90 vs 50-Watt Radiofrequency Applications for Pulmonary Vein Isolation: Experimental and Clinical Findings

2024 European Heart Rhythm Association/Heart Rhythm Society/Asia Pacific Heart Rhythm Society/Latin American Heart Rhythm Society expert consensus statement on catheter and surgical ablation of atrial fibrillation

In the last three decades, ablation of atrial fibrillation (AF) has become an evidence-based safe and efficacious treatment for managing the most common cardiac arrhythmia. In 2007, the first joint expert consensus document was issued, guiding healthcare professionals involved in catheter or surgical AF ablation. Mounting research evidence and technological advances have resulted in a rapidly changing landscape in the field of catheter and surgical AF ablation, thus stressing the need for regularly updated versions of this partnership which were issued in 2012 and 2017. Seven years after the last consensus, an updated document was considered necessary to define a contemporary framework for selection and management of patients considered for or undergoing catheter or surgical AF ablation. This consensus is a joint effort from collaborating cardiac electrophysiology societies, namely the European Heart Rhythm Association, the Heart Rhythm Society, the Asia Pacific Heart Rhythm Society, and the Latin American Heart Rhythm Society.

2024 European Heart Rhythm Association/Heart Rhythm Society/Asia Pacific Heart Rhythm Society/Latin American Heart Rhythm Society expert consensus statement on catheter and surgical ablation of atrial fibrillation

In the last three decades, ablation of atrial fibrillation (AF) has become an evidence-based safe and efficacious treatment for managing the most common cardiac arrhythmia. In 2007, the first joint expert consensus document was issued, guiding healthcare professionals involved in catheter or surgical AF ablation. Mounting research evidence and technological advances have resulted in a rapidly changing landscape in the field of catheter and surgical AF ablation, thus stressing the need for regularly updated versions of this partnership which were issued in 2012 and 2017. Seven years after the last consensus, an updated document was considered necessary to define a contemporary framework for selection and management of patients considered for or undergoing catheter or surgical AF ablation. This consensus is a joint effort from collaborating cardiac electrophysiology societies, namely the European Heart Rhythm Association, the Heart Rhythm Society (HRS), the Asia Pacific HRS, and the Latin American HRS.

Differences in Iron Kinetics during Cardiac Load between Patients with Atrial Fibrillation and Those with Sinus Rhythm

INTRODUCTION

The prevalence of atrial fibrillation (AF) increases with age. Although most AF cases are caused by irregular electrical impulses near the pulmonary vein, not all elderly individuals develop AF. Moreover, risk factors such as hypertension and diabetes do not always lead to AF, even in severe conditions such as pneumonia. We aimed to examine iron kinetics, including ferritin, in patients with AF and individuals in normal sinus rhythm (NSR) using peripheral blood samples.

METHODS

This case-control study included 178 patients who visited the outpatient clinic of a cardiovascular and arrhythmia specialist at the National Center for Geriatrics and Gerontology between August and October 2023. Patients with missing iron-related blood tests and those with pacemaker implantation were excluded. Iron parameters (ferritin, free iron, transferrin saturation) were compared between AF (n = 53) and NSR (n = 125) groups.

RESULTS

The AF group had higher log brain natriuretic peptide (BNP) levels, indicating increased cardiac load (AF 2.18 vs. NSR 1.53). However, there were no significant differences in iron parameters between the AF and NSR groups. After matching for age, sex, and coronary artery disease, the AF group showed an increasing trend in ferritin and a decreasing trend in free iron with BNP elevation, suggesting chronic inflammation. In contrast, the NSR group showed no significant changes in iron parameters with BNP elevation.

CONCLUSION

Patients with AF are more likely to have elevated ferritin levels and decreased free iron levels during cardiac overload. Thus, they are more likely to present with chronic inflammation associated with cardiac overload in AF. Future studies should investigate the mechanisms underlying this phenomenon and its implications for AF treatment.

