Pathophysiological mechanisms of atrial fibrillation: a translational appraisal

Artificial intelligence-derived electrocardiographic aging and risk of atrial fibrillation: a multi-national study

BACKGROUND AND AIMS

Artificial intelligence (AI) algorithms in 12-lead electrocardiogram (ECG) provides promising age prediction methods. This study investigated whether the discrepancy between ECG-derived AI-predicted age (AI-ECG age) and chronological age, termed electrocardiographic aging (ECG aging), is associated with atrial fibrillation (AF) risk.

METHODS

An AI-ECG age prediction model was developed using a large-scale dataset (1 533 042 ECGs from 689 639 participants) and validated with six independent and multi-national datasets (737 133 ECGs from 330 794 participants). The AI-ECG age gap was calculated across two South Korean cohorts [mean (standard deviation) follow-up: 4.1 (4.3) years for 111 483 participants and 6.1 (3.8) years for 37 517 participants], one UK cohort [3.0 (1.6) years; 40 973 participants], and one US cohort [12.9 (8.6) years; 90 639 participants]. Participants were classified into two groups: normal group (age gap < 7 years) and ECG-aged group (age gap ≥ 7 years). The predictive capability of ECG aging for new- and early-onset AF risk was assessed.

RESULTS

The mean AI-ECG ages were 51.9 (16.2), 47.4 (12.5), 68.4 (7.8), and 56.7 (14.6) years with age gaps of .0 (6.8), -.1 (6.0), 4.7 (8.7), and -1.4 (8.9) years in the two South Korean, UK, and US cohorts, respectively. In the ECG-aged group, increased risks of new-onset AF were observed with hazard ratios (95% confidence intervals) of 2.50 (2.24-2.78), 1.89 (1.46-2.43), 1.90 (1.55-2.33), and 1.76 (1.67-1.86) in the two South Korean, UK, and US cohorts, respectively. For early-onset AF, odds ratios were 2.89 (2.47-3.37), 1.94 (1.39-2.70), 1.58 (1.06-2.35), and 1.79 (1.62-1.97) in these cohorts compared with the normal group.

CONCLUSIONS

The AI-derived ECG aging was associated with the risk of new- and early-onset AF, suggesting its potential utility to identify individuals for AF prevention across diverse populations.

Effects of plant extracts and derivatives on cardiac K+, Nav, and Cav channels: a review

Natural products (NPs) are endless sources of compounds for fighting against several pathologies. Many dysfunctions, including cardiovascular disorders, such as cardiac arrhythmias have their modes of action regulation of the concentration of electrolytes inside and outside the cell targeting ion channels. Here, we highlight plant extracts and secondary metabolites' effects on the treatment of related cardiac pathologies on hERG, Nav, and Cav of cardiomyocytes. The natural product's pharmacology of expressed receptors like alpha-adrenergic receptors causes an influx of Ca2+ ions through receptor-operated Ca2+ ion channels. We also examine the NPs associated with cardiac contractions such as myocardial contractility by reducing the L-type calcium current and decreasing the intracellular calcium transient, inhibiting the K+ induced contractions, decreasing amplitude of myocyte shortening and showed negative ionotropic and chronotropic effects due to decreasing cytosolic Ca2+. We examine whether the NPs block potassium channels, particular the hERG channel and regulatory effects on Nav1.7.

Hypertension and Atrial Fibrillation: Bridging the Gap Between Mechanisms, Risk, and Therapy

Background and objectives: Atrial fibrillation (AF), the most prevalent sustained arrhythmia, poses a significant public health challenge due to its links with stroke, heart failure, and mortality. Hypertension, a primary modifiable cardiovascular risk factor, is a well-established risk factor for AF that facilitates structural and electrical changes in the atria, including dilation, fibrosis, and pressure overload. Material and Methods: we conducted a literature search regarding the shared mechanisms, risks and treatments of hypertension and atrial fibrillation. Results: The renin-angiotensin-aldosterone system plays a pivotal role in this remodelling and inflammation, increasing AF susceptibility. Uncontrolled hypertension complicates AF management, diminishing the effectiveness of mainstay treatments, including antiarrhythmic drugs, catheter ablation, and cardioversion. Effective blood pressure management, particularly with therapies targeting the renin-angiotensin-aldosterone system (RAAS), can lower the risk of new-onset AF and reduce the incidence of recurrent AF, enhancing the success of rhythm control strategies. These antihypertensive therapies mitigate myocardial hypertrophy and fibrosis and attenuate both atrial pressure strain and the inflammatory response, mitigating the substrates for AF. Conclusion: This review highlights the urgent need for integrated strategies that combine BP control, AF screening, and lifestyle modifications to minimise the burden of AF and its complications. Future research should investigate the specific mechanisms of cellular-level interactions associated with a hypertensive predisposition to AF, including systematic inflammation and the role of genetics, the impact of blood pressure variations on AF risk, and individualised treatment strategies specifically targeting the shared mechanisms, simultaneously propagating hypertension and AF.

Decreased METTL3 in atrial myocytes promotes atrial fibrillation

AIMS

Methyltransferase like 3 (METTL3) plays a crucial role in cardiovascular diseases, but its involvement in atrial fibrillation (AF) remains unclear. The study aims to explore the relationship between METTL3 and AF in atrial myocytes.

METHODS AND RESULTS

The protein level of METTL3 was evaluated in left atrial appendages (LAAs) from patients with persistent AF and in experimental AF models. cAMP-responsive element modulator (CREM) transgenic mice and CaCl2-acetylcholine (ACh)-injected mice were used as AF mice models. Methyltransferase like 3 was globally and atrial conditionally deleted in vivo to assess its role in AF. Confocal fluorescence microscopy was employed to examine calcium handling in atrial myocytes. Methylated RNA immunoprecipitation sequencing was performed to identify the downstream target genes of METTL3. Methyltransferase like 3 protein and RNA N6-methyladenosine (m6A) modification levels were significantly reduced in the LAAs of patients with AF and experimental AF models. Genetic inhibition of METTL3 promoted the development of AF in CREM transgenic mice and CaCl2-ACh-injected mice. Knockdown of METTL3 in atrial myocytes resulted in enhanced calcium handling. Reduced METTL3 levels increased SR Ca2+-ATPase Type 2a activity by up-regulating protocadherin gamma subfamily A, 10. Decreased METTL3 protein in atrial myocytes was attributed to down-regulation of cAMP-responsive element-binding protein 1/ubiquitin-specific peptidase 9 X-linked axis.

CONCLUSION

Our study established the pathophysiological role of METTL3 involved in the development of AF and provided a potential mechanism-based target for its treatment.

Hypermethylation of Hif3a and Ifltd1 is associated with atrial remodeling in pressure-overload murine model

Atrial remodeling is a major pathophysiological mechanism of atrial fibrillation (AF). Atrial remodeling progresses with aging and background diseases, including hypertension, heart failure, and AF itself. However, its mechanism of action and reversibility have not been completely elucidated. In this study, we investigated the involvement of DNA methylation in atrial remodeling. Mice underwent transverse aortic constriction (TAC) to generate a pressure overload model. After 14 days, the TAC-operated mice showed a significant increase in the atrium/body weight ratio and deposition of collagen fibers in the atria. A comprehensive analysis using RNA-sequencing (RNA-Seq) and methyl-CpG-binding domain sequencing (MBD-Seq) in the left atrial tissue identified Hif3a and Ifltd1 as showing increased DNA methylation in their promoter regions and decreased RNA expression. In addition, we created a transient pressure overload model by removing the aortic constriction 3 or 7 days after the initial TAC procedure (R3 or R7 groups). A reduction in RNA expression was achieved at R3 for Hif3a and at R7 for Ifltd1. Heterozygous Dnmt1 gene-targeting mice (Dnmt1mut) showed disappearance of the reduction in RNA expression and an increase in the atrium/body weight ratio. Altogether, DNA methylation contributed to at least part of atrial remodeling in the pressure overload mouse model.

Associations Between Albumin/Neutrophil-to-Lymphocyte Ratio Score and New-Onset Atrial Fibrillation in Patients with Acute Myocardial Infarction Undergoing PCI

Background

Inflammation was associated with the increased risk of atrial fibrillation (AF). As a novel inflammatory indicator, albumin/neutrophil-to-lymphocyte ratio score (ANS) has been demonstrated to associate with coronary artery disease. However, the relationship between ANS and new onset atrial fibrillation (NOAF) in patients with acute myocardial infarction (AMI) underwent PCI was not determined.

Methods

A total of 2410 AMI patients underwent PCI were consecutively included between March 2020 and December 2023. Patients were divided into NOAF group and control group according to the occurrence of NOAF during hospitalization. The ANS was calculated and analyzed, so as to determine its predictive value in the presence of NOAF in AMI patients after PCI.

