Detection and quantification of left atrial structural remodeling with delayed-enhancement magnetic resonance imaging in patients with atrial fibrillation

Unlocking the diagnostic potential of electrocardiograms through information transfer from cardiac magnetic resonance imaging

Cardiovascular diseases (CVD) can be diagnosed using various diagnostic modalities. The electrocardiogram (ECG) is a cost-effective and widely available diagnostic aid that provides functional information of the heart. However, its ability to classify and spatially localise CVD is limited. In contrast, cardiac magnetic resonance (CMR) imaging provides detailed structural information of the heart and thus enables evidence-based diagnosis of CVD, but long scan times and high costs limit its use in clinical routine. In this work, we present a deep learning strategy for cost-effective and comprehensive cardiac screening solely from ECG. Our approach combines multimodal contrastive learning with masked data modelling to transfer domain-specific information from CMR imaging to ECG representations. In extensive experiments using data from 40,044 UK Biobank subjects, we demonstrate the utility and generalisability of our method for subject-specific risk prediction of CVD and the prediction of cardiac phenotypes using only ECG data. Specifically, our novel multimodal pre-training paradigm improves performance by up to 12.19% for risk prediction and 27.59% for phenotype prediction. In a qualitative analysis, we demonstrate that our learned ECG representations incorporate information from CMR image regions of interest. Our entire pipeline is publicly available at https://github.com/oetu/MMCL-ECG-CMR.

Impact of catheter ablation on atrial fibrillation outcomes in various cardiomyopathies: findings from LGE-MRI quantified atrial fibrosis analysis

BACKGROUND

Cardiomyopathy (CM) is associated with atrial remodeling and atrial fibrillation (AF), often complicating rhythm management. Ventricular dysfunction contributes to AF through pressure and volume overload, while AF worsens ventricular function via tachycardia and irregular activation. Evidence suggests catheter ablation improves outcomes in CM patients, though success is influenced by the extent of atrial and ventricular remodeling.

METHODS

Patients undergoing their first catheter ablation for AF were divided into hypertrophic (HCM), ischemic (ICM), non-ischemic (NICM), and no-CM groups. Pre-ablation late-gadolinium enhancement cardiac magnetic imaging (LGE-MRI) was used to assess left atrial (LA) fibrosis burden and anatomical distribution. Patients were followed prospectively for arrhythmia recurrence.

RESULTS

A total of 552 patients, 39 HCM (69% obstructive), 39 ICM, 115 with NICM, and 359 without CM were included between January 2015 and December 2022. LA fibrosis was significantly higher in patients with CM (19.1 ± 7.5% vs. 16.5 ± 6.9%; P = 0.01). HCM and ICM had the greatest LA fibrosis among the different CM subtypes (21.3 ± 8.7% and 21.9 ± 9.1%, respectively). There was no significant difference in the regional distribution of fibrosis among the various groups. AF recurrence was observed in 321 (58.2%) after 456 (175-1204) days. Multivariate analysis revealed that compared to no CM, HCM was associated with a three-fold increase in AF recurrence (HR = 3.07, 95% CI 2.06-4.58, P < 0.001), followed by ICM (HR 1.61, 95%, CI 0.95-2.72; P = 0.07) and NICM (HR of 1.53, 95% CI 1.14-2.06; P = 0.05). LA fibrosis and volume index were independently associated with recurrence (HR = 1.03, 95% CI 1.01-1.06, P = 0.01 and HR = 1.02, 95% CI 1.01-1.03, P = 0.01). Genetic testing revealed key distinctions between HCM and NICM, with MYBPC3 and MYH7 as prominent genes in HCM and a heterogeneous genetic basis in NICM.

CONCLUSION

Hypertrophic cardiomyopathy is associated with the highest risk of AF recurrence followed by ischemic and non-ischemic cardiomyopathy after catheter ablation. LA fibrosis regional patterns did not differ between cardiomyopathy types, while overall fibrosis and volume predicted recurrence.

Novel Self-Calibrated Threshold-Free Probabilistic Fibrosis Signature Technique for 3D Late Gadolinium Enhancement MRI

Myocardial fibrosis is a crucial marker of heart muscle injury in several heart disease like myocardial infarction, cardiomyopathies, and atrial fibrillation (AF). Fibrosis and associated scarring (dense fibrosis) are also vital for assessing heart muscle pre- and post-intervention, such as evaluating left atrial (LA) fibrosis/scarring in patients undergoing catheter ablation for AF. Although cardiac MRI is the gold standard for fibrosis assessment, current quantification methods are unreliable due to their reliance on variable thresholding and sensitivity to MRI uncertainties, lacking standardization and reproducibility. Importantly, current methods focus solely on quantifying fibrosis volume ignoring the unique MRI characteristics of fibrosis density and unique distribution, that could better inform on disease severity. To address these issues, we propose a novel threshold-free self-calibrating probabilistic method called "Fibrosis Signatures." This method efficiently encodes ∼9 billion MRI intensity co-disparities per scan into standardized probability density functions, deriving a unique MRI fibrosis signature index (FSI). The FSI index quantitatively encodes fibrosis/scar extent, density, and distribution patterns simultaneously, providing a detailed assessment of burden/severity. Our self-calibrating design mitigates impacts of MRI uncertainties, ensuring robust evaluations pre- and post-intervention under varying MRI qualities. Extensively validated using a novel numerical phantom and 143 in vivo LA 3D MRIs of AF patients (pre- and post- ablation and serial post-ablation scans) and compared to 5 existing methods, our FSI index demonstrated strong correlations with traditional fibrosis measures and was able to quantify density and distribution pattern beyond entropy. FSI was up to 9 times more reliable and reproducible to MRI uncertainties (noise, segmentation, spatial resolution), highlighting its potential to improve cardiac MRI reliability and clinical utility.

Recurrent atrial fibrillation markers post radiofrequency catheter ablation

Atrial fibrillation (AF), the most common type of heart arrhythmia, is recognized as an independent risk factor for stroke. Fortunately, catheter ablation (CA) offers an effective treatment option for AF patients. However, numerous studies have reported suboptimal outcomes, as AF recurrence rates often remain elevated even after CA. Consequently, there exists a need for early identification of patients prone to recurrence, necessitating anti-inflammatory and/or antiarrhythmic treatment post-CA. The discovery and application of markers associated with AF recurrence could significantly aid in this early identification process. In this review, we present an overview of AF recurrence markers from three distinct perspectives (biochemical, imaging, and electrocardiographic markers).

Late gadolinium enhancement in areas with electrically fractionated potentials during sinus rhythm in patients with atrial fibrillation

The areas with electrically fractionated potentials (AEFP) during sinus rhythm are related to non-pulmonary vein triggers and may serve as substrates of atrial fibrillation (AF) maintenance. However, the histological properties of these compounds remain unclear. Therefore, we aimed to evaluate the late gadolinium enhancement (LGE) properties of AEFP in patients with AF. We enrolled 15 patients with AF who had undergone LGE magnetic resonance imaging before catheter ablation. AEFP in the left atrium was detected using the HD-Grid and NavX systems after pulmonary vein isolation. We compared LGE properties between AEFP and the surrounding non-fractionated areas (non-AEFP). LGE heterogeneity and density were evaluated through entropy (LGE entropy) and the volume ratio of the enhancement voxel (LGE volume ratio), respectively. Thirty-three AEFP were detected in the left atrium. LGE entropy and LGE volume ratio were significantly higher in AEFP than in non-AEFP [LGE entropy: 6.2 (6.1-6.4) vs. 5.9 (5.8-6.0), p ≤ 0.0001; LGE volume ratio: 23.0% (17.2-29.0%) vs. 10.4% (3.4-20.2%), p ≤ 0.0001]. The atrial voltages did not differ [2.4 (1.3-3.7) vs. 2.5 (1.9-3.1) mV, p = 0.96]. AF recurrence was more significantly found in patients with more than three AEFP than in those without it (log-rank test: p = 0.009). AEFP is likely to be distributed in heterogeneous and moderate LGE areas, regardless of the atrial voltage.

A comprehensive evaluation of the left atrium using cardiovascular magnetic resonance

Atrial disease or myopathy is a growing concept in cardiovascular medicine, particularly in the context of atrial fibrillation, as well as amyloidosis and heart failure. Among cardiac imaging modalities, cardiovascular magnetic resonance (CMR) is particularly well suited for a comprehensive assessment of atrial myopathy, including tissue characterization and hemodynamics. The goal of this review article is to describe clinical applications and make recommendations on pulse sequences as well as imaging parameters to assess the left atrium and left atrial appendage. Furthermore, we aimed to create an overview of current and promising future emerging applications of left atrium-specific CMR pulse sequences focusing on both electrophysiologic (EP) and non-EP applications.

Impact of left atrial myopathy and post-ablation remodeling on quality of life: a DECAAF II sub-analysis

BACKGROUND

Atrial fibrillation (AF) is associated with adverse remodeling of the left atrium (LA). The impact of the extent of atrial myopathy and post-ablation remodeling on quality-of-life (QoL) outcomes has not been studied.

