Approach to catheter ablation of left atrial flutters

Long-term outcomes after catheter ablation for idiopathic atypical atrial flutter

BACKGROUND

Idiopathic atypical (non-cavotricuspid isthmus-dependent) atrial flutter (IAAFL) may be seen in patients without structural heart disease and without previous cardiac surgery or ablation.

OBJECTIVE

This study sought to determine the patient characteristics, electrophysiologic and electroanatomic properties, and clinical outcomes after ablation in patients with IAAFL.

METHODS

We retrospectively compared IAAFL patients with cavotricuspid isthmus-dependent AFL (C-AFL) patients undergoing catheter ablation. The primary outcome was a composite of death from cardiovascular causes, ischemic stroke, and hospitalization for worsening of heart failure.

RESULTS

Of 180 patients who underwent catheter ablation for AFL, 89 were included in this study (22 IAAFL and 67 C-AFL). Electrophysiologic study showed significantly longer intra-atrial conduction time and lower atrial voltage during sinus rhythm in the IAAFL group compared with the C-AFL group. The atrial scar was observed in all 22 IAAFL patients, with the most common sites being the posterior or lateral wall of the right atrium in 10 (45.5%) and the anterior wall of the left atrium in 8 (36.4%). During 3.5 ± 2.8 years of follow-up, the composite primary end point occurred significantly more frequently in the IAAFL group (hazard ratio [HR], 3.45; 95% confidence interval [CI], 1.20-9.89; P = .015). In multivariable analysis, brain natriuretic peptide levels (HR, 1.01; 95% CI, 1.00-1.01, per 1 pg/mL; P = .01) and IAAFL (HR, 4.14; 95% CI, 1.21-14.07; P = .02) were independently associated with the primary outcome.

CONCLUSION

IAAFL in patients had distinct electrophysiologic features suggestive of atrial cardiomyopathy. These patients are at risk for development of cardiovascular adverse events after ablation.

Peak frequency mapping of atypical atrial flutter

INTRODUCTION

Peak frequency (PF) mapping is a novel method that may identify critical portions of myocardial substrate supporting reentry. The aim of this study was to describe and evaluate PF mapping combined with omnipolar voltage mapping in the identification of critical isthmuses of left atrial (LA) atypical flutters.

METHODS AND RESULTS

LA omnipolar voltage and PF maps were generated in flutter using the Advisor HD-Grid catheter (Abbott) and EnSite Precision Mapping System (Abbott) in 12 patients. Normal voltage was defined as ≥0.5 mV, low-voltage as 0.1-0.5 mV, and scar as <0.1 mV. PF distributions were compared with ANOVA and post hoc Tukey analyses. The 1 cm radius from arrhythmia termination was compared to global myocardium with unpaired t-testing. The mean age was 65.8 ± 9.7 years and 50% of patients were female. Overall, 34 312 points were analyzed. Atypical flutters most frequently involved the mitral isthmus (58%) or anterior wall (25%). Mean PF varied significantly by myocardial voltage: normal (335.5 ± 115.0 Hz), low (274.6 ± 144.0 Hz), and scar (71.6 ± 140.5 Hz) (p < .0001 for all pairwise comparisons). All termination sites resided in low-voltage regions containing intermediate or high PF. Overall, mean voltage in the 1 cm radius from termination was significantly lower than the remaining myocardium (0.58 vs. 0.95 mV, p < .0001) and PF was significantly higher (326.4 vs. 245.1 Hz, p < .0001).

CONCLUSION

Low-voltage, high-PF areas may be critical targets during catheter ablation of atypical atrial flutter.

