Lesion Index–Guided Ablation Facilitates Continuous, Transmural, and Durable Lesions in a Porcine Recovery Model

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.

A Novel Workflow for Electrophysiology Studies in Patients with Brugada Syndrome

Brugada Syndrome (BrS) is a primary electrical epicardial disease characterized by ST-segment elevation followed by a negative T-wave in the right precordial leads on the surface electrocardiogram (ECG), also known as the 'type 1' ECG pattern. The risk stratification of asymptomatic individuals with spontaneous type 1 ECG pattern remains challenging. Clinical and electrocardiographic prognostic markers are known. As none of these predictors alone is highly reliable in terms of arrhythmic prognosis, several multi-factor risk scores have been proposed for this purpose. This article presents a new workflow for processing endocardial signals acquired with high-density RV electro-anatomical mapping (HDEAM) from BrS patients. The workflow, which relies solely on Matlab software, calculates various electrical parameters and creates multi-parametric maps of the right ventricle. The workflow, but it has already been employed in several research studies involving patients carried out by our group, showing its potential positive impact in clinical studies. Here, we will provide a technical description of its functionalities, along with the results obtained on a BrS patient who underwent an endocardial HDEAM.

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, the Asia Pacific Heart Rhythm Society, and the Latin American Heart Rhythm Society .

Atrial Fibrillation Ablation: Current Practice and Future Perspectives

Catheter ablation to perform pulmonary vein isolation (PVI) is established as a mainstay in rhythm control of atrial fibrillation (AF). The aim of this review is to provide an overview of current practice and future perspectives in AF ablation. The main clinical benefit of AF ablation is the reduction of arrhythmia-related symptoms and improvement of quality of life. Catheter ablation of AF is recommended, in general, as a second-line therapy for patients with symptomatic paroxysmal or persistent AF, who have failed or are intolerant to pharmacological therapy. In selected patients with heart failure and reduced left-ventricular fraction, catheter ablation was proven to reduce all-cause mortality. Also, optimal management of comorbidities can reduce AF recurrence after AF ablation; therefore, multimodal risk assessment and therapy are mandatory. To date, the primary ablation tool in widespread use is still single-tip catheter radiofrequency (RF) based ablation. Additionally, balloon-based pulmonary vein isolation (PVI) has gained prominence, especially due to its user-friendly nature and established safety and efficacy profile. So far, the cryoballoon (CB) is the most studied single-shot device. CB-based PVI is characterized by high efficiency, convincing success rates, and a beneficial safety profile. Recently, CB-PVI as a first-line therapy for AF was shown to be superior to pharmacological treatment in terms of efficacy and was shown to reduce progression from paroxysmal to persistent AF. In this context, CB-based PVI gains more and more importance as a first-line treatment choice. Non-thermal energy sources, namely pulsed-field ablation (PFA), have garnered attention due to their cardioselectivity. Although initially applied via a basket-like ablation tool, recent developments allow for point-by-point ablation, particularly with the advent of a novel lattice tip catheter.

How to ablate the septo-pulmonary bundle: a case-based review of percutaneous ablation strategies to achieve roof line block

Electrical conduction through cardiac muscle fibres separated from the main myocardial wall by layers of interposed adipose tissue are notoriously difficult to target by endocardial ablation alone. They are a recognised important cause for procedural failure due to the difficulties of delivering sufficient energy via the endocardial radiofrequency catheter to reach the outer epicardial layer without risking adverse events of the otherwise thin walled atria. Left atrial ablations for atrial fibrillation (AF) and tachycardia are commonly affected by the presence of several epicardial structures, with the septo-pulmonary bundle (SPB), Bachmann's bundle, and the ligament of Marshall all posing substantial challenges for endocardial procedures. Delivery of a transmural lesion set is essential for sustained pulmonary vein isolation and for conduction block across linear atrial lines which in turn has been described to translate into a reduced AF/atrial tachycardia recurrence rate. To overcome the limitations of endocardial-only approaches, surgical ablation techniques for epicardial or combined hybrid endo-epicardial ablations have been described to successfully target these connections. Yet, these techniques confer an increase in procedure complexity, duration, cost, and morbidity. Alternatively, coronary venous system ethanol ablation has been successfully employed by sub-selecting the vein of Marshall to facilitate mitral isthmus line block, although this approach is naturally limited to this area by the coronary venous anatomy. Increased awareness of the pathophysiological relevance of these epicardial structures and their intracardiac conduction patterns in the era of high-resolution 3D electro-anatomical mapping technology has allowed greater understanding of their contribution to the persistence of AF as well as failure to achieve transmural block by traditional ablation approaches. This might translate into novel catheter ablation strategies with procedural success rates comparable to surgical 'cut-and-sew' techniques. This review aims to give an overview of percutaneous catheter ablation strategies to target the SPB, an important cause of failed block across the roof line and isolation of the left atrial posterior wall and/or the pulmonary veins. Existing and investigational technologies will be discussed and an outlook of future approaches provided.

