Contemporary catheter ablation of complex atrial tachycardias after prior atrial fibrillation ablation: pulsed field vs. radiofrequency current energy ablation guided by high-density mapping

AIMS

Catheter ablation (CA) of post-ablation left atrial tachycardias (LATs) can be challenging. So far, pulsed field ablation (PFA) has not been compared to standard point-by-point radiofrequency current (RFC) energy for LAT ablation. To compare efficacy of PFA vs. RFC in patients undergoing CA for LAT.

METHODS AND RESULTS

Consecutive patients undergoing LAT-CA were prospectively enrolled (09/2021-02/2023). After electro-anatomical high-density mapping, ablation with either a pentaspline PFA catheter or RFC was performed. Patients were matched 1:1. Ablation was performed at the assumed critical isthmus site with additional ablation, if necessary. Right atrial tachycardia (RAT) was ablated with RFC. Acute and chronic success were assessed. Fifty-six patients (n = 28 each group, age 70 ± 9 years, 75% male) were enrolled.A total of 77 AT (n = 67 LAT, n = 10 RAT; 77% macroreentries) occurred with n = 32 LAT in the PFA group and n = 35 LAT in the RFC group. Of all LAT, 94% (PFA group) vs. 91% (RFC group) successfully terminated to sinus rhythm or another AT during ablation (P = 1.0). Procedure times were shorter (PFA: 121 ± 41 vs. RFC: 190 ± 44 min, P < 0.0001) and fluoroscopy times longer in the PFA group (PFA: 15 ± 9 vs. RFC: 11 ± 6 min, P = 0.04). There were no major complications. After one-year follow-up, estimated arrhythmia free survival was 63% (PFA group) and 87% (RFC group), [hazard ratio 2.91 (95% CI: 1.11-7.65), P = 0.0473].

CONCLUSION

Pulsed field ablation of post-ablation LAT using a pentaspline catheter is feasible, safe, and faster but less effective compared to standard RFC ablation after one year of follow-up. Future catheter designs and optimization of the electrical field may further improve practicability and efficacy of PFA for LAT.

High-density mapping for ablation of atypical atrial flutters - procedural characteristics related to outcome

BACKGROUND

High-density (HD) mapping is increasingly used to characterize arrhythmic substrate for ablation of atypical atrial flutters (AAFl). However, results on clinical outcomes and factors that are associated with arrhythmia recurrence are scarce.

METHODS

Single-center, prospective, observational cohort study that enrolled patients with catheter ablation for AAFl using a HD mapping system and a grid-shaped mapping catheter. Procedural characteristics, rates of atrial flutter recurrence, and factors that were associated with atrial flutter recurrence were evaluated.

RESULTS

Sixty-one patients with a total of 94 AAFl were included in the cohort. HD mapping was used to successfully identify the flutter circuit of 80/94 AAFl. The circuit was not identified for 14/94 AAFl in 11 patients. Critical isthmuses were identified and ablated in 29 patients (48%). Acute procedural success was achieved in 52 patients (85%), and 37 patients (61%) remained free from atrial flutter recurrence during a follow up of 1.3 [1.0-2.1] years. Atrial flutter recurrence was univariably associated with presence of a non-identified flutter circuit (HR:2.6 95% CI [1.1-6.3], p = .04) and critical isthmus-targeted ablation (HR:0.4 [0.15-0.90], p = .03). In multivariable regression analyses, critical isthmus ablation remained significant (HR:0.4 [0.16-0.97], p = .04), whereas presence of a non-identified flutter did not (HR:2.4 [0.96-5.8], p = .06).

CONCLUSION

HD mapping was successfully used to identify the majority of AAFl circuits. Ablation resulted in freedom from atrial flutter recurrence in 61% of the cohort. Successful identification of all flutter circuits and critical isthmuses appears to be beneficial for long-term outcomes.

High density mapping of complex atrial tachycardia in patients after cardiac surgery

To provide an overview of the current application of high-density mapping (HDM) in the mechanism of complex atrial tachycardias (ATs). Complex ATs are frequently scar-related, after history of previous cardiac surgery and large scars. These scar-related ATs are difficult to manage medically and frequently recur after electrical cardioversion. HDM technologies have enabled rigorous elucidation of AT mechanisms in patients post cardiac surgery. This article showed the application of HDM technology in complex ATs from the mechanisms of complex ATs, the development of HDM technology, and the identification of scars or critical isthmus from HDM. HDM-guided approach is highly effective for identifying the ATs mechanism and critical isthmus.

High density mapping of atrial tachycardia in patients post cardiac surgery

Mapping and ablation of atrial tachycardia (AT) in patients who have had prior cardiac surgery can be a challenge for clinical electrophysiologists. High density mapping (HDM) technology has been widely used in these patients because it provides a better characterization of the substrate and the mechanisms with an unprecedented high resolution. In this review, we summarize how the latest HDM technologies can reveal the mechanism of AT in different types of patients post-cardiac surgery and guide a specifically tailored ablation strategy.

Automated three-dimensional activation versus conventional mapping for catheter ablation of atrial tachycardia - A prospective randomized trial

Background

The automated NavX Ensite Precision latency-map (LM) algorithm aims to identify atrial tachycardia (AT) mechanisms. However, data on a direct comparison of this algorithm with conventional mapping are scarce.

Methods

Patients scheduled for AT ablation were randomized to mapping with the LM- algorithm (LM group) or to conventional mapping (conventional only group: ConvO), using entrainment and local activation mapping techniques. Several outcomes were exploratively analyzed. Primary endpoint was intraprocedural AT Termination. If AT termination with only automated 3D-Mapping failed, additional conventional methods were applied (conversion).

