Bipolar Voltage Mapping for the Evaluation of Atrial Substrate: Can We Overcome the Challenge of Directionality?

Association between left atrial low-voltage area and induction and recurrence of macroreentrant atrial tachycardia in pulmonary vein isolation for atrial fibrillation

BACKGROUND

The relationship between induction and recurrence due to atrial tachycardia (AT) and left atrial (LA) matrix progression after atrial fibrillation (AF) ablation remains unclear.

METHODS

One hundred fifty-two consecutive patients with paroxysmal and persistent AF who underwent pulmonary vein isolation (PVI) and cavo-tricuspid isthmus (CTI) ablation and achieved sinus rhythm before the procedure were classified into three groups according to the AT pattern induced after the procedure: group N (non-induced), F (focal pattern), and M (macroreentrant pattern) in 3D mapping.

RESULTS

The total rate of AT induction was 19.7% (30/152) in groups F (n = 13) and M (n = 17). Patients in group M were older than those in groups N and F, with higher CHADS2/CHA2DS2-VASc values, left atrial enlargement, and low-voltage area (LVA) size of LA. The receiver operating characteristic curve determined that the cut-off LVA for macroreentrant AT induction was 8.8 cm2 (area under the curve [AUC]: 0.86, 95% confidence interval [CI]: 0.75-0.97). The recurrence of AT at 36 months in group N was 4.1% (5/122), and at the second ablation, all patients had macroreentrant AT. Patients with AT recurrence in group N had a wide LVA at the first ablation, and the cut-off LVA for AT recurrence was 6.5 cm2 (AUC 0.94, 95%CI 0.88-0.99). Adjusted multivariate analysis showed that only LVA size was associated with the recurrence of macroreentrant AT (odds ratio 1.21, 95%CI 1.04-1.51).

CONCLUSIONS

It is important to develop a therapeutic strategy based on the LVA size to suppress the recurrence of AT in these patients.

Localized Re-Entry Is a Frequent Mechanism of De Novo Atypical Flutter

BACKGROUND

Limited data exist about the origins and mechanisms of atypical atrial flutter that occurs in the absence of prior ablation or surgery.

OBJECTIVES

The aims of this study were to report a large cohort of patients who presented for catheter ablation of de novo atypical flutters, to identify the most common locations and mechanisms of arrhythmia, and to describe outcomes after ablation.

METHODS

Demographic, electrophysiological, and outcome data were collected for patients who underwent ablation of de novo atypical flutter.

RESULTS

The mechanisms of 85 atypical flutters were identified in 62 patients and localized to the left atrium (LA) in 58 and right atrium (RA) in 27. In the LA, mechanisms were classified as macro-re-entry in 29 (50%) and localized re-entry in 29 (50%), whereas in the RA, mechanisms were macro-re-entry in 8 (30%) and localized re-entry in 19 (70%) (proportion of localized re-entry in the LA vs. RA, P = 0.08). Nine patients had both localized and macro-re-entrant atypical flutters. In the LA, localized re-entry was commonly found in the anterior LA, followed by the pulmonary veins and septum. In the RA, localized re-entry was found at various sites, including the lateral or posterior RA, septum, and coronary sinus ostium. During 39.4 months (Q1-Q3: 18.2-65.8 months) of follow-up, atrial arrhythmias occurred in 66% of patients after a single ablation and in 50% after >1 ablation. Among patients who underwent repeat ablation, compared with the index arrhythmia, different tachycardia circuits or arrhythmias were documented in 13 of 18 cases (72%).

CONCLUSIONS

Atypical atrial flutters in patients without prior surgery or complex ablation are often due to localized re-entry (approximately 50% in the LA and a higher frequency in the RA). Other atrial tachycardias commonly occur during long-term follow-up following ablation, suggesting progressive atrial myopathy in these patients.

Predictors of Low Voltage Zone and Sex Differences in Low Voltage Zone Distribution in Patients with Atrial Fibrillation

Background

Previous studies have revealed the left atrial (LA) low voltage zone (LVZ) are tightly linked to the recurrence of atrial fibrillation (AF). Furthermore ablation that targets the LA LVZ can improve patient prognosis. The aim of this study was to identify potential clinical predictors of the LA LVZ, to investigate possible sex differences in the distribution of LA LVZ, and to examine the relationship between LA LVZ and AF recurrence.

Methods

A total of 108 patients who underwent AF catheter ablation and LA high-density electro-anatomic mapping were enrolled in the study. Of these, 56 patients with LA LVZ ≥ 5% were assigned to the LVZ group, while the remaining 52 patients with LA LVZ < 5% were assigned to the non-LVZ group. Clinical characteristics and laboratory results for all patients were collected and compared between the two groups.

Results

Multivariate logistic regression analysis revealed that persistent AF (odds ratio [OR] = 4.563, 95% confidence interval [CI]: 1.194-17.431, p = 0.026), left atrial volume (LAV, OR = 1.030, 95% CI: 1.001-1.061, p = 0.044) and brain natriuretic peptide (BNP, OR = 1.010, 95% CI: 1.002-1.019, p = 0.015) were independent predictors for the presence of LA LVZ. In addition, female sex (OR = 7.161, 95% CI: 1.518-33.792, p = 0.013), LAV (OR = 1.028, 95% CI: 1.002-1.055, p = 0.035) and BNP (OR = 1.009, 95% CI: 1.001-1.016, p = 0.018) were independent predictors of severe LA LVZ (LA LVZ > 20%). The extent of LVZ was significantly greater in females than in males (32.8% ± 15.5% vs. 23.5% ± 12.7%, p = 0.021), especially in the anterior (34.5% ± 16.7% vs. 20.0% ± 16.4%, p = 0.003) and septal (44.9% ± 17.1% vs. 29.0% ± 18.9%, p = 0.004) walls. During follow-up, AF recurrence was significantly higher in patients with LA LVZ than in those without LA LVZ (31.3% vs. 12.8%, respectively, p = 0.023).