Progress in atrial fibrillation ablation during 25 years of Europace journal

The first edition of Europace journal in 1999 came right around the time of the landmark publication of the electrophysiologists from Bordeaux, establishing how elimination of ectopic activity from the pulmonary veins (PVs) resulted in a marked reduction of atrial fibrillation (AF). The past 25 years have seen an incredible surge in scientific interest to develop new catheters and energy sources to optimize durability and safety of ablation, as well as study the mechanisms for AF and devise ablation strategies. While ablation in the beginning was performed with classic 4 mm tip catheters that emitted radiofrequency (RF) energy to create tissue lesions, this evolved to using irrigation and contact force (CF) measurement while increasing power. Also, so-called single-shot devices were developed with balloons and arrays to create larger contiguous lesions, and energy sources changed from RF current to cryogenic ablation and more recently pulsed field ablation with electrical current. Although PV ablation has remained the basis for every AF ablation, it was soon recognized that this was not enough to cure all patients, especially those with non-paroxysmal AF. Standardized approaches for additional ablation targets have been used but have not been satisfactory in all patients so far. This led to highly technical mapping systems that are meant to unravel the drivers for the maintenance of AF. In the following sections, the development of energies, strategies, and tools is described with a focus on the contribution of Europace to publish the outcomes of studies that were done during the past 25 years.

Trends over the recent 6 years in ablation modalities and strategies, post-ablation medication, and clinical outcomes of atrial fibrillation ablation

Background

Ablation strategies and modalities for atrial fibrillation (AF) have transitioned over the past decade, but their impact on post-ablation medication and clinical outcomes remains to be fully investigated.

Methods

We divided 682 patients who had undergone AF ablation in 2014-2019 (420 paroxysmal AFs [PAF], 262 persistent AFs [PerAF]) into three groups according to the period, that is, the 2014-2015 (n = 139), 2016-2017 (n = 244), and 2018-2019 groups (n = 299), respectively.

Results

Persistent AF became more prevalent and the left atrial (LA) diameter larger over the 6 years. Extra-pulmonary vein (PV)-LA ablation was more frequently performed in the 2014-2015 group than in the 2016-2017 and 2018-2019 groups (41.1% vs. 9.1% and 8.1%; p < .001). The 2-year freedom rate from AF/atrial tachycardias for PAF was similar among the three groups (84.0% vs. 83.1% vs. 86.7%; p = .98) but lowest in the 2014-2015 group for PerAF (63.9% vs. 82.7% and 86.3%; p = .025) despite the highest post-ablation antiarrhythmic drug use. Cardiac tamponade was significantly decreased in the 2018-2019 group (3.6% vs. 2.0% vs. 0.33%; p = 0.021). There was no difference in the 2-year clinically relevant events among the three groups.

Conclusion

Although ablation was performed in a more diseased LA and extra-PV-LA ablation was less frequent in recent years, the complication rate decreased, and AF recurrences for PAF remained unchanged, but that for PerAF decreased. Clinically relevant events remained unchanged over the recent 6 years, suggesting that the impact of the recent ablation modalities and strategies on remote clinically relevant events may be small during this study period.

Risk factors for late reconnections after circumferential pulmonary vein isolation guided by lesion size index - Data from repeat invasive electrophysiology procedure

Background

Late reconnections (LR) of pulmonary veins (PVs) after wide antral circumferential ablation (WACA) using point-to-point radiofrequency (RF) ablation are common. Lesion size index (LSI) is a novel marker of lesion quality proposed by Ensite Precision mapping system, expected to improve PV isolation durability. This study aimed to assess the durability of LSI-guided PVI and the risk factors for LR of PVs.

Methods

The prospective study included 33 patients with paroxysmal atrial fibrillation (PAF) who underwent (1) the index LSI-guided WACA procedure (with target LSI of 5.5-6.0 for anterior and 5.0-5.5 for posterior WACA segments) and (2) the 3-month protocol-mandated re-mapping procedure in all patients, irrespective of AF recurrence after the index procedure. Ablation parameters reported by Ensite mapping system were collected retrospectively. The inter-lesion distance (ILD) between all adjacent WACA lesions was calculated off-line. Association between index ablation parameters and the LRs of PVs at 3 months was analyzed.

Results

The median patient age was 61 (IQR: 53-64) years and 55% of them were males. At index procedure, the first-pass WACA isolation rate was higher for the left PVs than the right PVs (64 vs. 33%, p = 0.014). In addition, a low acute reconnection rates were observed, as follows: in 12.1% of patients, in 6.1% of WACA circles, in 3.8% of WACA segments and in 4.5% of PVs. However, the 3-month remapping study revealed LR of PV in 63.6% of patients, 37.9% of WACA circles, 20.5% of WACA segments and 26.5% of PVs. The LRs were identified mostly along the left anterior WACA segment. Independent risk factors for the LR of WACA were left-sided WACA location (OR 3.216 [95%CI: 1.065-9.716], p = 0.038) and longer ILD (OR 1.256 [95%CI: 1.035-1.523] for each 1-mm increase, p = 0.021). The ILD of > 8.0 mm showed a predictive value for the LR of WACA, with the sensitivity of 84% and specificity of 46%. A single case of cardiac tamponade occurred following the re-mapping invasive procedure. No other complications were encountered.

Conclusion

Although the LSI-guided PVI ensures a consistent PVI during the index procedure, LRs of PVs are still common. Besides the LSI, the PVI durability requires an optimal ILD between adjacent lesions, especially along the anterior lateral ridge.

In vivo tissue temperature during lesion size index-guided 50W ablation versus 30W ablation: A porcine study

BACKGROUND

Neither the actual in vivo tissue temperatures reached with lesion size index (LSI)-guided high-power short-duration (HPSD) ablation for atrial fibrillation nor the safety profile has been elucidated.

METHODS

We conducted a porcine study (n = 7) 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 reached during 50 W-HPSD ablation with those reached during standard (30 W) ablation, both targeting an LSI of 5.0 (5-15 g contact force).