Results

A total of 63 patients (mean 67 years, 34 % female) were enrolled. In the LM group (n = 31), the correct AT mechanism was identified in 14 patients (45 %) using the algorithm alone compared to 30 patients (94 %) with conventional methods. Time to termination of the first AT was not different between groups (LM group 34 ± 20 vs. ConvO 43.1 ± 28.3 min; p = 0.2). However, when AT termination did not occur with LM algorithm, time to termination prolonged significantly (65 ± 35 min; p = 0.01). After applying conventional methods (conversion), procedural termination rates did not differ between LM group (90 %) vs. ConvO (94 %) (p = 0.3). During a follow-up time of 20 ± 9 months, no differences were observed in clinical outcomes.

Conclusion

In this small prospective, randomized study, the use of the LM algorithm alone may lead to AT termination, but less accurate than conventional methods.

Non-Iatrogenic Localized-Reentrant Figure of Eight Atrial Tachycardias in the Superior Vena Cava

Introduction

The superior vena cava (SVC) is an important non-pulmonary venous foci of atrial fibrillation (AF) and is known as the arrhythmogenic site of scar-related atrial tachycardia (AT). Scar-related ATs may occur after catheter ablation and open heart surgery; however, idiopathic AT rarely occurs. Case Presentation. A 77-year-old male with terminal diabetic nephropathy complained of dialysis-induced hypotension due to AF and was admitted to our hospital for catheter ablation. Here, we report a case of non-iatrogenic localized-reentrant figure of eight AT in the SVC.

Conclusion

SVC has the arrhythmogenic potential for re-entrant tachycardia, and the development of mapping technology can reveal arrhythmogenic mechanisms.

Characterization of temporal electrical activity patterns for detection of critical isthmus regions of recurrent atypical atrial flutter

INTRODUCTION

Identifying the critical isthmus region (CIR) of atrial re-entry tachycardias (AT) is challenging. The Lumipoint® (LP) software, developed for the Rhythmia® mapping system, aims to facilitate the successful ablation of ATs by identifying the CIR.

OBJECTIVE

The objective of this study was to evaluate the quality of LP regarding the percentage of arrhythmia-relevant CIR in patients with atypical atrial flutter (AAF).

METHODS

In this retrospective study, we analyzed 57 AAF forms. Electrical activity (EA) was mapped over tachycardia cycle length resulting in a two-dimensional EA pattern. The hypothesis was that EA minima suggest potential CIRs with slow-conduction-zone.

RESULTS

A total of n = 33 patients were included, with the majority of patients being already preablated (69.7%). LP algorithm identified a mean of 2.4 EA minima and 4.4 suggested CIRs per AAF form. Overall, we observed a low probability of identifying only the relevant CIR (POR) at 12.3% but a high probability that at least one CIR is detected (PALO) at 98.2%. Detailed analysis revealed EA minima depth (≤20%) and width (>50 ms) as the best predictors of relevant CIRs. Wide minima occurred rarely (17.5%), while low minima were more frequently present (75.4%). Minima depth of EA ≤ 20% showed the best PALO/POR overall (95% and 60%, respectively). Analysis in recurrent AAF ablations (five patients) revealed that CIR in de novo AAF was already detected by LP during the index procedure.

CONCLUSION

The LP algorithm provides an excellent PALO (98.2%), but poor POR (12.3%) to detect the CIR in AAF. POR improved by preselection of the lowest and widest EA minima. In addition, there might be the role of initial bystander CIRs becoming relevant for future AAFs.

Pulsed field ablation in patients with complex consecutive atrial tachycardia in conjunction with ultra-high density mapping: Proof of concept

INTRODUCTION

Catheter-ablation (CA) of consecutive left atrial tachycardias (LAT) can be challenging. Pulsed field ablation (PFA) yields a novel nonthermal CA technology for treatment of atrial fibrillation (AF). There is no data regarding PFA of LAT. This study sought to investigate PFA of consecutive LAT following prior CA of AF.

METHODS

Consecutive patients with LAT underwent ultrahigh-density (UHDx) mapping. Subsequent to identification of the AT mechanism, PFA was performed at the assumed critical sites for LAT maintenance. Continuous ablation lines were performed if required and evaluated with pre- and post-PFA HDx-mapping.

RESULTS

Fifteen patients (age 70 ± 10, male 73%) who underwent 3.6 ± 2 prior AF-CA procedures were included. The total mean procedure and fluoroscopy times were 141 ± 43 and 18 ± 10 min, respectively. All 19 of 19 (100%) LAT were successfully ablated with PFA. Two AT located at the right atria required RF-ablation. LAT were identified as localized reentry (n = 1) and macro-reentry LAT (n = 18) and targeted with PFA. All LAT terminated with PFA either to sinus rhythm (9/15) or a secondary AT (6/15 and subsequently to SR); 63% (12/19) terminated with the first PFA-application. All lines (13 roof, 11 anterior, 1 mitral) were blocked. LA-posterior-wall isolation (LAPWI) was successfully achieved when performed (10/10). AF/AT free survival was 80% (12/15) after 153 [88-207] days of follow-up. No procedure-related complications occurred.

CONCLUSION

PFA of consecutive LAT is feasible and safe. Successful creation of ablation lines and LAPWI can be achieved in a short time. PFA may offer the opportunity for effective ablation of atrial arrhythmias beyond AF.