High efficiency single-catheter workflow for radiofrequency atrial fibrillation ablation in the QDOT catheter era

BACKGROUND

High-power short-duration (HPSD) ablation may improve the consistency and efficiency of pulmonary vein isolation (PVI). The novel QDOT Micro™ catheter (Biosense Webster, Inc.) with temperature feedback and microelectrodes aims to enhance PVI efficiency and safety. This study wants to evaluate the feasibility, safety, and efficiency of a standardized single-catheter workflow for PVI using QDOT (Q-FLOW).

METHODS

The Q-FLOW includes single transeptal access, radiofrequency encircling of the PVs using a power of 50 W in a temperature/flow-controlled mode, and validation of the circles with microelectrodes. A 1:1 propensity-matched cohort of patients treated with conventional power-controlled ablation using a circular mapping catheter (CMC-FLOW) was used to compare procedural and clinical outcomes.

RESULTS

A total of 150 consecutive atrial fibrillation patients (paroxysmal 67%, persistent 33%) were included. First-pass isolation rate was 86%. Procedural time, X-ray time, and dose were significantly lower for the Q-FLOW vs the CMC-FLOW (67.2 ± 17.9 vs 88.3 ± 19.2 min, P < 0.001; 3.0 ± 1.9 vs 5.0 ± 2.4 min, P < 0.001; 4.3 ± 1.9 vs 6.4 ± 2.3 Gycm2, P < 0.001). Complications were numerically but not significantly lower in the Q-FLOW group (2 [1.3%] vs 7 [4.7%], P = 0.091). There was no difference in arrhythmia recurrence at 12 months (atrial arrhythmia-free survival rate, 87.5% vs 84.4%, P = 0.565).

CONCLUSION

A streamlined single-catheter workflow for PVI using QDOT was feasible and safe, resulting in a high rate of first-pass isolation and a low complication rate. The Q-FLOW further improved the efficiency of PVI compared to the standard CMC-FLOW, without difference in the 12-month outcome.

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.

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.

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.

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.

2024 European Heart Rhythm Association/Heart Rhythm Society/Asia Pacific Heart Rhythm Society/Latin American Heart Rhythm Society expert consensus statement on catheter and surgical ablation of atrial fibrillation

In the last three decades, ablation of atrial fibrillation (AF) has become an evidence-based safe and efficacious treatment for managing the most common cardiac arrhythmia. In 2007, the first joint expert consensus document was issued, guiding healthcare professionals involved in catheter or surgical AF ablation. Mounting research evidence and technological advances have resulted in a rapidly changing landscape in the field of catheter and surgical AF ablation, thus stressing the need for regularly updated versions of this partnership which were issued in 2012 and 2017. Seven years after the last consensus, an updated document was considered necessary to define a contemporary framework for selection and management of patients considered for or undergoing catheter or surgical AF ablation. This consensus is a joint effort from collaborating cardiac electrophysiology societies, namely the European Heart Rhythm Association, the Heart Rhythm Society, the Asia Pacific Heart Rhythm Society, and the Latin American Heart Rhythm Society .

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.

Procedural performance and outcome after pulsed field ablation for pulmonary vein isolation: comparison with a reference radiofrequency database

Aims

Pulsed field ablation (PFA) is a promising ablation technique for pulmonary vein isolation (PVI) with appealing advantages over radiofrequency (RF) including speed, tissue selectivity, and the promise of enhanced durability. In this study, we determine the procedural performance, efficacy, safety, and durability of PFA and compare its performance with a dataset of optimized RF ablation.

Methods and results

After propensity score matching, we compared 161 patients who received optimized RF-guided PVI in the PowerPlus study (CLOSE protocol) with 161 patients undergoing PFA-guided PVI for paroxysmal or persistent atrial fibrillation (AF; pentaspline basket catheter). The median age was 65 years with 78% paroxysmal AF in the PFA group (comparable characteristics in the RF group). Pulsed field ablation-guided PVI was obtained in all patients with a procedure time of 47 min (vs. 71 min in RF, P < 0.0001) and a fluoroscopy time of 15 min (vs. 11 min in RF, P < 0.0001). One serious adverse event [transient ischaemic attack] occurred in a patient with thrombocytosis (0.6 vs. 0% in RF). During the 6-month follow-up, 24 and 27 patients experienced a recurrence with 20 and 11 repeat procedures in the PFA and the RF groups, respectively (P = 0.6 and 0.09). High-density mapping revealed a status of 4 isolated veins in 7/20 patients in the PFA group and in 2/11 patients in the RF group (35 vs. 18%, P = 0.3).