RESULTS

T_max  (maximum tissue temperature when the thermocouple was located ≤5 mm from the catheter tip) reached during HPSD ablation was modestly higher than that reached during standard ablation (58.0 ± 10.1°C vs. 53.6 ± 9.2°C; p = .14) and peak tissue temperature correlated inversely with the distance between the catheter tip and the thermocouple, regardless of the power settings (HPSD: r = -0.63; standard: r = -0.66). Lethal temperature (≥50°C) reached 6.3 ± 1.8 s and 16.9 ± 16.1 s after the start of HPSD and standard ablation, respectively (p = .002), and it was best predicted at a catheter tip-to-thermocouple distance cut point of 2.8 and 5.3 mm, respectively. All lesions produced by HPSD ablation and by standard ablation were transmural. There was no difference between HPSD ablation and standard ablation in the esophageal injury rate (70% vs. 75%, p = .81), but the maximum distance from the esophageal adventitia to the injury site tended to be shorter (0.94 ± 0.29 mm vs. 1.40 ± 0.57 mm, respectively; p = .09).

CONCLUSIONS

Actual tissue temperatures reached with LSI-guided HPSD ablation appear to be modestly higher, with a shorter distance between the catheter tip and thermocouple achieving lethal temperature, than those reached with standard ablation. HPSD ablation lasting <6 s may help minimize lethal thermal injury to the esophagus lying at a close distance.

Augmented wide area circumferential catheter ablation for reduction of atrial fibrillation recurrence (AWARE) trial: Design and rationale

BACKGROUND

Recurrence of atrial fibrillation (AF) after a pulmonary vein isolation procedure is often due to electrical reconnection of the pulmonary veins. Repeat ablation procedures may improve freedom from AF but are associated with increased risks and health care costs. A novel ablation strategy in which patients receive "augmented" ablation lesions has the potential to reduce the risk of AF recurrence.

OBJECTIVE

The Augmented Wide Area Circumferential Catheter Ablation for Reduction of Atrial Fibrillation Recurrence (AWARE) Trial was designed to evaluate whether an augmented wide-area circumferential antral (WACA) ablation strategy will result in fewer atrial arrhythmia recurrences in patients with symptomatic paroxysmal AF, compared with a conventional WACA strategy.

METHODS/DESIGN

The AWARE trial was a multicenter, prospective, randomized, open, blinded endpoint trial that has completed recruitment (ClinicalTrials.gov NCT02150902). Patients were randomly assigned (1:1) to either the control arm (single WACAlesion set) or the interventional arm (augmented- double WACA lesion set performed after the initial WACA). The primary outcome was atrial tachyarrhythmia (AA; atrial tachycardia [AT], atrial flutter [AFl] or AF) recurrence between days 91 and 365 post catheter ablation. Patient follow-up included 14-day continuous ambulatory ECG monitoring at 3, 6, and 12 months after catheter ablation. Three questionnaires were administered during the trial- the EuroQuol-5D (EQ-5D) quality of life scale, the Canadian Cardiovascular Society Severity of Atrial Fibrillation scale, and a patient satisfaction scale.

DISCUSSION

The AWARE trial was designed to evaluate whether a novel approach to catheter ablation reduced the risk of AA recurrence in patients with symptomatic paroxysmal AF.

Calculated parameters of luminal esophageal temperatures predict esophageal injury following conventional and high-power short-duration radiofrequency pulmonary vein isolation

BACKGROUND

Luminal esophageal temperature (LET) monitoring is not associated with reduced esophageal injury following pulmonary vein isolation (PVI).

OBJECTIVE

Detailed analysis of (the temporal and spatial gradients of) LET measurements may better predict the risk for esophageal injury.

METHODS

Between January 2020 and December 2021, LET maxima, duration of LET rise above baseline, and area under the LET curve (AUC) were calculated offline and correlated with (endoscopy and endoscopic ultrasound detected) esophageal injury (i.e., mucosal esophageal lesions [ELs], periesophageal edema, and gastric motility disorders) following PVI using moderate-power moderate-duration (MPMD [25-30 W/25-30s]) and high-power short-duration (HPSD [50 W/13s]) radiofrequency (RF) settings.

RESULTS

63 patients (69 ± 9 years old, 32 male, 51 MPMD and 12 HPSD) were studied. The esophageal injury was frequent (40% in both groups), mucosal ELs were more common with MPMD, and edema was frequently observed following HPSD. RF-duration, total RF-energy at the left atrial (LA) posterior wall, and distance between LA and esophagus were not different between patients with/without esophageal injury. In contrast, to LET and LET duration above baseline, AUC was the best predictor and significantly increased in patients with esophageal injury (3422 vs. 2444 K^. s).

CONCLUSION

For both ablation strategies, AUC of the LET curves best predicted esophageal injury. HPSD is associated with similar rates of esophageal injury when (mostly subclinical) periesophageal alterations (that are of unclear clinical relevance) are included. Whether integration of these calculated LET parameters is useful to prevent esophageal injury remains to be seen.

Impact of baseline impedance of pulmonary vein antrum on success of catheter ablation for paroxysmal atrial fibrillation guided by ablation index

Objective

Ablation index (AI) is an effective ablation quality marker. Impedance is also an important factor for lesion formation. The present study evaluated the influence of the baseline impedance in the effect of ablation for atrial fibrillation (AF) guided by AI.

Methods

This was a retrospective study. 101 patients with paroxysmal AF (PAF) were enrolled. All patients underwent radiofrequency ablation guided by the same AI strategy. The ablation strategy was pulmonary vein (PV) isolation with non-PV triggers ablation. The baseline impedance of the ablation points was recorded. The patients were followed up every 3 months or so.