Treatment of Atrial Tachycardia Arising after Superior Transseptal Approach Mitral Valve Surgery: Insights from Ultra High-Density Mapping to Prevent Atrioventricular Block

INTRODUCTION

Mitral valve surgery employing a superior transseptal approach (STA) is associated with arrhythmogenicity and intra-atrial conduction delay, despite being optimal for visualization of the surgical field. It is sometimes difficult to treat atrial tachycardias (AT) that arise after STA. To investigate AT circuits that arise after STA in detail in order to identify the optimal ablation line, using ultra high-resolution mapping (UHRM).

METHODS

We retrospectively analyzed 12 AT from 10 patients (median age 70 years, 9 males) who had undergone STA surgery. The tachycardias were mapped using the Rhythmia mapping system (Boston Scientific, Natick, Massachusetts).

RESULTS

The 12 STA-related AT (STA-AT) circuits were classifiable as follows according to location of the optimal ablation line: (1) peri-septal incision STA-AT (n = 3), (2) cavotricuspid isthmus dependent STA-AT (n = 7) and (3) biatrial tachycardia (n = 2). Radiofrequency (RF) application terminated 11 of the 12 STA-AT. We found that difference in STA-AT circuit type was due to characteristics of the septal incision line made for STA. UHRM was important in identifying optimal ablation sites that did not create additional conduction disturbances in the right atrium.

CONCLUSIONS

ATs after STA involve complex arrhythmia circuits due to multiple and long incision lines in the right atrium. Accurate understanding of the arrhythmia circuit and sinus conduction in the right atrium after STA is recommended for treating post-surgical tachycardia in a minimally invasive manner. This article is protected by copyright. All rights reserved.

[Catheter ablation : Developments and technique selection]

Atrial fibrillation (AF) is the most common arrhythmia and an important risk factor for the occurrence of cardiovascular events. According to current guidelines, rhythm-controlling therapy is recommended only for symptomatic AF. Even in symptomatic AF there is still only a class IIa-recommendation for catheter ablation as initial therapy in paroxysmal AF. Meanwhile, current studies have shown an advantage of the early rhythm control compared to a rate control, as well as a benefit of catheter ablation compared to antiarrhythmic drug (AAD) treatment. The gold standard of catheter ablation for AF therapy is pulmonary vein isolation, which has been mainly radiofrequency-based in the past. However, cryoablation as a first-line therapy of paroxysmal AF is increasingly gaining importance, as the latest studies showed shorter procedure times, lower reintervention rates and improved life quality after cryoablation. Nevertheless, using these standard techniques, the risk of adverse events is still given through collateral damage. The field high-power short duration ablation is currently topic of ongoing AF research, which describes a radiofrequency ablation with higher energy levels, given over shorter duration, with a consecutive lower recurrence rate as well as procedure time. The new ablation techniques also include the pulsed field ablation, which allows ablation through very fast delivery of electrical pulses and causes isolated damage to myocardial cells without collateral damage. This promising technique passed the efficiency and safety testing in preclinical studies. To validate this technique further randomized trials are needed.

Ablation of Left Atrial Tachycardia following Catheter Ablation of Atrial Fibrillation: 12-Month Success Rates

The treatment of atrial tachycardia following catheter ablation of atrial fibrillation is often challenging. Electrophysiological studies using high-resolution 3D mapping systems have contributed significantly to their understanding, and new ablation approaches have shown high rates of acute terminations with low recurrences for the clinical AT. However, patient populations are very heterogeneous, and long-term data of the freedom from any atrial tachycardia or any arrhythmia are still sparse. To evaluate long-term success, a unified patient population and predefined ablation strategies are preferred. In this study, we present 12-month success and mean 30 month follow-up data of catheter ablation of left atrial tachycardia. All 35 patients had a history of pulmonary vein isolation (PVI), 71% of which had a previous substrate modification. A total of 54 ATs, with a mean cycle length 297 ± 86 ms, 31 macro-reentries, and 4 localized reentries, were targeted. The ablation strategy to be used was given by the study protocol, depending on the type of reentry and the number of critical isthmuses. All available ablation strategies were included: standard (anatomical) lines, individual lines, critical isthmuses, and focal ablation. All ATs were terminated by ablation. A total of 91% terminated upon the first ablation strategy. Freedom from any AT after 12 months was 82%, and from any arrhythmia, it was 77%. The multi-procedure success after 30 months was 65% for any AT and 55% for any arrhythmia. In conclusion, individual ablation strategies based on the reentry mechanism and the number of critical isthmuses seems promising and demonstrates a high long-term clinical success. Tachycardia comprising a single critical isthmus can be ablated by critical isthmus ablation only. These patients present with the highest 12-month and long-term success rates.

The isthmus characteristics of scar-related macroreentrant atrial tachycardia in patients with and without cardiac surgery

INTRODUCTION

Identifying the critical isthmus (CI) in scar-related macroreentrant atrial tachycardia (AT) is challenging, especially for patients with cardiac surgery. We aimed to investigate the electrophysiological characteristics of scar-related macroreentrant ATs in patients with and without cardiac surgery.

METHODS

A prospective study of 31 patients (mean age 59.4 ± 9.81 years old) with scar-related macroreentrant ATs were enrolled for investigation of substrate properties. Patients were categorized into the nonsurgery (n = 18) and surgery group (n = 13). The CIs were defined by concealed entrainment, conduction velocity less than 0.3 m/s, and the presence of local fractionated electrograms.