Conclusions

In this study cohort, persistent AF, LAV and BNP were independent predictors of LA LVZ. Furthermore, female sex, LAV and BNP were independent predictors of severe LA LVZ. Females had a significantly greater extent of LVZ than males, especially in the anterior and septal walls. Patients with LA LVZ had a higher risk of recurrent AF.

Left atrial conduction times and regional velocities in persistent atrial fibrillation patients with and without fibrotic atrial cardiomyopathy

Despite the progress in understanding left atrial substrate and arrhythmogenesis, only little is known about conduction characteristics in atrial fibrillation patients with various stages of fibrotic atrial cardiomyopathy (FACM). This study evaluates left atrial conduction times and conduction velocities based on high-density voltage and activation maps in sinus rhythm (CARTO®3 V7) of 53 patients with persistent atrial fibrillation (LVEF 60% (55-60 IQR), LAVI 39 ml/m2 (31-47 IQR), LApa 24 ± 6 cm2). Measurements were made in low voltage areas (LVA ≤ 0.5 mV) and normal voltage areas (NVA ≥ 1.5 mV) at the left atrial anterior and posterior walls. Maps of 28 FACM and 25 no FACM patients were analyzed (19 FACM I/II, 9 FACM III/IV, LVA 14 ± 11 cm2). Left atrial conduction time averaged to 110 ± 24 ms but was shown to be prolonged in FACM (119 ms, + 17%) when compared to no FACM patients (101 ms, p = 0.005). This finding was pronounced in high-grade FACM (III/IV) (133 ms, + 31.2%, p = 0.001). In addition, the LVA extension correlated significantly with the left atrial conduction time (r = 0.56, p = 0.002). Conduction velocities were overall slower in LVA than in NVA (0.6 ± 0.3 vs. 1.3 ± 0.5 m/s, -51%, p < 0.001). Anterior conduction appeared slower than posterior, which was significant in NVA (1 vs. 1.4 m/s, -29%, p < 0.001) but not in LVA (0.6 vs. 0.8 m/s, p = 0.096). FACM has a significant influence on left atrial conduction characteristics in patients with persistent atrial fibrillation. Left atrial conduction time prolongs with the grade of FACM and the quantitative expanse of LVA up to 31%. LVAs show a 51% conduction velocity reduction compared to NVA. Moreover, regional conduction velocity differences are present in the left atrium when comparing anterior to posterior walls. Our data may influence individualized ablation strategies.

Baseline left atrial low-voltage area predicts recurrence after pulmonary vein isolation: WAVE-MAP AF results

AIMS

Electro-anatomical mapping may be critical to identify atrial fibrillation (AF) subjects who require substrate modification beyond pulmonary vein isolation (PVI). The objective was to determine correlations between pre-ablation mapping characteristics and 12-month outcomes after a single PVI-only catheter ablation of AF.

METHODS AND RESULTS

This study enrolled paroxysmal AF (PAF), early persistent AF (PsAF; 7 days-3 months), and non-early PsAF (>3-12 months) subjects undergoing de novo PVI-only radiofrequency catheter ablation. Sinus rhythm (SR) and AF voltage maps were created with the Advisor HD Grid™ Mapping Catheter, Sensor Enabled™ for each subject, and the presence of low-voltage area (LVA) (low-voltage cutoffs: 0.1-1.5 mV) was investigated. Follow-up visits were at 3, 6, and 12 months, with a 24-h Holter monitor at 12 months. A Cox proportional hazards model identified associations between mapping data and 12-month recurrence after a single PVI procedure. The study enrolled 300 subjects (113 PAF, 86 early PsAF, and 101 non-early PsAF) at 18 centres. At 12 months, 75.5% of subjects were free from AF/atrial flutter (AFL)/atrial tachycardia (AT) recurrence. Univariate analysis found that arrhythmia recurrence did not correlate with AF diagnosis, but LVA was significantly correlated. Low-voltage area (<0.5 mV) >28% of the left atrium in SR [hazard ratio (HR): 4.82, 95% confidence interval (CI): 2.08-11.18; P = 0.0003] and >72% in AF (HR: 5.66, 95% CI: 2.34-13.69; P = 0.0001) was associated with a higher risk of AF/AFL/AT recurrence at 12 months.

CONCLUSION

Larger extension of LVA was associated with an increased risk of arrhythmia recurrence. These subjects may benefit from substrate modification beyond PVI.

Electrogram Morphology Recurrence for Mapping Persistent Atrial Fibrillation: Initial vs Redo Catheter Ablation

BACKGROUND

Electrogram (EGM) morphology recurrence (EMR) mapping of persistent atrial fibrillation (AF) quantifies consistency of activation and is expected to be high and rapid near AF drivers.

OBJECTIVES

The purpose of this study was to compare EMR in left atria (LA) and right atria (RA) in patients undergoing first vs redo ablation for persistent AF.

METHODS

Multisite LA/RA mapping (LA: 281 ± 176 sites/patient; RA: 239 ± 166 sites/patient) before persistent AF ablation was performed in 42 patients (30 males, age 63 ± 9 years) undergoing first (Group 1, n = 32) or redo ablation (Group 2, n = 10). After cross-correlation of each automatically detected EGM with every other EGM per recording, the most recurrent electrogram morphology was identified and its frequency (Rec%) and recurrence cycle length (CLR) were computed.