Results

In total, 88 (3.7%) individuals developed NOAF during hospitalization. We found that NOAF was associated with older age, greater LA, higher NT-proBNP, ANS and Killip ≥ 2. The ANS exhibited an accurately predictive value for the NOAF (area under the curve [AUC], 0.695; 95% CI, 0.649-0.740, P < 0.001). Moreover, when divided into three groups according to the tertile of ANS, patients in tertile 1 (lowest in ANS) showed a 2.214-fold increased risk of NOAF in comparison to those in the tertile 3 (HR, 2.214; 95% CI 1.804-5.101; P = 0.029).

Conclusion

ANS is a robust tool for the prediction of NOAF in AMI patients underwent PCI. Therefore ANS could be used for risk prediction and optimal management for NOAF in AMI patients after PCI.

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.

Simulation-free prediction of atrial fibrillation inducibility with the fibrotic kernel signature

Computational models of atrial fibrillation (AF) can help improve success rates of interventions, such as ablation. However, evaluating the efficacy of different treatments requires performing multiple costly simulations by pacing at different points and checking whether AF has been induced or not, hindering the clinical application of these models. In this work, we propose a classification method that can predict AF inducibility in patient-specific cardiac models without running additional simulations. Our methodology does not require re-training when changing atrial anatomy or fibrotic patterns. To achieve this, we develop a set of features given by a variant of the heat kernel signature that incorporates fibrotic pattern information and fiber orientations: the fibrotic kernel signature (FKS). The FKS is faster to compute than a single AF simulation, and when paired with machine learning classifiers, it can predict AF inducibility in the entire domain. To learn the relationship between the FKS and AF inducibility, we performed 2371 AF simulations comprising 6 different anatomies and various fibrotic patterns, which we split into training and a testing set. We obtain a median F1 score of 85.2% in test set and we can predict the overall inducibility with a mean absolute error of 2.76 percent points, which is lower than alternative methods. We think our method can significantly speed-up the calculations of AF inducibility, which is crucial to optimize therapies for AF within clinical timelines. An example of the FKS for an open source model is provided in https://github.com/tbanduc/FKS_AtrialModel_Ferrer.git.

Unipolar Voltage for Better Characterizing Left Atrium Substrates: Comparing the Predictive Efficacy for Recurrence Post Atrial Fibrillation Ablation in a Post Hoc Analysis of STABLE-SR-III Trial

BACKGROUND

While bipolar voltage (BV) is acknowledged as an indicator of viable cardiomyocyte activation, unipolar recording has emerged as an alternative technique due to its advantage of providing a wider field of view. This study aims to compare the efficacy of unipolar voltage (UV) versus BV in predicting ablation recurrence in atrial fibrillation patients.

METHODS

In Substrate Ablation in the Left Atrium during Sinus Rhythm Trial III, 375 patients completed the follow-up with preserved mapping data were included in the analysis. For each patient, the mean UV and BV was obtained from the electrograms sampled in left atrium (LA).

RESULTS

Totally 301 patients experience the primary endpoint within 23.0 ± 9.2 months. While both low UV and BV had significant associations with long-term recurrence of atrial tachyarrhythmia (ATa), only mean UV was independently associated with the outcome. The model by UV with ablation feature had higher discriminatory power to predict ATa recurrence compared with BV model (area under the curve [AUC]: 0.858 vs. 0.757, p < 0.001). In subgroup analysis, UV reveals more powerful predictive efficacy compared with BV, with the AUC 0.843 versus 0.751 (p < 0.001) in circumferential pulmonary vein isolation (CPVI) alone cohort and 0.882 versus 0.750 (p < 0.001) in CPVI plus cohort, respectively.

CONCLUSION

UV exhibits higher efficacy for predicting long-term ATa recurrence after ablation compared with BV in elderly patients with atrial fibrillation regardless of whether the patient accepts substrate modification. The outcome suggests that unipolar recording may better characterize LA fibrosis by capturing more comprehensive transmural features than bipolar signals.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov; URL: https://www.

CLINICALTRIALS

gov. Unique Identifier: NCT03462628.

Atrial Fibrosis in Atrial Fibrillation: Mechanistic Insights, Diagnostic Challenges, and Emerging Therapeutic Targets

Atrial fibrosis is a hallmark of atrial cardiomyopathy and plays a pivotal role in the pathogenesis of atrial fibrillation (AF), contributing to its onset and progression. The mechanisms underlying atrial fibrosis are multifaceted, involving stretch-induced fibroblast activation, oxidative stress, inflammation, and coagulation pathways. Variations in fibrosis types-reactive and replacement fibrosis-are influenced by patient-specific factors such as age, sex, and comorbidities, complicating therapeutic approaches. The heterogeneity of fibrosis leads to distinct electrophysiological abnormalities that promote AF via reentrant activity and enhanced automaticity mechanisms. Despite advancements in imaging, such as late gadolinium enhancement CMR and electroanatomical mapping, challenges in accurately quantifying fibrosis persist. Emerging therapeutic strategies include antifibrotic agents targeting the renin-angiotensin-aldosterone system, novel pathways like TGF-β signaling, and cardio-metabolic drugs like SGLT2 inhibitors and GLP-1 receptor agonists. Innovative interventions, including microRNA modulation and lipid nanoparticle-based therapies, show promise but require validation. Knowledge gaps remain in correlating clinical outcomes with fibrosis patterns and optimizing diagnostic tools. Future research should focus on precise phenotyping, integrating advanced imaging with molecular biomarkers, and conducting robust trials to evaluate antifibrotic therapies' efficacy in reducing AF burden and related complications.

Stroke in Athletes with Atrial Fibrillation: A Narrative Review

Atrial fibrillation (AF) is the most common sustained arrhythmia, linked with a significantly heightened risk of stroke. While moderate exercise reduces AF risk, high-level endurance athletes paradoxically exhibit a higher incidence. However, their stroke risk remains uncertain due to their younger age, higher cardiovascular fitness, and lower rate of comorbidities. Several key studies highlight that AF may increase the risk of stroke in endurance athletes, particularly those over 65. However, the overall risk within this population remains relatively low. Notably, older male athletes show a higher AF incidence but experience lower stroke risk than their non-athletic counterparts. Regular physical activity prior to a first stroke appears to reduce mortality, though recurrent stroke risk in athletes with AF mirrors that of non-athletes, despite an elevated AF incidence. Management of AF in athletes is complex, with limited evidence guiding anti-thrombotic strategies. In this setting, specific recommendations are sparse, particularly in sports where bleeding risk is heightened. Individualized management, emphasizing shared decision-making, is critical to balance stroke prevention with athletic performance. Rhythm control strategies, such as catheter ablation, may be a reasonable first-line treatment option for athletes, particularly in those desiring to avoid long-term medication. This review synthesizes the current literature on the incidence, predictors, and management of stroke in athletes with AF.

The impact of atrial voltage and conduction velocity phenotypes on atrial fibrillation recurrence

Introduction

Low atrial voltage and slow conduction velocity (CV) have been associated with atrial fibrillation (AF); however, their interaction and relative importance as early disease markers remain incompletely understood. We aimed to elucidate the relationship between atrial voltage and CV using high-density electroanatomic (HDE) maps of patients with AF.

Methods

HDE maps obtained during sinus rhythm in 52 patients with AF and five healthy controls were analysed. Atrial voltage and CV maps were generated, and their correlations were assessed. Subgroup analyses were performed based on clinically relevant factors such as AF type, CV, and voltage levels. Finally, cluster analysis was conducted to identify distinct phenotypes within the population, reflecting different patterns of conduction and voltage.

Results

A moderate positive correlation was found between the mean atrial voltage and CV (r = 0.570). Subgroup analysis revealed differences in voltage (p = 0.0044) but not in global CV (p = 0.42), with no significant differences between AF types. Three distinct phenotypes emerged: normal voltage/normal CV, normal voltage/low CV, and low voltage/low CV, with distinct recurrence rates, suggesting different disease progression paths. Slower atrial CV was identified as a significant predictor of arrhythmia recurrence at 12 and 24 months after AF ablation, surpassing the predictive potential of atrial voltage.

Conclusion

Atrial voltage and CV analyses revealed distinct phenotypes. Lower atrial CV emerged as a significant predictor of AF recurrence, exceeding the predictive significance of atrial voltage. These findings emphasise the importance of considering CV and voltage in managing AF and offer potential insights for personalised strategies.

A Titin Missense Variant Causes Atrial Fibrillation

Rare and common genetic variants contribute to the risk of atrial fibrillation (AF). Although ion channels were among the first AF candidate genes identified, rare loss-of-function variants in structural genes such as TTN have also been implicated in AF pathogenesis partly by the development of an atrial myopathy, but the underlying mechanisms are poorly understood. While TTN truncating variants (TTNtvs) have been causally linked to arrhythmia and cardiomyopathy syndromes, the role of missense variants (mvs) remains unclear. We report that rare TTNmvs are associated with adverse clinical outcomes in AF patients and we have identified a mechanism by which a TTNmv (T32756I) causes AF. Modeling the TTN-T32756I variant using human induced pluripotent stem cell-derived atrial cardiomyocytes (iPSC-aCMs) revealed that the mutant cells display aberrant contractility, increased activity of a cardiac potassium channel (KCNQ1, Kv7.1), and dysregulated calcium homeostasis without compromising the sarcomeric integrity of the atrial cardiomyocytes. We also show that a titin-binding protein, the Four-and-a-Half Lim domains 2 (FHL2), has increased binding with KCNQ1 and its modulatory subunit KCNE1 in the TTN-T32756I-iPSC-aCMs, enhancing the slow delayed rectifier potassium current (I ks). Suppression of FHL2 in mutant iPSC-aCMs normalized the I ks, supporting FHL2 as an I ks modulator. Our findings demonstrate that a single amino acid change in titin not only affects function but also causes ion channel remodeling and AF. These findings emphasize the need for high-throughput screening to evaluate the pathogenicity of TTNmvs and establish a mechanistic link between titin, potassium ion channels, and sarcomeric proteins that may represent a novel therapeutic target.

