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

Multi-modal integration of MRI and global chamber charge density mapping for the evaluation of atrial fibrillation

Atrial fibrillation (AF) is the most prevalent clinical arrhythmia, posing significant mortality and morbidity challenges. Outcomes of current catheter ablation treatment strategies are suboptimal, highlighting the need for innovative approaches. A major obstacle lies in the inability to comprehensively assess both structural and functional remodelling in AF. Combining magnetic resonance imaging (MRI)'s detailed structural insights with global chamber charge density mapping (CDM)'s functional mapping capabilities holds promise for advancing AF management. Our research introduces a novel tool for three-dimensional reconstruction of left atrial geometries from MRI, facilitating integration into CDM systems. We comprehensively assess our tool by generating three-dimensional left atrial meshes from MRIs of eight patients with AF and compare them with the established CDM intra-chamber ultrasound approach utilizing both geometric and clinical parameters. We apply the CDM inverse algorithm to both sets of reconstructions in order to compare derived conductions across various heart rhythms and AF conduction patterns. Finally, we explore the potential utility of our integrated pipeline through an exploration of the relationship between AF conduction patterns and their proximity to adjacent thoracic structures. Ultimately, this multifaceted approach aims to unveil insights into AF mechanisms, potentially improving treatment outcomes through personalized ablation strategies targeting arrhythmogenic atrial substrate.

Leveraging 3D Atrial Geometry for the Evaluation of Atrial Fibrillation: A Comprehensive Review

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia associated with significant morbidity and mortality. Managing risk of stroke and AF burden are pillars of AF management. Atrial geometry has long been recognized as a useful measure in achieving these goals. However, traditional diagnostic approaches often overlook the complex spatial dynamics of the atria. This review explores the emerging role of three-dimensional (3D) atrial geometry in the evaluation and management of AF. Advancements in imaging technologies and computational modeling have enabled detailed reconstructions of atrial anatomy, providing insights into the pathophysiology of AF that were previously unattainable. We examine current methodologies for interpreting 3D atrial data, including qualitative, basic quantitative, global quantitative, and statistical shape modeling approaches. We discuss their integration into clinical practice, highlighting potential benefits such as personalized treatment strategies, improved outcome prediction, and informed treatment approaches. Additionally, we discuss the challenges and limitations associated with current approaches, including technical constraints and variable interpretations, and propose future directions for research and clinical applications. This comprehensive review underscores the transformative potential of leveraging 3D atrial geometry in the evaluation and management of AF, advocating for its broader adoption in clinical practice.

Quantitative analysis of fractionated electrogram area of left atrium during right atrial pacing as an indicator of left atrial electrical remodeling in patients with atrial fibrillation

Background

The clinical significance of left atrial local electrogram fractionation after restoration of sinus rhythm in patients with atrial fibrillation (AF) has not been elucidated.

Methods

We evaluated ultrahigh-resolution maps of the left atrium (LA) during RA pacing acquired after pulmonary vein isolation in 40 patients with AF. The association between low-voltage area (LVA, <0.5 mV), fractionated electrogram area (FEA, the highlighted area with LUMIPOINT™ Complex Activation), the interval from onset of LA activation to wavefront collision at the mitral isthmus (LA activation time), and wave propagation velocity (WPV) was evaluated quantitatively.

Results

The total LVA, total FEA with ≥5.0 peaks or ≥7.0 peaks were 7.0 ± 7.9 cm2, 15.9 ± 12.9 cm2, and 5.2 ± 7.5 cm2, respectively. These areas were predominantly observed in the anteroseptal region. Total LVA, total FEA with ≥5.0 peaks, and total FEA with ≥5.0 peaks in the normal voltage area (NVA: ≥0.5 mV) correlated with LA activation time (R = 0.69, 0.75, and 0.71; each p < .0001). In the anterior wall, these areas correlated with regional mean WPV (R = -0.75, -0.83, and - 0.55; each p < .0001) and the extent of slow conduction area (SCA) with WPV <0.3 m/s (R = 0.89, 0.84, 0.33; p < .0001 for LVA and FEA, p < .05 for FEA located in NVA). The anterior wall FEA with ≥7.0 peaks and that in the NVA showed a better correlation in predicting anterior wall SCA (R = 0.92 and 0.86, each p < .0001).