Conclusion

Pulsed field ablation fulfils the promise of offering a short and safe PVI procedure, even when compared with optimized RF in experienced hands. Pulmonary vein reconnection is the dominant cause of recurrence and tempers the expectation of a high durability rate with PFA.

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.

Long-Term Durability of High- and Very High-Power Short-Duration PVI by Invasive Remapping: The HPSD Remap Study

BACKGROUND

High-power short-duration ablation has shown impressive efficacy and safety for pulmonary vein isolation (PVI); however, initial efficacy results with very high power short-duration ablation were discouraging. This study compared the long-term durability of PVI performed with a 90- versus 50-W power setting.

METHODS

Patients were randomized 1:1 to undergo PVI with the QDOT catheter using a power setting of 90 or 50 W. Three months after the index procedure, patients underwent a repeat electrophysiology study to identify pulmonary vein reconnections. Patients were followed for 12 months to detect AF recurrences.

RESULTS

We included 46 patients (mean age, 64 years; women, 48%). Procedure (76 versus 84 minutes; P =0.02), left atrial dwell (63 versus 71 minutes; P =0.01), and radiofrequency (303 versus 1040 seconds; P <0.0001) times were shorter with 90- versus 50-W procedures, while the number of radiofrequency applications was higher with 90 versus 50 W (77 versus 67; P =0.01). There was no difference in first-pass isolation (83% versus 82%; P =1.0) or acute reconnection (4% versus 14%; P =0.3) rates between 90 and 50 W. Forty patients underwent a repeat electrophysiology study. Durable PVI on a per PV basis was present in 72/78 (92%) versus 68/77 (88%) PVs in the 90- and 50-W energy setting groups, respectively; effect size: 72/78-68/77=0.040, lower 95% CI=-0.051 (noninferiority limit=-0.1, ie, noninferiority is met). No complications occurred. There was no difference in 12-month atrial fibrillation-free survival between the 90- and 50-W groups (P =0.2).

CONCLUSIONS

Similarly high rates of durable PVI and arrhythmia-free survival were achieved with 90 and 50 W. Procedure, left atrial dwell, and radiofrequency times were shorter with 90 W compared with 50 W. The sample size is too small to conclude the safety and long-term efficacy of the high and very high-power short-duration PVI; further studies are needed to address this topic.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT05459831.

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.

Safety and effectiveness of the first contact force ablation catheter with a flexible tip

Background

Catheter ablation is an established therapy for paroxysmal atrial fibrillation (PAF). The TactiFlex Ablation Catheter, Sensor Enabled (TactiFlex SE) is a next-generation radiofrequency ablation catheter incorporating fiber optics-based contact force-sensing technology with a flexible, laser-cut tip.

Objective

The study sought to evaluate the safety and effectiveness of the TactiFlex SE ablation catheter for treatment of drug-refractory PAF.

Methods

The TactiFlex AF investigational device exemption was a prospective, nonrandomized, multicenter clinical study. Enrollment began on June 26, 2020 and completed June 18, 2021. Subjects with PAF underwent de novo pulmonary vein isolation and, if indicated, ablation for typical atrial flutter. Subjects were followed for 12 months.

Results

Of the 355 subjects enrolled at 37 sites worldwide, 334 underwent ablation with the TactiFlex SE catheter. The Kaplan-Meier estimate of 12-month freedom from AF/atrial flutter (AFL)/atrial tachycardia recurrence was 72.9% (95% confidence interval [CI] 95% CI 67.2%-77.8%) and clinical success was 83.6% (95% CI 95% CI 78.1%-87.2%). As-treated analyses compared subjects treated at high power (left atrium time-averaged power setting 40-50 W; n = 222) vs low power (<40 W; n = 97). The Kaplan-Meier estimate of 12-month freedom from AF/AFL/atrial tachycardia recurrence was 76.4% (95% CI 69.3%-82.0%) and clinical success was 83.9% (95% CI 77.5%-88.6%) in the high-power group compared with 66.8% (95% CI 56.1%-75.5%) and 80.7% (95% CI 70.8%- 87.5%), respectively, in the low-power group. The primary safety event rate in all treated subjects was 4.3%; 4.1% in the HP group and 5.2% in the LP group (P = .7671).