OBJECTIVE

The aim of our study was to investigate the association between atrial myopathy and post-ablation remodeling on quality-of-life outcomes in patients with persistent AF.

METHODS

We conducted an analysis of DECAAF II participants who underwent late-gadolinium enhancement MRI (LGE-MRI) before and after AF ablation. We assessed atrial myopathy and post-ablation atrial remodeling, scar formation, and fibrosis coverage with ablation. QoL metrics were assessed using the Short Form Survey (SF-36) and Atrial Fibrillation Severity Scale (AFSS). Uni- and multivariable regression models were developed for this analysis.

RESULTS

Six hundred thirteen patients with persistent AF were included in our analyses. At baseline, AFSS burden and total AFSS score were 18.94 ± 7.35 and 12.24 ± 8.17, respectively. Following ablation, all QoL and AFSS metrics improved in both the pulmonary vein isolation (PVI) and MRI-guided fibrosis ablation groups. On average, one unit of post-ablation reduction in left atrial volume index (LAVI) was associated with an improvement of 0.085 in total AFSS score (p = 0.001), 0.01 in shortness of breath with activity (p < 0.001), 0.15 in AF burden (p < 0.001), - 0.016 in global well-being (p = 0.018), 0.519 in health change (p < 0.001), 0.19 in vitality (vitality (p = 0.01), and 0.27 in physical functioning (p = 0.001). Baseline fibrosis and residual fibrosis post-ablation were associated with improved vitality and general health.

CONCLUSION

Atrial myopathy and post-ablation atrial remodeling significantly impact QoL in patients with persistent AF undergoing ablation.

Quantification of atrial cardiomyopathy disease severity by electroanatomic voltage mapping and cardiac magnetic resonance imaging

INTRODUCTION

Atrial late gadolinium enhancement (Atrial-LGE) and electroanatomic voltage mapping (Atrial-EAVM) quantify the anatomical and functional extent of atrial cardiomyopathy. We aimed to explore the relationships between, and outcomes from, these modalities in patients with atrial fibrillation undergoing ablation.

METHODS

Patients undergoing first-time ablation had disease severities quantified using both Atrial-LGE and Atrial-EAVM. Correlations between modalities and their relationships with clinical features and arrhythmia recurrence were assessed.

RESULTS

In 123 atrial fibrillation patients (60 ± 10 years), Atrial-EAVM was moderately correlated with Atrial-LGE (r = .34, p < .001), with a mean fibrosis burden of 47.2% ± 14.91%. Agreement was strongest in the highest tertile of fibrosis burden (mean of differences 16.8% (95% CI = -24.4% to 57.9%, p = .433). Fibrosis burden was greater for Atrial-LGE than Atrial-EAVM (50.7% ± 10.7% vs. 13.7% ± 7.13%, p < .005) for patients in the lowest tertile who were younger, had smaller atria and a greater frequency of paroxysmal atrial fibrillation. Both Atrial EAVM and Atrial LGE were associated with recurrence of arrhythmia following ablation (Atrial-LGE HR = 1.02 (95% CI = 1.01-1.04), p = .047; Atrial-EAVM HR = 1.02 (95% CI = 1.005-1.03), p = .007). A low fibrosis burden (<15%) by Atrial-EAVM identified patients with very low arrhythmia recurrence. In contrast, a much higher fibrosis burden (>66%) by Atrial-LGE identified patients failing to respond to ablation.

CONCLUSIONS

We demonstrate for the first time that the level of agreement between Atrial-EAVM and Atrial-LGE is dependent on the level of atrial cardiomyopathy disease severity. The functional consequences of atrial cardiomyopathy are most evident in patients with the highest anatomical extent of disease.

Atrial structural remodeling and atrial fibrillation substrate: A histopathological perspective

Atrial fibrillation (AF) substrate progresses with the advancement of atrial structural remodeling, resulting in AF perpetuation and recurrence. Although fibrosis is considered a hallmark of atrial structural remodeling, the histological background has not been fully elucidated because obtaining atrial specimens is difficult, especially in patients not undergoing open-heart surgery. Bipolar voltage reduction evaluated using electroanatomic mapping during AF ablation is considered a surrogate marker for the progression of structural remodeling; however, histological validation is lacking. We developed an intracardiac echocardiography-guided endomyocardial atrial biopsy technique to evaluate atrial structural remodeling in patients undergoing catheter ablation for nonvalvular AF. The histological factors associated with a decrease in bipolar voltage were interstitial fibrosis, as well as an increase in myocardial intercellular space preceding fibrosis, myofibrillar loss, and a decrease in cardiomyocyte nuclear density, which is a surrogate marker for cardiomyocyte density. Cardiomyocyte hypertrophy is closely associated with a decrease in cardiomyocyte nuclear density, suggesting that hypertrophic changes compensate for cardiomyocyte loss. Electron microscopy also revealed that increased intercellular spaces indicated the leakage of plasma components owing to increased vascular permeability. Additionally, amyloid deposition was observed in 4 % of biopsy cases. Only increased intercellular space and interstitial fibrosis were significantly higher for long-standing persistent AF than for paroxysmal AF and associated with recurrence after AF ablation, suggesting that this interstitial remodeling is the AF substrate. An increase in intercellular space that occurs early in AF formation is a therapeutic target for the AF substrate, which prevents irreversible interstitial degeneration due to collagen accumulation. This endomyocardial atrial biopsy technique will allow the collection of atrial tissue from a wide variety of patients and significantly facilitate the elucidation of the mechanisms of atrial cardiomyopathy, structural remodeling, and AF substrates.

β-Hydroxybutyrate and Citrate Synthase as Potential Diagnostic Biomarkers in Aging-Related Atrial Fibrillation

The incidence of atrial fibrillation (AF) increases with age; however, the precise mechanisms by which aging elevates AF risk and the effective biomarkers for managing AF in elderly patients remain unclear. We analyzed plasma samples from 100 elderly AF patients, 100 young and 100 elderly patients without atrial fibrillation (NAF), along with left atrial tissues obtained from both AF and NAF patients following valve replacement. Our findings indicate reduced levels of β-OHB and citrate synthase (CS) activity in elderly AF patients compared to their NAF counterparts. Statistical analysis revealed a protective association between β-OHB and CS activity concerning the occurrence of elderly AF. Furthermore, atrial tissues from elderly AF patients exhibited mitochondrial dysfunction, structural remodeling, and low-voltage areas. These results suggest that dysregulation of β-OHB levels and CS activity may contribute to aging-related AF by affecting mitochondrial function and atrial remodeling, highlighting their potential as diagnostic biomarkers for this condition.

Integrated Management of Persistent Atrial Fibrillation

The global incidence of atrial fibrillation is on the rise. Atrial fibrillation, a complex disease, heightens the likelihood of heart failure, stroke, and mortality, necessitating careful attention. Controlling heart rate and rhythm, addressing risk factors, and preventing strokes are fundamental in treating atrial fibrillation. Catheter ablation stands out as the primary approach for atrial fibrillation rhythm control. Nevertheless, the limited success rates pose a significant challenge to catheter ablation, particularly for persistent atrial fibrillation. Various adjunctive ablation techniques are currently under investigation to enhance the effectiveness of catheter ablation. This review provides an overview of the current state of the art and the latest optimized treatments for persistent atrial fibrillation in the areas of rhythm control, heart rate control, and risk factor management.

Evolution in electrophysiology 100 years after Einthoven: translational and computational innovations in rhythm control of atrial fibrillation

In 1924, the Dutch physiologist Willem Einthoven received the Nobel Prize in Physiology or Medicine for his discovery of the mechanism of the electrocardiogram (ECG). Anno 2024, the ECG is commonly used as a diagnostic tool in cardiology. In the paper 'Le Télécardiogramme', Einthoven described the first recording of the now most common cardiac arrhythmia: atrial fibrillation (AF). The treatment of AF includes rhythm control, aiming to alleviate symptoms and improve quality of life. Recent studies found that early rhythm control might additionally improve clinical outcomes. However, current therapeutic options have suboptimal efficacy and safety, highlighting a need for better rhythm-control strategies. In this review, we address the challenges related to antiarrhythmic drugs (AADs) and catheter ablation for rhythm control of AF, including significant recurrence rates and adverse side effects such as pro-arrhythmia. Furthermore, we discuss potential solutions to these challenges including novel tools, such as atrial-specific AADs and digital-twin-guided AF ablation. In particular, digital twins are a promising method to integrate a wide range of clinical data to address the heterogeneity in AF mechanisms. This may enable a more mechanism-based tailored approach that may overcome the limitations of previous precision medicine approaches based on individual biomarkers. However, several translational challenges need to be addressed before digital twins can be routinely applied in clinical practice, which we discuss at the end of this narrative review. Ultimately, the significant advances in the detection, understanding, and treatment of AF since its first ECG documentation are expected to help reduce the burden of this troublesome condition.