RESULTS

In Groups 1 and 2, minimum CLR was 172.8 ± 26.0 milliseconds (LA: 178.2 ± 37.6 milliseconds, RA: 204.4 ± 34.0 milliseconds, P = 0.0005) and 186.5 ± 28.3 milliseconds (LA: 196.1 ± 38.1 milliseconds vs RA: 199.0 ± 30.2 milliseconds, P = 0.75), with Rec% 94.7% ± 10% and 93.8% ± 9.2%. Group 2 minimum CLR was not different from Group 1 (P = 0.20). Shortest CLR was in the LA in 84% of Group 1 and 50% of Group 2 patients (P = 0.04). Only 1 of 10 patients in Group 2 had the shortest CLR in the pulmonary veins (PVs) compared with 19 of 32 in Group 1 (P = 0.01). Most sites (77.6%) had Rec% <50%.

CONCLUSIONS

EMR identified the shortest CLR sites in the PVs in 59% of patients undergoing initial persistent AF ablation, consistent with reported success rates of ∼50% for PV isolation. The majority of sites have low recurrence and may reflect bystander sites not critical for maintaining AF. EMR provides a robust new method for quantifying consistency and rapidity of activation direction at multiple atrial sites.

Interatrial conduction time is associated with left atrial low voltage area and predicts the recurrence after single atrial fibrillation ablation

Background

Interatrial conduction time (IACT) prolongs in fibrotic left atrium. We tested the hypothesis that IACT is related to left atrial low voltage area (LVA) and predicts the recurrence after single atrial fibrillation (AF) ablation.

Methods

One hundred sixty-four consecutive AF patients (79 non-paroxysmal) who underwent initial ablation in our institute were analyzed. IACT and LVA were defined as interval from the onset of P-wave to the basal left atrial appendage (P-LAA) activation, and area with bipolar electrogram < 0.5 mV covering over 5% of the total left atrial surface area during sinus rhythm, respectively. Pulmonary vein antrum isolation, non-PV foci ablation, and atrial tachycardia (AT) ablation were performed without substrate modification.

Results

LVA was frequently identified in patients with prolonged P-LAA ≥ 84 ms (n  = 28) compared with patients with P-LAA < 84 ms (n  = 136). Patients with P-LAA ≥ 84 ms were older (71 ± 10 vs. 65 ± 10 years, p  = .0061), and had more frequent non-paroxysmal AF (75% vs. 43%, p  = .0018), larger left atrial diameter (43.5 ± 4.5 vs. 39.3 ± 5.7 mm, p  = .0003), and higher E/e' ratio (14.4 ± 6.5 vs. 10.5 ± 3.7, p  < .0001) compared with P-LAA < 84 ms patients. After a mean follow-up period of 665 ± 153 days, Kaplan-Meier curve analysis showed that AF/AT recurrences was more frequently observed in patients with prolonged P-LAA (Log-rank p  = .0001). Additionally, univariate analysis revealed that P-LAA prolongation (OR = 1.055 per 1 ms, 95% CI: 1.028-1.087, p  < .0001) and the existence of LVA (OR = 5.000, 95% CI: 1.653-14.485 p  = .0053) were predictors of AF/AT recurrences after single AF ablation.

Conclusions

Our results suggested that prolonged IACT as measured by P-LAA was associated with LVA and predicts AT/AF recurrence after single AF ablation.

Low voltage-guided ablation of posterior wall improves 5-year arrhythmia-free survival in persistent atrial fibrillation

INTRODUCTION

The posterior wall (PW) has been proposed as a standard target for ablation beyond pulmonary vein antral isolation (PVI) in patients with persistent atrial fibrillation (AF). However, studies have shown inconsistent outcomes with the addition of PW ablation. The presence or absence of low voltage on the PW may explain these inconsistencies. We evaluated whether PW ablation based on the presence or absence of low voltage improves long-term arrhythmia-free outcomes.

METHODS

We retrospectively reviewed 5-year follow-up in 152 consecutive patients who received either standard ablation (SA) with PVI alone or PVI + PW ablation (PWA) based on physician discretion (n = 77) or voltage-guided ablation (VGA) with PVI and addition of PWA only if low voltage was present on the PW (n = 75).

RESULTS

The two groups were well matched for baseline characteristics. At 5-year follow-up, 64% of patients receiving VGA were atrial tachyarrhythmia (AT)/AF free compared to 34% receiving SA (HR 0.358 p < .005). PWA had similar AF recurrence in SA and VGA groups (0.30 vs. 0.27 p = .96) but higher AT recurrence when comparing SA and VGA groups (0.39 vs. 0.15 p = .03). In multivariate analysis, both VGA and PWA predicted AF arrhythmia-free survival (HR 0.33, p = .001 and HR 0.20, p = .008, respectively). For AT, VGA predicted arrhythmia-free survival (HR 0.22, p = .028), while PWA predicted AT recurrence (HR 4.704, p = .0219).

CONCLUSION

VGA of the posterior wall ablation beyond PVI in persistent AF significantly improves long-term arrhythmia-free survival when compared with non-voltage-guided ablation. PW ablation without voltage-guidance reduced AF recurrence but at the cost of a higher incidence of AT.