Conclusion

Quantitative analysis of FEA together with LVA may facilitate the assessment of LA electrical remodeling.

What determines the optimal pharmacological treatment of atrial fibrillation? Insights from in silico trials in 800 virtual atria

The best pharmacological treatment for each atrial fibrillation (AF) patient is unclear. We aim to exploit AF simulations in 800 virtual atria to identify key patient characteristics that guide the optimal selection of anti-arrhythmic drugs. The virtual cohort considered variability in electrophysiology and low voltage areas (LVA) and was developed and validated against experimental and clinical data from ionic currents to ECG. AF sustained in 494 (62%) atria, with large inward rectifier K+ current (IK1 ) and Na+ /K+ pump (INaK ) densities (IK1 0.11 ± 0.03 vs. 0.07 ± 0.03 S mF-1 ; INaK 0.68 ± 0.15 vs. 0.38 ± 26 S mF-1 ; sustained vs. un-sustained AF). In severely remodelled left atrium, with LVA extensions of more than 40% in the posterior wall, higher IK1 (median density 0.12 ± 0.02 S mF-1 ) was required for AF maintenance, and rotors localized in healthy right atrium. For lower LVA extensions, rotors could also anchor to LVA, in atria presenting short refractoriness (median L-type Ca2+ current, ICaL , density 0.08 ± 0.03 S mF-1 ). This atrial refractoriness, modulated by ICaL and fast Na+ current (INa ), determined pharmacological treatment success for both small and large LVA. Vernakalant was effective in atria presenting long refractoriness (median ICaL density 0.13 ± 0.05 S mF-1 ). For short refractoriness, atria with high INa (median density 8.92 ± 2.59 S mF-1 ) responded more favourably to amiodarone than flecainide, and the opposite was found in atria with low INa (median density 5.33 ± 1.41 S mF-1 ). In silico drug trials in 800 human atria identify inward currents as critical for optimal stratification of AF patient to pharmacological treatment and, together with the left atrial LVA extension, for accurately phenotyping AF dynamics. KEY POINTS: Atrial fibrillation (AF) maintenance is facilitated by small L-type Ca2+ current (ICaL ) and large inward rectifier K+ current (IK1 ) and Na+ /K+ pump. In severely remodelled left atrium, with low voltage areas (LVA) covering more than 40% of the posterior wall, sustained AF requires higher IK1 and rotors localize in healthy right atrium. For lower LVA extensions, rotors can also anchor to LVA, if the atria present short refractoriness (low ICaL ) Vernakalant is effective in atria presenting long refractoriness (high ICaL ). For short refractoriness, atria with fast Na+ current (INa ) up-regulation respond more favourably to amiodarone than flecainide, and the opposite is found in atria with low INa . The inward currents (ICaL and INa ) are critical for optimal stratification of AF patient to pharmacological treatment and, together with the left atrial LVA extension, for accurately phenotyping AF dynamics.

Abnormal Conduction Zone Detected by Isochronal Late Activation Mapping Accurately Identifies the Potential Atrial Substrate and Predicts the Atrial Fibrillation Ablation Outcome After Pulmonary Vein Isolation

BACKGROUND

The presence of abnormal substrate of left atrium is a predictor of atrial fibrillation (AF) recurrence after pulmonary vein isolation. We aimed to investigate the isochronal late activation mapping to access the abnormal conduction velocity for predicting AF ablation outcome.

METHODS

Forty-five paroxysmal AF patients (30 males, 57.8±8.7 years old) who underwent pulmonary vein isolation were enrolled. Isochronal late activation mapping was retrospectively constructed with 2 different windows of interest: from onset of P wave to onset of QRS wave on surface electrocardiography (W1) and 74 ms tracking back from the end of P wave (W2). Deceleration zone was defined as regions with 3 isochrones (DZa) or ≥4 isochrones (DZb) within a 1 cm radius on the isochronal late activation mapping, and the estimated conduction velocity (ECV) are 0.27 m/s and <0.20 m/s for DZa and DZb, respectively in W2. The distribution of deceleration zone was compared with the location of low-voltage zone (bipolar voltage ≤0.5 mV). Any recurrence of atrial arrhythmias was defined as the primary end point during follow ups after a 3-month blanking period.