Maintenance mechanism of paroxysmal atrial fibrillation from the activation occurring within the pulmonary vein: analysis using non-contact mapping

It is unclear how pulmonary veins (PVs) maintain paroxysmal atrial fibrillation (AF). To clarify the PV's arrhythmogenic role, we examined PV activation sequences during paroxysmal AF. Left superior PV (LSPV) endocardial non-contact mapping was performed after a right PV isolation in 13 paroxysmal AF patients. Activation sequences within the LSPV before and during left-sided PVs ablation were analyzed, and those in complex fractionated atrial electrogram (CFAE) areas were compared with those in non-CFAE areas. CFAEs were observed in the LSPV's proximal half (area; 8.8 ± 3.2cm2) occupying 19.9 ± 6.0% of LSPV. The number of pivoting activations, wave breaks, and fusions over CFAE areas were significantly higher than those over non-CFE areas (25.5 ± 9.3 vs. 4.5 ± 4.8 times/s, p < 0.0001; 9.1 ± 5.3 vs. 1.4 ± 1.8 times/s, p < 0.0001; 13.0 ± 4.6 vs. 5.4 ± 4.4 times/s, p < 0.0001). The conduction velocities in CFAE areas were significantly slower than in non-CFAE areas (0.6 ± 0.2 vs. 1.7 ± 0.8 m/s, p < 0.001). After delivery of ablation lesions around the left-sided PVs (13.2 ± 7.4 applications), the PV activation became organized with a loss of CFAE areas, and the frequency of the LSPV's pivoting activation, wave break, and fusion significantly decreased compared to that pre-ablation (7.3 ± 10.9 vs. 30.0 ± 11.6 times/s, p < 0.001; 2.1 ± 5.3 vs. 10.5 ± 6.2 times/s, p < 0.002; 6.0 ± 6.6 vs. 18.4 ± 8.2 times/s, p < 0.001). Subsequently, AF terminated before the left-sided PV isolation in all patients. In conclusion, high-frequency random reentry associated with pivoting activation, wave break, and fusion within the LSPV, observed mostly over CFAE areas, maintained AF. Linear ablation lesions around the PV suppressed random reentry, resulting in the loss of CFAEs and AF termination.

Oxidative stress and atrial fibrillation

Atrial fibrillation (AF) is the most common sustained arrhythmia in clinical practice. Though the pathogenesis of AF is complex and is not completely understood, many studies suggest that oxidative stress is a major mechanism in pathophysiology of AF. Through multiple mechanisms, reactive oxygen species (ROS) lead to the formation of an AF substrate that facilitates the development and maintenance of AF. In this review article, we provide an update on the different mechanisms by which oxidative stress promotes atrial remodeling. We then discuss several therapeutic strategies targeting oxidative stress for the prevention or treatment of AF. Considering the complex biology of ROS induced remodeling, and the evolution of ROS sources and compartmentalization during AF progression, there is a definite need for improvement in timing, targeting and reduction of off-target effects of therapeutic strategies targeting oxidative injury in AF.

Fractional-order modeling of myocardium structure effects on atrial fibrillation electrograms

Atrial fibrillation (AF) is the most common cardiac arrhythmia with mechanisms of initiation and sustaining that are not fully understood. The clinical procedure for AF contemplates the analysis of the atrial electrograms, whose morphology has been correlated with the underlying structure of the atrial myocardium. This study employs a mathematical model incorporating fractional calculus to simulate cardiac electrical conduction, accounting for tissue structural inhomogeneities using complex-valued orders. Simulations of different wavefront propagation patterns were performed, and virtual electrograms were analyzed using an asymmetry factor. Our results evinced that the shapes of the action potential and the propagating wavefront can be modulated through the fractional order under both healthy and AF conditions. Moreover, the asymmetry factor changes with variations in the fractional order. For a given propagation pattern under AF conditions, variation intervals for the asymmetry factor can be generated by forming sets of simulations with different configurations for the fractional order, representing diverse samples of atrial tissue with varying degrees of structural heterogeneity. This approach successfully reproduces the electrogram negative deflection predominance seen in AF patients, which standard integer-order models cannot predict. Our fractional-order conduction model aligns with the effects of atrial structure on the electrical dynamics observed in clinical AF. Therefore, it offers a valuable tool for studying cardiac electrophysiology, encompassing both electrical and structural interactions of the tissue within a unified model.

Translation of pathophysiological mechanisms of atrial fibrosis into new diagnostic and therapeutic approaches

Atrial fibrosis is one of the main manifestations of atrial cardiomyopathy, an array of electrical, mechanical and structural alterations associated with atrial fibrillation (AF), stroke and heart failure. Atrial fibrosis can be both a cause and a consequence of AF and, once present, it accelerates the progression of AF. The pathophysiological mechanisms leading to atrial fibrosis are diverse and include stretch-induced activation of fibroblasts, systemic inflammatory processes, activation of coagulation factors and fibrofatty infiltrations. Importantly, atrial fibrosis can occur in different forms, such as reactive and replacement fibrosis. The diversity of atrial fibrosis mechanisms and patterns depends on sex, age and comorbidity profile, hampering the development of therapeutic strategies. In addition, the presence and severity of comorbidities often change over time, potentially causing temporal changes in the mechanisms underlying atrial fibrosis development. This Review summarizes the latest knowledge on the molecular and cellular mechanisms of atrial fibrosis, its association with comorbidities and the sex-related differences. We describe how the various patterns of atrial fibrosis translate into electrophysiological mechanisms that promote AF, and critically appraise the clinical applicability and limitations of diagnostic tools to quantify atrial fibrosis. Finally, we provide an overview of the newest therapeutic interventions under development and discuss relevant knowledge gaps related to the association between clinical manifestations and pathological mechanisms of atrial fibrosis and to the translation of this knowledge to a clinical setting.

Ablation-induced left atrial mechanical dysfunction recovers in weeks after ablation

BACKGROUND

The immediate impact of catheter ablation on left atrial mechanical function and the timeline for its recovery in patients undergoing ablation for atrial fibrillation (AF) remain uncertain. The mechanical function response to catheter ablation in patients with different AF types is poorly understood.

METHODS

A total of 113 AF patients were included in this retrospective study. Each patient had three magnetic resonance imaging (MRI) studies in sinus rhythm: one pre-ablation, one immediate post-ablation (within 2 days after ablation), and one post-ablation follow-up MRI (≤ 3 months). We used feature tracking in the MRI cine images to determine peak longitudinal atrial strain (PLAS). We evaluated the change in strain from pre-ablation, immediately after ablation to post-ablation follow-up in a short-term study (< 50 days) and a 3-month study (3 months after ablation).

RESULTS

The PLAS exhibited a notable reduction immediately after ablation, compared to both pre-ablation levels and those observed in follow-up studies conducted at short-term (11.1 ± 9.0 days) and 3-month (69.6 ± 39.6 days) intervals. However, there was no difference between follow-up and pre-ablation PLAS. The PLAS returned to 95% pre-ablation level within 10 days. Paroxysmal AF patients had significantly higher pre-ablation PLAS than persistent AF patients in pre-ablation MRIs. Both type AF patients had significantly lower immediate post-ablation PLAS compared with pre-ablation and post-ablation PLAS.

CONCLUSION

The present study suggested a significant drop in PLAS immediately after ablation. Left atrial mechanical function recovered within 10 days after ablation. The drop in PLAS did not show a substantial difference between paroxysmal and persistent AF patients.

Risk of atrial fibrillation in patients with systemic sclerosis: a nationwide population-based study

OBJECTIVE

Atrial fibrillation (AF) is the most common arrhythmia in the general population, causing substantial economic burden, morbidity and mortality. The incidence rate and risk of AF in patients with SSc are unclear. We aimed to assess the incidence rate of AF in patients with SSc and the risk of incident AF in patients with SSc compared with the general population.

METHODS

The Korean National Health Insurance Service database was used as the data source. Patients with claims data for SSc between 2010 and 2017 were extracted from the database along with 1:5 age- and sex-matched controls. The index date was the earliest date with claims data for SSc between 2010 and 2017. The follow-up duration was from the index date to 2019. Multivariable Cox proportional hazard models were used to estimate the hazard ratio (HR) and 95% CI for AF in patients with SSc.