RESULTS

Among the 31 patients, a total of 65 reentrant circuits and 76 CIs were identified on the coherent map. The scar in the surgical group is larger than the nonsurgical group (18.81 ± 9.22 vs. 10.23 ± 5.34%, p = .016). The CIs in surgical group have longer CI length (15.27 ± 4.89 vs. 11.20 ± 2.96 mm, p = .004), slower conduction velocity (0.46 ± 0.19 vs. 0.69 ± 0.14 m/s, p < .001), and longer total activation time (45.34 ± 9.04 vs. 38.24 ± 8.41%, p = .016) than those in the nonsurgical group. After ablation, 93.54% of patients remained in sinus rhythm during a follow-up of 182 ± 19 days.

CONCLUSION

The characteristics of the isthmus in macroreentrant AT are diverse, especially for surgical scar-related AT. The identification of CIs can facilitate the successful ablation of scar-related ATs.

Specific electrogram characteristics impact substrate ablation target area in patients with scar-related ventricular tachycardia-insights from automated ultrahigh-density mapping

INTRODUCTION

Substrate-based catheter ablation approaches to ventricular tachycardia (VT) focus on low-voltage areas and abnormal electrograms. However, specific electrogram characteristics in sinus rhythm are not clearly defined and can be subject to variable interpretation. We analyzed the potential ablation target size using automatic abnormal electrogram detection and studied findings during substrate mapping in the VT isthmus area.

METHODS AND RESULTS

Electrogram characteristics in 61 patients undergoing scar-related VT ablation using ultrahigh-density 3D-mapping with a 64-electrode mini-basket catheter were analyzed retrospectively. Forty-four complete substrate maps with a mean number of 10319 ± 889 points were acquired. Fractionated potentials detected by automated annotation and manual review were present in 43 ± 21% of the entire low-voltage area (<1.0 mV), highly fractionated potentials in 7 ± 8%, late potentials in 13 ± 15%, fractionated late potentials in 7 ± 9% and isolated late potentials in 2 ± 4%, respectively. Highly fractionated potentials (>10 ± 1 fractionations) were found in all isthmus areas of identified VT during substrate mapping, while isolated late potentials were distant from the critical isthmus area in 29%.

CONCLUSION

The ablation target area varies enormously in size, depending on the definition of abnormal electrograms. Clear linking of abnormal electrograms with critical VT isthmus areas during substrate mapping remains difficult due to a lack of specificity rather than sensitivity. However, highly fractionated, low-voltage electrograms were found to be present in all critical VT isthmus sites.

Ablation of Atrial Fibrillation in Patients With Hypertrophic Cardiomyopathy: Treatment Strategy, Characteristics of Consecutive Atrial Tachycardia and Long-Term Outcome

Background

Atrial fibrillation (AF) is common in patients with hypertrophic cardiomyopathy (HCM) and is associated with a deterioration of clinical status. Ablation of symptomatic AF is an established therapy, but in HCM, the characteristics of recurrent atrial arrhythmias and the long‐term outcome are uncertain.

Methods and Results

Sixty‐five patients with HCM (aged 64.5±9.9 years, 42 [64.6%] men) underwent AF ablation. The ablation strategy included pulmonary vein isolation in all patients and ablation of complex fractionated atrial electrograms or subsequent atrial tachycardias (AT) if appropriate. Paroxysmal, persistent AF, and a primary AT was present in 13 (20.0%), 51 (78.5%), and 1 (1.5%) patients, respectively. Twenty‐five (38.4%) patients developed AT with a total number of 54 ATs. Stable AT was observed in 15 (23.1%) and unstable AT in 10 (15.3%) patients. The mechanism was characterized as a macroreentry in 37 (68.5%), as a localized reentry in 12 (22.2%), a focal mechanism in 1 (1.9%), and not classified in 4 (7.4%) ATs. After 1.9±1.2 ablation procedures and a follow‐up of 48.1±32.5 months, freedom of AF/AT recurrences was demonstrated in 60.0% of patients. No recurrences occurred in 84.6% and 52.9% of patients with paroxysmal and persistent AF, respectively (P<0.01). Antiarrhythmic drug therapy was maintained in 24 (36.9%) patients.

Conclusions

AF ablation in patients with HCM is effective for long‐term rhythm control, and especially patients with paroxysmal AF undergoing pulmonary vein isolation have a good clinical outcome. ATs after AF ablation are frequently observed in HCM. Freedom of atrial arrhythmia is achieved by persistent AF ablation in a reasonable number of patients even though the use of antiarrhythmic drug therapy remains high.

Scar identification, quantification, and characterization in complex atrial tachycardia: a path to targeted ablation?

Successful catheter ablation of scar-related atrial tachycardia depends on correct identification of the critical isthmus. Often, this is a represented by a small bundle of viable conducting tissue within a low-voltage area. It's identification depends on the magnitude of the signal/noise ratio. Ultra-high density mapping, multipolar catheters with small (eventually unidirectional) and closely-spaced electrodes improves low-voltage electrogram detection. Background noise limitation is also of major importance for improving the signal/noise ratio. Electrophysiological properties of the critical isthmus and the characteristics of the local bipolar electrograms have been recently demonstrated as hallmarks of successful ablation sites in the setting of scar-related atrial tachycardia.

A novel assessment of local impedance during catheter ablation: initial experience in humans comparing local and generator measurements

AIMS

A novel measure of local impedance (LI) has been found to predict lesion formation during radiofrequency current (RFC) catheter ablation. The aim of this study was to investigate the utility of this novel approach, while comparing LI to the well-established generator impedance (GI).