Results

During a median follow-up of 12 (4–14) months, freedom from AF/atrial tachycardia recurrence were 82.2%. No difference existed in baseline characteristics between the success group and the recurrence group. The average baseline impedance was 124.3 ± 9.7 Ω. The baseline impedance of the ablation points in success group was lower compared to the recurrence group (122.9 ± 9.4 vs. 130.5 ± 8.8 Ω, P < 0.01). The ratio of impedance drop in the success group was higher than the recurrence group ([8.8 ± 1.4]% vs. [8.1 ± 1.2]%, P = 0.03). Multivariate analysis revealed that baseline impedance, PAF duration and AI were the independent predictors of AF recurrence. The cumulative free of recurrence rate of low-impedance group (≤ 124 Ω, n = 54) was higher than that of high-impedance group.

Conclusion

Baseline impedance correlates with clinical outcome of radiofrequency ablation for PAF guided by AI. Higher impedance in the same AI strategy may result in an ineffective lesion which probably causes recurrence.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-022-02530-y.

In vivo Lesion Index (LSI) validation in percutaneous radiofrequency catheter ablation

INTRODUCTION

Lesion Index (LSI) has been developed to predict lesion efficacy during radiofrequency (RF) catheter ablation. However, its value in predicting lesions size has still to be established. The aim of our study was to assess the lesions size reproducibility for pre-specified values of LSI reached during RF delivery in an in vivo beating heart.

METHODS

Ablation lesions were created with different values of LSI in 7 domestic pigs by means of a contact force sensing catheter (TactiCath^TM , Abbott). Lesions were identified during RF delivery by means of a 3D mapping system (EnSite^TM Precision, Abbott) and measured after heart explantation. Histology was carried out after gross examination on the first 3 lesions to confirm the accuracy of the macroscopic evaluation.

RESULTS

A total of 64 myocardial lesions were created. Thirty-nine lesions were excluded from the analysis for the following reasons: histological confirmation of macroscopic lesion measurement (n=3), transmurality (n=24), unfavorable anatomic position (n=10), not macroscopically identifiable (n=2). In a final set of 25 non-transmural lesions, injury width and depth were respectively 4.6±0.6 mm and 2.6±0.8 mm for LSI=4, 7.3±0.8 mm and 4.7±0.6 mm for LSI=5, and 8.6±1.2 mm and 7.2±1.1 mm for LSI=6. A strong linear correlation was observed between LSI and lesion width (r=0.87, p<0.00001) and depth (r=0.89, p<0.00001). Multiple linear regression analysis identified LSI as the only ablation parameter that significantly predicted lesion width (p<0.001) and depth (p<0.001).

CONCLUSION

In our in vivo study, LSI proved highly predictive of lesion size and depth. This article is protected by copyright. All rights reserved.

Radiofrequency Ablation: Four Decades Later, Still Optimizing Lesion Characterization

Intracardiac catheter ablation was first introduced in the early 1980s with a direct current shock used as the energy source. This article is protected by copyright. All rights reserved.

Recurrent atrial arrhythmia in a randomised controlled trial comparing contact force-guided and contact force-blinded ablation for typical atrial flutter

BACKGROUND

Contact force (CF)-guided catheter ablation (CA) is a novel technology developed to improve efficacy and reduce complications. In a randomised controlled trial (RCT), we previously documented that after 3 months, rate of persistent conduction block was similar with and without using CF while performing CA for typical atrial flutter (AFL). Clinical effect of CF on recurrent arrhythmia is unknown. Our objective is to study recurrent atrial arrhythmia during 12-month follow-up in a RCT investigating whether CF-guided CA for typical AFL is superior to CF-blinded CA.

METHODS

Patients were randomised 1:1 to CA guided by CF (intervention group) or blinded to CF (control group). After 12 months, patients attended clinical check-up preceded by a 5-day ambulatory Holter monitor recording. Primary outcome was any recurrent atrial arrhythmia ≥ 30 s within 12 months and documented in 12-lead ECG or Holter monitor recording.

RESULTS

We included 156 patients, four patients withdrew consent and two died during follow-up. Thus, 150 patients were included in final analysis. Recurrent arrhythmia was detected in 36 of 77 (47%) patients in the intervention group, and 32 of 73 patients (44%) in the control group (p = 0.51). Atrial fibrillation was detected in 23 (30%) and 29 (40%) patients in the intervention and control groups respectively. AFL was detected in 11 (14%) and 5 (7%) patients in the intervention and control groups respectively.

CONCLUSIONS

Contact force-guided ablation for typical atrial flutter does not reduce recurrent atrial arrhythmia after 12-month follow-up as compared with ablation blinded for contact force.

Impact of power and contact force on index-guided radiofrequency lesions in an ex vivo porcine heart model

PURPOSE

Lesion size index (LSI) and ablation index (AI) are markers of lesion quality that incorporate power, contact force (CF) and time in a weighted formula to estimate lesion size. Although accurate predicting lesion depth in vitro, their precision in lesion size estimation has not been well established for certain power and CF settings. We conducted an experimental ex vivo study to analyse the effect of power and CF in size and morphology of ablation lesions in a porcine heart model.

METHODS

Twenty-four sets of 10 perpendicular epicardial radiofrequency applications were performed with two commercially available catheters (TactiCath, Sensor Enabled; and SmartTouch) on porcine left ventricle submerged in 37 °C saline, combining different power (25, 30, 35, 40, 50 and 60 W) and CF (10 and 20 g) settings, and aiming at a lower (LSI/AI of 5/400) or higher (LSI/AI of 6/550) index. After each application, lesions were cross-sectioned and measured.