RESULTS

Overall, 2519 patients with SSc and 12 595 age- and sex-matched controls were included. Over a mean follow-up duration of 5.2 years (s.d. 2.6), the incidence rates of AF were 3.52 and 1.68 per 1000 person-years for patients with SSc and controls, respectively. Compared with controls, patients with SSc had a significantly higher risk of incident AF [adjusted HR 2.095 (95% CI 1.466, 2.994)].

CONCLUSION

Patients with SSc had a 2-fold higher risk of incident AF than controls. Given the significant economic burden, morbidity and mortality that AF poses, close monitoring for incident AF in patients with SSc is warranted.

A comprehensive review of finerenone-a third-generation non-steroidal mineralocorticoid receptor antagonist

Multiple studies have shown that finerenone (BAY 94-8862), a third-generation non-steroidal mineralocorticoid receptor antagonist (MRA), possesses different or superior mechanisms of action to traditional MRAs. Specifically, animal and cell-based experiments have demonstrated that this compound exerts multiple effects including fibrosis inhibition, reduced pulmonary artery pressure, improved diabetic retinopathy, enhanced endothelial functions, metabolic optimization as well as reduced oxidative stress, thereby exerting overall positive effects on renal and cardiovascular diseases. Consequently, clinical research, such as the FIGARO-DKD and FIDELIO-DKD trials, has demonstrated dual benefits for patients with type 2 diabetes mellitus and chronic kidney disease (T2DM-CKD), especially by validating MRAs' potential in reducing risks of renal and cardiovascular composite endpoints. Currently, cardiovascular indications for finerenone are limited to patients with T2DM-CKD, while its use in non-T2DM CKD patients remains at clinical trial stages. Despite showing good safety and efficacy in T2DM-CKD patients, there are insufficient corresponding data for those presenting chronic kidney disease without diabetes (ndCKD). Furthermore, the application of this compound in diseases such as primary aldosteronism and its association with cancer risk need to be further validated through larger-scale and longer-term clinical studies. Nevertheless, the development of finerenone provides an additional option for treating cardiovascular and renal diseases. With further research, it is expected that finerenone will be relevant to a broader range of CKD patient populations by addressing current knowledge gaps to comprehensively evaluate its clinical value and potentially alter existing treatment strategies. The current review aims to comprehensively analyze the basic research and clinical advancements involving finerenone in order to explore its prospects for treating cardiovascular and renal diseases, while addressing unmet needs in current treatment strategies. Additionally, through a comprehensive analysis of relevant research findings, a deeper understanding of finerenone's drug characteristics will be provided alongside scientific guidance for future treatment strategies and their clinical significance.

Influencing factors and predictive model for left atrial appendage emptying velocity in nonvalvular AF patients

Background

Atrial fibrillation (AF) is the most common cardiac arrhythmia, significantly increasing the risk of death and stroke. The left atrial appendage (LAA) plays a crucial role in the development of AF. Reduced left atrial appendage emptying velocity (LAAEV) is an important indicator of nonvalvular AF, associated with thrombosis and recurrence after catheter ablation. This study aims to identify factors influencing LAAEV and construct a predictive model for LAAEV in nonvalvular AF patients.

Methods

This retrospective cohort study included 1,048 nonvalvular AF patients hospitalized at the Second Hospital of Hebei Medical University from January 1, 2015, to December 31, 2021. Patients underwent transthoracic and transesophageal echocardiography and had complete laboratory data. Statistical analyses included binary logistic regression and multiple linear regression to identify independent predictors of reduced LAAEV and construct a predictive model.

Results

Patients were divided into two groups: reduced LAAEV (<40 cm/s) and normal LAAEV (≥40 cm/s). The reduced LAAEV group included 457 patients (43.61%), with significant differences in age, gender, alcohol consumption, heart failure (HF), ischemic stroke, AF type, resting heart rate, CHA2DS2-VASc score, serum creatinine (SCR), serum uric acid (SUA), estimated glomerular filtration rate (eGFR), glycated hemoglobin (HbA1C), β2 macroglobulin (B2M), left atrial diameter (LAD), and left ventricular ejection fraction (LVEF) compared to the normal LAAEV group. Logistic regression analysis identified age (OR 0.974, 95% CI 0.951-0.997, P = 0.028), HF (OR 0.637, 95% CI 0.427-0.949, P = 0.027), AF type [Persistent AF vs. PAF (OR 0.063, 95% CI 0.041-0.095, P = 0) Long-standing Persistent AF vs. PAF (OR 0.077, 95% CI 0.043-0.139, P = 0)], LAD (OR 0.872, 95% CI 0.836-0.91, P < 0.001), and LVEF (OR 1.057, 95% CI 1.027-1.089, P = 0) as independent predictors of reduced LAAEV. Multiple linear regression analysis included age, AF type, LAD, and LVEF in the final predictive model, explaining 43.5% of the variance in LAAEV (adjusted R² = 0.435).

Conclusion

Age, HF, type of AF, LAD, and LVEF are independent predictors of reduced LAAEV. The predictive model (LAAEV = 96.567-15.940 × AFtype-1.309 × LAD-0.18 × Age + 37.069 × LVEF) demonstrates good predictive value, aiding in the initial assessment and management of nonvalvular AF patients.

Toxicity profiles of immune checkpoint inhibitors in nervous system cancer: a comprehensive disproportionality analysis using FDA adverse event reporting system

BACKGROUND

Immune-related adverse events (irAEs) always occur during treatment with immune checkpoint inhibitors (ICIs). Patients with nervous system cancer (NSC) may gain clinical benefit from ICIs, but irAEs in NSC patients are rarely examined. Therefore, our study systematically summarized reports of irAEs in NSC.

METHODS

We obtained information from the FDA adverse event reporting system from the first quarter (Q1) of 2013 to the fourth quarter (Q4) of 2022. We examined use of a combination of ICIs and chemotherapy (ICI_Chemo) or chemotherapy only (ICI_Chemo) for patients with NSC. Multiple disproportionality analyses were applied to assess irAEs. Multiomics data from the gene expression omnibus (GEO) database were analyzed to explore potential molecular mechanisms associated with irAEs in NSC patients.

RESULTS

Fourteen irAEs were identified in 8,357 NSC patients after removing duplicates; the top five events were seizure, confused state, encephalopathy, muscular weakness and gait disturbance. Older patients were more likely to develop irAEs than were younger patients. From the start of ICIs_Chemo to irAE occurrence, there was a significant difference in the time to onset of irAEs between age groups. irAEs may occur via mechanisms involving the inflammatory response, secretion of inflammatory mediators, and aberrant activation of pathologic pathways.

CONCLUSIONS

This study helps to characterize irAEs in NSC patients treated with ICIs. We combined GEO database analysis to explore the potential molecular mechanisms of irAEs. The results of this study provide a basis for improving the toxic effects of ICIs in NSC patients.

The Role of the Autonomic Nervous System as Both "Trigger and "Substrate" in Atrial Fibrillation

Several complex mechanisms, working alone, or together, initiate and maintain atrial fibrillation (AF). At disease onset, pulmonary vein-atrial triggers, producing ectopy, predominate. Then, as AF progresses, a shift toward substrate occurs, which AF also self-perpetuates. The autonomic nervous system (ANS) plays an important role as trigger and substrate. Although the efferent arm of the ANS as AF trigger is well-established, there is emerging evidence to show that (1) the ANS is a substrate for AF and (2) afferent or regulatory ANS dysfunction occurs in AF patients. These findings could represent a mechanism for the progression of AF.

Atrial fibrillation burden: a new outcome predictor and therapeutic target

Atrial fibrillation (AF), the most common sustained cardiac arrhythmia, is not a dichotomous disease trait. Technological innovations enable long-term rhythm monitoring in many patients and can estimate AF burden. These technologies are already used to detect and monitor AF. This review describes the relation between AF burden and outcomes and potential effects of AF burden reduction. A lower AF burden is associated with a lower risk of stroke and heart failure in patients with AF: stroke risk without anticoagulation is lower in patients with device-detected AF and a low AF burden (stroke rate 1%/year) than in patients with persistent and permanent AF (stroke rate 3%/year). Paroxysmal AF shows intermediate stroke rates (2%/year). Atrial fibrillation burden-reducing interventions can reduce cardiovascular outcomes in patients with AF: early rhythm control reduces cardiovascular events including stroke and heart failure in patients with recently diagnosed AF and cardiovascular conditions. In patients with heart failure and AF, early rhythm control and AF ablation, interventions that reduce AF burden, reduce mortality and heart failure events. Recent technological innovations allow to estimate AF burden in clinical care, creating opportunities and challenges. While evidence remains limited, the existing data already suggest that AF burden reduction could be a therapeutic goal. In addition to anticoagulation and treatment of cardiovascular conditions, AF burden reduction emerges as a therapeutic goal. Future research will define the AF burden that constitutes a relevant risk of stroke and heart failure. Technologies quantifying AF burden need careful validation to advance the field.