METHODS AND RESULTS

In 25 consecutive patients with a history of atrial fibrillation, catheter ablation was guided by a 3D-mapping system measuring LI in addition to GI via an ablation catheter tip with three incorporated mini-electrodes. Local impedance and GI before and during RFC applications were studied. In total, 381 RFC applications were analysed. The baseline LI was higher in high-voltage areas (>0.5 mV; LI: 110.5 ± 13.7 Ω) when compared with intermediate-voltage sites (0.1-0.5 mV; 90.9 ± 10.1 Ω, P < 0.001), low-voltage areas (<0.1 mV; 91.9 ± 16.4 Ω, P < 0.001), and blood pool LI (91.9 ± 9.9 Ω, P < 0.001). During ablation, mean LI drop (△LI; 13.1 ± 9.1 Ω) was 2.15 times higher as mean GI drop (△GI) (6.1 ± 4.2 Ω, P < 0.001). Baseline LI correlated with △LI: a mean LI of 99.9 Ω predicted a △LI of 12.9 Ω [95% confidence interval (12.1-13.6), R2 0.41; P < 0.001]. This relationship was weak for baseline GI predicting △GI (R2 0.06, P < 0.001). Catheter movements were represented by rapid LI changes. The duration of an RFC application was not predictive for catheter-tissue coupling with no further change of △LI (P = 0.247) nor △GI (P = 0.376) during prolonged ablation.

CONCLUSION

Local impedance can be monitored during ablation. Compared with the sole use of GI, baseline LI is a better predictor of impedance drops during ablation and may provide useful insights regarding lesion formation. However, further studies are needed to investigate if this novel approach is useful to guide catheter ablation.

Acute safety, effectiveness, and real-world clinical usage of ultra-high density mapping for ablation of cardiac arrhythmias: results of the TRUE HD study

AIMS

The objective of this study was to verify acute safety, performance, and usage of a novel ultra-high density mapping system in patients undergoing ablation procedure in a real-world clinical setting.

METHODS AND RESULTS

The TRUE HD study enrolled patients undergoing catheter ablation with mapping for all arrhythmias (excluding de novo atrial fibrillation) who were followed for 1 month. Safety was determined by collecting all serious adverse events and adverse events associated with the study devices. Performance was determined as the composite of: ability to map the arrhythmia/substrate, complete the ablation applications, arrhythmia termination (where applicable), and ablation validation. Use of mapping system in the ablation validation workflow was also evaluated. Among the 519 patients who underwent a complete (504) or attempted (15) procedure, 21 (4%) serious ablation-related complications were collected, with 3 (0.57%) potentially related to the mapping catheter. Four hundred and twenty treated patients resulted in a successful procedure confirmed by arrhythmia-specific validation techniques (83.3%; 95% confidence interval: 79.8-86.5%). A total of 1419 electroanatomical maps were created with a median acquisition time of 9:23 min per map. Of these, 372 maps in 222 (44%) patients were collected for ablation validation purposes. Following validation mapping, 162/222 (73%) patients required additional ablation.

CONCLUSION

In the TRUE HD study mapping was associated with rates of acute success and complications consistent with previously published reports. Importantly, a low percentage of events (0.57%) was attributed to the mapping catheter. When performed, validation mapping was useful for identifying additional targets for ablation in the majority of patients.

Outcome after tailored catheter ablation of atrial tachycardia using ultra-high-density mapping

INTRODUCTION

Tailored catheter ablation of atrial tachycardias (ATs) is increasingly recommended as a potentially easy treatment strategy in the era of high-density mapping (HDM). As follow-up data are sparse, we here report outcomes after HDM-guided ablation of ATs in patients with prior catheter ablation or cardiac surgery.

METHODS AND RESULTS

In 250 consecutive patients (age 66.5 ± 0.7 years, 58% male) with ATs (98% prior catheter ablation, 13% prior cardiac surgery) an HDM-guided catheter ablation was performed with the support of a 64-electrode mini-basket catheter. A total of 354 ATs (1.4 ± 0.1 ATs per patient; mean cycle length 304 ± 4.3 ms; 64% macroreentry, 27% localized reentry, and 9% focal) with acute termination of 95% were targeted in the index procedure. A similar AT as in the index procedure recurred in five patients (2%) after a median follow-up time of 535 days (interquartile range (IQR) 25th-75th percentile: 217-841). Tailored ablation of reentry ATs with freedom from any arrhythmia was obtained in 53% after a single procedure and in 73% after 1.4 ± 0.4 ablation procedures (range: 1-4). A total of 228 patients (91%) were free from any arrhythmia recurrence after 210 days (IQR: 152-494) when including optimal usual care.

CONCLUSIONS

Tailored catheter ablation of ATs guided by HDM has a high acute success rate. The recurrence rate of the index AT is low. In patients with extensive atrial scaring further ablation procedures need to be considered to achieve freedom from any arrhythmia.

[Therapeutic management of nonvalvular atrial fibrillation]

Atrial fibrillation (AF) is the most frequent persistent cardiac arrhythmia and is associated with an increased mortality. Therefore, an effective differential treatment of patients is mandatory. After a risk stratification oral anticoagulation (OAC) should be initiated depending on the individual stroke risk of each patient. Alternatively, in the presence of contraindications for OAC and an increased risk for bleeding and/or stroke, the implantation of a left atrial appendage closure device can be considered. Symptomatic patients should undergo a rhythm control strategy if possible. Based on the risk-benefit considerations, catheter ablation (CA) of AF plays an increasingly important role in establishing long-term medicinal rhythm control. A pulmonary vein isolation can lead to freedom from AF for 1 year in 70-80% of patients with paroxysmal AF (and approximately 50% in persistent AF). So far, a survival advantage of CA could only be shown in patients with heart failure, so that in most cases this is only a symptomatic treatment for improvement in the quality of life.