Conclusion

TactiFlex SE is safe and effective for treatment of drug-refractory PAF and concomitant AFL and enables more efficient procedures than previous generation catheters.

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.

Impact of baseline pool impedance on lesion metrics and steam pops in catheter ablation

INTRODUCTION

Little is known about the impact of blood-pool local impedance (LI) on lesion characteristics and the incidence of steam pops.

METHODS

Radiofrequency applications at a range of powers (30, 40, and 50 W), contact forces (CF) (5, 15, and 25 g), and durations (15, 30, 45, and 120 s) using perpendicular/parallel catheter orientation were performed in 40 excised porcine preparations, using a catheter capable of monitoring LI (StablePoint©, Boston Scientific). To simulate the variability in blood-pool impedance, the saline-pool LI was modulated by calibrating saline concentrations. Lesion characteristics were compared under three values of saline-pool LI: 120, 160, and 200 Ω.

RESULTS

Of 648 lesions created, steam pops occurred in 175 (27.0%). When power, CF, time, and catheter orientation were adjusted, ablation at a saline-pool impedance of 160 or 200 Ω more than doubled the risk of steam pops compared with a saline-pool impedance of 120 Ω (Odds ratio = 2.31; p = .0002). Lesions in a saline-pool impedance of 120 Ω were significantly larger in surface area (50 [38-62], 45 [34-56], and 41 [34-60] mm2 for 120, 160, and 200 Ω, p < .05), but shallower in depth (4.0 [3-5], 4.4 [3.2-5.3], and 4.5 [3.8-5.5] mmfor 120, 160, and 200 Ω, respectively, p < .05) compared with the other two settings. The correlation between the absolute LI-drop and lesion size weakened as the saline-pool LI became higher (e.g., 120 Ω group (r2  = .30, r2  = .18, and r2  = .16, respectively for 120, 160, and 200 Ω), but the usage of %LI-drop (= absolute LI-drop/initial LI) instead of absolute LI-drop may minimize this effect.

CONCLUSIONS

In an experimental model, baseline saline-pool impedance significantly affects the lesion metrics and the risk of steam pops.

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.

Comparison of three different approaches to very high-power short-duration ablation using the QDOT-MICRO catheter

BACKGROUND/OBJECTIVES

The QDOT-MICRO™ catheter allows very high-power and short-duration (vHPSD) ablation. This study aimed to investigate lesion characteristics using different ablation settings.

METHODS

Radiofrequency applications (90 W/4 s, temperature-control mode with 55°C or 60°C target) were performed in excised porcine myocardium using three different approaches: single (SA), double nonrepetitive (DNRA), and double repetitive applications (DRA). Applications were performed with an interval of 1 min for DNRA, and without interval for DRA.

RESULTS

A total of 480 lesions were analyzed. Lesion depth and volume were largest for DRA followed by DNRA and SA regardless of catheter direction (depth: 3.8 vs. 3.3 vs. 2.6 mm, p < .001 for all comparisons; volume: 176.6 vs. 145.1 vs. 97.0 mm³ , p < .001 for all comparisons). Surface area was significantly larger for DRA than for SA (45.1 vs. 38.3 mm² , p < .001) and larger for DNRA than for SA (44.5 vs. 38.3 mm² , p < .001), but was similar between DRA and DNRA (45.1 vs. 44.5 mm² , p = .54). Steam-pops more frequently occurred for DRA than for SA (15.6% vs. 4.4%, p = .004) and DNRA (15.6% vs. 6.9%, p = .061), but the incidence was similar between SA and DNRA (4.4% vs. 6.9%, p = 1). Although surface area and lesion volume were larger in lesions with steam-pops than without steam-pops (46.5 vs. 38.1 mm² , p = .018 and 128.3 vs. 96.8 mm³ , p = .068, respectively), lesions were not deeper (pop(+): 2.5 mm vs. pop(-): 2.6 mm, p = .75).