Transesophageal Echocardiography Improves Precision in Transseptal Puncture Compared to Fluoroscopy in Left Atrial Electrophysiological Procedures

Background: Complex arrhythmias often arise from the left side of the heart, necessitating established electrophysiological (EP) procedures like 3D-mapping-assisted radiofrequency (RF) ablations or pulmonary vein isolation (PVI). These procedures typically require transseptal access, emphasizing the critical role of achieving an optimal catheter position through a precise transseptal puncture (TSP). Commonly employed imaging methods for TSP guidance include fluoroscopy and interventional echocardiography. Despite their routine use, there is limited evidence on which imaging modality offers superior catheter positioning for EP procedures, and safety concerns regarding transseptal punctures with imaging remain underexplored. This study aims to systematically evaluate the feasibility, safety, and accuracy of echo-guided TSP compared to fluoroscopy-guided TSP. Methods: In this prospective study, 150 consecutive patients undergoing left atrial EP procedures were enrolled between October 2023 and February 2024 at the Ulm University Heart Center. Following optimal fluoroscopy-guided transseptal needle positioning at the interatrial septum, the catheter placement was further verified using transesophageal echocardiography (TEE). Adjustments were made in cases of suboptimal needle positioning observed in TEE. The fluoroscopically achieved septal positions were categorized based on TEE images as optimal, suboptimal, poor, or dangerous. Results: Among the 150 patients included (58.0% male), fluoroscopy achieved optimal, suboptimal, and poor/dangerous positions in 32.7%, 43.3%, and 24.0%, respectively. After TEE-guided adjustments, optimal and suboptimal positions were achieved in 59.3% and 40.7% of patients, respectively. No instances of poor or dangerous transseptal needle positions were observed under TEE guidance. Conclusions: TEE-guided TSP emerges as a feasible, more accurate, and safer imaging method for transseptal punctures in EP procedures.

Identification of the dominant loop of a dual-loop macro-reentry left atrial flutter without prior intervention using high-density mapping technology: A case report

BACKGROUND

Left atrial flutter without prior cardiac interventions is uncommon, especially dual-loop macro-reentry atrial flutter. The critical step to ablate dual-loop macro-reentry atrial flutter is to identify the dominant loop and key isthmus. Although entrainment mapping could help identify the dominant loop and key isthmus, it may alter or terminate tachycardia. High-density mapping allows the generation of electroanatomic maps without altering or terminating tachycardia.

CASE SUMMARY

Here, we report a case of symptomatic left atrial flutter without prior intervention. In this case, high-density mapping revealed a dual-loop macro-reentry around the mitral annulus and central scar of the anterior wall. The propagation result showed that the dominant loop was around the mitral annulus, and the key isthmus was between the central scar and mitral annulus. The atrial flutter terminated successfully after ablation was performed.

CONCLUSION

In this case, we demonstrate that high-density mapping technology may help identify the dominant loop of dual-loop atrial flutter without entrainment, which makes ablation easier.

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.

Atypisches Vorhofflattern

Im Gegensatz zum typischen Vorhofflattern handelt es sich beim atypischen Vorhofflattern um eine heterogene Gruppe von rechts- und linksatrialen Makro- bzw. Localized-Reentry-Tachykardien, deren kritischer Bestandteil zur Aufrechterhaltung der Tachykardie nicht der cavotrikuspidale Isthmus ist. Atypisches Vorhofflattern tritt gehäuft nach vorangegangener Katheterablation sowie nach herzchirurgischen Eingriffen auf. Die intraprozedurale Erfolgsrate während der Ablation ist hoch, wobei die Rezidivrate von strukturellen Veränderungen der Vorhöfe sowie des zugrundeliegenden Mechanismus abhängig ist. Dieser Artikel bietet einen Überblick über die Mechanismen sowie über Mapping- und Ablationsstrategien der häufigsten Formen von rechts- und linksatrialem atypischem Vorhofflattern. Dieser Beitrag ist Teil der Serie „EP-Basics“ zur gezielten Fortbildung im Bereich Invasive Elektrophysiologie. Grundlagen, Klinik und Therapie des atypischen Vorhofflatterns werden mit Fokus auf klinisch relevante Aspekte dargelegt. Vorgehensweise und Befunde der invasiven elektrophysiologischen Diagnostik und die Ablationsbehandlung bilden den Schwerpunkt dieses Artikels.

Substrate-based ablation of atypical atrial flutter in patients with atrial cardiomyopathy

Background

Standard therapy of atypical atrial flutter (AFL) aims at deploying ablation lines between two non-conducting anatomical structures, thereby creating a line of block within the re-entry circuit. We have developed an ablation strategy, where we incorporate voltage information as a surrogate for atrial fibrosis from the electro-anatomical map (EAM) during AFL ablation procedures to create individualized, substrate-based ablation lines along the area of most pronounced low-voltage within the reentry-circuit.