Identification of critical isthmus using coherent mapping in patients with scar-related atrial tachycardia

INTRODUCTION

Accurate identification of slow conducting regions in patients with scar-related atrial tachycardia (AT) is difficult using conventional electrogram annotation for cardiac electroanatomic mapping (EAM). Estimating delays between neighboring mapping sites is a potential option for activation map computation. We describe our initial experience with CARTO 3 Coherent Mapping (Biosense Webster Inc,) in the ablation of complex ATs.

METHODS

Twenty patients (58 ± 10 y/o, 15 males) with complex ATs were included. We created three-dimensional EAMs using CARTO 3 system with CONFIDENSE and a high-resolution mapping catheter (Biosense Webster Inc). Local activation time and coherent maps were used to aid in the identification of conduction isthmus (CI) and focal origin sites. System-defined slow or nonconducting zones and CI, defined by concealed entrainment (postpacing interval < 20 ms), CV < 0.3 m/s and local fractionated electrograms were evaluated.

RESULTS

Twenty-six complex ATs were mapped (mean: 1.3 ± 0.7 maps/pt; 4 focal, 22 isthmus-dependent). Coherent mapping was better in identifying CI/breakout sites where ablation terminated the tachycardia (96.2% vs 69.2%; P = .010) and identified significantly more CI (mean/chamber 2.0 ± 1.1 vs 1.0 ± 0.7; P < .001) with narrower width (19.8 ± 10.5 vs 43.0 ± 23.9 mm; P < .001) than conventional mapping. Ablation at origin and CI sites was successful in 25 (96.2%) with long-term recurrence in 25%.

CONCLUSIONS

Coherent mapping with conduction velocity vectors derived from adjacent mapping sites significantly improved the identification of CI sites in scar-related ATs with isthmus-dependent re-entry better than conventional mapping. It may be used in conjunction with conventional mapping strategies to facilitate recognition of slow conduction areas and critical sites that are important targets of ablation.

Impact of mapping points in high-density mapping of the left atrium

PURPOSE

Currently, high-density mapping techniques are being discussed for more precise voltage mapping, lesion validation after pulmonary vein isolation (PVI) and superior left atrial tachycardia (LAT) mapping. However, the quality of high-density maps varies according to different mapping systems, multipolar catheter (MPC) types and numbers of mapping points. The aim of this study was to evaluate the impact of different numbers of mapping points in high-density mapping on validity.

METHODS

From February 2016 to August 2018, 154 patients with previous PVI ablation and recurrent atrial fibrillation (AF) or left atrial tachycardia (LAT) were mapped by Orion™ multipolar catheter and Rhythmia HDx™ mapping system at our centre. Of those, 90 maps from 25 patients [11 male patients/14 female patients; age 76 ± 12 years] with 8000 to 16,000 mapping points in the primary map were collected. All maps were evaluated offline by two independent and blinded electrophysiologists regarding the following issues: (1) Is PVI observable in all veins? (2) Does voltage map cover the whole left atrium? (3) Does activation map display one or more isthmuses? The 90 maps consist of 30 maps with deactivated 24 of 64 electrodes of MPC with < 1000 mapping points (A), 30 maps with deactivated 16 of 64 electrodes of MPC and 2000 to 6000 mapping points (B) and 30 primary maps with 8000 to 16,000 mapping points (C).

RESULTS

For (A), only in one map (3.3%), for (B) in 20 maps (66.7%, p < 0.05) and for (C) in 24 maps (80%) both investigators agreed with evaluable PVI in all veins. Investigators were able to assess whether the voltage map covered the whole left atrium and the same low voltage areas in (A) in 0 maps, in (B) in 16 maps (53%, p < 0.05) and in (C) in 23 maps (77%, p < 0.05). Also, investigators were able to locate the same critical isthmuses in the activation maps in (A) in 0 maps, in (B) in 2 maps (7%) and in (C) in 20 maps (67%, p < 0.05).

CONCLUSIONS

In order to achieve comparable high-density maps which are verified by independent investigators, a minimum of 2000 to 6000 mapping points are required in the majority of voltage maps to evaluate PVI and low voltage areas. To define the critical isthmuses in activations maps, 8000 mapping points or more might be necessary. High-density maps with more than 8000 points increase the interrater reliability.

Advanced mapping strategies for ablation therapy in adults with congenital heart disease

Background

Ultra-high density mapping (HDM) is a promising tool in the treatment of patients with complex arrhythmias. In adults with congenital heart disease (CHD), rhythm disorders are among the most common complications but catheter ablation can be challenging due to heterogenous anatomy and complex arrhythmogenic substrates. Here, we describe our initial experience using HDM in conjunction with novel automated annotation algorithms in patients with moderate to great CHD complexity.

Methods

We studied a series of consecutive adult patients with moderate to great CHD complexity and an indication for catheter ablation due to symptomatic arrhythmia. HDM was conducted using the Rhythmia™ mapping system and a 64-electrode mini-basket catheter for identification of anatomy, voltage, activation pattern and critical areas of arrhythmia for ablation guidance. To investigate novel advanced mapping strategies, postprocedural signal processing using the Lumipoint™ software was applied.