CONCLUSIONS

DNRA produces larger lesions than SA without increasing the risk of steam-pops. DRA produces the largest lesions among the three groups, but with an increased risk of steam-pops. Even with steam-pops, lesions do not become deeper in vHPSD ablation.

In vivo tissue temperatures during 90 W/4 sec-very high power-short-duration (vHPSD) ablation versus ablation index-guided 50 W-HPSD ablation: A porcine study

INTRODUCTION

Neither the actual in vivo tissue temperatures reached with 90 W/4 s-very high-power short-duration (vHPSD) ablation for atrial fibrillation nor the safety and efficacy profile have been fully elucidated.

METHODS

We conducted a porcine study (n = 15) in which, after right thoracotomy, we implanted 6-8 thermocouples epicardially in the superior vena cava, right pulmonary vein, and esophagus close to the inferior vena cava. We compared tissue temperatures close to a QDOT MICRO catheter, between during 90 W/4 s-vHPSD ablation during ablation index (AI: target 400)-guided 50 W-HPSD ablation, both targeting a contact force of 8-15 g.

RESULTS

Maximum tissue temperature reached during 90 W/4 s-vHPSD ablation did not differ significantly from that during 50 W-HPSD ablation (49.2 ± 8.4°C vs. 50.0 ± 12.1°C; p = .69) and correlated inversely with distance between the catheter tip and the thermocouple, regardless of the power settings (r = -0.52 and r = -0.37). Lethal temperature (≥50°C) was best predicted at a catheter tip-to-thermocouple distance cut-point of 3.13 and 4.27 mm, respectively. All lesions produced by 90 W/4 s-vHPSD or 50 W-HPSD ablation were transmural. Although there was no difference in the esophageal injury rate (50% vs. 66%, p = .80), the thermal lesion was significantly shallower with 90 W/4 s-vHPSD ablation than with 50W-HPSD ablation (381.3 ± 127.3 vs. 820.0 ± 426.1 μm from the esophageal adventitia; p = .039).

CONCLUSION

Actual tissue temperatures reached with 90 W/4 s-vHPSD ablation appear similar to those with AI-guided 50 W-HPSD ablation, with the distance between the catheter tip and target tissue being shorter for the former. Although both ablation settings may create transmural lesions in thin atrial tissues, any resulting esophageal thermal lesions appear shallower with 90 W/4 s-vHPSD ablation.

High-power short-duration versus low-power long-duration ablation guided by the ablation index

AIMS

To compare the two different ablation strategies, both guided by the Ablation Index (AI), in the setting of atrial fibrillation (AF) ablation: high-power short-duration (HPSD) ablation using 40 W on the posterior wall and 50 W elsewhere versus low-power long-duration (LPLD) using 25 W posteriorly and 35 W elsewhere.

METHODS

Prospective, multicenter nonrandomized, noninferiority study of consecutive patients referred for paroxysmal AF ablation from January 2018 to July 2019. Ablation was guided by the AI (≥500 for anterior segments, ≥450 for the roof and inferior segments and 400 posteriorly) and an interlesion distance (ILD) ≤ 6 mm. Patients were separated into two groups: HPSD vs LPLD. Acute reconnection (after adenosine trial) and 2-year outcomes were assessed.

RESULTS

160 patients (61% males, median age of 62 [IQR 51-69] years), fulfilled the study inclusion criteria - 80 patients (316 pulmonary veins [PV]) in the HPSD group and 80 patients (314 PV) in the LPLD. The probability of acute PV reconnection was similar between both groups: 2.2% in HPSD, 95%CI 0.6% to 3.8% vs. 3.4% in LPLD, 95%CI 1.4% to 5.4%; p < 0.001 for noninferiority. Median PV ablation time (20 min vs 30 min, p < 0.01) and procedure duration (80 min vs 100 min, p < 0.001) were shorter in the HPSD group. After a median follow-up of 26 months, arrhythmia recurrence was similar between groups (17.5% in HPSD group vs. 18.8% in LPLD group, p = 0.79).