Atrial fibrosis identification with unipolar electrogram eigenvalue distribution analysis in multi-electrode arrays

Abstract

Atrial fibrosis plays a key role in the initiation and progression of atrial fibrillation (AF). Atrial fibrosis is typically identified by a peak-to-peak amplitude of bipolar electrograms (b-EGMs) lower than 0.5 mV, which may be considered as ablation targets. Nevertheless, this approach disregards signal spatiotemporal information and b-EGM sensitivity to catheter orientation. To overcome these limitations, we propose the dominant-to-remaining eigenvalue dominance ratio (EIGDR) of unipolar electrograms (u-EGMs) within neighbor electrode cliques as a waveform dispersion measure, hypothesizing that it is correlated with the presence of fibrosis. A simulated 2D tissue with a fibrosis patch was used for validation. We computed EIGDR maps from both original and time-aligned u-EGMs, denoted as \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathcal {R}$$\end{document}R and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathcal{R}^{\mathcal{A}}$$\end{document}RA, respectively, also mapping the gain in eigenvalue concentration obtained by the alignment, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\Delta \mathcal{R}^{\mathcal{A}}$$\end{document}ΔRA. The performance of each map in detecting fibrosis was evaluated in scenarios including noise and variable electrode-tissue distance. Best results were achieved by \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathcal{R}^{\mathcal{A}}$$\end{document}RA, reaching 94% detection accuracy, versus the 86% of b-EGMs voltage maps. The proposed strategy was also tested in real u-EGMs from fibrotic and non-fibrotic areas over 3D electroanatomical maps, supporting the ability of the EIGDRs as fibrosis markers, encouraging further studies to confirm their translation to clinical settings.

Graphical Abstract

Upper panels: map of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathcal {R}^{\mathcal {A}}$$\end{document}RA from 3×3 cliques for Ψ= 0^∘ and bipolar voltage map V^b-m, performed assuming a variable electrode-to-tissue distance and noisy u-EGMs (noise level σ_v = 46.4 μV ). Lower panels: detected fibrotic areas (brown), using the thresholds that maximize detection accuracy of each map

Current Understanding of Atrial Fibrillation Recurrence After Atrial Fibrillation Ablation: From Pulmonary Vein to Epicardium

Recurrence of atrial fibrillation (AF) after catheter ablation is common, with pulmonary vein (PV) reconnection considered the most likely cause. However, technologies such as contact force-sensing, irrigated catheters, and ablation index (AI)-guided ablation strategies have resulted in more durable PV isolation. As a result, it is difficult to predict which patients will develop AF recurrence despite durable PV isolation, with evolving non-PV atrial substrates thought to be a key contributor to late recurrences. Deciphering the complex mechanisms of AF recurrence beyond the cornerstone of PV isolation therefore remains challenging. Recently, there have been several important advances that may lead to better understanding and treatment of this challenging clinical entity: percutaneous epicardial access and mapping, late gadolinium enhancement magnetic resonance imaging (LGE-MRI), improvements in high-resolution electroanatomic mapping, and new ablation energy sources, specifically pulsed-field ablation. This review aims to synthesize the current literature in an effort to better understand arrhythmia mechanisms and treatment targets in patients with AF/Atrial tachycardia (AT) recurrence post-ablation. This article is protected by copyright. All rights reserved.

Alcohol Consumption Is Associated With Postablation Recurrence but Not Changes in Atrial Substrate in Patients With Atrial Fibrillation: Insight from a High-Density Mapping Study

Background

The association between alcohol consumption, atrial substrate, and outcomes after atrial fibrillation (AF) ablation remains controversial. This study evaluated the impacts of drinking on left atrial substrate and AF recurrence after ablation.

Methods and Results

We prospectively enrolled 110 patients with AF without structural heart disease (64±12 years) from 2 institutions. High‐density left atrial electroanatomic mapping was performed using a high‐density grid multipolar catheter. We investigated the impact of alcohol consumption on left atrial voltage, left atrial conduction velocity, and AF ablation outcome. Patients were classified as abstainers (<1 drink/wk), mild drinkers (1–7 drinks/wk), or moderate‐heavy drinkers (>7 drinks/wk). High‐density mapping (mean 2287±600 points/patient) was performed on 49 abstainers, 27 mild drinkers, and 34 moderate‐heavy drinkers. Low‐voltage zone and slow‐conduction zone were identified in 39 (35%) and 54 (49%) patients, respectively. There was no significant difference in the proportions of low‐voltage zone and slow‐conduction zone among the 3 groups. The success rate after a single ablation was significantly lower in drinkers than in abstainers (79.3% versus 95.9% at 12 months; mean follow‐up, 18±8 months; P=0.013). The success rate after a single or multiple ablations was not significantly different among abstainers and drinkers. In multivariate analysis, alcohol consumption (P=0.02) and the presence of a low‐voltage zone (P=0.032) and slow‐conduction zone (P=0.02) were associated with AF recurrence after a single ablation, while low‐voltage zone (P=0.023) and slow‐conduction zone (P=0.024) were associated with AF recurrence after a single or multiple ablations.

Conclusions

Alcohol consumption was associated with AF recurrence after a single ablation but not changes in atrial substrate.

Prediction of Type and Recurrence of Atrial Fibrillation after Catheter Ablation via Left Atrial Electroanatomical Voltage Mapping Registration and Multilayer Perceptron Classification: A Retrospective Study

Atrial fibrillation (AF) is a common cardiac arrhythmia and affects one to two percent of the population. In this work, we leverage the three-dimensional atrial endocardial unipolar/bipolar voltage map to predict the AF type and recurrence of AF in 1 year. This problem is challenging for two reasons: (1) the unipolar/bipolar voltages are collected at different locations on the endocardium and the shapes of the endocardium vary widely in different patients, and thus the unipolar/bipolar voltage maps need aligning to the same coordinate; (2) the collected dataset size is very limited. To address these issues, we exploit a pretrained 3D point cloud registration approach and finetune it on left atrial voltage maps to learn the geometric feature and align all voltage maps into the same coordinate. After alignment, we feed the unipolar/bipolar voltages from the registered points into a multilayer perceptron (MLP) classifier to predict whether patients have paroxysmal or persistent AF, and the risk of recurrence of AF in 1 year for patients in sinus rhythm. The experiment shows our method classifies the type and recurrence of AF effectively.