Mechanisms of stretch-induced electro-anatomical remodeling and atrial arrhythmogenesis

Atrial fibrillation (AF) is the most common cardiac rhythm disorder, often occurring in the setting of atrial distension and elevated myocardialstretch. While various mechano-electrochemical signal transduction pathways have been linked to AF development and progression, the underlying molecular mechanisms remain poorly understood, hampering AF therapies. In this review, we describe different aspects of stretch-induced electro-anatomical remodeling as seen in animal models and in patients with AF. Specifically, we focus on cellular and molecular mechanisms that are responsible for mechano-electrochemical signal transduction and the development of ectopic beats triggering AF from pulmonary veins, the most common source of paroxysmal AF. Furthermore, we describe structural changes caused by stretch occurring before and shortly after the onset of AF as well as during AF progression, contributing to longstanding forms of AF. We also propose mechanical stretch as a new dimension to the concept "AF begets AF", in addition to underlying diseases. Finally, we discuss the mechanisms of these electro-anatomical alterations in a search for potential therapeutic strategies and the development of novel antiarrhythmic drugs targeted at the components of mechano-electrochemical signal transduction not only in cardiac myocytes, but also in cardiac non-myocyte cells.

Analysis of drug-induced and spontaneous cardioversions reveals similar patterns leading to termination of atrial fibrillation

Introduction

The mechanisms leading to the conversion of atrial fibrillation (AF) to sinus rhythm are poorly understood. This study describes the dynamic behavior of electrophysiological parameters and conduction patterns leading to spontaneous and pharmacological AF termination.

Methods

Five independent groups of goats were investigated: (1) spontaneous termination of AF, and drug-induced terminations of AF by various potassium channel inhibitors: (2) AP14145, (3) PA-6, (4) XAF-1407, and (5) vernakalant. Bi-atrial contact mapping was performed during an open chest surgery and intervals with continuous and discrete atrial activity were determined. AF cycle length (AFCL), conduction velocity and path length were calculated for each interval, and the final conduction pattern preceding AF termination was evaluated.

Results

AF termination was preceded by a sudden episode of discrete activity both in the presence and absence of an antiarrhythmic drug. This episode was accompanied by substantial increases in AFCL and conduction velocity, resulting in prolongation of path length. In 77% ± 4% of all terminations the conduction pattern preceding AF termination involved medial to lateral conduction along Bachmann's bundle into both atria, followed by anterior to posterior conduction. This finding suggests conduction block in the interatrial septum and/or pulmonary vein area as final step of AF termination.

Conclusion

AF termination is preceded by an increased organization of fibrillatory conduction. The termination itself is a sudden process with a critical role for the interplay between spatiotemporal organization and anatomical structure.

Atrial Fibrillation, Atrial Myopathy, and Thromboembolism: The Additive Value of Echocardiography and Possible New Horizons for Risk Stratification

Atrial fibrillation (AF) is the most common cardiac sustained arrhythmia, and it is associated with increased stroke and dementia risk. While the established paradigm attributes these complications to blood stasis within the atria and subsequent thrombus formation with cerebral embolization, recent evidence suggests that atrial myopathy (AM) may play a key role. AM is characterized by structural and functional abnormalities of the atria, and can occur with or without AF. Moving beyond classifications based solely on episode duration, the 4S-AF characterization has offered a more comprehensive approach, incorporating patient's stroke risk, symptom severity, AF burden, and substrate assessment (including AM) for tailored treatment decisions. The "ABC" pathway emphasizes anticoagulation, symptom control, and cardiovascular risk modification and emerging evidence suggests broader benefits of early rhythm control strategies, potentially reducing stroke and dementia risk and improving clinical outcomes. However, a better integration of AM assessment into the current framework holds promise for further personalizing AF management and optimizing patient outcomes. This review explores the emerging concept of AM and its potential role as a risk factor for stroke and dementia and in AF patients' management strategies, highlighting the limitations of current risk stratification methods, like the CHA2DS2-VASc score. Echocardiography, particularly left atrial (LA) strain analysis, has shown to be a promising non-invasive tool for AM evaluation and recent studies suggest that LA strain analysis may be a more sensitive risk stratifier for thromboembolic events than AF itself, with some studies showing a stronger association between LA strain and thromboembolic events compared to traditional risk factors. Integrating it into routine clinical practice could improve patient management and targeted therapies for AF and potentially other thromboembolic events. Future studies are needed to explore the efficacy and safety of anticoagulation in AM patients with and without AF and to refine the diagnostic criteria for AM.

Levosimendan and Atrial Fibrillation: A Meta-Analysis of Randomized Controlled Trials

BACKGROUND

Atrial fibrillation (AF) is a prevalent complication associated with levosimendan; however, it remains uncertain whether there are any disparities in the effects of levosimendan on non-postoperative and postoperative AF.

OBJECTIVES

This study aimed to evaluate the levosimendan effect on non-postoperative and postoperative AF by conducting a meta-analysis of randomized control trials (RCTs).

METHODS

PubMed, Embase, Cochrane Library, and other databases were searched. Pairs of reviewers identified RCTs that compared levosimendan and placebo or other therapies, and the results reported AF events data. Random effects models were used (at a significance level of 5%).

RESULTS

Twenty-nine eligible trials comprising 6550 participants were included, eleven of which evaluated the non-postoperative AF incidence, and 18 included postoperative AF. The analysis revealed that levosimendan elevated the AF risk significantly in the non-postoperative group (OR, 1.62; 95% CI: 1.19-2.20; p=0.002) and reduced the AF incidence in the postoperative group (OR, 0.65; 95% CI: 0.44-0.96; p=0.03). AF occurrence decreased more significantly in patients who used levosimendan after cardiac surgery (OR, 0.53; 95% CI: 0.32-0.88; p=0.02) than in patients who used levosimendan before cardiac surgery (OR, 0.67; 95% CI: 0.42-1.06; p=0.09). Moreover, The AF risk was significantly elevated by levosimendan large bolus dose (bolus dose≥12 μg/kg) (OR, 1.44; 95% CI: 1.10-1.88; p=0.004) and decreased by small bolus dose of levosimendan (bolus dose<12 μg/kg) (OR, 0.64; 95% CI: 0.34-1.20; p=0.16).

CONCLUSION

Levosimendan was linked to an increased non-postoperative AF incidence. The employment of levosimendan was effective in preventing postoperative AF.

Compartmentalization proteomics revealed endolysosomal protein network changes in a goat model of atrial fibrillation

Endolysosomes (EL) are known for their role in regulating both intracellular trafficking and proteostasis. EL facilitate the elimination of damaged membranes, protein aggregates, membranous organelles and play an important role in calcium signaling. The specific role of EL in cardiac atrial fibrillation (AF) is not well understood. We isolated atrial EL organelles from AF goat biopsies and conducted a comprehensive integrated omics analysis to study the EL-specific proteins and pathways. We also performed electron tomography, protein and enzyme assays on these biopsies. Our results revealed the upregulation of the AMPK pathway and the expression of EL-specific proteins that were not found in whole tissue lysates, including GAA, DYNLRB1, CLTB, SIRT3, CCT2, and muscle-specific HSPB2. We also observed structural anomalies, such as autophagic-vacuole formation, irregularly shaped mitochondria, and glycogen deposition. Our results provide molecular information suggesting EL play a role in AF disease process over extended time frames.

Repurposing Metformin for the Treatment of Atrial Fibrillation: Current Insights

Metformin is an orally effective anti-hyperglycemic drug that despite being introduced over 60 years ago is still utilized by an estimated 120 to 150 million people worldwide for the treatment of type 2 diabetes (T2D). Metformin is used off-label for the treatment of polycystic ovary syndrome (PCOS) and for pre-diabetes and weight loss. Metformin is a safe, inexpensive drug with side effects mostly limited to gastrointestinal issues. Prospective clinical data from the United Kingdom Prospective Diabetes Study (UKPDS), completed in 1998, demonstrated that metformin not only has excellent therapeutic efficacy as an anti-diabetes drug but also that good glycemic control reduced the risk of micro- and macro-vascular complications, especially in obese patients and thereby reduced the risk of diabetes-associated cardiovascular disease (CVD). Based on a long history of clinical use and an excellent safety record metformin has been investigated to be repurposed for numerous other diseases including as an anti-aging agent, Alzheimer's disease and other dementias, cancer, COVID-19 and also atrial fibrillation (AF). AF is the most frequently diagnosed cardiac arrythmia and its prevalence is increasing globally as the population ages. The argument for repurposing metformin for AF is based on a combination of retrospective clinical data and in vivo and in vitro pre-clinical laboratory studies. In this review, we critically evaluate the evidence that metformin has cardioprotective actions and assess whether the clinical and pre-clinical evidence support the use of metformin to reduce the risk and treat AF.

Cost-Effectiveness and Budget Impact Analysis of Apixaban and Rivaroxaban Versus Warfarin in the Prevention of Stroke in Patients With Non-Valvular Atrial Fibrillation (NVAF) in Iran

INTRODUCTION

This study evaluates the cost-effectiveness of Apixaban and Rivaroxaban, compared to Warfarin, for stroke prevention in patients with non-valvular atrial fibrillation in Iran.