CONCLUSIONS

In paroxysmal AF patients treated with the Ablation Index, a HPSD strategy is noninferior to the more standard LPLD ablation, while allowing for quicker procedures with shorter ablation times.

Very High-Power Ablation for Contiguous Pulmonary Vein Isolation: Results From the Randomized POWER PLUS Trial

BACKGROUND

Very high-power, short-duration (90-W/4-second) ablation for pulmonary vein isolation (PVI) may reduce procedural times. However, shorter applications with higher power may impact lesion quality.

OBJECTIVES

In this multicenter, randomized controlled trial, we compared procedural efficiency, efficacy, and safety of PVI using 90-W/4-second ablation to 35/50-W ablation.

METHODS

Patients with paroxysmal or persistent atrial fibrillation undergoing first-time PVI were randomized to pulmonary vein encirclement with contiguous applications using very high-power, short-duration applications (90 W over 4 seconds) or 35/50-W applications (titrated up to ablation index >550 anteriorly and >400 posteriorly). Prospective endpoints were procedural efficiency (procedure time and first-pass isolation), safety (including esophageal endoscopic evaluation), and 6-month effectiveness using repetitive Holter monitoring.

RESULTS

One hundred eighty patients were randomized, 90 to the 90-W group (mean age: 64.2 ± 8.9 years) and 90 to the 35/50-W group (mean age: 62.3 ± 10.8 years). Procedural time was shorter in the 90-W group vs the 35/50-W group (70 [interquartile range: 60-80] vs 75 [interquartile range: 65-88.3] minutes; P = 0.009). A nonsignificant trend towards lower rates of first-pass isolation was seen in the 90-W group (83.9% vs 90%; P = 0.0852). No major complications were observed in both groups with esophageal injury occurring in 1 patient per group. At 6 months, 17% of patients in the 90-W group vs 15% in the 35/50-W group experienced recurrent arrhythmia (P = 0.681).

CONCLUSIONS

Contiguous ablation using very high-power, short-duration applications results in a significant but modest reduction in procedure time with similar safety and 6-month efficacy vs a conventional approach. A hybrid approach combining both ablation modalities might be the most optimal strategy. (POWER PLUS [Very High Power Ablation in Patients With Atrial Fibrillation Schedule for a First Pulmonary Vein Isolation]; NCT04784013).

Characterization of high-power and very-high-power short-duration radiofrequency lesions performed with a new-generation catheter and a temperature-control ablation mode

INTRODUCTION

High-power short-duration (HPSD) has been proposed to shorten procedure times while maintaining efficacy and safety. We evaluated the differences in size and geometry between radiofrequency lesions obtained with this method and conventional ones.

METHODS AND RESULTS

Twenty-eight sets of 10 perpendicular radiofrequency applications were performed with two commercially available catheters: a temperature-controlled HPSD catheter (QDot-Micro) and a conventional power-controlled catheter (Thermocool SmartTouch) on porcine left ventricle. Different power settings (35, 40, 50, and 90 W), contact force (CF; 10 and 20 g), ablation index (AI; 400 and 550), and application times were combined to create conventional (35-40 W), HPSD (50 W) and very-high-power short-duration (VHPSD; 90 W) lesions, that were cross-sectioned and measured. About 4-s VHPSD lesions were smaller, shallower, and thinner than HPSD performed with the QDot-Micro catheter in any scenario of CF or AI (61 ± 7.8 mm³ , 6.1 ± 0.3 mm wide, and 2.9 ± 0.1 mm deep with 10 g; 72.2 ± 0.5 mm³ , 6.8 ± 0.3 mm wide, and 2.9 ± 0.2 mm deep with 20 g). Conventional and HPSD lesions performed with the temperature-controlled catheter were generally bigger, deeper, and wider than the ones obtained with the power-controlled catheter, as well as more consistent in size. This was especially true with the lower CF and AI scenario, while differences were less notable with other setting combinations.

CONCLUSION

VHPSD lesions performed with QDot-Micro catheter were smaller than any other lesions, which is especially attractive for posterior left atrial wall ablation. On the contrary, conventional-powered and HPSD lesions performed with this catheter were equally sized (or even bigger with lower CF and AI objectives), as well as more consistent in size, which would guarantee transmurality in other locations.