Objective

The aim of this study was to evaluate acute procedural success and long-term outcome of a substrate-based ablation (SBA) strategy in comparison to a standard anatomically based ablation (ABA) strategy for the ablation of atypical AFL.

Methods

Patients that underwent ablation for AFL at our institution were included. SBA procedures were compared to ABA procedures. Endpoints were acute termination of AFL and recurrence of the index AFL or any other AFL during follow-up.

Results

We included 47 patients, 24 individuals (51.1%) in the SBA group and 23 patients (48.9%) in the ABA group. Most patients had signs of atrial cardiomyopathy, namely enlarged left atrial diameter (LAD) and extended amount of left atrial low-voltage areas (LVA). Termination of AFL occurred in 27 of 29 (93.1%) AFL in the SBA group and in 28 of 31 (90.3%) AFL in the ABA group (p = 0.99). Freedom from recurrence of any atypical AFL after 2.5 years was 21.5% in the ABA group compared to 48.8% in the SBA group (p = 0.047).

Conclusion

Substrate-based ablation is as effective as an anatomically-based ablation in the acute termination of AFL but yields better rhythm outcome with less recurrence of AFL in patients with atrial cardiomyopathy.

Comparison of the Anterior Septal Line and Mitral Isthmus Line for Perimitral Atrial Flutter Ablation Using Robotic Magnetic Navigation

Background

Perimitral atrial flutter (PMAFL) is one of the most common macro-reentrant left atrial tachycardias. Mitral isthmus (MI) linear ablation is a common strategy for the treatment of PMAFLs, and anterior septum (AS) linear ablation has emerged as a novel ablation approach. We aimed at assessing the effectiveness of AS linear ablation using robotic magnetic navigation for PMAFL ablation.

Methods

In this retrospective study, a total of 36 consecutive patients presented with AFL as the unique arrhythmia or accompanied with atrial fibrillation (AF) who underwent catheter ablation were enrolled. Patients were classified into two groups according to the different ablation strategies, the MI line group (10 patients) and the AS line group (26 patients).

Results

The clinical baseline characteristics of patients in the two groups were nearly identical. There were no significant differences in procedure time (148.7 ± 46.1 vs. 123.2 ± 30.1 min, P=0.058) or radiofrequency ablation time (25.9 ± 11.4 vs. 23.5 ± 12.6 min) between the two groups. Fluoroscopy time was longer in the MI line group (8.0 ± 4.4 vs. 5.1 ± 2.7 min, P=0.024), and the acute success rate was higher in the AS line group versus the MI line group (96.2% vs. 70%, P=0.025). The long-term freedom from arrhythmia survival rate was higher in the AS line group (73%) than in the MI line group (40%) after a mean follow-up time of 37.4 months with a 3-month blanking period (P=0.049).

Conclusions

AS linear ablation is an effective and safe strategy for PMAFL ablation using robotic magnetic navigation.

Extended early meets late for assessment of conduction block along an ablation line

PURPOSE

The purpose of the study was to investigate the usefulness of the extended early meets late (EEML) feature of the HD Coloring software for confirmation of bidirectional block along an ablation line.

METHODS

A single-center prospective observational study of consecutive patients with atypical atrial flutter or persistent atrial fibrillation submitted to catheter ablation including linear lesions from January 2019 to June 2020, with confirmation of bidirectional block across ablation lines assessed with the feature EEML and a multipolar catheter was conducted. Patients were divided into two groups - those with versus those without bidirectional block - and different EEML thresholds were analyzed to assess which one had the better sensitivity and specificity to predict block.