RESULTS

Four hundred eighty lesions were performed. For a given target index and CF, significant differences in lesion volume and depth with different power were observed with both catheters, generally with smaller lesions using higher power. Lesions performed with CF of 10 g were particularly smaller with TactiCath compared to SmartTouch; lesions with CF of 20 g aiming a low LSI/AI were, however, bigger; lesions with CF of 20 g aiming a high LSI/AI were similar. In general, high-power lesions were wider and shallower than low-power lesions, especially with SmartTouch.

CONCLUSION

Size and morphology of index-guided radiofrequency lesions varied significantly with different power and CF settings.

Radiofrequency ablation to achieve durable pulmonary vein isolation

Pulmonary vein isolation (PVI) by radiofrequency (RF) ablation is an important alternative to antiarrhythmic drugs in the treatment of symptomatic atrial fibrillation. However, the inability to consistently achieve durable isolation of the pulmonary veins hampers the long-term efficacy of PVI procedures. The large number of factors involved in RF lesion formation and the complex interplay of these factors complicate reliable creation of durable and transmural ablation lesions. Various surrogate markers of ablation lesion formation have been proposed that may provide information on RF lesion completeness. Real-time assessment of these surrogates may aid in the creation of transmural ablation lesions, and therefore, holds potential to decrease the risk of PV reconnection and consequent post-PVI arrhythmia recurrence. Moreover, titration of energy delivery until lesions is transmural may prevent unnecessary ablation and subsequent adverse events. Whereas several surrogate markers of ablation lesion formation have been described over the past decades, a 'gold standard' is currently lacking. This review provides a state-of-the-art overview of ablation strategies that aim to enhance durability of RF-PVI, with special focus on real-time available surrogates of RF lesion formation in light of the biophysical basis of RF ablation.

High-power, short-duration ablation for atrial fibrillation: Pros and cons

This article reviews and compares the rationale and evidence supporting high-power, short-duration radiofrequency (RF) ablation with those of conventional-power, conventional-duration RF ablation for atrial fibrillation (AF). The pros and cons of each approach, biophysics of ablation, pre-clinical studies informing clinical utilization, and the accumulated clinical evidence are presented. Both conventional-power, conventional-duration RF ablation and high-power, short-duration ablation are similarly safe, and effective approaches for AF ablation. Theoretical advantages of high-power, short-duration ablation, including greater procedure efficiency and limited conductive heating of collateral structures, must be weighed against the narrower safety margin related to rapid energy delivery during high power ablation.

Efficacy and safety of ablation index-guided catheter ablation for atrial fibrillation: an updated meta-analysis

AIMS

Despite recent advances in catheter ablation for atrial fibrillation (AF), pulmonary vein reconnection (PVR), and AF recurrence remain significantly high. Ablation index (AI) is a new method incorporating contact force, time, and power that should optimize procedural outcomes. We aimed to evaluate the efficacy and safety of AI-guided catheter ablation compared to a non-AI-guided approach.

METHODS AND RESULTS

A systematic search was performed on MEDLINE (via PubMED), EMBASE, COCHRANE, and European Society of Cardiology (ESC) databases (from inception to 1 July 2019). We included only studies that compared AI-guided with non-AI-guided catheter ablation of AF. Eleven studies reporting on 2306 patients were identified. Median follow-up period was 12 months. Ablation index-guided ablation had a significant shorter procedural time (141.0 vs. 152.8 min, P = 0.01; I2 = 90%), ablation time (21.8 vs. 32.0 min, P < 0.00001; I2 = 0%), achieved first-pass isolation more frequently [odds ratio (OR) = 0.09, 95%CI 0.04-0.21; 93.4% vs. 62.9%, P < 0.001; I2 = 58%] and was less frequently associated with acute PVR (OR = 0.37, 95%CI 0.18-0.75; 18.0% vs 35.0%; P = 0.006; I2 = 0%). Importantly, atrial arrhythmia relapse post-blanking was significantly lower in AI compared to non-AI catheter ablation (OR = 0.41, 95%CI 0.25-0.66; 11.8% vs. 24.9%, P = 0.0003; I2 = 35%). Finally, there was no difference in complication rate between AI and non-AI ablation, with the number of cardiac tamponade events in the AI group less being numerically lower (OR = 0.69, 95%CI 0.30-1.60, 1.6% vs. 2.5%, P = 0.39; I2 = 0%).

CONCLUSIONS

These data suggest that AI-guided catheter ablation is associated with increased efficacy of AF ablation, while preserving a comparable safety profile to non-AI catheter ablation.

Predicting early reconnection after cryoballoon ablation with procedural and biophysical parameters

BACKGROUND

Predicting early reconnection/dormant conduction (ERC) immediately after pulmonary vein isolation (PVI) can avoid a waiting period with adenosine testing.

OBJECTIVE

To identify procedural and biophysical parameters predicting ERC.

METHODS

Consecutive atrial fibrillation (AF) patients undergoing a first cryoballoon ablation (Arctic Front Advance) between 2014 and 2017 were included. ERC was defined as manifest or dormant pulmonary vein (PV) reconnection with adenosine 30 minutes after PVI. Time to isolation (TTI), balloon temperatures (BT), and thawing times were evaluated as potential predictors for ERC. Based on a multivariable model, cut-off-values were defined and a formula was constructed to be used in clinical practice.