Grid-mapping catheters versus PentaRay catheters for left atrial mapping on ensite precision mapping system

INTRODUCTION

Areas displaying reduced bipolar voltage are defined as low-voltage areas (LVAs). Moreover, left atrial (LA) LVAs after pulmonary vein isolation (PVI) have been reported as a predictor of recurrent atrial fibrillation (AF). In this study, we compared grid mapping catheter (GMC) with PentaRay catheter (PC) for LA voltage mapping on Ensite Precision mapping system.

METHODS

Twenty-six consecutive patients with LVAs and border zone within the LA were enrolled. After achieving PVI, voltage mapping under high right atrial pacing for 600 ms was performed twice using each catheter type (GMC first, PC next). Furthermore, LVA was defined as a region with a bipolar voltage of <0.50, and border zone was defined as a region with a bipolar voltage of <1.0, or <1.5 mV.

RESULTS

Compared with PC, using GMC, voltage mapping contained more mapping points (20 242 [15 859, 26 013] vs. 5589 [4088, 7649]; p < .0001), and more mapping points per minute(1428 [1275, 1803] vs. 558 [372, 783]; p < .0001). In addition, LVA and border zone size using GMC was significantly less than that reported using PC: <1.0 mV (5.9 cm² [2.9, 20.2] vs. 13.9 cm² [6.3, 24.1], p  =  .018) and <1.5 mV voltage cutoff (10.6 cm² [6.6, 27.2] vs. 21.6 cm² [12.6, 35.0], p  =  .005).

CONCLUSION

Bipolar voltage amplitude estimated by GMC was significantly larger than that estimated by PC on Ensite Precision mapping system. GMC may be able to find highly selective identification of LVAs with lower prevalence and smaller LVA and border zone size.

Spectral characterisation of ventricular intracardiac potentials in human post-ischaemic bipolar electrograms

Abnormal ventricular potentials (AVPs) are frequently referred to as high-frequency deflections in intracardiac electrograms (EGMs). However, no scientific study performed a deep spectral characterisation of AVPs and physiological potentials in real bipolar intracardiac recordings across the entire frequency range imposed by their sampling frequency. In this work, the power contributions of post-ischaemic physiological potentials and AVPs, along with some spectral features, were evaluated in the frequency domain and then statistically compared to highlight specific spectral signatures for these signals. To this end, 450 bipolar EGMs from seven patients affected by post-ischaemic ventricular tachycardia were retrospectively annotated by an experienced cardiologist. Given the high variability of the morphologies observed, three different sub-classes of AVPs and two sub-categories of post-ischaemic physiological potentials were considered. All signals were acquired by the CARTO® 3 system during substrate-guided catheter ablation procedures. Our findings indicated that the main frequency contributions of physiological and pathological post-ischaemic EGMs are found below 320 Hz. Statistical analyses showed that, when biases due to the signal amplitude influence are eliminated, not only physiological potentials show greater contributions below 20 Hz whereas AVPs demonstrate higher spectral contributions above ~ 40 Hz, but several finer differences may be observed between the different AVP types.

Atrial Structural Remodeling in Patients With Atrial Fibrillation Is a Diffuse Fibrotic Process: Evidence From High-Density Voltage Mapping and Atrial Biopsy

Background

Low‐voltage areas (LVAs) in the atria of patients with atrial fibrillation are considered local fibrosis. We hypothesized that voltage reduction in the atria is a diffuse process associated with fibrosis and that the presence of LVAs reflects a global voltage reduction.

Methods and Results

We examined 140 patients with atrial fibrillation and 13 patients with a left accessory pathway (controls). High‐density bipolar voltage mapping was performed using a grid‐mapping catheter during high right atrial pacing. Global left atrial (LA) voltage (V_GLA) in the whole LA and regional LA voltage (V_RLA) in 6 anatomic regions were evaluated with the mean of the highest voltage at a sampling density of 1 cm². Patients with atrial fibrillation were categorized into quartiles by V_GLA. LVAs were evaluated at voltage cutoffs of 0.1, 0.5, 1.0, and 1.5 mV. Twenty‐eight patients with atrial fibrillation also underwent right atrial septum biopsy, and the fibrosis extent was quantified. Voltage at the biopsy site (V_biopsy) was recorded. V_GLA results by category were Q1 (<4.2 mV), Q2 (4.2–5.6 mV), Q3 (5.7–7.0 mV), and Q4 (≥7.1 mV). V_RLA at any region was reduced as V_GLA decreased. V_GLA and V_RLA did not differ between Q4 and controls. The presence of LVAs increased as V_GLA decreased at any voltage cutoff. Biopsies revealed 11±6% fibrosis, which was inversely correlated with both V_biopsy and V_GLA (r=–0.71 and –0.72, respectively). V_biopsy was correlated with V_GLA (r=0.82).

Conclusions

Voltage reduction in the LA is a diffuse process associated with fibrosis. Presence of LVAs reflects diffuse voltage reduction of the LA.

Predictors of recurrence of atrial tachyarrhythmias after pulmonary vein isolation by functional and structural mapping of nonparoxysmal atrial fibrillation

BACKGROUND

This study aimed to evaluate the predictors of recurrence of atrial tachyarrhythmias by structural and functional mapping: voltage, dominant frequency (DF), and rotor mapping after a pulmonary vein isolation (PVI) in nonparoxysmal atrial fibrillation (AF) patients.

METHODS

A total of 66 nonparoxysmal AF patients were prospectively investigated. After the PVI, an online real-time phase mapping system was used to detect the location of rotors with critical nonpassively activated ratios (%NPs) of ≧50% in each left atrial (LA) segment, and high-DFs of ≧7 Hz were simultaneously mapped. After restoring sinus rhythm, low-voltage areas (LVAs < 0.5 mV) were mapped using the Advisor HD grid catheter (HDG).