Image quality assessment and automation in late gadolinium-enhanced MRI of the left atrium in atrial fibrillation patients

BACKGROUND

Late gadolinium-enhanced (LGE) MRI has become a widely used technique to non-invasively image the left atrium prior to catheter ablation. However, LGE-MRI images are prone to variable image quality, with quality metrics that do not necessarily correlate to the image's diagnostic quality. In this study, we aimed to define consistent clinically relevant metrics for image and diagnostic quality in 3D LGE-MRI images of the left atrium, have multiple observers assess LGE-MRI image quality to identify key features that measure quality and intra/inter-observer variabilities, and train and test a CNN to assess image quality automatically.

METHODS

We identified four image quality categories that impact fibrosis assessment in LGE-MRI images and trained individuals to score 50 consecutive pre-ablation atrial fibrillation LGE-MRI scans from the University of Utah hospital image database. The trained individuals then scored 146 additional scans, which were used to train a convolutional neural network (CNN) to assess diagnostic quality.

RESULTS

There was excellent agreement among trained observers when scoring LGE-MRI scans, with inter-rater reliability scores ranging from 0.65 to 0.76 for each category. When the quality scores were converted to a binary diagnostic/non-diagnostic, the CNN achieved a sensitivity of 0.80 ± 0.06 and a specificity of 0.56 ± 0.10 .

CONCLUSION

The use of a training document with reference examples helped raters achieve excellent agreement in their quality scores. The CNN gave a reasonably accurate classification of diagnostic or non-diagnostic 3D LGE-MRI images of the left atrium, despite the use of a relatively small training set.

Cardiovascular positron emission tomography imaging of fibroblast activation: A review of the current literature

Fibrosis is one of the key healing responses to injury, especially within the heart, where it helps to maintain structural integrity following acute insults such as myocardial infarction. However, if it becomes dysregulated, then fibrosis can become maladaptive, leading to adverse remodelling, impaired cardiac function and heart failure. Fibroblast activation protein is exclusively expressed by activated fibroblasts, the key effector cells of fibrogenesis, and has a unique extracellular domain that is an ideal ligand for novel molecular imaging probes. Fibroblast activation protein inhibitor (FAPI) radiotracers have been developed for positron emission tomography (PET) imaging, demonstrating high selectivity for activated fibroblasts across a range of different pathologies and disparate organ systems. In this review, we will summarise the role of fibroblast activation protein in cardiovascular disease and how FAPI radiotracers might improve the assessment and treatment of patients with cardiovascular diseases.

Cardiac Arrhythmia: Molecular Mechanisms and Therapeutic Strategies

Arrhythmias are divided into supraventricular and ventricular, depending on where they originate [...].

A novel network with enhanced edge information for left atrium segmentation from LGE-MRI

Introduction

Automatic segmentation of the left atrium (LA) constitutes a crucial pre-processing step in evaluating heart structure and function during clinical interventions, such as image-guided radiofrequency ablation of atrial fibrillation. Despite prior research on LA segmentation, the low contrast in medical images exacerbates the challenge of distinguishing various tissues, rendering accurate boundary delineation of the target area formidable. Moreover, class imbalance due to the small target size further complicates segmentation.

Methods

This study aims to devise an architecture that augments edge information for LA segmentation from late gadolinium enhancement magnetic resonance imaging. To intensify edge information within image features, this study introduces an Edge Information Enhancement Module (EIEM) to the foundational network. The design of EIEM is grounded in exploring edge details within target region features learned from images. Additionally, it incorporates a Spatially Weighted Cross-Entropy loss function tailored for EIEM, introducing constraints on different regions based on the importance of pixels to edge segmentation, while also mitigating class imbalance through weighted treatment of positive and negative samples.

Results

The proposed method is validated on the 2018 Atrial Segmentation Challenge dataset. Compared with other state-of-the-art algorithms, the proposed algorithm demonstrated a significant improvement with an average symmetric surface distance of 0.684 mm and achieved a commendable Dice coefficient of 0.924, implicating the effectiveness of enhancing edge information.

Discussion

The method offers a practical framework for precise LA localization and segmentation, particularly strengthening the algorithm's effectiveness in improving segmentation outcomes for irregular protrusions and discrete multiple targets. Additionally, the generalizability of our model was evaluated on the heart dataset from the Medical Segmentation Decathlon (MSD) challenge, confirming its robustness across different clinical scenarios involving LA segmentation.

Hyperenhancement of LA Wall by Three-Dimensional High-Resolution Late Gadolinium-Enhanced MRI and Recurrence of AF After Catheter Ablation

Background/Objectives: This study investigated the relationship between LA (LA) enhancement on three-dimensional (3D) late gadolinium enhancement (LGE) MRI and recurrence after catheter ablation in patients with AF (AF). Methods: A total of one hundred patients with AF (mean age: 68 ± 9 years, 50% with paroxysmal AF) were included in this study. Each patient underwent a high-resolution 3D LGE MRI prior to catheter ablation, allowing for detailed imaging of the LA wall. Quantitative analysis of the enhancement was performed using dedicated software designed for volumetric measurements of LA LGE. Recurrence of AF was monitored over a 90-day period following the ablation procedure. The primary outcome was the correlation between the volume of LGE in the LA and the recurrence of AF. Results: Multivariate analysis confirmed that the volume of LA LGE, defined as the volume exceeding 1SD above the mean signal intensity of the LA, was an independent predictor of recurrence [hazard ratio: 1.16 (95%CI: 1.04-1.29, p = 0.0057)]. The area under the curve for recurrence prediction using 3D LGE MRI was 0.74 (95%CI: 0.63-0.86), with an optimal threshold of 11.72 mL, providing a sensitivity of 55% (95%CI: 32-77%) and a specificity of 86% (95%CI: 77-93%). Conclusions: LA enhancement assessed by high-resolution LGE MRI may serve as a valuable imaging marker for predicting the recurrence in patients with AF following catheter ablation.

Radiofrequency ablation guided by real-time cardiovascular magnetic resonance

Cardiovascular magnetic resonance (CMR) is gaining ground in guiding electrophysiology (EP)-based ablation procedures of typical atrial flutter and atrial fibrillation, allowing for the avoidance of radiation exposure for patients and operators and reducing the risk of occupational illnesses. CMR allows comprehensive assessment of cardiac anatomy and provides tissue characterization by identifying pathological substrates, such as myocardial scars and edema, identified with the implementation of late gadolinium enhancement and T2-weighted short-tau inversion recovery sequences. Intraprocedural imaging is useful for real-time catheter tracking during the ablation procedure while simultaneously providing visualization of cardiac anatomy. Additionally, CMR facilitates the evaluation of the ablation procedure accuracy by acquiring edema-sensitive sequences, thereby aiding in preventing early complications. This report serves as a primer for radiologists and illustrates the value of CMR in planning and performing the ablation procedure, as well as its role in post-procedural imaging.

Body mass index as a determinant of scar formation post-AF ablation: Insights from DECAAF II

INTRODUCTION

Obesity is implicated in adverse atrial remodeling and worse outcomes in patients with atrial fibrillation. The objective of this study is to assess the effect of body mass index (BMI) on ablation-induced scar formation on late gadolinium enhancement cardiac magnetic resonance imaging (LGE-CMR).

METHODS

We conducted an analysis of DECAAF II participants who underwent LGE-CMR scans to measure scar formation 3 months after catheter ablation. Ablation parameters and lesion delivery were not dependent on BMI. The effect of BMI on ablation success was explored.

RESULTS

Our analyses included 811 patients. Comorbidities were more prevalent in obese patients. Baseline left atrial volume was higher in obese individuals, 118, 126, 135, 140, and 143 mm3 for normal weight, overweight, obese grade 1, 2, and 3, respectively (p < .001). BMI was associated with scar formation (R = -0.135, p < .001), with patients with Class 3 obesity having the lowest percentage of ablation-induced scar, 11.1%, 10.3%, 9.5%, 8.8%, 6.8% by ascending BMI group. There was an inverse correlation between BMI and the amount of fibrosis covered by ablation scar, 24%, 23%, 21%, and 18% by ascending BMI group (p = .001). For the fibrosis-guided ablation group, BMI was associated with residual fibrosis (R = 0.056, p = .005).

CONCLUSION

Obese patients have lower ablation scar formation, covered fibrosis, and more residual fibrosis postablation compared to nonobese patients, regardless of ablation parameters including impedance drop.