Safety and Efficacy of a Novel Approach to Pulmonary Vein Isolation Using Prolonged Apneic Oxygenation

BACKGROUND

Improved ablation catheter-tissue contact results in more effective ablation lesions. Respiratory motion causes catheter instability, which impacts durable pulmonary vein isolation (PVI).

OBJECTIVES

This study sought to evaluate the safety and efficacy of a novel ablation strategy involving prolonged periods of apneic oxygenation during PVI.

METHODS

We conducted a multicenter, prospective controlled study of 128 patients (mean age 63 ± 11 years; 37% women) with paroxysmal atrial fibrillation undergoing PVI. Patients underwent PVI under general anesthesia using serial 4-minute runs of apneic oxygenation (apnea group; n = 64) or using standard ventilation settings (control group; n = 64). Procedural data, arterial blood gas samples, catheter position coordinates, and ablation lesion characteristics were collected.

RESULTS

Baseline characteristics between the 2 groups were similar. Catheter stability was significantly improved in the apnea group, as reflected by a decreased mean catheter displacement (1.55 ± 0.97 mm vs 2.25 ± 1.13 mm; P < 0.001) and contact force SD (4.9 ± 1.1 g vs 5.2 ± 1.5 g; P = 0.046). The percentage of lesions with a mean catheter displacement >2 mm was significantly lower in the apnea group (22% vs 44%; P < 0.001). Compared with the control group, the total ablation time to achieve PVI was reduced in the apnea group (18.8 ± 6.9 minutes vs 23.4 ± 7.8 minutes; P = 0.001). There were similar rates of first-pass PVI, acute PV reconnections and dormant PV reconnections between the two groups.

CONCLUSIONS

A novel strategy of performing complete PVI during apneic oxygenation results in improved catheter stability and decreased ablation times without adverse events. (Radiofrequency Ablation of Atrial Fibrillation Under Apnea; NCT04170894).

Very High-Power Short-Duration (HPSD) Ablation for Pulmonary Vein Isolation: Short and Long-Term Outcome Data

Background: Circumferential pulmonary vein isolation (PVI) using radiofrequency ablation (RFA) is a standard of care intervention for patients with symptomatic atrial fibrillation (AF). During follow-up, a substantial number of patients need a redo procedure due to reconnections on the basis of insufficient non-transmural ablation lesions. High-power short-duration ablation (HPSD) is expected to create efficient lesions while causing fewer complications than in conventional RFA settings. The aim of this study was to compare one-year outcome data of very HPSD (90 Watt, 4 s) to a strategy using 50 Watt HPSD ablation guided by the CLOSE protocol using the Ablation Index (AI), an arbitrary unit composed of power, contact force and ablation time. Methods: We retrospectively analyzed short and long-term (median follow-up 23.2 ± 9.9 months) outcome data from 52 patients that were scheduled for first-do-symptomatic PVI. A very HPSD ablation protocol with 90 Watt and a 4 s duration cut-off was compared to an HPSD CLOSE approach (50 Watts; AI 550 at the anterior LA wall; AI 400 at the posterior LA wall, the roof and the floor) in terms of freedom from AF recurrence in a long-term electrocardiogram (ECG) over a five days surveillance period. To gain an impression of the subjective sense of wellbeing, the Atrial Fibrillation Effects on QualiTy-of-Life (AFEQT) score was recorded. Results: Overall freedom from AF was found in 81% (90 W 4 s) vs. 87.5% (50 W), (p = 0.52). There were 3 AF recurrences during the blanking period (90 W 4 s) vs. 1 (50 W). Within each population, one patient was scheduled for a redo-PVI-procedure. The AFEQT score was in favor of the 90 Watt 4 s approach (86.1 vs. 77.5; p = 0.37). Conclusion: Within our relatively small studied population, we found hints that in addition to shortening ablation times and radiation exposure without significantly increasing the rate of relevant intraprocedural complications, very high power short-duration ablation (90 W 4 s) provides comparable efficacy rates after one year.