RESULTS

Sixty-four of 66 (97%) AF patients had minimum to mild LVAs regardless of an enlarged LAD and LA volume (45 ± 6.0 mm and 141 ± 29 ml). There were no significant differences in the max and mean DF values and %NPs between the patients with and without recurrent atrial tachyarrhythmias. However, there was a significant difference in the LVA/LA surface area between the patients with and without recurrent atrial tachyarrhythmias (p = .004). Atrial tachyarrhythmia freedom was significantly greater in those with LVAs of ≤3.3% than in those >3.3% after one procedure over 11.6 ± 0.8 months of follow-up (77.1% vs. 33.3%, p < .001). In a multivariate analysis, the LVA/LA surface area after the PVI (HR 1.079; CI, 1.025-1.135, p = .003) was an independent predictor of AF recurrence.

CONCLUSIONS

The predictor of atrial tachyarrhythmia recurrence after the PVI was LVAs rather than DFs and rotors in nonparoxysmal AF patients.

Association between serum inflammatory biomarkers and atrial low voltage in patients with atrial fibrillation: A phase 1 FIB-MARK study

Background

The mechanisms leading to atrial fibrosis in patients with atrial fibrillation (AF), especially in relation to inflammation, remain unclear.

Methods and Results

Forty biomarkers were measured in peripheral blood samples collected prior to catheter ablation, and the association with left atrial (LVZ) was evaluated in 16 consecutive patients. The median %LVZ was 17%. In Pearson’s correlation analysis, interleukin(IL)-17A and interferon(IFN)-γ showed the most significant positive and negative correlations with %LVZ (R = 0.35 and 0.43, P < 0.001). Furthermore, the IL-17A/IFN-γ ratio was significantly associated with %LVZ (R = 0.65, P = 0.007), as was the macrophage inflammatory protein (MIP)-1δ/IFN-γ ratio (R = 0.73, P = 0.001). The area under the receiver operator characteristics curves of the IL-17A/IFN-γ and MIP-1δ/IFN-γ ratios for detecting severe LVZ (%LVZ ≥ 10% as a reference standard) were 0.88 and 0.90, respectively. The IL-17A/IFN-γ ratio was significantly higher in patients with severe LVZ than those without (1.41 versus 0.97, P = 0.01). Furthermore, the sensitivity, specificity, and accuracy for detecting severe LVZ were 60%, 100%, and 75.0%, respectively, at a cut-off value of 1.3.

Conclusions

Among inflammatory biomarkers, the serum IL-17A/IFN-γ ratio was associated with severe left atrial LVZ in patients with AF. However, further studies are needed to clarify the role of inflammatory biomarkers in the development and progression of atrial fibrosis in patients with AF.

Characterization of Atrial Propagation Patterns and Fibrotic Substrate With a Modified Omnipolar Electrogram Strategy in Multi-Electrode Arrays

Introduction: The omnipolar electrogram method was recently proposed to try to generate orientation-independent electrograms. It estimates the electric field from the bipolar electrograms of a clique, under the assumption of locally plane and homogeneous propagation. The local electric field evolution over time describes a loop trajectory from which omnipolar signals in the propagation direction, substrate and propagation features, are derived. In this work, we propose substrate and conduction velocity mapping modalities based on a modified version of the omnipolar electrogram method, which aims to reduce orientation-dependent residual components in the standard approach. Methods: A simulated electrical propagation in 2D, with a tissue including a circular patch of diffuse fibrosis, was used for validation. Unipolar electrograms were calculated in a multi-electrode array, also deriving bipolar electrograms along the two main directions of the grid. Simulated bipolar electrograms were also contaminated with real noise, to assess the robustness of the mapping strategies against noise. The performance of the maps in identifying fibrosis and in reproducing unipolar reference voltage maps was evaluated. Bipolar voltage maps were also considered for performance comparison. Results: Results show that the modified omnipolar mapping strategies are more accurate and robust against noise than bipolar and standard omnipolar maps in fibrosis detection (accuracies higher than 85 vs. 80% and 70%, respectively). They present better correlation with unipolar reference voltage maps than bipolar and original omnipolar maps (Pearson's correlations higher than 0.75 vs. 0.60 and 0.70, respectively). Conclusion: The modified omnipolar method improves fibrosis detection, characterization of substrate and propagation, also reducing the residual sensitivity to directionality over the standard approach and improving robustness against noise. Nevertheless, studies with real electrograms will elucidate its impact in catheter ablation interventions.

Electroanatomic voltage mapping for tissue characterization beyond arrhythmia definition: A systematic review

Three-dimensional (3D) reconstruction by means of electroanatomic mapping (EAM) systems, allows for the understanding of the mechanism of focal or re-entrant arrhythmic circuits, which can be identified by means of dynamic (activation and propagation) and static (voltage) color-coded maps. However, besides this conventional use, EAM may offer helpful anatomical and functional information for tissue characterisation in several clinical settings. Today, data regarding electromechanical myocardial viability, scar detection in ischaemic and nonischaemic cardiomyopathy and arrhythmogenic right ventricle dysplasia (ARVC/D) definition are mostly consolidated, while emerging results are becoming available in contexts such as Brugada syndrome and cardiac resynchronisation therapy (CRT) implant procedures. As part of an invasive procedure, EAM has not yet been widely adopted as a stand-alone tool in the diagnostic path. We aim to review the data in the current literature regarding the use of 3D EAM systems beyond the definition of arrhythmia.

A new interpretation of nonpulmonary vein substrates of the left atrium in patients with atrial fibrillation

BACKGROUND

Substrate analysis of the left atrium in patients undergoing atrial fibrillation ablation has limitations when performed by means of simple bipolar acquisition.

OBJECTIVE

To evaluate the incidence of low-voltage zones (LVZs) through maps constructed by means of various catheters: multipolar (MC), omnipolar (OC), and circular catheters (CMCs) with the 3D electro-anatomical systems (3d-S) CARTO3 and EnSite Precision.