Late Gadolinium Enhancement of Nonischemic Cardiomyopathy at 5.0 T versus 3.0 T: A Crossover Design Study

Purpose To compare the acquisition time, image quality, and late gadolinium enhancement (LGE) visualization and quantification on phase-sensitive inversion recovery (PSIR) images using 5.0-T versus 3.0-T cardiac MRI. Materials and Methods In this prospective crossover study, 49 participants (mean ± SD age, 43.7 years ± 13.1; 39 men) suspected or diagnosed with nonischemic cardiomyopathy were enrolled from April 2023 to March 2024 and randomly assigned to group 1 (5.0-T followed by 3.0-T LGE cardiac MRI) or group 2 (3.0-T followed by 5.0-T LGE cardiac MRI). PSIR images were acquired at spatial resolutions of 1.2, 0.9, and 1.6 mm. Image quality and LGE were qualitatively evaluated using a five-point Likert scale by two readers, and signal-to-noise ratio, contrast-to-noise ratio, and LGE mass were quantitatively assessed. Bland-Altman plots were used to evaluate interreader agreement. Results There was no evidence of a difference in the acquisition time for obtaining a single-layer PSIR image at 5.0 T compared with 3.0 T (P > .05 for all), irrespective of resolutions at 1.2, 0.9, and 1.6 mm. The 5.0-T PSIR images demonstrated better image quality and LGE visualization compared with 3.0-T images, particularly at 1.2 mm (image quality: median 5 [IQR, 5-5] vs median 5 [IQR, 4-5]; P = .004; LGE score: median 5 [IQR, 5-5] vs median 4.25 [IQR, 4-5]; P < .001). No evidence of differences in image quality or LGE scores was found between 5.0-T and 3.0-T cardiac MRI at 1.6-mm resolution. Signal-to-noise ratio and contrast-to-noise ratio were higher on 5.0-T PSIR images across all resolutions compared with 3.0-T images (P < .001 for all), but no evidence of a difference was found in LGE mass measurements. Conclusion The study demonstrates that 5.0-T PSIR imaging offers better image quality and LGE visualization than 3.0-T PSIR, particularly at a 1.2-mm resolution, in individuals with nonischemic cardiomyopathy. Keywords: MRI, Cardiac, Heart, Comparative Studies, Nonischemic Cardiomyopathy, Late Gadolinium Enhancement, Phase-Sensitive Inversion Recovery Supplemental material is available for this article. ©RSNA, 2024.

2024 European Heart Rhythm Association/Heart Rhythm Society/Asia Pacific Heart Rhythm Society/Latin American Heart Rhythm Society expert consensus statement on catheter and surgical ablation of atrial fibrillation

In the last three decades, ablation of atrial fibrillation (AF) has become an evidence-based safe and efficacious treatment for managing the most common cardiac arrhythmia. In 2007, the first joint expert consensus document was issued, guiding healthcare professionals involved in catheter or surgical AF ablation. Mounting research evidence and technological advances have resulted in a rapidly changing landscape in the field of catheter and surgical AF ablation, thus stressing the need for regularly updated versions of this partnership which were issued in 2012 and 2017. Seven years after the last consensus, an updated document was considered necessary to define a contemporary framework for selection and management of patients considered for or undergoing catheter or surgical AF ablation. This consensus is a joint effort from collaborating cardiac electrophysiology societies, namely the European Heart Rhythm Association, the Heart Rhythm Society, the Asia Pacific Heart Rhythm Society, and the Latin American Heart Rhythm Society.

Diffuse functional and structural abnormalities in fibrosis: Potential structural basis for sustaining atrial fibrillation

BACKGROUND

Structural remodeling has been associated with increased incidence of atrial fibrillation, but how fibrotic regions allow atrial fibrillation to be sustained remains unclear.

OBJECTIVE

With a novel transgenic goat model, we evaluated structural and functional differences between structurally remodeled and healthy regions of the atria.

METHODS

A novel transgenic goat model with cardiac-specific overexpression of transforming growth factor β1 was used. Ex vivo cardiac magnetic resonance imaging and histology were used to evaluate differences in fibrosis, fiber disarray, and structural anisotropy. Functional analysis examined conduction speeds and direction heterogeneity. By use of underlying fiber orientation obtained with diffusion tensor imaging, conduction anisotropy was calculated.

RESULTS

The transgenic goats had on average 21% of the left atria labeled fibrotic, determined from ex vivo cardiac magnetic resonance imaging. The histology samples within the labeled fibrotic regions showed an increase in fibrosis percentage. Fractional anisotropy, a measurement of structural anisotropy, was lower, whereas fiber direction heterogeneity, a measurement of the angle difference of the fiber from its neighbors, was greater, indicating increased fiber disarray in fibrotic regions. The fibrotic regions had slower conduction speeds and more aligned conduction directions, potentially allowing unidirectional conduction block to develop. Conduction anisotropy, measured on the underlying fiber directions, was found to be lower in the fibrotic regions.

CONCLUSION

Fibrotic regions had slower conduction, and propagation tended to flow more unidirectionally. The direction of propagation differs from the underlying fiber direction, leading to lower conduction anisotropy. Functional and structural abnormalities of the fibrotic tissue may allow fibrotic regions to serve as a substrate for an arrhythmia to develop and to be sustained.

Functional and Structural Remodeling as Atrial Fibrillation Progresses in a Persistent Atrial Fibrillation Canine Model

BACKGROUND

Contractile, electrical, and structural remodeling has been associated with atrial fibrillation (AF), but the progression of functional and structural changes as AF sustains has not been previously evaluated serially.

OBJECTIVES

Using a rapid-paced persistent AF canine model, the authors aimed to evaluate the structural and functional changes serially as AF progresses.

METHODS

Serial electrophysiological studies in a chronic rapid-paced canine model (n = 19) prior to AF sustaining and repeated at 1, 3, and 6 months of sustained AF were conducted to measure changes in atrial conduction speed and direction. Cardiac late gadolinium enhancement magnetic resonance imaging was performed prior to and following sustained AF to evaluate structural remodeling.

RESULTS

As AF progressed, the overall area of the left atrium with fibrosis increased. Over time, conduction speeds slowed, with speeds decreasing by 0.15 m/s after 3 months and 0.26 m/s after 6 months of sustained AF. Regions that developed fibrosis experienced greater slowing compared with healthy regions (0.32 ± 0.01 m/s decrease vs 0.21 ± 0.01 m/s decrease; P < 0.001). Conduction directions became more aligned (conduction direction heterogeneity decreased from 19.7 ± 0.1° to 17.5 ± 0.1° after 6 months of sustained AF; P < 0.001). Fibrotic regions had a greater decrease in conduction direction heterogeneity (2.7 ± 0.3° vs 2.0 ± 0.2°; P = 0.008).

CONCLUSIONS

As AF progressed, functional changes occurred globally throughout the left atrium. Conduction speed slowed, and conduction directions became more aligned over time, with the greatest changes occurring within regions that developed fibrosis.

QTc interval prolongation and risk of atrial fibrillation recurrence: a meta-analysis and observational cohort study

Introduction

Corrected QT interval (QTc) is a ventricular repolarization marker on electrocardiography. Previous studies evaluated its value in predicting atrial fibrillation (AF) occurrence. However, its predictive efficacy for AF recurrence remains controversial.

Methods

We searched PubMed and Google databases for studies before January 2024 evaluating the association between QTc interval and AF incidence. A meta-analysis of the eligible datasets was conducted using Bazett's formula, with subgroup analysis to explore the heterogeneity. Additionally, thirty-eight patients with AF who underwent radiofrequency catheter ablation were enrolled and followed-up for 3-36 months. Univariate and multivariate Cox models were used to calculate the hazard ratios (HRs) and determine the relationship between clinical factors and AF recurrence. Kaplan-Meier survival analysis and ROC curve were conducted to assess the impact and predictive efficacy of individual factors.

Results

Eleven datasets from nine eligible studies were enrolled and meta-analysed. We found that patients with prolonged QTc interval was associated with a significantly higher AF incidence risk, and the risk increased with every 10-ms prolongation. However, this association was not significant in the AF recurrence subgroup. In our prospective cohort, the preoperative body mass index, QTc, left atrial diameter (LAD), and uric acid levels influenced AF recurrence. Multivariate Cox regression analysis identified LAD as an independent factor affecting AF recurrence in patients with a high predictive efficiency. Kaplan-Meier survival analysis showed that increased LAD (>4.5 cm) was associated with postoperative AF recurrence.

Discussion

Therefore, LAD has better predictive power and can be an indicator for predicting postoperative AF recurrence.

Research Priorities for Atrial Fibrillation in Australia: A Statement From the Australian Cardiovascular Alliance Clinical Arrhythmia Theme

Atrial fibrillation (AF) is highly prevalent in the Australian community, ranking amongst the highest globally. The consequences of AF are significant. Stroke, dementia and heart failure risk are increased substantially, hospitalisations are amongst the highest for all cardiovascular causes, and Australians living with AF suffer from substantial symptoms that impact quality of life. Australian research has made a significant impact at the global level in advancing the care of patients living with AF. However, new strategies are required to reduce the growing incidence of AF and its associated healthcare demand. The Australian Cardiovascular Alliance (ACvA) has led the development of an arrhythmia clinical theme with the objective of tackling major research priorities to achieve a reduction in AF burden across Australia. In this summary, we highlight these research priorities with particular focus on the strengths of Australian research and the strategies needed to move forward in reducing incident AF and improving outcomes for those who live with this chronic condition.

Atrial fibrillation substrate and impaired left atrial function: a cardiac MRI study

AIMS

Structural and fibrotic remodelling is a well-known contributor to the atrial fibrillation (AF) substrate. Epicardial adipose tissue (EAT) is increasingly recognized as a contributor through electrical remodelling in the atria. We aimed to assess the association of LA fibrosis and EAT with LA strain and function using cardiac magnetic resonance (CMR) imaging in patients with AF.