RESULTS

Pulmonary vein isolation was performed in all patients, and there were 2 patients (4.4%) received additional extrapulmonary vein ablation. After a mean follow-up of 12.7±4.5 months, recurrence of AF occurred in 14 patients (31.1%). Patients with the presence of DZb in W2 had higher AF recurrence (Kaplan-Meier event rate estimates: HR, 9.41 [95% CI, 2.61-33.90]; log-rank P<0.0001). There were 52.6% of the DZb locations in W2 comparable to the distributions of low-voltage zone and 47.4% DZb were distributed in the area without low-voltage zone.

CONCLUSIONS

Deceleration zone detected by isochronal late activation mapping represents a critical AF substrate, it accurately predicts the AF recurrence following ablation in patients with paroxysmal AF.

Early diagnosis and better rhythm management to improve outcomes in patients with atrial fibrillation: the 8th AFNET/EHRA consensus conference

Despite marked progress in the management of atrial fibrillation (AF), detecting AF remains difficult and AF-related complications cause unacceptable morbidity and mortality even on optimal current therapy. This document summarizes the key outcomes of the 8th AFNET/EHRA Consensus Conference of the Atrial Fibrillation NETwork (AFNET) and the European Heart Rhythm Association (EHRA). Eighty-three international experts met in Hamburg for 2 days in October 2021. Results of the interdisciplinary, hybrid discussions in breakout groups and the plenary based on recently published and unpublished observations are summarized in this consensus paper to support improved care for patients with AF by guiding prevention, individualized management, and research strategies. The main outcomes are (i) new evidence supports a simple, scalable, and pragmatic population-based AF screening pathway; (ii) rhythm management is evolving from therapy aimed at improving symptoms to an integrated domain in the prevention of AF-related outcomes, especially in patients with recently diagnosed AF; (iii) improved characterization of atrial cardiomyopathy may help to identify patients in need for therapy; (iv) standardized assessment of cognitive function in patients with AF could lead to improvement in patient outcomes; and (v) artificial intelligence (AI) can support all of the above aims, but requires advanced interdisciplinary knowledge and collaboration as well as a better medico-legal framework. Implementation of new evidence-based approaches to AF screening and rhythm management can improve outcomes in patients with AF. Additional benefits are possible with further efforts to identify and target atrial cardiomyopathy and cognitive impairment, which can be facilitated by AI.

Targeted ablation of residual pulmonary vein potentials in atrial fibrillation ablation through ultra-high-density mapping: insights from the CHARISMA registry

INTRODUCTION

Low-voltage activity beyond pulmonary veins (PVs) may contribute to the failure of ablation of atrial fibrillation (AF) in the long term. We aimed to assess the presence of gaps (PVG) and residual potential (RAP) within the antral scar by means of an ultra-high density mapping (UHDM) system.

METHODS

We studied consecutive patients from the CHARISMA registry who were undergoing AF ablation and had complete characterization of residual PV antral activity. The Lumipoint^TM (Boston Scientific) map-analysis tool was used sequentially on each PV component. The ablation endpoint was PV isolation (PVI) and electrical quiescence in the antral region.

RESULTS

Fifty-eight cases of AF ablation were analyzed. A total of 86 PVGs in 34 (58.6%) patients and 44 RAPs in 34 patients (58.6%) were found. In 16 (27.6%) cases, we found at least one RAP in patients with complete absence of PV conduction. RAPs showed a lower mean voltage than PVG (0.3±0.2mV vs 0.7±0.5mV, p<0.0001), whereas the mean number of EGM peaks was higher (8.4±1.4 vs 3.2±1.5, p<0.0001). The percentage of patients in whom RAPs were detected through Lumipoint^TM was higher than through propagation map analysis (58.6% vs 36.2%, p=0.025). Acute procedural success was 100%, with all PVs successfully isolated and RAPs completely abolished in all study patients. During a mean follow-up of 453±133 days, 6 patients (10.3%) suffered an AF/AT recurrence.

CONCLUSION

Local vulnerabilities in antral lesion sets were easily discernible by means of the UHDM system in both de novo and redo patients when no PV conduction was present.