METHODS

To assess LVZs, we acquired maps by means of CMC and MC in the voltage range 0.05-0.5 mV in 70 consecutive patients in sinus rhythm. In the case of OC only, we made an intra-patient comparison of bipolar maps constructed by means of the along and across, and HD-Wave configurations of the EnSite 3d-S in the ranges of 0.05-0.5 and 0.5-1.0 mV. On the basis of this comparison, we chose the range that best identified LVZs as a set of different colors (SDC) compatible with patchy fibrosis (qualitative analysis). Subsequently, we detected the voltage values corresponding to purple and gray points, close to SDC, and the value inside corresponding to blue, green, and red colors, and we evaluated the color change in other voltage ranges. Finally, we performed a quantitative analysis of LVZs by applying the qualitative characteristics described above.

RESULTS

On the basis of our settings, for OC, the optimal range identifying LVZs was 0.3-0.6 mV. OC revealed smaller LVZs than MC (P < .05 or P < .001), except in the lateral wall. No significant differences were observed between CMCs.

CONCLUSIONS

In our experience, OC does not present the limits of bipolar HD maps, though further studies are needed in order to confirm that 0.3-0.6 mV is the optimal voltage range within which to identify LVZs.

Substrate mapping of the left atrium in persistent atrial fibrillation: spatial correlation of localized complex conduction patterns in global charge-density maps to low-voltage areas in 3D contact bipolar voltage maps

Purpose

This study aimed to investigate the spatial relationship between low-voltage areas (LVAs) in bipolar voltage mapping (BVM) and localized complex conduction (LCC)-cores in a global, non-contact, charge-density-based imaging, and mapping system (AcM).

Methods

Patients with history of index PVI for PsAF and scheduled for a repeat ablation procedure for recurrence of the same arrhythmia were enrolled between August 2018 and February 2020. All patients underwent both substrate mappings of the left atrium (LA) with the CARTO 3D map-ping system and with AcM.

Results

Ten patients where included in our analysis. All presented with persistency of PVI in all veins at the moment of repeat procedure. There was no linear relationship in BVM maps between SR and CSd (correlation coefficient 0.31 ± 0.15), SR and CSp (0.36 ± 0.12) and CSd and CSp (0.43 ± 0.10). The % overlap of localized irregular activation (LIA), localized rotational activation (LRA) and Focal (F) regions with LVA was lower at 0.2 mV compared to 0.5 mV (4.97 ± 7.39%, 3.27 ± 5.25%, 1.09 ± 1.92% and 12.59 ± 11.81%, 7.8 ± 9.20%, 4.62 ± 5.27%). Sensitivity and specificity are not significantly different when comparing composite maps with different LVA cut-offs. AURC was 0.46, 0.48, and 0.39 for LIA, LRA, and Focal, respectively.

Conclusion

Due to wave front direction dependency, LVAs mapped with BVM in sinus rhythm and during coronary sinus pacing only partially overlap in patients with PsAF. LCC-cores mapped during PsAF partially co-localize with LVAs.

Is the abnormal conduction zone of the left atrium a precursor to a low voltage area in patients with atrial fibrillation?

BACKGROUND

The abnormal conduction zone (ACZ) in the left atrium (LA) has attracted attention as an arrhythmia source in atrial fibrillation (AF). We investigated the hypothesis that the ACZ is related to the low voltage area (LVA) or the LA anatomical contact areas (CoAs) with other organs.

METHODS AND RESULTS

We studied 100 patients (49 non-paroxysmal AF, 66 males, and 67.9 ± 9.9 years) who received catheter ablation for AF. High-density LA mapping during high right atrial pacing was constructed. Isochronal activation maps were created at 5-ms interval setting, and the ACZ was identified on the activation map by locating a site with isochronal crowding of ≥3 isochrones, which are calculated as ≤27 cm/s. The LVA was defined as the following; mild ( < 1.3 mV), moderate (<1.0 mV), and severe LVA (<0.5 mV). The CoAs (ascending aorta-anterior LA, descending aorta-posterior LA, and vertebrae-posterior LA) were assessed using computed tomography. The ACZ was linearly distributed, and observed in 95 patients (95%). The ACZ was most frequently observed in the anterior wall region (77%). A longer ACZ was significantly associated with a larger LA size and a prevalence of non-PAF. The 51.2 ± 36.2% of ACZ overlapped with mild LVA, 32.9 ± 32.8% of ACZ with moderate LVA, and 14.6 ± 22.0% of ACZ with severe LVA. In contrast, only 25.6 ± 28.0% of ACZ matched with the CoAs.

CONCLUSION

The ACZ reflects LA electrical remodeling and may be a precursor finding of the low voltage zone and not the LA CoAs in patients with atrial fibrillation.

Q. M. Muskens A, Boersma E, de Groot NMS, Brundel BJJM. Evaluating Serum Heat Shock Protein Levels as Novel Biomarkers for Atrial Fibrillation

Background: Staging of atrial fibrillation (AF) is essential to understanding disease progression and the accompanied increase in therapy failure. Blood-based heat shock protein (HSP) levels may enable staging of AF and the identification of patients with higher risk for AF recurrence after treatment. Objective: This study evaluates the relationship between serum HSP levels, presence of AF, AF stage and AF recurrence following electrocardioversion (ECV) or pulmonary vein isolation (PVI). Methods: To determine HSP27, HSP70, cardiovascular (cv)HSP and HSP60 levels, serum samples were collected from control patients without AF and patients with paroxysmal atrial fibrillation (PAF), persistent (PeAF) and longstanding persistent (LSPeAF) AF, presenting for ECV or PVI, prior to intervention and at 3-, 6- and 12-months post-PVI. Results: The study population (n = 297) consisted of 98 control and 199 AF patients admitted for ECV (n = 98) or PVI (n = 101). HSP27, HSP70, cvHSP and HSP60 serum levels did not differ between patients without or with PAF, PeAF or LSPeAF. Additionally, baseline HSP levels did not correlate with AF recurrence after ECV or PVI. However, in AF patients with AF recurrence, HSP27 levels were significantly elevated post-PVI relative to baseline, compared to patients without recurrence. Conclusions: No association was observed between baseline HSP levels and the presence of AF, AF stage or AF recurrence. However, HSP27 levels were increased in serum samples of patients with AF recurrence within one year after PVI, suggesting that HSP27 levels may predict recurrence of AF after ablative therapy.