METHODS AND RESULTS

LA fibrosis was assessed using late gadolinium enhancement CMR, LA EAT was assessed using the fat-water separation Dixon sequence, and feature tracking was applied to assess global longitudinal strain in its three components [reservoir (GLRS), conduit (GLCdS), and contractile (GLCtS)]. LA emptying fraction and LA volume were measured using the cine sequences. All CMR images were acquired in sinus rhythm. One hundred one AF patients underwent pre-ablation CMR (39% female, average age 62 years). LA fibrosis was negatively associated with the three components of global longitudinal strain (GLRS: R = -0.35, P < 0.001; GLCdS: R = -0.24, P = 0.015; GLCtS: R = -0.2, P = 0.046). Out of the different sections of the LA, fibrosis in the posterior and lateral walls was most negatively correlated with GLRS (R = -0.32, P = 0.001, and R = -0.33, P = 0.001, respectively). LA EAT was negatively correlated with GLCdS (R = -0.453, P < 0.001). LA fibrosis was negatively correlated with LA emptying fraction but LA EAT was not (R = -0.27, P = 0.007, and R = -0.22, P = 0.1, respectively). LA EAT and fibrosis were both positively correlated with LA volume (R = 0.38, P = 0.003, and R = 0.24, P = 0.016, respectively).

CONCLUSION

LA fibrosis, a major component of the AF substrate, and EAT, an important contributor, are associated with a worsening LA function through strain analysis by CMR.

The spatial overlap between left atrial epicardial adipose tissue and fibrosis is not associated to clinical stage of atrial fibrillation

Left atrial (LA) epicardial adipose tissue (EAT) and wall fibrosis are both proven to contribute to the pathogenesis and progression of atrial fibrillation (AF). The theory of LA wall fibrosis induction by local EAT infiltration, paracrine secretions, and activation of the inflammatory process is strongly advocated, but the imaging evidence for anatomical proximity of the two tissue types and its association to AF stage is lacking. Accordingly, the aim of the study was to analyse the spatial overlap between LA EAT and adjacent wall fibrosis using 3D Dixon water-fat separated late gadolinium enhancement (LGE-Dixon) MRI and correlate the findings with the clinical AF stage. Forty-two AF patients (18 paroxysmal, 10 persistent, and 14 permanent) and nine non-AF patients were scanned. The permanent AF patients had greater LA volume and EAT than the paroxysmal group. The LA fibrosis area showed the same trend. The LA EAT-fibrosis overlap area was small and there was no significant difference between the three AF stages. There was no significant relationship between LA EAT- fibrosis overlap area and AF type. The findings shed light on the complex interplay between LA fibrosis and EAT during the progression from paroxysmal to permanent AF.

Metabolic remodelling in atrial fibrillation: manifestations, mechanisms and clinical implications

Atrial fibrillation (AF) is a continually growing health-care burden that often presents together with metabolic disorders, including diabetes mellitus and obesity. Current treatments often fall short of preventing AF and its adverse outcomes. Accumulating evidence suggests that metabolic disturbances can promote the development of AF through structural and electrophysiological remodelling, but the underlying mechanisms that predispose an individual to AF are aetiology-dependent, thus emphasizing the need for tailored therapeutic strategies to treat AF that target an individual's metabolic profile. AF itself can induce changes in glucose, lipid and ketone metabolism, mitochondrial function and myofibrillar energetics (as part of a process referred to as 'metabolic remodelling'), which can all contribute to atrial dysfunction. In this Review, we discuss our current understanding of AF in the setting of metabolic disorders, as well as changes in atrial metabolism that are relevant to the development of AF. We also describe the potential of available and emerging treatment strategies to target metabolic remodelling in the setting of AF and highlight key questions and challenges that need to be addressed to improve outcomes in these patients.

Atrial Fibrillation and Underlying Structural and Electrophysiological Heterogeneity

As atrial fibrillation (AF) progresses from initial paroxysmal episodes to the persistent phase, maintaining sinus rhythm for an extended period through pharmacotherapy and catheter ablation becomes difficult. A major cause of the deteriorated treatment outcome is the atrial structural and electrophysiological heterogeneity, which AF itself can exacerbate. This heterogeneity exists or manifests in various dimensions, including anatomically segmental structural features, the distribution of histological fibrosis and the autonomic nervous system, sarcolemmal ion channels, and electrophysiological properties. All these types of heterogeneity are closely related to the development of AF. Recognizing the heterogeneity provides a valuable approach to comprehending the underlying mechanisms in the complex excitatory patterns of AF and the determining factors that govern the seemingly chaotic propagation. Furthermore, substrate modification based on heterogeneity is a potential therapeutic strategy. This review aims to consolidate the current knowledge on structural and electrophysiological atrial heterogeneity and its relation to the pathogenesis of AF, drawing insights from clinical studies, animal and cell experiments, molecular basis, and computer-based approaches, to advance our understanding of the pathophysiology and management of AF.

Extensive ablation for elderly patients with persistent atrial fibrillation: insights from the EARNEST-PVI prospective randomized trial

BACKGROUND

In patients with persistent atrial fibrillation (AF), extensive ablation for substrate modification, such as linear ablation or complex fractionated atrial electrogram ablation in addition to pulmonary vein isolation (PVI) remains controversial. Previous studies investigating extensive ablation have demonstrated its varying efficacy, suggesting the possible heterogeneity of its efficacy. Aging is a major risk factor for AF and is associated with atrial remodeling. We aimed to compare the efficacy and safety of the extensive ablation strategy compared with PVI alone strategy between young and elderly patients.

METHODS

This study is a post-hoc analysis of the multicenter, randomized controlled, noninferiority trial investigating the efficacy and safety of PVI-only (PVI-alone arm) compared with extensive ablation (PVI-plus arm) in patients with persistent AF (EARNEST-PVI trial). We divided the overall population into 2 groups based on age and assessed treatment effects.

RESULTS

In the young group (age <65 years, N = 206), there was no significant difference in the recurrence rate between the PVI-alone group and PVI-plus group [hazard ratio (HR): 1.00, 95 % CI: 0.57-1.73, p = 0.987], whereas the recurrence rate was significantly lower in the PVI-plus group compared to the PVI-alone group in the elderly group (age ≥65 years, N = 291) (HR: 0.47, 95 % CI: 0.29-0.76, p = 0.0021) (p for interaction = 0.0446). There were no fatal procedural complications.

CONCLUSION

In patients with persistent AF, the extensive ablation strategy was more effective than the PVI-alone strategy in elderly patients, while the effectiveness of both approaches was comparable in young patients.

TRIAL REGISTRATION

URL: https://clinicaltrials.gov; Unique identifier: NCT03514693. URL: https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000022454 Unique ID issued by UMIN: UMIN000019449.

Assessment of Left Atrial Fibrosis by Cardiac Magnetic Resonance Imaging in Ischemic Stroke Patients Without Atrial Fibrillation: A Systematic Review and Meta-Analysis

BACKGROUND

Left atrial (LA) fibrosis is a marker of atrial cardiomyopathy and has been reported to be associated with both atrial fibrillation and ischemic stroke. Elucidating this relationship is clinically important as LA fibrosis could serve as a surrogate biomarker of LA cardiomyopathy. The objective of this study is to investigate the association of LA fibrosis and embolic stroke of undetermined source (ESUS) using cardiac magnetic resonance imaging.

METHODS AND RESULTS

Following an International Prospective Register of Systematic Reviews-registered protocol, 3 blinded reviewers performed a systematic review for studies that quantified the degree of LA fibrosis in patients with ESUS as compared with healthy patients from inception to February 2024. A meta-analysis was conducted in the mean difference. From 7 studies (705 patients), there was a significantly higher degree of LA fibrosis in patients with ESUS compared with healthy controls (MD, 5.71% [95% CI, 3.55%-7.87%], P<0.01). The degree of LA fibrosis was significantly higher in patients with atrial fibrillation than healthy controls (MD, 8.22% [95% CI, 5.62%-10.83%], P<0.01). A similar degree of LA fibrosis was observed in patients with ESUS compared with patients with atrial fibrillation (MD, -0.92% [95% CI, -2.29% to 0.44%], P=0.35).

CONCLUSIONS

A significantly higher degree of LA fibrosis was found in patients with ESUS as compared with healthy controls. This suggests that LA fibrosis may play a significant role in the pathogenesis of ESUS. Further research is warranted to investigate LA fibrosis as a surrogate biomarker of atrial cardiomyopathy and recurrent stroke risk in patients with ESUS.

Extensive ablation for persistent atrial fibrillation patients with mitral regurgitation: Insights from the EARNEST-PVI prospective randomized trial

BACKGROUND

Extensive ablation in addition to pulmonary vein isolation (PVI) in patients with persistent atrial fibrillation (AF) has not yielded consistent results, indicating diversity in their efficacy. Mitral regurgitation (MR) associated with AF may indicate a higher prevalence of arrhythmogenic substrate, suggesting potential benefits of extensive ablation for these patients.