Results

In 19 patients (53±3 years; 53% male), 21 consecutive ablation procedures were conducted. Procedures included ablation of atrial fibrillation (n=7; 33%), atrial tachycardia (n=11; 52%), atrioventricular accessory pathway (n=1; 5%), the atrioventricular node (n=1; 5%) and ventricular arrhythmias (n=4; 19%). A total of 23 supraventricular and 8 ventricular arrhythmias were studied with the generation of 56 complete high density maps (atrial n=43; ventricular n=11, coronary sinus n=2) and an average of 12,043±1,679 mapping points. Multiple arrhythmias were observed in n=7 procedures (33% of procedures; range of arrhythmias detected 2-4). A total range of 1-4 critical areas were defined per procedure and treated within a radiofrequency application time of 16 (interquartile range 12-45) minutes. Postprocedural signal processing using Lumipoint™ allowed rapid annotation of fractionated signals within specific windows of interest. This supported identification of a practical critical isthmus in 20 out of 27 completed atrial and ventricular tachycardia activation maps.

Conclusions

Our findings suggest that HDM in conjunction with novel automated annotation algorithms provides detailed insights into arrhythmia mechanisms and might facilitate tailored catheter ablation in patients with moderate to great CHD complexity.

Overdrive pacing mapping: An alternative approach used in scar associated localized atrial tachycardia

BACKGROUND

Mapping and ablation of localized reentry atrial tachycardia (AT) can be challenging, especially in those with varying cycle length (CL).

OBJECTIVE

We attempted to use the traditional maneuver of overdrive pacing to facilitate AT mapping.

METHODS

Data were collected from 12 patients with localized ATs. All patients had prior cardiac surgery or prior atrial fibrillation ablation. Overdrive pacing mapping (ODPM) was performed to find independent local activity (ILA) and compared with conventional activation mapping (CAM) during ongoing AT to determine its accuracy and efficacy. Patients with macro-reentry AT around the tricuspid or mitral annulus were excluded.

RESULTS

Twelve patients with 14 localized ATs were included. All 14 ATs including 4 (29%) with varying CL successfully completed ODPM and had the ILA, although two ATs terminated during ODP and required repeated mapping. Radiofrequency ablation focused on critical sites with ILA was successful in all 12 patients. Using CAM, however, 6 of 14 ATs (43%) mapping attempts were aborted due to AT termination (2 ATs) or varying CL (4 ATs), and only 5 of 8 (63%) located "critical sites" were ultimately confirmed by entrainment and ablation results. After 25 ± 9 months of follow-up, no patient had AT recurrence.

CONCLUSION

Our preliminary results demonstrated that ODPM is superior to CAM in ATs that were poorly sustained or with varying CL and is a useful supplement to CAM.

Focal atrial tachycardia ablation: Highly successful with conventional mapping

BACKGROUND/OBJECTIVE

Radiofrequency catheter ablation (RFCA) of focal atrial tachycardia (FAT) traditionally is guided by conventional endocardial mapping of earliest atrial activation; however, more recently electro-anatomical mapping is heralded as a more effective, albeit more expensive, tool to guide ablation. Herein we present the results of conventional mapping-guided RFCA. Apropos, we conducted a literature search of studies reporting > 10 FAT patients submitted to RFCA.

METHODS AND RESULTS

Conventional mapping-guided RFCA, performed in 63 FAT patients (aged 42.4 + 17.3 years; 14 with incessant tachycardia and 12 with tachycardiomyopathy (TCM)), was successful in 61 (96.8%) patients, applied for single foci in 59 (93.7%) and two foci in 4 patients, right (n = 46) or left sided (n = 17). The earliest atrial activation time at the ablation site was 41.3 ± 16.2 ms. Fluoroscopy time averaged 27.3 + 18.7 min, and procedure lasted 2.6 + 1.7 h. Complications occurred in two patients (sinus pauses in one needing a pacemaker and a large inguinal hematoma in one). Over 29.0 + 22.9 months, four patients (6.5%) had recurrences, of whom three were successfully re-ablated. All patients with TCM showed gradual improvement to normalization over 4-6 months. Literature search showed that RFCA success is equally high when guided with either conventional (88.5%) or electro-anatomical mapping (90%) with similar recurrences (9.6% vs. 9.5%).

CONCLUSION

Conventional mapping-guided RFCA of FAT had high success (96.8%) with low complication (3.2%) and recurrence rates (6.5%). TCM was fully reversible. These results are comparable to those achieved with the more expensive electro-anatomical mapping, which may be reserved for more complex cases or for those failing the conventional approach.

Spatio-temporal Analysis of Multichannel Atrial Electrograms Based on a Concept of Active Areas

Atrial tachycardia and atrial flutter are frequent arrhythmia that occur spontaneously and after ablation of atrial fibrillation. Depolarization waves that differ significantly from sinus rhythm propagate across the atria with high frequency (typically 140 to 220 beats per minute). A detailed and personalized analysis of the spread of depolarization is imperative for a successful ablation therapy. Thus, catheters with several electrodes are employed to measure multichannel electrograms inside the atria. Here we propose a new concept for spatio-temporal analysis of multichannel electrograms during atrial tachycardia and atrial flutter. It is based on the calculation of simultaneously active areas. The method allows to identify atrial tachycardia and to automatically distinguish between subtypes of focal activity, micro-reentry and macro-reentry.

[High-resolution 3D mapping : Opportunities and limitations of the Rhythmia™ mapping system]

Three-dimensional mapping systems are used for the characterization and treatment of complex arrhythmias, such as atrial reentrant tachycardias, atrial fibrillation, or ventricular tachycardia. The Rhythmia™ mapping system (Boston Scientific, Natick, MA, USA) belongs to a novel generation of mapping systems that are able to rapidly create high-density and high-resolution three-dimensional maps in an automated manner. Mapping is performed with a magnetic- and impedance-based tracked bidirectional deflectable 64-pole basket catheter (IntellaMap Orion™, Boston Scientific). Based on previous studies, the system is effective and safe for the treatment of complex atrial and ventricular arrhythmias.