Confirmation of Pulmonary Vein Isolation with High-Density Mapping: Comparison to Traditional Workflows

Pulmonary vein isolation (PVI) is the cornerstone of atrial fibrillation (AF) ablation. Yet tools and techniques used for confirmation of PVI vary greatly, and it is unclear whether the use of any particular combination of tools and techniques provides greater sensitivity for identifying gaps periprocedurally. It has been suggested the use of a high-density mapping catheter, which enables simultaneous recording of adjacent bipolar EGMs in two directions, may provide improved sensitivity for gap identification. Anonymized, acute procedural data was prospectively collected in AF ablation cases utilizing various workflows for confirmation of PVI. Post-hoc analysis was performed to evaluate the incidence of gaps detected by different diagnostic catheter technologies, including a high-density mapping catheter and circular mapping catheters (CMCs), and common techniques such as pacing the ablation lines. A total of 139 cases were included across three subgroup analyses: 99 cases were included in an indirect comparison of three mapping catheter technologies, revealing gaps in 36.7%, 38.9%, and 81.8% of cases utilizing a 10-pole CMC, 20-pole CMC, and a high-density mapping catheter, respectively; a direct comparison of diagnostic catheter technologies in 18 cryoballoon ablation cases revealed residual gaps in 22.2% of patients identified by high-density mapping which were missed previously with the use of a 3.3F CMC; in 22 cases utilizing a technique of pacing the ablation lines, high-density mapping identified residual gaps in 68.2% of patients. This proof of concept analysis demonstrated that the use of a high-density catheter which records orthogonal bipoles simultaneously, appears to improve acute detection of gaps in PVI lines relative to other commonly utilized techniques and technologies. The long-term impact of ablating these concealed gaps remains unclear. Further study, including direct comparison of diagnostic catheter technologies in a randomized setting with long-term followup, is warranted.

Left Atrial Structural Remodelling in Non-Valvular Atrial Fibrillation: What Have We Learnt from CMR?

Left atrial structural, functional and electrical remodelling are linked to atrial fibrillation (AF) pathophysiology and mirror the phrase “AF begets AF”. A structurally remodelled left atrium (LA) is fibrotic, dysfunctional and enlarged. Fibrosis is the hallmark of LA structural remodelling and is associated with increased risk of stroke, heart failure development and/or progression and poorer catheter ablation outcomes with increased recurrence rates. Moreover, increased atrial fibrosis has been associated with higher rates of stroke even in sinus-rhythm individuals. As such, properly assessing the fibrotic atrial cardiomyopathy in AF patients becomes necessary. In this respect, late-gadolinium enhancement cardiac magnetic resonance (LGE-CMR) imaging is the gold standard in imaging myocardial fibrosis. LA structural remodelling extension offers both diagnostic and prognostic information and influences therapeutic choices. LGE-CMR scans can be used before the procedure to better select candidates and to aid in choosing the ablation technique, during the procedure (full CMR-guided ablations) and after the ablation (to assess the ablation scar). This review focuses on imaging several LA structural remodelling CMR parameters, including size, shape and fibrosis (both extension and architecture) and their impact on procedure outcomes, recurrence risk, as well as their utility in relation to the index procedure timing.

Association of fragmented QRS with left atrial scarring in patients with persistent atrial fibrillation undergoing radiofrequency catheter ablation

BACKGROUND

Fragmented QRS (fQRS) on 12-lead electrocardiography is a noninvasive marker of intramyocardial conduction delay due to ventricular scarring that has not previously been studied in atrial fibrillation.

OBJECTIVE

The purpose of this study was to assess the association of fQRS with left atrial (LA) scarring in patients with persistent atrial fibrillation (PsAF) undergoing first catheter ablation.

METHODS

A total of 376 patients with PsAF were enrolled. Severity of LA scarring was assessed using electroanatomic mapping. Narrow fQRS was defined by the presence of an additional R wave (R') or notching in the nadir of the S wave, or the presence of >1 R' in 2 contiguous leads corresponding to inferior, lateral, or anterior myocardial regions.

RESULTS

Both any degree (97.3% vs 63.3%) and severe (42.2% vs 6.3%) LA scarring were higher in patients with fQRS. Age and fQRS were found to be independent predictors of severe LA scarring. At multiple ventricular regions, fQRS had diagnostic accuracy of 79.8% for prediction of severe LA scarring. Nonpulmonary vein triggers were more often detected and ablated in patients with fQRS and severe LA scarring (84.4% vs 70%; P = .001). Atrial tachyarrhythmia recurrence was observed in 131 patients (34.8%) during 18.9 ± 7.7 months of follow-up, which was significantly higher in patients with fQRS (53.2% vs 16.8%). In multivariate analysis, fQRS was found to be a significant predictor of recurrence (hazard ratio 4.65; 95% interval confidence 2.91-7.42; P <.001).

CONCLUSION

The study results showed that fQRS is a simple, available, and noninvasive marker, and that fQRS at multiple ventricular regions is significantly associated with the severity of LA scarring in PsAF patients.