RESULTS

During the 24-month enrollment period, a total of 94 patients were included (50% males, mean age of 64 ± 10 years, 60% with structural heart disease) - 55 patients with versus 39 patients without confirmed a bidirectional block. Activation maps were performed during atrial pacing, with a median number of 1340 (interquartile range 1135-2060) points acquired in 11 ± 3 min, and a mean mapped cycle length of 287 ± 51 ms. The EEML feature was highly useful in detecting bidirectional block along ablation lines, with a 25% threshold value showing the highest discriminative performance (area under the curve of 0.93), 95% sensitivity and 92% specificity in predicting block.

CONCLUSIONS

The EEML feature of the HD Coloring software is a useful addition to the CARTO mapping system for assessment of block across an ablation line. The threshold value of 25% is the most accurate.

Non-invasive characterisation of macroreentrant atrial tachycardia types from a vectorcardiographic approach with the slow conduction region as a cornerstone

BACKGROUND AND OBJECTIVES

Macroreentrant atrial tachyarrhythmias (MRATs) can be caused by different reentrant circuits. The treatment for each MRAT type may require ablation at different sites, either at the right or left atria. Unfortunately, the reentrant circuit that drives the arrhythmia cannot be ascertained previous to the electrophysiological intervention.

METHODS

A noninvasive approach based on the comparison of atrial vectorcardiogram (VCG) loops is proposed. An archetype for each group was created, which served as a reference to measure the similarity between loops. Methods were tested in a variety of simulations and real data obtained from the most common right (peritricuspid) and left (perimitral) macroreentrant circuits, each divided into clockwise and counterclockwise subgroups. Adenosine was administered to patients to induce transient AV block, allowing the recording of the atrial signal without the interference of ventricular signals. From the vectorcardiogram, we measured intrapatient loop consistence, similarity of the pathway to archetypes, characterisation of slow velocity regions and pathway complexity.

RESULTS

Results show a considerably higher similarity with the loop of its corresponding archetype, in both simulations and real data. We found the capacity of the vectorcardiogram to reflect a slow velocity region, consistent with the mechanisms of MRAT, and the role that it plays in the characterisation of the reentrant circuit. The intra-patient loop consistence was over 0.85 for all clinical cases while the similarity of the pathway to archetypes was found to be 0.85 ± 0.03, 0.95 ± 0.03, 0.87 ± 0.04 and 0.91 ± 0.02 for the different MRAT types (and p<0.02 for 3 of the 4 groups), and pathway complexity also allowed to discriminate among cases (with p<0.05).

CONCLUSIONS

We conclude that the presented methodology allows us to differentiate between the most common forms of right and left MRATs and predict the existence and location of a slow conduction zone. This approach may be useful in planning ablation procedures in advance.

Catheter Ablation of Left Atrial Posterior Wall Tachycardia Guided by Electroanatomic Mapping in a Young Patient

Focal atrial tachycardias (ATs) arising from the left atrium (LA) most commonly originate from the ostium of the pulmonary vein, the superior mitral annulus, the body of the coronary sinus, the LA septum, and the LA appendage. Focal ATs originating from the posterior wall of the LA are extremely rare. A 34-year-old male patient presented to the cardiology outpatient clinic complaining of palpitation. Electrocardiography showed a tachycardia at a ventricular rate of 150 bpm and a narrow QRS complex. Therefore, an electrophysiological study was performed, which was consistent with an AT. The patient underwent an electrophysiological study in tachycardias with narrow QRS complexes. The diagnostic electrophysiological findings were consistent with an AT. The AT cycle length was found to be 405 ms with variability in the ventriculoatrial interval. Simultaneous LA anatomical and activation mapping was performed during the AT using a 3D electroanatomic mapping system (CARTO) and a quadripolar unidirectional irrigated tip catheter. The activation mapping revealed that the earliest endocardial activation site was at the posterior wall of the LA, where the local electrogram was 72 ms and 35 ms before the coronary sinus reference and the P-wave onset, respectively. The activation mapping also showed centrifugal spreading and mid-diastolic, fractionated signals on the posterior wall. Radiofrequency ablation was successfully performed with 30-watt power at the site of the earliest atrial activation, with a fractionated electrogram terminating the tachycardia. LA posterior ATs are a rare form of AT. The electroanatomic mapping method enables the accurate localization of the LA focal tachycardia, and a high success rate is achieved with ablation therapy.

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.