METHODS

This post-hoc analysis of the EARNEST-PVI trial compared PVI alone versus an extensive ablation strategy (PVI-plus) in persistent AF patients, stratified by MR presence. The primary endpoint of the study was the recurrence of AF. The secondary endpoints included death, cerebral infarction, and procedure-related complications.

RESULTS

The trial included 495 eligible patients divided into MR and non-MR groups. The MR group consisted of 192 patients (89 in the PVI-alone arm and 103 in the PVI-plus arm), while the non-MR group had 303 patients (158 in the PVI-alone arm and 145 in the PVI-plus arm). In the non-MR group, recurrence rates were similar between PVI-alone and PVI-plus arms (Log-rank P = 0.47, Hazard ratio = 0.85 [95%CI: 0.54-1.33], P = 0.472). However, in the MR group, PVI-plus was significantly more effective in preventing AF recurrence (Log-rank P = 0.0014, Hazard ratio = 0.40 [95%CI: 0.22-0.72], P = 0.0021). No significant differences were observed in secondary endpoints between the two arms.

CONCLUSIONS

For persistent AF patients with mild or greater MR, receiving PVI-plus was superior to PVI-alone in preventing AF recurrence. Conversely, for patients without MR, the effectiveness of extensive ablation was not demonstrated. These findings suggest tailoring ablation strategies based on MR presence can lead to better outcomes in AF management.

Beyond pulmonary vein isolation: approaches to treat patients with persistent atrial fibrillation

INTRODUCTION

Atrial fibrillation (AF) is the most common arrhythmia. Catheter ablation is a successful rhythm control strategy in paroxysmal AF, but it has demonstrated dramatically lower AF-free survival rates in patients with persistent AF. In recent years, myriad novel rhythm control strategies have been developed, each with the promise of improved persistent AF ablation success.

AREAS COVERED

This review discusses multiple novel techniques and approaches to persistent AF. Authors identified relevant papers by searching PubMed and Google Scholar databases and considered all papers identified, regardless of publication date. It begins by discussing recent advances in electrogram analysis that yielded improved AF-free survival following persistent AF catheter ablation. Next, it discusses several trials revealing the shortcomings of MRI in guiding persistent AF ablation. Finally, it discusses one nascent technique (Vein of Marshall ablation) and technology (AI-assisted electrogram analysis) who have shown promise in improving persistent AF ablation.

EXPERT OPINION

In the authors' expert opinions, upcoming persistent AF ablations will utilize a stepwise approach of (1) ensuring PV isolation, (2) Vein of Marshall ablation and (3) AI-assisted ablation to optimize future persistent AF ablation outcomes. This approach systematically addresses arrhythmogenic sources beyond the pulmonary veins, the historical treatment target.

2024 European Heart Rhythm Association/Heart Rhythm Society/Asia Pacific Heart Rhythm Society/Latin American Heart Rhythm Society expert consensus statement on catheter and surgical ablation of atrial fibrillation

In the last three decades, ablation of atrial fibrillation (AF) has become an evidence-based safe and efficacious treatment for managing the most common cardiac arrhythmia. In 2007, the first joint expert consensus document was issued, guiding healthcare professionals involved in catheter or surgical AF ablation. Mounting research evidence and technological advances have resulted in a rapidly changing landscape in the field of catheter and surgical AF ablation, thus stressing the need for regularly updated versions of this partnership which were issued in 2012 and 2017. Seven years after the last consensus, an updated document was considered necessary to define a contemporary framework for selection and management of patients considered for or undergoing catheter or surgical AF ablation. This consensus is a joint effort from collaborating cardiac electrophysiology societies, namely the European Heart Rhythm Association, the Heart Rhythm Society, the Asia Pacific Heart Rhythm Society, and the Latin American Heart Rhythm Society.

Relaxin suppresses atrial fibrillation, reverses fibrosis and reduces inflammation in aged hearts

Healthy aging results in cardiac structural and electrical remodeling that increase susceptibility to cardiovascular diseases. Relaxin has shown broad cardioprotective effects including anti-fibrotic, anti-arrhythmic and anti-inflammatory outcomes in multiple models. This paper focuses on the cardioprotective effects of Relaxin in a rat model of aging. Sustained atrial or ventricular fibrillation are readily induced in the hearts of aged but not young control animals. Treatment with Relaxin suppressed this arrhythmogenic response by increasing conduction velocity, decreasing fibrosis and promoting substantial cardiac remodeling. Relaxin treatment resulted in a significant increase in the levels of: Nav1.5, Cx43, βcatenin and Wnt1 in rat hearts. In isolated cardiomyocytes, Relaxin increased Nav1.5 expression. These effects were mimicked by CHIR 99021, a pharmacological activator of canonical Wnt signaling, but blocked by the canonical Wnt inhibitor Dickkopf1. Relaxin prevented TGF-β-dependent differentiation of cardiac fibroblasts into myofibroblasts while increasing the expression of Wnt1; the effects of Relaxin on cardiac fibroblast differentiation were blocked by Dickkopf1. RNASeq studies demonstrated reduced expression of pro-inflammatory cytokines and an increase in the expression of α- and β-globin in Relaxin-treated aged males. Relaxin reduces arrhythmogenicity in the hearts of aged rats by reduction of fibrosis and increased conduction velocity. These changes are accompanied by substantial remodeling of the cardiac tissue and appear to be mediated by increased canonical Wnt signaling. Relaxin also exerts significant anti-inflammatory and anti-oxidant effects in the hearts of aged rodents. The mechanisms by which Relaxin increases the expression of Wnt ligands, promotes Wnt signaling and reprograms gene expression remain to be determined.

Modification of the pulmonary vein antrum is associated with recurrence after durable pulmonary vein isolation for paroxysmal atrial fibrillation

BACKGROUND

Although previous studies have shown the isolated areas after pulmonary vein isolation (PVI) using cryoballoons (CB) (CB-PVI), no studies have investigated the association between the isolated area and recurrence of atrial fibrillation (AF) and atrial tachycardia (AT). This single-center observational study investigated the association between the ablated area and recurrence rate after durable CB-PVI for paroxysmal AF.

METHODS

This study included 76 patients with paroxysmal AF who underwent CB-PVI and established durable PVI with a second procedure, regardless of AF/AT recurrence, 6 months after the first procedure. To compare the ablated zones, we quantified the left- and right-sided PV antral isolation areas and non-ablated posterior wall (PW) area. We examined non-ablated areas of the PW and AF/AT recurrence in the chronic phase.

RESULTS

In total, 16 of the 76 patients had AF/AT recurrence. The mean follow-up duration was 34 months. The non-ablated PW area (14.0 ± 4.6 cm2 vs. 11.5 ± 3.7 cm2; p = 0.0213) and the ratio of the non-ablated PW area to the whole PW area (NAPW) (52.9 ± 9.1% vs. 44.8 ± 9.8%; p = 0.003) were significantly higher in the AF/AT recurrence group than in the AF/AT non-recurrence group. NAPW > 50% was an independent predictor of AF/AT recurrence.

CONCLUSION

The NAPW after durable CB-PVI is associated with AF/AT recurrence. PW isolation or additional applications on the PV antrum with cryoballoon may be considered in addition to PVI in paroxysmal AF, especially in patients with dilated left atria.

Failure of intravenous nifekalant cardioversion as an independent predictor for persistent atrial fibrillation recurrence after catheter ablation

AIMS

Nifekalant is a class III antiarrhythmic drug that exerts antiarrhythmic effects by inhibiting rapid rectifying potassium channels and extending the effective refractory period of cardiomyocytes. It has a high success rate in converting atrial fibrillation (AF) to sinus rhythm. Whether the failure of intravenous nifekalant cardioversion is an independent predictor for persistent AF recurrence after catheter ablation has not been reported.

METHODS

A total of 92 patients with drug-refractory persistent AF were retrospectively enrolled. After all ablations, intravenous nifekalant was administrated. Patients were assigned to the success group (group 1) and failure group (group 2) based on nifekalant cardioversion results and followed for 12 months to note any episode of atrial arrhythmia recurrence.

RESULTS

Each group included 46 patients. After 12 months of follow-up, nine (19.6%) patients from group 1 and 23 (50.0%) patients from group 2 had a recurrence of atrial tachyarrhythmia (P = 0.002). AF duration and type 2 diabetes were strongly associated with failure of intravenous nifekalant cardioversion. Univariable Cox proportional hazard regression showed that failure of intravenous nifekalant cardioversion, AF duration, and type 2 diabetes were potential risk factors. Multivariable Cox proportional hazard regression showed that failure of nifekalant cardioversion was statistically associated with AF recurrence (adjusted RR = 2.257, 95% CI: 1.006-5.066, P = 0.048). Failure of intravenous nifekalant cardioversion could bring a positive effect on the prognostic differentiation when added into the multivariable model (0.767 ± 0.042 vs. 0.774 ± 0.045, P = 0.025).

CONCLUSION

Failure of nifekalant cardioversion is an independent predictor for persistent AF recurrence after catheter ablation.