Initial single centre experience with the novel Rhythmia© high density mapping system in an all comer collective of 400 electrophysiological patients

BACKGROUND

A novel, automatically annotating ultra-high density mapping system (Rhythmia©, Boston Scientific) collects a high number and quality of electrograms (EGMs). So far, data on general use in the electrophysiological laboratory are sparse.

METHODS

We retrospectively analyzed all our ablations using Rhythmia and recorded patient clinical data, procedural parameters, and mapping parameters including the count of EGMs, mapping time, and mapping volume. Where appropriate, procedural parameters were compared over time to assess a learning curve.

RESULTS

400 patients underwent ablation of atrial fibrillation (n = 202), typical (n = 16) or atypical atrial flutter (n = 49), VT (n = 48), PVC (n = 35), accessory pathways (n = 14), AVNRT (n = 4), and focal atrial tachycardia (n = 32). System use was feasible, as no procedure had to be stopped for technical reasons and no ablation had to be withheld because of mapping failure, and safe, with an overall complication rate of 2.25%. Initial restrictions in manoeuvrability of the mapping catheter were overcome rapidly, as indicated by a significant decrease of fluoroscopy time (20 vs. 14 min, p = 0.02), use of contrast agent (50 vs. 40 ml; p < 0.01), and (not significant) lower procedure times (194 vs. 170 min; p = 0.12; comparing the first with the last third of patients undergoing pulmonary vein isolation only procedure). Ablation of complex left atrial, focal and ventricular tachycardias benefited from the reliable automatic annotation of a high number of EGMs.

CONCLUSION

The use of the Rhythmia is feasible and safe. Initial restrictions in manoeuvrability of the Orion mapping catheter were overcome rapidly. The procedures that benefit the most from ultra-high density mapping are complex left atrial tachycardias, focal tachycardias, and ventricular tachycardias.

[Mapping and ablation of cardiac arrhythmias : Never forget where you are coming from]

With the rapid development of new mapping and imaging technologies as well as catheter ablation technologies, it is increasingly important to understand the basic concepts of conventional mapping and ablation of cardiac arrhythmias. Prerequisite for successful ablation is the exact identification of the tachycardia mechanism and subsequent localization of the origin or tachycardic substrate. Only intracardiac electrograms provide decisive information regarding activation time and signal morphology. In some arrhythmias, it is necessary to supplement conventional mapping with so-called pace and/or entrainment mapping. This article aims to discuss and demonstrate the fundamentals of intracardiac mapping as it relates to the mapping and ablation of supraventricular and ventricular arrhythmias based on representative clinical cases. Modern three-dimensional mapping methods make it possible to individually optimize established ablation strategies with significantly better spatial resolution. The authors aimed to demonstrate that intracardiac uni- and bipolar electrograms provide essential information about timing and morphology guiding successful catheter ablation. Furthermore, our article provides useful information about conventional cardiac mapping techniques including activation mapping, pace mapping, and individual substrate mapping.

Visualizing Localized Reentry With Ultra-High Density Mapping in Iatrogenic Atrial Tachycardia: Beware Pseudo-Reentry

BACKGROUND

The activation pattern of localized reentry (LR) in atrial tachycardia remains incompletely understood. We used the ultra-high density Rhythmia mapping system to study activation patterns in LR.

METHODS AND RESULTS

LR was suggested by small rotatory activations (carousels) containing the full spectrum of the color-coded map. Twenty-three left-sided atrial tachycardias were mapped in 15 patients (age: 64±11 years). 16 253±9192 points were displayed per map, collected over 26±14 minutes. A total of 50 carousels were identified (median 2; quartiles 1-3 per map), although this represented LR in only n=7 out of 50 (14%): here, rotation occurred around a small area of scar (<0.03 mV; 12±6 mm diameter). In LR, electrograms along the carousel encompassed the full tachycardia cycle length, and surrounding activation moved away from the carousel in all directions. Ablating fractionated electrograms (117±18 ms; 44±13% of tachycardia cycle length) within the carousel interrupted the tachycardia in every LR case. All remaining carousels were pseudo-reentrant (n=43/50 [86%]) occurring in areas of wavefront collision (n=21; median 0.5; quartiles 0-2 per map) or as artifact because of annotation of noise or interpolation in areas of incomplete mapping (n=22; median 1, quartiles 0-2 per map). Pseudo-reentrant carousels were incorrectly ablated in 5 cases having been misinterpreted as LR.

CONCLUSIONS

The activation pattern of LR is of small stable rotational activations (carousels), and this drove 30% (7/23) of our postablation atrial tachycardias. However, this appearance is most often pseudo-reentrant and must be differentiated by interpretation of electrograms in the candidate circuit and activation in the wider surrounding region.

Catheter ablation of hemodynamically unstable ventricular tachycardia in ischemic cardiomyopathy using high-resolution mapping

Catheter ablation is a recommended therapy option for ventricular tachycardia (VT). The antegrade transseptal approach for targeting VT with left ventricular origin is feasible with the high-resolution basket catheter. High-resolution mapping offers the potential to quickly acquire detailed voltage and activation maps. This may help to identify the crucial VT-substrate even in patients with huge scar areas and hemodynamically unstable VT.