METHOD

A Markov model with a 30-year time horizon was employed to simulate and assess different treatment strategies' cost-effectiveness. The study population comprised Iranian adults with NVAF, identified through specialist consultations, hospital visits, and archival record reviews. Direct medical costs, direct nonmedical, and indirect costs were included. Quality-adjusted life years (QALY) were assessed using an EQ-5D questionnaire. This study utilized a cost-effectiveness threshold of $11 134 per QALY.

RESULTS

Apixaban demonstrated superior cost-effectiveness compared to Rivaroxaban and Warfarin. Over 30 years, total costs were lower in the Apixaban and Rivaroxaban groups compared to the Warfarin group ($126.18 and $109.99 vs. $150.49). However, Apixaban showed higher total QALYs gained compared to others (0.134 vs. 0.133 and 0.116). The incremental cost-effectiveness ratio for comparing Apixaban to Warfarin was calculated at -1332.83 cost per QALY, below the threshold of $11 134, indicating Apixaban's cost-effectiveness. Sensitivity analyses confirmed the robustness of the findings, with ICER consistently remaining below the threshold. Over 5 years (2024-2028) of Apixaban usage, the incremental cost starts at USD 70 250 296 in the first year and gradually rises to USD 71 770 662 in the fifth year. DSA and PSA were assessed to prove the robustness of the results.

CONCLUSION

This study shows that Apixaban is a cost-effective option for stroke prevention in non-valvular atrial fibrillation patients in Iran compared to Warfarin.

Sodium-glucose cotransporter-2 inhibitors and incidence of atrial fibrillation in older adults with type 2 diabetes: a retrospective cohort analysis

Objectives

To investigate the risk of atrial fibrillation (AF) with sodium-glucose cotransporter-2 inhibitors (SGLT2is) compared to dipeptidyl peptidase-4 inhibitor (DPP4i) use in older US adults and across diverse subgroups.

Methods

We conducted a retrospective cohort analysis using claims data from 15% random samples of Medicare fee-for-service beneficiaries. Patients were adults with type 2 diabetes (T2D), no preexisting AF, and were newly initiated on SGLT2i or DPP4i. The outcome was the first incident AF. Inverse probability treatment weighting (IPTW) was used to balance the baseline covariates between the treatment groups including sociodemographics, comorbidities, and co-medications. Cox regression models were used to assess the effect of SGLT2i compared to DPP4i on incident AF.

Results

Of the 97,436 eligible individuals (mean age 71.2 ± 9.8 years, 54.6% women), 1.01% (n = 983) had incident AF over a median follow-up of 361 days. The adjusted incidence rate was 8.39 (95% CI: 6.67-9.99) and 11.70 (95% CI: 10.9-12.55) per 1,000 person-years in the SGLT2i and DPP4i groups, respectively. SGLT2is were associated with a significantly lower risk of incident AF (HR 0.73; 95% CI, 0.57 to 0.91; p = 0.01) than DPP4is. The risk reduction of incident AF was significant in non-Hispanic White individuals and subgroups with existing atherosclerotic cardiovascular diseases and chronic kidney disease.

Conclusion

Compared to the use of DPP4i, that of SGLT2i was associated with a lower risk of AF in patients with T2D. Our findings contribute to the real-world evidence regarding the effectiveness of SGLT2i in preventing AF and support a tailored therapeutic approach to optimize treatment selection based on individual characteristics.

Electrophysiological Effects of the Sodium-Glucose Co-Transporter-2 (SGLT2) Inhibitor Dapagliflozin on Human Cardiac Potassium Channels

The sodium-glucose co-transporter-2 (SGLT2) inhibitor dapagliflozin is increasingly used in the treatment of diabetes and heart failure. Dapagliflozin has been associated with reduced incidence of atrial fibrillation (AF) in clinical trials. We hypothesized that the favorable antiarrhythmic outcome of dapagliflozin use may be caused in part by previously unrecognized effects on atrial repolarizing potassium (K+) channels. This study was designed to assess direct pharmacological effects of dapagliflozin on cloned ion channels Kv11.1, Kv1.5, Kv4.3, Kir2.1, K2P2.1, K2P3.1, and K2P17.1, contributing to IKur, Ito, IKr, IK1, and IK2P K+ currents. Human channels coded by KCNH2, KCNA5, KCND3, KCNJ2, KCNK2, KCNK3, and KCNK17 were heterologously expressed in Xenopus laevis oocytes, and currents were recorded using the voltage clamp technique. Dapagliflozin (100 µM) reduced Kv11.1 and Kv1.5 currents, whereas Kir2.1, K2P2.1, and K2P17.1 currents were enhanced. The drug did not significantly affect peak current amplitudes of Kv4.3 or K2P3.1 K+ channels. Biophysical characterization did not reveal significant effects of dapagliflozin on current-voltage relationships of study channels. In conclusion, dapagliflozin exhibits direct functional interactions with human atrial K+ channels underlying IKur, IKr, IK1, and IK2P currents. Substantial activation of K2P2.1 and K2P17.1 currents could contribute to the beneficial antiarrhythmic outcome associated with the drug. Indirect or chronic effects remain to be investigated in vivo.

Systematic in-silico evaluation of fibrosis effects on re-entrant wave dynamics in atrial tissue

Despite the key role of fibrosis in atrial fibrillation (AF), the effects of different spatial distributions and textures of fibrosis on wave propagation mechanisms in AF are not fully understood. To clarify these aspects, we performed a systematic computational study to assess fibrosis effects on the characteristics and stability of re-entrant waves in electrically-remodelled atrial tissues. A stochastic algorithm, which generated fibrotic distributions with controlled overall amount, average size, and orientation of fibrosis elements, was implemented on a monolayer spheric atrial model. 245 simulations were run at changing fibrosis parameters. The emerging propagation patterns were quantified in terms of rate, regularity, and coupling by frequency-domain analysis of correspondent synthetic bipolar electrograms. At the increase of fibrosis amount, the rate of reentrant waves significantly decreased and higher levels of regularity and coupling were observed (p < 0.0001). Higher spatial variability and pattern stochasticity over repetitions was observed for larger amount of fibrosis, especially in the presence of patchy and compact fibrosis. Overall, propagation slowing and organization led to higher stability of re-entrant waves. These results strengthen the evidence that the amount and spatial distribution of fibrosis concur in dictating re-entry dynamics in remodeled tissue and represent key factors in AF maintenance.

Predictive Value of Serum microRNA-29b-3p in Recurrence of Atrial Fibrillation After Radiofrequency Catheter Ablation

Objective

Atrial fibrillation (AF) is a common arrhythmia. This study explored serum miR-29b-3p expression in AF patients and its value in predicting AF recurrence after radiofrequency catheter ablation (RFCA).

Methods

Totally 100 AF patients who underwent RFCA were enrolled, with 100 individuals without AF as controls. Serum miR-29b-3p expression in participants was determined using RT-qPCR. The correlation between miR-29b-3p and atrial fibrosis markers (FGF-21/FGF-23) was assessed by Pearson analysis. The diagnostic efficacy of serum miR-29b-3p and FGF-21/FGF-23 in predicting AF recurrence after RFCA was analyzed by the receiver operating characteristic (ROC) curves. The Kaplan-Meier method was adopted to evaluate the effect of miR-29b-3p expression on the incidence of AF recurrence after RFCA. The independent risk factors for AF recurrence after RFCA were analyzed by logistic regression analysis.

Results

Serum miR-29b-3p was poorly expressed in AF patients. After RFCA, AF patients showed elevated serum miR-29b-3p expression. Serum miR-29b-3p expression in AF patients negatively correlated with serum FGF-21 and FGF-23 concentrations. The cut-off values of serum miR-29b-3p, FGF-21, and FGF-23 in identifying AF recurrence were 0.860 (sensitivity: 100.00%, specificity: 39.71%), 222.2 pg/mL (sensitivity: 96.88%, specificity: 32.35%) and 216.3 ng/mL (sensitivity: 53.13%, specificity: 70.59%), respectively. Patients with low miR-29b-3p expression had a significantly higher incidence of AF recurrence than patients with high miR-29b-3p expression. Serum miR-29b-3p expression was one of the independent risk factors for AF recurrence after RFCA.

Conclusion

Low miR-29b-3p expression in AF patients has certain predictive values and is one of the independent risk factors for AF recurrence after RFCA.

