ablation; (2) High-power short duration (HPSD) ablation; (3) THERMOCOOL SMARTTOUCH™ SF (STSF). The vHPSD ablation group was prospectively recruited while the HPSD and STSF group were retrospectively collected. Primary outcomes were procedural success, PVI duration, ablation duration and incidence of perioperative adverse events. Secondary outcomes were intraprocedural morphine and midazolam requirement. Results: A total of 175 patients were included in the study with 100, 30 and 45 patients in the vHPSD, HPSD and STSF group, respectively. PVI was successfully attained in all vHPSD patients. vHPSD demonstrated significantly reduced time required for PVI and total energy application in comparison to the HPSD and STSF groups (67.7 ± 29.7 vs. 92.9 ± 25.7 vs. 93.6 ± 29.1 min, p < 0.0001; 9.87 ± 4.16 vs. 33.9 ± 7.49 vs. 36.0 ± 10.5 min, p < 0.0001, respectively). Intravenous morphine and midazolam requirement was lower in the vHPSD group compared to the HPSD and STSF groups (10.2 ± 3.43 vs. 16.1 ± 4.58 vs. 15.3 ± 3.94 mg, p < 0.0001; 4.04 ± 3.24 vs. 8.63 ± 5.22 vs. 8.58 ± 4.72 mg, p < 0.0001). One cardiac tamponade was observed in both the vHPSD and HPSD groups while the STSF group exhibited an embolic stoke and two pericardial effusions that did not require drainage. Conclusions: In this study, vHPSD demonstrated a comparable safety profile to the other treatment arms. Procedural duration and energy application time was substantially reduced along with sedation requirement notwithstanding the limitations of observational study design, these preliminary findings are promising with respect to periprocedural outcomes and safety of vHPSD however longitudinal outcomes will be essential to assessing the overall efficacy of this novel technology.

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.

Feasibility and Safety Assessment of RF Double Applications in Very High-Power Short-Duration Ablation.

BACKGROUND: The QDOT-MICRO catheter enables very-high-power and short-duration (vHPSD) ablation. However, low first-pass isolation rates have been reported, possibly due to shallow lesion formation, necessitating deeper lesions to improve treatment outcomes. OBJECTIVES: This study aimed to confirm the safety and efficacy of double Radiofrequency (RF) applications of vHPSD ablation in an in vivo beating swine heart model. METHODS: Eighteen swine were anesthetized and underwent vHPSD ablation with the QDOT-MICRO catheter at 90W for 4 seconds, targeting a contact force of 10g. RF applications were performed as single (SA) and double applications (DA) with 4-8 seconds rest intervals. Lesion surface area and volume were measured post-ablation. RESULTS: A total of 337 atrial lesions and 74 ventricular lesions were created. Both 4-6s DA and 7-8s DA produced significantly larger and deeper lesions compared to SA, with atrial surface lengths averaging 9.0mm for 4-6s DA, 9.2mm for 7-8s DA, and 8.0mm for SA. Transmurality was observed at 100% for 4-6s and 7-8s DA, while it was 94% for SA (p=0.002). Ventricular lesion metrics followed similar trends. Except for 1 event of tiny char formation in 4s DA in the ventricle, neither steam-pops nor char formation was observed in either the atrium or the ventricle. CONCLUSIONS: In an in vivo swine heart model, DA with 4-6s and 7-8s intervals create deeper and wider lesions than 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.

Impact of contact force on the lesion characteristics of very high-power short-duration ablation using a QDOT-MICRO catheter.

Background: Lesion size is reported to become larger as contact force (CF) increases. However, this has not been systematically evaluated in temperature-guided very high-power short-duration (vHPSD) ablation, which was therefore the purpose of this study. Methods: Radiofrequency applications (90 W/4 s, temperature-control mode) were performed in excised porcine myocardium with four different CFs of 5, 15, 25, and 35 g using QDOT-MICRO™ catheter. Ten lesions for each combination of settings were created, and lesion metrics and steam-pops were compared. Results: A total of 320 lesions were analyzed. Lesion depth, surface area, and volume were smallest for CF of 5 g than for 15, 25, and 35 g (depth: 2.7 mm vs. 2.9 mm, 3.0 mm, 3.15 mm, p < .01; surface area: 38.4 mm2 vs. 41.8 mm2, 43.3 mm2, 41.5 mm2, p < .05; volume: 98.2 mm3 vs. 133.3 mm3, 129.4 mm3, 126.8 mm3, p < .01 for all pairs of groups compared to CF = 5 g). However, no significant differences were observed between CFs of 15-35 g. Average power was highest for CF of 5 g, followed by 15, 25, and 35 g (83.2 W vs. 82.1 W vs. 77.1 W vs. 66.1 W, p < .01 for all pairs), reflecting the higher incidence of temperature-guided power titration with greater CFs (5 g:8.8% vs. 15 g:52.5% vs. 25 g:77.5% vs. 35 g:91.2%, p < .01 for all pairs except for 25 g vs. 35 g). The incidence of steam-pops did not significantly differ between four groups (5 g:3.8% vs. 15 g:10% vs. 25 g:6.2% vs. 35 g:2.5%, not significant for all pairs). Conclusions: For vHPSD ablation, lesion size does not become large once the CF reaches 15 g, and the risk of steam-pops may be mitigated through power titration even in high CFs.

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.

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.