CLINICAL TRIAL REGISTRATION

Catheter Ablation of Arrhythmias with a High-Density Mapping System in Real-World Practice (CHARISMA). URL: http://clinicaltrials.gov/Identifier: NCT03793998 This article is protected by copyright. All rights reserved.

Application of dynamic display technology to identify gaps after pulmonary vein isolation in catheter ablation of atrial fibrillation

BACKGROUND

The identification of post pulmonary vein isolation (PVI) gaps by activation and voltage maps is time-consuming. This study aimed to investigate the characteristics, efficiency and accuracy of LiveView dynamic display module (EnSite™ Dynamic Display; Abbott, Abbott Park, IL, USA) in unmasking post PVI gaps and conduction block line.

METHOD

Twenty four patients with paroxysmal atrial fibrillation (PAF) who failed to achieve first-pass PVI or with recurrent PAF were enrolled. Ninety-six pulmonary veins (PVs) were evaluated, and gaps were identified in 25 (26.0%) PVs. The gap location was confirmed by activation and propagation maps; 110 frames on gaps and 118 frames on block lines were analyzed by using LiveView module. We defined isochronal crowding in the local activation time (LAT) mode as three colors between two adjacent electrodes. Each frame was classified as with or without isochronal crowding in LAT mode and one/continuous color or isochronal discontinuity in reentrant mode. The gray color inside the PVs was considered to represent conduction block.

RESULT

The isochronal crowding could be found on both gap and block line in LAT mode, whereas isochronal discontinuity only presented on the block line in reentrant mode. The sensitivity and specificity of isochronal discontinuity or gray color in reentrant mode to identify block line were 61.0% and 100%, respectively. The sensitivity and specificity of isochronal crowding or gray color in LAT mode to identify block line were 71.2% and 71.8%, respectively.

CONCLUSION

Reentrant mode in LiveView module is very specific in identifying block lines. We proposed an efficient, practical algorithm to differentiate the block line from PV gaps.

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.

Left heart function evaluation of patients with essential hypertension and paroxysmal atrial fibrillation by two-dimensional speckle tracking imaging combined with real-time three-dimensional ultrasound imaging

Background

This study aims to assess the value of two-dimensional speckle tracking imaging (2D-STI) combined with real-time 3-dimensional echocardiography (RT-3DE) in evaluating left heart function in patients with combined ETH and PAF.

Methods

A prospective study was designed, and the research period was from January 2017 to January 2020. A PAF observation group comprised of patients with ETH and PAF, a PAF control group of patients with ETH but without PAF, and a healthy volunteer group referred to as the healthy group, each comprised of 50 patients was established. All patients underwent routine ultrasound imaging examination using 2D-STI and RT-3DE. The interventricular septum thickness (IVST), left and right atrioventricular diameter (LAD), left ventricular posterior wall thickness (PWT), left ventricular ejection fraction (LVEF), the mean left atrium peak strain (mSs, mSe, mSa), strain rate (mSRs, mSRe, mSRa), the left ventricular mass (LVM), left ventricular mass index (LVMI), and left atrial total emptying volume (LATEV), the left atrial volume index (LAVI), left atrial total emptying fraction (LATEF), left atrium expansion index (LAEI), left atrium passive ejection fraction (LAPEF), and left atrial active ejection fraction (LAAEF) were calculated. Patients in the PAF observation group received telmisartan combined with rosuvastatin after diagnosis and 12- and 24-month-follow up visits were conducted. During these visits, 2D-STI combined with RT-3DE was used to evaluate cardiac function and each patient's blood pressure was monitored.

Results

Patients in the PAF observation group had a significantly longer course of ETH than patients in the PAF control group (13.5±4.4 vs. 10.32±5.6, P=0.002). The comparison of routine 2D-STI and RT-3DE ultrasound indexes among the three groups also showed significant differences (P<0.01). During the 2-year follow-up period, the IVST, LAD, PWT, and LVEF of remaining patients significantly improved as treatment progressed (P<0.05). The LAVI, LATEF, and LAEI also improved significantly as the treatment progressed (P<0.05). After 12 months of treatment, the recurrence rate of atrial fibrillation was 16.33% (8/45) and after 24 months this was 34.21% (13/38).

Conclusions

Cardiac function could be evaluated comprehensively by 2D-STI combined with RT-3DE in patients with ETH combined with PAF at initial diagnosis and follow-up.