The SK4 channel allosteric blocker, BA6b9, reduces atrial fibrillation substrate in rats with reduced ejection fraction

Atrial fibrillation (AF), the most common cardiac arrhythmia, is strongly associated with several comorbidities including heart failure (HF). AF in general, and specifically in the context of HF, is progressive in nature and associated with poor clinical outcomes. Current therapies for AF are limited in number and efficacy and do not target the underlying causes of atrial remodeling such as inflammation or fibrosis. We previously identified the calcium-activated SK4 K+ channels, which are preferentially expressed in the atria relative to the ventricles in both rat and human hearts, as attractive druggable target for AF treatment. Here, we examined the ability of BA6b9, a novel allosteric inhibitor of SK4 channels that targets the specific calmodulin-PIP2 binding domain, to alter AF susceptibility and atrial remodeling in a systolic HF rat postmyocardial infarction (post-MI) model. Daily BA6b9 injection (20 mg/kg/day) for 3 weeks starting 1-week post-MI prolonged the atrial effective refractory period, reduced AF induction and duration, and dramatically prevented atrial structural remodeling. In the post-MI left atrium (LA), pronounced upregulation of the SK4 K+ channel was observed, with corresponding increases in collagen deposition, α-SMA levels, and NLRP3 inflammasome expression. Strikingly, BA6b9 treatment reversed these changes while also significantly reducing the lateralization of the atrial connexin Cx43 in the LA of post-MI rats. Our findings indicate that the blockade of SK4 K+ channels using BA6b9 not only favors rhythm control but also remarkably reduces atrial structural remodeling, a property that is highly desirable for novel AF therapies, particularly in patients with comorbid HF.

Administration of USP7 inhibitor p22077 alleviates Angiotensin II (Ang II)-induced atrial fibrillation in Mice

Atrial fibrillation (AF), the most common cardiac arrhythmia, is an important contributor to mortality and morbidity. Ubquitin-specific protease 7 (USP7), one of the most abundant ubiquitin-specific proteases (USP), participated in many cellular events, such as cell proliferation, apoptosis, and tumourigenesis. However, its role in AF remains unknown. Here, the mice were treated with Ang II infusion to induce the AF model. Echocardiography was used to measure the atrial diameter. Electrical stimulation was programmed to measure the induction and duration of AF. The changes in atrial remodeling were measured using routine histologic analysis. Here, a significant increase in USP7 expression was observed in Ang II-stimulated atrial cardiomyocytes and atrial tissues, as well as in atrial tissues from patients with AF. The administration of p22077, the inhibitor of USP7, attenuated Ang II-induced inducibility and duration of AF, atrial dilatation, connexin dysfunction, atrial fibrosis, atrial inflammation, and atrial oxidase stress, and then inhibited the progression of AF. Mechanistically, the administration of p22077 alleviated Ang II-induced activation of TGF-β/Smad2, NF-κB/NLRP3, NADPH oxidases (NOX2 and NOX4) signals, the up-regulation of CX43, ox-CaMKII, CaMKII, Kir2.1, and down-regulation of SERCA2a. Together, this study, for the first time, suggests that USP7 is a critical driver of AF and revealing USP7 may present a new target for atrial fibrillation therapeutic strategies.

Evaluation of left atrial strain imaging and integrated backscatter as predictors of recurrence in patients with paroxysmal, persistent, and long-standing persistent atrial fibrillation undergoing catheter ablation

BACKGROUND

Impaired left atrial (LA) strain predicts atrial fibrillation (AF) recurrence after catheter ablation (CA), but currently there is no cut-off to guide patient selection for CA. Integrated backscatter (IBS) is a promising tool for noninvasive quantification of myocardial fibrosis. The aim of this study was to compare LA strain and IBS between paroxysmal, persistent, and long-standing persistent AF and evaluate their association with AF recurrence after CA.

METHODS

Analysis of consecutive patients with symptomatic paroxysmal and persistent AF who underwent CA. LA phasic strain, strain rate and IBS were assessed by two-dimensional speckle-tracking at baseline.

RESULTS

We analyzed 78 patients, 31% with persistent AF (46% long-standing AF), 65% male, mean age 59 ± 14 years, who underwent CA and were followed-up for 12 months. AF recurrence occurred in 22 (28%) patients. LA phasic strain parameters were significantly impaired in patients with AF recurrence and were independent predictors of AF recurrence in a multivariable analysis. LA reservoir strain (LASr) < 18% predicted AF recurrence with 86% sensitivity and 71% specificity, with a higher predictive power compared to LA volume index (LAVI). LASr < 22% in paroxysmal AF and LASr < 12% in persistent AF correlated with AF recurrence. Increased IBS was a predictor of AF recurrence in patients with paroxysmal AF.

CONCLUSION

LA phasic strain parameters were predictors of AF recurrence after CA, independently of LAVI and AF subtype. LASr < 18% showed a higher predictive power compared to LAVI. Further studies are needed to investigate the role of IBS as a predictor of AF recurrence.

Advancements in gene therapy approaches for atrial fibrillation: Targeted delivery, mechanistic insights and future prospects

Atrial fibrillation (AF) remains a complex and challenging arrhythmia to treat, necessitating innovative therapeutic strategies. This review explores the evolving landscape of gene therapy for AF, focusing on targeted delivery methods, mechanistic insights, and future prospects. Direct myocardial injection, reversible electroporation, and gene painting techniques are discussed as effective means of delivering therapeutic genes, emphasizing their potential to modulate both structural and electrical aspects of the AF substrate. The importance of identifying precise targets for gene therapy, particularly in the context of AF-associated genetic, structural, and electrical abnormalities, is highlighted. Current studies employing animal models, such as mice and large animals, provide valuable insights into the efficacy and limitations of gene therapy approaches. The significance of imaging methods for detecting atrial fibrosis and guiding targeted gene delivery is underscored. Activation mapping techniques offer a nuanced understanding of AF-specific mechanisms, enabling tailored gene therapy interventions. Future prospects include the integration of advanced imaging, activation mapping, and percutaneous catheter-based techniques to refine transendocardial gene delivery, with potential applications in both ventricular and atrial contexts. As gene therapy for AF progresses, bridging the translational gap between preclinical models and clinical applications is imperative for the successful implementation of these promising approaches.

Left atrial function of patients with atrial fibrillation undergoing thoracoscopic hybrid ablation

OBJECTIVES

Thoracoscopic hybrid ablation is an effective and safe rhythm control strategy for patients with complex forms of atrial fibrillation. Its effect on left atrial function has not yet been studied.

METHODS

In a retrospective single-centre analysis of patients undergoing thoracoscopic hybrid ablation, the left atrial emptying fraction was calculated using the biplane modified Simpson method in the apical 2- and 4-chamber views on transthoracic echocardiography. Left atrial strain (reservoir, conduction and contractility) was quantified using dedicated software.

RESULTS

Sixty-seven patients were included (mean age 64 years, long-standing persistent atrial fibrillation in 69%, median atrial fibrillation history duration 64 months). At baseline, left atrial function and contractility were poor. The reservoir and contractile strain improved postprocedure compared to baseline [15 (standard deviation (SD): 8) and 17 (SD: 6); P = 0.013; 3 (SD: 5) and 4 (SD: 4), P = 0.008], whereas the left atrial volume indexed to the body surface area was reduced [51 ml/m2 (SD: 14) and 47 ml/m2 (SD: 18), P = 0.0024]. In patients with preoperative (long-standing) persistent atrial fibrillation and in patients with rhythm restoration, improvements in the emptying fraction, (reservoir and contractile) strain and the left ventricular ejection fraction were observed, whereas the left atrial volume decreased (P < 0.05).

CONCLUSIONS

In this cohort of patients with severely diseased left atria, improvement in left atrial contractility and in the emptying fraction after thoracoscopic hybrid ablation for atrial fibrillation in patients with persistent atrial fibrillation is mainly due to rhythm restoration. Interestingly, the procedure itself also results in improved left atrial reservoir strain and reversed left atrial remodelling by reducing left atrial volume.

Interactions between calcium-induced arrhythmia triggers and the electrophysiological-anatomical substrate underlying the induction of atrial fibrillation

Atrial fibrillation (AF) is the most common cardiac arrhythmia and is sustained by spontaneous focal excitations and re-entry. Spontaneous electrical firing in the pulmonary vein (PV) sleeves is implicated in AF generation. The aim of this simulation study was to identify the mechanisms determining the localisation of AF triggers in the PVs and their contribution to the genesis of AF. A novel biophysical model of the canine atria was used that integrates stochastic, spontaneous subcellular Ca2+ release events (SCRE) with regional electrophysiological heterogeneity in ionic properties and a detailed three-dimensional model of atrial anatomy, microarchitecture and patchy fibrosis. Simulations highlighted the importance of the smaller inward rectifier potassium current (IK1 ) in PV cells compared to the surrounding atria, which enabled SCRE more readily to result in delayed-afterdepolarisations that induced triggered activity. There was a leftward shift in the dependence of the probability of triggered activity on sarcoplasmic reticulum Ca2+ load. This feature was accentuated in 3D tissue compared to single cells (Δ half-maximal [Ca2+ ]SR  = 58 μM vs. 22 μM). In 3D atria incorporating electrical heterogeneity, excitations preferentially emerged from the PV region. These triggered focal excitations resulted in transient re-entry in the left atrium. Addition of fibrotic patches promoted localised emergence of focal excitations and wavebreaks that had a more substantial impact on generating AF-like patterns than the PVs. Thus, a reduced IK1 , less negative resting membrane potential, and fibrosis-induced changes of the electrotonic load all contribute to the emergence of complex excitation patterns from spontaneous focal triggers. KEY POINTS: Focal excitations in the atria are most commonly associated with the pulmonary veins, but the mechanisms for this localisation are yet to be elucidated. We applied a multi-scale computational modelling approach to elucidate the mechanisms underlying such localisations. Myocytes in the pulmonary vein region of the atria have a less negative resting membrane potential and reduced time-independent potassium current; we demonstrate that both of these factors promote triggered activity in single cells and tissues. The less negative resting membrane potential also contributes to heterogeneous inactivation of the fast sodium current, which can enable re-entrant-like excitation patterns to emerge without traditional conduction block.