RESULTS

A total of 136 patients (60 ± 10 years, 96 male, 95% paroxysmal AF) were included. ERC was found in 40 (29%) patients (ERC group) and in 53 of 575 (9%) veins. Procedural and total ablation time and the number of unsuccessful freezes were significantly longer/higher in the ERC group compared to the non-ERC group (150 ± 40 vs 125 ± 34 minutes; 24 ± 5 vs 17 ± 4 minutes, and 38% vs 24%, respectively (P = .028). Multivariable analysis showed that a higher nadir balloon temperature (hazard ratio [HR] 1.17 [1.09-1.23, P < .001), a higher number of unsuccessful freezes (HR 1.69 [1.15-2.49], P = .008) and a longer TTI (HR 1.02 [1.01-1.03], P < .001) were independently associated with ERC, leading to the following formula: 0.02 × TTI + 0.5 × number of unsuccessful freezes + 0.2 × nadir BT with a cut-off value of ≤-6.7 to refrain from a waiting period with adenosine testing.

CONCLUSION

Three easily available parameters were associated with ERC. Using these parameters during ablation can help to avoid a 30-minute waiting period and adenosine testing.

Lesion size and adjacent tissue damage assessment with high power and short duration radiofrequency ablation: comparison to conventional radiofrequency ablation power setting

There is increased interest in creating high-power short duration (HPSD) ablation lesions in the field of atrial fibrillation (AF) radiofrequency ablation (RFA). We evaluated the lesion characteristics and collateral damage using two separate RFA protocols setting (HPSD: 50 W and 7 s vs control: 25 W and 30 s) in vitro model. Sixteen freshly killed porcine hearts were obtained, and the atrium and ventricle slabs were harvested for ablation. The each slabs were placed in a tissue bath with circulating 0.9% NaCl at maintained temperature 37 °C. RFA was performed with 4 mm tip irrigated force sensing catheter. All lesions were ablated under recording the electrical parameters using with Ensite Navx system (St. Jude Medical, St. Paul, Minnesota). After RFA, lesion characteristics were assessed for each lesion. Thirty-five lesions were made for each ablation protocol (total 70 lesions for analysis). Ablation parameters were similar between two groups (HPSD vs control; impedance drop (Ω): 34.2 ± 13.1 vs 36.1 ± 8.65 P = 0.49, contact force (g): 13.9 ± 4.37 vs 14.6 ± 5.09, P = 0.51, lesion size index: 4.8 ± 0.52 vs 4.73 ± 0.59, P = 0.62). Although the lesion volume was similar, the HPSD ablation creates wider but more shallower lesions compared to control group (HPSD vs control; lesion volume: 29.6 ± 18.1 mm³ vs 35.5 ± 17.1 mm³ P = 0.16, lesion diameter: 4.98 ± 0.91 mm vs 4.45 ± 0.74 mm P = 0.0095, lesion depth: 2.2 ± 0.76 mm vs 2.8 ± 1.56 mm P = 0.046). Of these, 38 lesions were assessed for adjacent tissue damage and adjacent tissue damages were more frequent seen in control group (HPSD vs control; 1/19 (5.26%) vs 6/19 (31.5%), P = 0.036). Effective lesions were made with HPSD, thereby reducing RFA procedure time. Although the lesion volume was similar between two groups, collateral damage was less seen in HPSD group attributed by lesion characteristics.

Initial experience of the High-Density Grid catheter in patients undergoing catheter ablation for atrial fibrillation

PURPOSE

A significant proportion of patients undergoing catheter ablation for atrial fibrillation (AF) experience arrhythmia recurrence. This is mostly due to pulmonary vein reconnection (PVR). Whether mapping using High-Density Wave (HDW) technology is superior to standard bipolar (SB) configuration at detecting PVR is unknown. We aimed to evaluate the efficacy of HDW technology compared to SB mapping in identifying PVR.

METHODS

High-Density (HD) multipolar Grid catheters were used to create left atrial geometries and voltage maps in 36 patients undergoing catheter ablation for AF (either due to recurrence of an atrial arrhythmia from previous AF ablation or de novo AF ablation). Nineteen SB maps were also created and compared. Ablation was performed until pulmonary vein isolation was achieved.

RESULTS

Median time of mapping with HDW was 22.3 [IQR: 8.2] min. The number of points collected with HDW (13299.6±1362.8 vs 6952.8±841.9, p<0.001) and used (2337.3±158.0 vs 1727.5±163.8, p<0.001) was significantly higher compared to SB. Moreover, HDW was able to identify more sleeves (16 for right and 8 for left veins), where these were confirmed electrically silent by SB, with significantly increased PVR sleeve size as identified by HDW (p<0.001 for both right and left veins). Importantly, with the use of HDW, the ablation strategy changed in 23 patients (64% of targeted veins) with a significantly increased number of lesions required as compared to SB for right (p=0.005) and left veins (p=0.003).

CONCLUSION

HDW technology is superior to SB in detecting pulmonary vein reconnections. This could potentially result into a significant change in ablation strategy and possibly to increased success rate following pulmonary vein isolation.

OpenEP: A Cross-Platform Electroanatomic Mapping Data Format and Analysis Platform for Electrophysiology Research

BACKGROUND

Electroanatomic mapping systems are used to support electrophysiology research. Data exported from these systems is stored in proprietary formats which are challenging to access and storage-space inefficient. No previous work has made available an open-source platform for parsing and interrogating this data in a standardized format. We therefore sought to develop a standardized, open-source data structure and associated computer code to store electroanatomic mapping data in a space-efficient and easily accessible manner.

METHODS

A data structure was defined capturing the available anatomic and electrical data. OpenEP, implemented in MATLAB, was developed to parse and interrogate this data. Functions are provided for analysis of chamber geometry, activation mapping, conduction velocity mapping, voltage mapping, ablation sites, and electrograms as well as visualization and input/output functions. Performance benchmarking for data import and storage was performed. Data import and analysis validation was performed for chamber geometry, activation mapping, voltage mapping and ablation representation. Finally, systematic analysis of electrophysiology literature was performed to determine the suitability of OpenEP for contemporary electrophysiology research.