Optimizing ventricular tachycardia ablation through imaging-based assessment of arrhythmic substrate: A comprehensive review and roadmap for the future

Ventricular tachycardia (VT) is a life-threatening heart rhythm and has long posed a complex challenge in the field of cardiology. Recent developments in advanced imaging modalities have aimed to improve comprehension of underlying arrhythmic substrate for VT. To this extent, high-resolution cardiac magnetic resonance (CMR) and cardiac computed tomography (CCT) have emerged as tools for accurately visualizing and characterizing scar tissue, fibrosis, and other critical structural abnormalities within the heart, providing novel insights into VT triggers and substrate. However, clinical implementation of knowledge derived from these advanced imaging techniques in improving VT treatment and guiding invasive therapeutic strategies continues to pose significant challenges. A pivotal concern lies in the absence of standardized imaging protocols and analysis methodologies, resulting in a large variance in data quality and consistency. Furthermore, the clinical significance and outcomes associated with VT substrate characterization through CMR and CCT remain dynamic and subject to ongoing evolution. This highlights the need for refinement of these techniques before their reliable integration into routine patient care can be realized. The primary objectives of this study are twofold: firstly, to provide a comprehensive overview of the studies conducted over the last 15 years, summarizing the current available literature on imaging-based assessment of VT substrate. Secondly, to critically analyze and evaluate the selected studies, with the aim of providing valuable insights that can inform current clinical practice and future research.

2024 European Heart Rhythm Association/Heart Rhythm Society/Asia Pacific Heart Rhythm Society/Latin American Heart Rhythm Society expert consensus statement on catheter and surgical ablation of atrial fibrillation

In the last three decades, ablation of atrial fibrillation (AF) has become an evidence-based safe and efficacious treatment for managing the most common cardiac arrhythmia. In 2007, the first joint expert consensus document was issued, guiding healthcare professionals involved in catheter or surgical AF ablation. Mounting research evidence and technological advances have resulted in a rapidly changing landscape in the field of catheter and surgical AF ablation, thus stressing the need for regularly updated versions of this partnership which were issued in 2012 and 2017. Seven years after the last consensus, an updated document was considered necessary to define a contemporary framework for selection and management of patients considered for or undergoing catheter or surgical AF ablation. This consensus is a joint effort from collaborating cardiac electrophysiology societies, namely the European Heart Rhythm Association, the Heart Rhythm Society (HRS), the Asia Pacific HRS, and the Latin American HRS.

Computational modeling of cardiac electrophysiology and arrhythmogenesis: toward clinical translation

The complexity of cardiac electrophysiology, involving dynamic changes in numerous components across multiple spatial (from ion channel to organ) and temporal (from milliseconds to days) scales, makes an intuitive or empirical analysis of cardiac arrhythmogenesis challenging. Multiscale mechanistic computational models of cardiac electrophysiology provide precise control over individual parameters, and their reproducibility enables a thorough assessment of arrhythmia mechanisms. This review provides a comprehensive analysis of models of cardiac electrophysiology and arrhythmias, from the single cell to the organ level, and how they can be leveraged to better understand rhythm disorders in cardiac disease and to improve heart patient care. Key issues related to model development based on experimental data are discussed, and major families of human cardiomyocyte models and their applications are highlighted. An overview of organ-level computational modeling of cardiac electrophysiology and its clinical applications in personalized arrhythmia risk assessment and patient-specific therapy of atrial and ventricular arrhythmias is provided. The advancements presented here highlight how patient-specific computational models of the heart reconstructed from patient data have achieved success in predicting risk of sudden cardiac death and guiding optimal treatments of heart rhythm disorders. Finally, an outlook toward potential future advances, including the combination of mechanistic modeling and machine learning/artificial intelligence, is provided. As the field of cardiology is embarking on a journey toward precision medicine, personalized modeling of the heart is expected to become a key technology to guide pharmaceutical therapy, deployment of devices, and surgical interventions.

Assessing the arrhythmogenic propensity of fibrotic substrate using digital twins to inform a mechanisms-based atrial fibrillation ablation strategy

Atrial fibrillation (AF), the most common heart rhythm disorder, may cause stroke and heart failure. For patients with persistent AF with fibrosis proliferation, the standard AF treatment-pulmonary vein isolation-has poor outcomes, necessitating redo procedures, owing to insufficient understanding of what constitutes good targets in fibrotic substrates. Here we present a prospective clinical and personalized digital twin study that characterizes the arrhythmogenic properties of persistent AF substrates and uncovers locations possessing rotor-attracting capabilities. Among these, a portion needs to be ablated to render the substrate not inducible for rotors, but the rest (37%) lose rotor-attracting capabilities when another location is ablated. Leveraging digital twin mechanistic insights, we suggest ablation targets that eliminate arrhythmia propensity with minimum lesions while also minimizing the risk of iatrogenic tachycardia and AF recurrence. Our findings provide further evidence regarding the appropriate substrate ablation targets in persistent AF, opening the door for effective strategies to mitigate patients' AF burden.

A Long Atrial Electromechanical Interval is Associated with Arrhythmic Recurrence after Catheter Ablation: How to Find What Has Been Lost

Background

Atrial fibrillation (AF) results in electrical and structural remodeling of the atria, which extent is known to be associated with a higher AF recurrence rate after catheter ablation (CA). Recently, a novel echocardiographic parameter derived from tissue Doppler imaging (TDI) [PA-TDI] has been introduced to assess the total atrial activation time, as a noninvasive surrogate of fibrosis and remodeling. The aim of the study is to investigate the role of PA-TDI interval as a predictor of AF ablation efficacy.

Methods

We retrospectively included patients with paroxysmal symptomatic drug-refractory AF referred to our institution for CA procedure, who presented sinus rhythm at admission. A complete transthoracic echocardiogram was performed before the ablation procedure, including the assessment of PA-TDI interval.

Results

From January 2015 to April 2018, 128 patients (mean age: 61.86 ± 9.08 years, 68% male, body surface area: 1.97 ± 0.21 mq, body mass index: 26.98 ± 3.86 kg/mq, and ejection fraction: 59% ±6.06%) with symptomatic drug-refractory AF who received radiofrequency CA were enrolled. During the follow-up of 15.80 ± 6.7 months, 30 patients (23%) developed AF recurrence out of the blanking period. Compared with those without recurrence (group 1), patients with recurrence (group 2) had a larger left atrium (LA) size (Group 1 vs. Group 2: mean LA area: 22.2 ± 4.6 cmq vs. 25 ± 6.6 cmq, P = 0.015; mean indexed LA volume: 35 ± 10 mL/mq vs. 40 ± 12 mL/mq, P = 0.04) and longer PA-TDI interval (Group 1 vs. Group 2: 162 ± 33 ms vs. 133 ± 26 ms, P < 0.0001). A cutoff of PA-TDI > 150 ms identified patients with recurrence after ablation with a sensibility of 82% and specificity of 83% (area under the curve 0.879).

Conclusions

The total activation time assessed by PA-TDI is an independent predictor of AF recurrence and can be used to predict the efficacy of transcatheter ablation.

Atrial Fibrillation Termination as a Predictor for Persistent Atrial Fibrillation Ablation: A Systemic Review and Meta-Analysis of Prospective Studies

Background: In this systematic review and meta-analysis, we aimed to validate the predictive role of atrial fibrillation (AF) termination in long-term arrhythmia recurrence. Method: Our search encompassed databases including MEDLINE, EMBASE, PubMed, and the Cochrane Library up to August 1, 2021. Three independent reviewers conducted screening and data extraction. The data included ablation strategy, recurrence mode, AF termination mode, numbers of patients, and recurrence cases in the termination and nontermination groups. The primary endpoint was the recurrence of atrial arrhythmia at long-term follow-up (≥ 12 months). Results: Our analysis included 22 publications, with 11 prospective studies being eligible for further meta-analysis. Among these, 14 studies reported significantly lower rates of arrhythmia recurrence in the AF termination group compared to the nontermination group. Among seven studies involving 1114 patients that examined single procedure outcomes, the pooled estimated effect was RR 0.78 (95% CI 0.68-1.90) with an I 2 value of 57%. Subgroup analysis focusing on termination mode as sinus rhythm yielded a pooled estimated effect of RR 0.74 (95% CI 0.59-0.92) with an I 2 value of 47%. Additionally, analysis of seven studies involving 1433 patients for repeat procedures demonstrated a significant preference for the AF termination group (RR 0.83, 95% CI 0.71-0.97, I 2 = 84%). Subgroup analysis indicated reduced heterogeneity when the termination mode was sinus rhythm (RR 0.68, 95% CI 0.51-0.90, I 2 = 57%). Conclusion: Our study establishes that AF termination serves as an effective predictor for the success of persistent AF ablation procedures. This finding holds potential implications for clinical practice and contributes to our understanding of long-term arrhythmia recurrence in the context of AF termination.