RESULTS

The average time to parse clinical datasets was 400 ± 162 s per patient. OpenEP data was two orders of magnitude smaller than compressed clinical data (OpenEP: 20.5 ± 8.7 Mb, vs clinical: 1.46 ± 0.77 Gb). OpenEP-derived geometry metrics were correlated with the same clinical metrics (Area: R 2 = 0.7726, P < 0.0001; Volume: R 2 = 0.5179, P < 0.0001). Investigating the cause of systematic bias in these correlations revealed OpenEP to outperform the clinical platform in recovering accurate values. Both activation and voltage mapping data created with OpenEP were correlated with clinical values (mean voltage R 2 = 0.8708, P < 0.001; local activation time R 2 = 0.8892, P < 0.0001). OpenEP provides the processing necessary for 87 of 92 qualitatively assessed analysis techniques (95%) and 119 of 136 quantitatively assessed analysis techniques (88%) in a contemporary cohort of mapping studies.

CONCLUSIONS

We present the OpenEP framework for evaluating electroanatomic mapping data. OpenEP provides the core functionality necessary to conduct electroanatomic mapping research. We demonstrate that OpenEP is both space-efficient and accurately representative of the original data. We show that OpenEP captures the majority of data required for contemporary electroanatomic mapping-based electrophysiology research and propose a roadmap for future development.

Standardised computed tomographic assessment of left atrial morphology and tissue thickness in humans

AIMS

Left atrial (LA) remodelling is a common feature of many cardiovascular pathologies and is a sensitive marker of adverse cardiovascular outcomes. The aim of this study was to establish normal ranges for LA parameters derived from coronary computed tomographic angiography (CCTA) imaging using a standardised image processing pipeline to establish normal ranges in a previously described cohort.

METHODS

CCTA imaging from 193 subjects recruited to the Budapest GLOBAL twin study was analysed. Indexed LA cavity volume (LACVi), LA surface area (LASAi), wall thickness and LA tissue volume (LATVi) were calculated. Wall thickness maps were combined into an atlas. Indexed LA parameters were compared with clinical variables to identify early markers of pathological remodelling.

RESULTS

LACVi is similar between sexes (31 ml/m2 v 30 ml/m2) and increased in hypertension (33 ml/m2 v 29 ml/m2, p = 0.009). LASAi is greater in females than males (47.8 ml/m2 v 45.8 ml/m2 male, p = 0.031). Median LAWT was 1.45 mm. LAWT was lowest at the inferior portion of the posterior LA wall (1.14 mm) and greatest in the septum (median = 2.0 mm) (p < 0.001). Conditions known to predispose to the development of AF were not associated with differences in tissue thickness.

CONCLUSIONS

The reported LACVi, LASAi, LATVi and tissue thickness derived from CCTA may serve as reference values for this age group and clinical characteristics for future studies. Increased LASAi in females in the absence of differences in LACVi or LATVi may indicate differential LA shape changes between the sexes. AF predisposing conditions, other than sex, were not associated with detectable changes in LAWT.Clinical trial registration:http://www.ClinicalTrials.gov/NCT01738828.

HPSD ablation for AF high-power short-duration RF ablation for atrial fibrillation: A review

This manuscript reviews the literature for all in silico, ex vivo, in vitro, in vivo and clinical studies of high-power short-duration (HPSD) radiofrequency (RF) ablations. It reviews the biophysics of RF energy delivery applicable to HPSD and the use of surrogate endpoints to guide the duration of HPSD ablations. In silico modeling shows that a variety of settings in power, contact force and RF duration can result in the same surrogate endpoint value of ablation index and several HPSD combinations produce lesion volumes similar to a low-power long-duration (LPLD) RF application. HPSD lesions are broader with more endocardial effect and are slightly shallower but still transmural. The first 10 s of RF application is most important for lesion formation with diminishing effect beyond 20 s. The ideal contact force is 10-20 g with only a small effect beyond 30 g. In vitro and in vivo models confirm that HPSD makes transmural lesions that are often broader and shallower, and with proper settings, result in fewer steam pops than LPLD. One randomized trial shows better outcomes with HPSD and validates lesion size index as a surrogate endpoint. Clinical studies of HPSD using comparator groups of LPLD ablations uniformly show shorter procedure times and shorter total RF energy delivery for HPSD. HPSD generally has a higher first pass vein isolation rate and a lower acute vein reconnection rate than LPLD. Although not dramatically different from LPLD, long-term freedom from atrial fibrillation and complication rates seem slightly better with HPSD.

Optimizing Impedance Change Measurement During Radiofrequency Ablation Enables More Accurate Characterization of Lesion Formation

OBJECTIVES

This study sought to determine whether a novel impedance thermal imaging system (ITIS) provides an impedance measurement that is better correlated with lesion dimensions than circuit impedance during radiofrequency (RF) ablation.

BACKGROUND

A 5- to 10-Ω impedance drop is clinically used to corroborate an effective RF ablation lesion. However, the contribution of local tissue heating to circuit impedance change is small and dependent on the local environment of the catheter and placement of the grounding patch.

METHODS

ITIS uses ablation catheter and skin electrodes to perform 4-terminal impedance measurements with separate voltage sensing and current injection electrode pairs. Seven sheep underwent endocardial ventricular irrigated RF ablation at 40 W for 60 s. ITIS impedance and circuit impedance were both measured throughout ablation. When the sheep were sacrificed, ablation lesions were cut along their long axis; the depth, width, and surface area of the cut surface were measured.

RESULTS

A total of 68 RF ablations were performed, with a median depth of 3.5 mm (interquartile range [IQR]: 2.1 to 4.9 mm), width of 8.3 mm (IQR: 5.7 to 10.8 mm), and surface area of 23.8 mm² (IQR: 9.3 to 43.0 mm²). ITIS impedance change had good correlation with lesion depth, width, and surface area (R = 0.76, R = 0.87, and R = 0.87, respectively); and superior to circuit impedance for lesion depth, width, and surface area (p = 0.0018, p = 0.0004, and p = 0.0001, respectively).

CONCLUSIONS

By optimizing the current path and using 4-terminal impedance measurement during RF ablation, the contribution of tissue temperature changes to measured impedance is better standardized to provide a more reliable measure than conventional ablation circuit impedance.

The force stability of tissue contact and lesion size index during radiofrequency ablation: An ex-vivo study

INTRODUCTION

Radiofrequency (RF) ablation is a commonly used tool in the invasive electrophysiology laboratory to treat a variety of rhythm disorders. Reliable creation of transmural ablation lesions is crucial for long-term success. Lesion size index (LSI) is a multiparametric index that incorporates time, power, contact force (CF), and impedance data recorded during RF ablation in a weighted formula and has been shown to predict the extent of myocardial tissue lesions. Whether the force stability of contact influences lesion size in LSI-guided ablations is unknown.

OBJECTIVES

The aim of this study was to analyze the influence of the force stability of contact on lesion size during LSI-guided ablations in an ex-vivo model.

METHODS AND RESULTS

A total of 267 RF lesions (n = 6 hearts) were created on porcine myocardial slabs by using an open-tip irrigated ablation catheter with the following settings: 35 W with either intermittent (varied between 0 and up to 20 g), variable (10 to 20 g), or constant tissue contact (15 g) in a perpendicular or parallel fashion (applied manually) up to a target LSI of either 5 or 6. Subsequently, lesion width and depth were determined. Lesion width was mainly influenced by catheter tip orientation and LSI, whereas lesion depth was mainly influenced by LSI alone. The force stability of catheter contact had no relevant impact on lesion width or depth.

CONCLUSION

The force stability of catheter contact has only little effect on lesion depth or width in LSI-guided catheter ablation while the catheter orientation primarily affects lesion width.

High-power, Short-duration Radiofrequency Ablation for the Treatment of AF

High-power, short-duration (HPSD) ablation for the treatment of AF is emerging as an alternative to ablation using conventional ablation generator settings characterised by lower power and longer duration. Although the reported potential advantages of HPSD ablation include less tissue oedema and collateral tissue damage, a reduction in procedural time and superior ablation lesion formation, clinical studies of HPSD ablation validating these observations are limited. One of the main challenges for HPSD ablation has been the inability to adequately assess temperature and lesion formation in real time. Novel catheter designs may improve the accuracy of intra-ablation temperature recording and correspondingly may improve the safety profile of HPSD ablation. Clinical studies of HPSD ablation are on-going and interpretation of the data from these and other studies will be required to ascertain the clinical value of HPSD ablation.

Lesion Index Titration Using Contact-Force Technology Enables Safe and Effective Radiofrequency Lesion Creation at the Root of the Aorta and Pulmonary Artery

BACKGROUND

Ablation of some myocardial substrates requires catheter-based radiofrequency delivery at the root of a great artery. We studied the safety and efficacy parameters associated with catheter-based radiofrequency delivery at the root of the aorta and pulmonary artery.

METHODS

Thirty-six pigs underwent in-vivo catheter-based ablation under continuous contact-force and lesion index (power, contact-force, and time) monitoring during 60-s radiofrequency delivery with an open-irrigated tip catheter. Twenty-eight animals were allocated to groups receiving 40 W (n=9), 50 W (n=10), or 60 W (n=9) radiofrequency energy, and acute (n=22) and chronic (n=6) arterial wall damage was quantified by multiphoton microscopy in ex vivo samples. Adjacent myocardial lesions were quantified in parallel samples. The remaining 8 pigs were used to validate safety and efficacy parameters.

RESULTS

Acute collagen and elastin alterations were significantly associated with radiofrequency power, although chronic assessment revealed vascular wall recovery in lesions without steam pop. The main parameters associated with steam pops were median peak temperature >42°C and impedance falls >23 ohms. Unlike other parameters, lesion index values of 9.1 units (interquartile range, 8.7-9.8) were associated with the presence of adjacent myocardial lesions in both univariate ( P=0.03) and multivariate analyses ( P=0.049; odds ratio, 1.99; 95% CI, 1.02-3.98). In the validation group, lesion index values using 40 W over a range of contact-forces correlated with the size of radiofrequency lesions (R²=0.57; P=0.03), with no angiographic or histopathologic signs of coronary artery damage.

CONCLUSIONS

Lesion index values obtained during 40 W radiofrequency applications reliably monitor safe and effective lesion creation at the root of the great arteries.

Ablation of persistent atrial fibrillation: Challenges and solutions

Catheter ablation is commonly used for treatment of persistent atrial fibrillation (AF). Pulmonary vein isolation (PVI) is still the cornerstone for the procedure, however, outcomes are consistently lower compared to paroxysmal AF. It is hypothesized that it could be due to lack of durable lesions or the presence of non-PV targets that remain after PVI. Numerous advances in ablation catheter technologies and mapping systems may potentially achieve lower recurrence rates in the future. Ongoing research is required to discover the best technique for persistent AF ablation. The purpose of this review is to describe the new, developing technologies that may improve the outcome of this procedure in the persistent AF population.