Associations of the fibrosis-4 index with left atrial low-voltage areas and arrhythmia recurrence after catheter ablation: cardio-hepatic interaction in patients with atrial fibrillation

Background

The relationship between liver fibrosis and left atrial (LA) remodeling in atrial fibrillation (AF) remains uncertain. We examined the associations between the fibrosis-4 (FIB4) index, an indicator of liver fibrosis, and both LA low-voltage areas (LVAs) on electroanatomic mapping and AF recurrence postablation.

Methods

We recruited 343 patients who underwent radiofrequency catheter ablation (RFCA) or cryoballoon ablation (CBA) for AF. First, the association between the FIB4 index and LA LVAs (<0.5 mV) was evaluated in RFCA using electroanatomic mapping (n = 214). Next, the utility of a FIB4 index ≥1.3, recommended cut-off value of liver fibrosis, was verified to assess the risk for AF recurrence in CBA without additional LVA ablation (n = 129).

Results

Patients with a FIB4 index ≥1.3 had a higher prevalence of LA LVAs (>5 cm2) compared to those without. Additionally, the quantitative size of LVAs showed a positive correlation with the FIB4 index (R = .642, p < .001). In multivariate logistic models, a FIB4 index ≥1.3 was related to the presence of LVAs after adjusting for LA diameter, right atrial end-systolic area, and nonparoxysmal AF (odds ratio 2.508; p = 0.039). In CBA, AF recurrence rate was 13.1% during 3-12 months postablation. In multivariate Cox models, a FIB4 index ≥1.3 was an important predictor of AF recurrence (hazard ratio 3.796; p = .037), suggesting that LVAs might be associated with AF recurrence after CBA.

Conclusion

The FIB4 index was a novel predictor of the existence of LA LVAs on electroanatomic mapping and AF recurrence after CBA.

Prevalence and impact of pulmonary hypertension on acute decompensated heart failure with preserved ejection fraction hospitalizations: A five-year retrospective analysis

Heart Failure with Preserved Ejection Fraction (HFpEF) is a major and common cardiovascular condition with widely variable clinical outcomes. Pulmonary hypertension (PH) often co-exists with HFpEF and tends to affect patient outcomes; this study aims to identify the impact of PH on the clinical outcome of patients admitted to the hospital with acute HFpEF exacerbations. We analyzed data from the National Inpatient Sample between 2016 and 2020, focusing on 464,438 acute HFpEF exacerbation hospitalizations. Outcomes were compared between those with PH (27.1 %) and those without PH (72.9 %). HFpEF hospitalizations with PH exhibited elevated in-hospital mortality (adjusted odds ratio [aOR]: 1.20, 95 % confidence interval [95 CI]: 1.08-1.31, P < 0.05), prolonged length of stay (adjusted β: 0.90 days, P < 0.05), and increased overall costs (adjusted β: $2,858, P < 0.05). Furthermore, HFpEF hospitalizations with PH demonstrated higher rates of atrial fibrillation, ventricular tachycardia, right ventricular failure, and conduction abnormalities. This population also displayed an increased incidence of acute hypoxic respiratory failure, necessitating increased non-invasive and mechanical ventilation. The co-existence of PH in HFpEF presents an increased risk of mortality and morbidity, with higher healthcare costs and the need for ventilatory support, in addition to higher risks of cardiovascular and pulmonary complications. Therefore, an early diagnosis of PH in patients with HFpEF is crucial, and further research is required to determine appropriate management.

Association of beat-to-beat P-wave analysis index to the extent of left atrial low-voltage areas in patients with paroxysmal atrial fibrillation

BACKGROUND

Left atrial (LA) fibrosis has been shown to be associated with atrial fibrillation (AF) recurrence. Beat-to-beat (B2B) index is a non-invasive classifier, based on B2B P-wave morphological and wavelet analysis, shown to be associated with AF incidence and recurrence. In this study, we tested the hypothesis that the B2B index is associated with the extent of LA low-voltage areas (LVAs) on electroanatomical mapping.

METHODS

Patients with paroxysmal AF scheduled for pulmonary vein isolation, without evident structural remodeling, were included. Pre-ablation electroanatomical voltage maps were used to calculate the surface of LVAs (<0.5 mV). B2B index was compared between patients with small versus large LVAs.

RESULTS

35 patients were included (87% male, median age 62). The median surface area of LVAs was 7.7 (4.4-15.8) cm2 corresponding to 5.6 (3.3-12.1) % of LA endocardial surface. B2B index was 0.57 (0.52-0.59) in patients with small LVAs (below the median) compared to 0.65 (0.56-0.77) in those with large LVAs (above the median) (p = 0.009). In the receiver operator characteristic curve analysis for predicting large LVAs, the c-statistic was 0.75 (p = 0.006) for B2B index and 0.81 for the multivariable model including B2B index (multivariable p = 0.04) and P-wave duration.

CONCLUSION

In patients with paroxysmal AF without overt atrial myopathy, B2B P-wave analysis appears to be a useful non-invasive correlate of low-voltage areas-and thus fibrosis-in the LA. This finding establishes a pathophysiological basis for B2B index and its potential usefulness in the selection process of patients who are likely to benefit most from further invasive treatment.

RAS Dataset: A 3D Cardiac LGE-MRI Dataset for Segmentation of Right Atrial Cavity

The current challenge in effectively treating atrial fibrillation (AF) stems from a limited understanding of the intricate structure of the human atria. The objective and quantitative interpretation of the right atrium (RA) in late gadolinium-enhanced magnetic resonance imaging (LGE-MRI) scans relies heavily on its precise segmentation. Leveraging the potential of artificial intelligence (AI) for RA segmentation presents a promising solution. However, the successful implementation of AI in this context necessitates access to a substantial volume of annotated LGE-MRI images for model training. In this paper, we present a comprehensive 3D cardiac dataset comprising 50 high-resolution LGE-MRI scans, each meticulously annotated at the pixel level. The annotation process underwent rigorous standardization through crowdsourcing among a panel of medical experts, ensuring the accuracy and consistency of the annotations. Our dataset represents a significant contribution to the field, providing a valuable resource for advancing RA segmentation methods.

Left atrial remodeling and voltage-guided ablation outcome in obese patients with persistent atrial fibrillation

Background

Obesity is a risk factor for atrial fibrillation (AF). Data regarding left atrial (LA) remodeling in obese patients are scarce. Whether obesity favors AF recurrence after catheter ablation (CA) is still controversial. We assessed the distribution of epicardial atrial fat on computed tomography (CT), LA bipolar voltage, low-voltage zone (LVZ) extent, and the outcome of voltage-guided ablation of persistent AF in obese and non-obese patients.

Methods

A total of 139 patients with persistent AF undergoing a first voltage-guided ablation were enrolled and divided into two groups: 74 were non-obese and 65 were obese. Epicardial adipose tissue (EAT) was assessed on a CT scanner. LA endocardial voltage maps were obtained using a 3D mapping system in sinus rhythm. LVZ was defined as a bipolar peak-to-peak voltage amplitude <0.5 mV.

Results

LA volume, voltage, and EAT amount were similar in the two groups. LVZ was less frequent in obese patients [12 (18.8%) vs. 26 (35.1%), p = 0.05], particularly on the anterior wall. The posterior and lateral EATs were correlated with posterior and lateral LVZ extent, respectively, in obese patients. After 36 months of follow-up, the AF-free survival rate was similar. Lateral EAT [odds ratio (OR) 1.21, 95% confidence interval (CI) 1-1.4, p = 0.04] and P-wave duration (OR 1.03, 95% CI 1-1.05, p = 0.03), but not body mass index (BMI), were predictors of AF recurrence after CA.

Conclusion

In obese patients, LVZ was less marked than in non-obese patients with similar LA volumes, voltage, and EAT amounts. In obese patients, posterior and lateral EATs were correlated with posterior and lateral LVZ extents. Obese patients had a similar and favorable 36-month outcome after AF ablation. BMI was not predictive of AF recurrence.

Current experimental and early investigational agents for cardiac fibrosis: where are we at?

INTRODUCTION

Myocardial fibrosis (MF) is induced by factors activating pro-fibrotic pathways such as acute and prolonged inflammation, myocardial ischemic events, hypertension, aging process, and genetically-linked cardiomyopathies. Dynamics and characteristics of myocardial fibrosis development are very different. The broad range of myocardial fibrosis presentations suggests the presence of multiple potential targets.

AREA COVERED

Heart failure treatment involves medications primarily aimed at counteracting neurohormonal activation. While these drugs have demonstrated efficacy against MF, not all specifically target inflammation or fibrosis progression with some exceptions such as RAAS inhibitors. Consequently, new therapies are being developed to address this issue. This article is aimed to describe anti-fibrotic drugs currently employed in clinical practice and emerging agents that target specific pathways, supported by evidence from both preclinical and clinical studies.

EXPERT OPINION

Despite various preclinical findings suggesting the potential utility of new drugs and molecules for treating cardiac fibrosis in animal models, there is a notable scarcity of clinical trials investigating these effects. However, the pathology of damage and repair in the heart muscle involves a complex network of interconnected inflammatory pathways and various types of immune cells. Our comprehension of the positive and negative roles played by specific immune cells and cytokines is an emerging area of research.