Aldehyde Dehydrogenase 2 (ALDH2) Deficiency, Obesity, and Atrial Fibrillation Susceptibility: Unraveling the Connection

Atrial fibrillation (AF), characterized by structural remodeling involving atrial myocardial degradation and fibrosis, is linked with obesity and transforming growth factor beta 1 (TGF-β1). Aldehyde dehydrogenase 2 (ALDH2) deficiency, highly prevalent in East Asian people, is paradoxically associated with a lower AF risk. This study investigated the impact of ALDH2 deficiency on diet-induced obesity and AF vulnerability in mice, exploring potential compensatory upregulation of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme-oxygenase 1 (HO-1). Wild-type (WT) and ALDH2*2 knock-in (KI) mice were administered a high-fat diet (HFD) for 16 weeks. Despite heightened levels of reactive oxygen species (ROS) post HFD, the ALDH2*2 KI mice did not exhibit a greater propensity for AF compared to the WT controls. The ALDH2*2 KI mice showed equivalent myofibril degradation in cardiomyocytes compared to WT after chronic HFD consumption, indicating suppressed ALDH2 production in the WT mice. Atrial fibrosis did not proportionally increase with TGF-β1 expression in ALDH2*2 KI mice, suggesting compensatory upregulation of the Nrf2 and HO-1 pathway, attenuating fibrosis. In summary, ALDH2 deficiency did not heighten AF susceptibility in obesity, highlighting Nrf2/HO-1 pathway activation as an adaptive mechanism. Despite limitations, these findings reveal a complex molecular interplay, providing insights into the paradoxical AF-ALDH2 relationship in the setting of obesity.

Optoelectronic control of cardiac rhythm: Toward shock-free ambulatory cardioversion of atrial fibrillation

Atrial fibrillation (AF) is the most prevalent cardiac arrhythmia, progressive in nature, and known to have a negative impact on mortality, morbidity, and quality of life. Patients requiring acute termination of AF to restore sinus rhythm are subjected to electrical cardioversion, which requires sedation and therefore hospitalization due to pain resulting from the electrical shocks. However, considering the progressive nature of AF and its detrimental effects, there is a clear need for acute out-of-hospital (i.e., ambulatory) cardioversion of AF. In the search for shock-free cardioversion methods to realize such ambulatory therapy, a method referred to as optogenetics has been put forward. Optogenetics enables optical control over the electrical activity of cardiomyocytes by targeted expression of light-activated ion channels or pumps and may therefore serve as a means for cardioversion. First proof-of-principle for such light-induced cardioversion came from in vitro studies, proving optogenetic AF termination to be very effective. Later, these results were confirmed in various rodent models of AF using different transgenes, illumination methods, and protocols, whereas computational studies in the human heart provided additional translational insight. Based on these results and fueled by recent advances in molecular biology, gene therapy, and optoelectronic engineering, a basis is now being formed to explore clinical translations of optoelectronic control of cardiac rhythm. In this review, we discuss the current literature regarding optogenetic cardioversion of AF to restore normal rhythm in a shock-free manner. Moreover, key translational steps will be discussed, both from a biological and technological point of view, to outline a path toward realizing acute shock-free ambulatory termination of AF.

The new era of cardiovascular research: revolutionizing cardiovascular research with 3D models in a dish

Cardiovascular research has heavily relied on studies using patient samples and animal models. However, patient studies often miss the data from the crucial early stage of cardiovascular diseases, as obtaining primary tissues at this stage is impracticable. Transgenic animal models can offer some insights into disease mechanisms, although they usually do not fully recapitulate the phenotype of cardiovascular diseases and their progression. In recent years, a promising breakthrough has emerged in the form of in vitro three-dimensional (3D) cardiovascular models utilizing human pluripotent stem cells. These innovative models recreate the intricate 3D structure of the human heart and vessels within a controlled environment. This advancement is pivotal as it addresses the existing gaps in cardiovascular research, allowing scientists to study different stages of cardiovascular diseases and specific drug responses using human-origin models. In this review, we first outline various approaches employed to generate these models. We then comprehensively discuss their applications in studying cardiovascular diseases by providing insights into molecular and cellular changes associated with cardiovascular conditions. Moreover, we highlight the potential of these 3D models serving as a platform for drug testing to assess drug efficacy and safety. Despite their immense potential, challenges persist, particularly in maintaining the complex structure of 3D heart and vessel models and ensuring their function is comparable to real organs. However, overcoming these challenges could revolutionize cardiovascular research. It has the potential to offer comprehensive mechanistic insights into human-specific disease processes, ultimately expediting the development of personalized therapies.

Overcoming Uncertainties in Electrogram-Based Atrial Fibrillation Mapping: A Review

In clinical rhythmology, intracardiac bipolar electrograms (EGMs) play a critical role in investigating the triggers and substrates inducing and perpetuating atrial fibrillation (AF). However, the interpretation of bipolar EGMs is ambiguous due to several aspects of electrodes, mapping algorithms and wave propagation dynamics, so it requires several variables to describe the effects of these uncertainties on EGM analysis. In this narrative review, we critically evaluate the potential impact of such uncertainties on the design of cardiac mapping tools on AF-related substrate characterization. Literature suggest uncertainties are due to several variables, including the wave propagation vector, the wave's incidence angle, inter-electrode spacing, electrode size and shape, and tissue contact. The preprocessing of the EGM signals and mapping density will impact the electro-anatomical representation and the features extracted from the local electrical activities. The superposition of multiple waves further complicates EGM interpretation. The inclusion of these uncertainties is a nontrivial problem but their consideration will yield a better interpretation of the intra-atrial dynamics in local activation patterns. From a translational perspective, this review provides a concise but complete overview of the critical variables for developing more precise cardiac mapping tools.

Impact of diagnosis-to-ablation time on clinical outcomes in patients with early-onset atrial fibrillation

BACKGROUND

Evidence was lacking for the early choice of radiofrequency ablation (RFA) among patients with early-onset atrial fibrillation (AF).

HYPOTHESIS

This study aimed to explore whether earlier RFA was associated with better clinical outcomes among early-onset AF patients.

METHODS

Patients, who were diagnosed with AF before 45 years and underwent their first RFA procedures at baseline of the China Atrial Fibrillation registry, were enrolled and divided into four diagnosis-to-ablation time (DAT) groups: DAT ≤ 1 year, 1 year < DAT ≤ 3 years, 3 years < DAT ≤ 6 years, and DAT > 6 years. Another group of nonablation patients, who were newly diagnosed with AF and younger than 45 years, were also included. Adjusted associations of groups with composite cardiovascular events (cardiovascular death, embolism, major hemorrhages, or cardiac rehospitalization) or recurrent AF were analyzed using Cox proportional hazards models.

RESULTS

Among 1694 patients who underwent their first RFA at enrollment, incidences of composite cardiovascular outcomes were increasing with extension of DAT (DAT ≤ 1 year: 6.1/100 person-years, 1 year < DAT ≤ 3 years: 7.9/100 person-years, 3 years < DAT ≤ 6 years: 7.6/100 person-years, DAT > 6 years: 10.5/100 person-years; p < .001). In comparison with DAT > 6 years group, the DAT ≤ 1 year group was associated with reduced risk of cardiovascular events (adjusted hazard ratio, HR [95% confidence interval, CI] = 0.64 [0.47-0.87], p = .005) and AF recurrence (adjusted HR [95% CI] = 0.70 [0.57-0.88], p = .002). Associations remained similar after stratified by AF types. Compared to nonablation group (n = 413), DAT ≤ 1year patients tended to show lower cardiovascular risk (adjusted HR [95% CI] = 0.78 [0.58-1.05], p = .099) and lower risk of recurrent AF (adjusted HR [95% CI] = 0.46 [0.38-0.55], p < .001).

CONCLUSIONS

A shorter DAT was associated with a lower risk of cardiovascular events and recurrent AF for early-onset AF patients.

Sacubitril/valsartan attenuates atrial conduction disturbance and electrophysiological heterogeneity with ameliorating fibrosis in mice

Background

Sacubitril/valsartan (SacVal) has been shown to improve the prognosis of heart failure; however, whether SacVal reduces the occurrence of atrial fibrillation (AF) in heart failure has not yet been elucidated. In this study, we aimed to determine whether SacVal is effective in reducing the occurrence of AF in heart failure and identify the underlying mechanism of its electrophysiological effect in mice.

Methods

Adult male mice underwent transverse aortic constriction, followed by SacVal, valsartan, or vehicle treatment for two weeks. Electrophysiological study (EPS) and optical mapping were performed to assess the susceptibility to AF and the atrial conduction properties, and fibrosis was investigated using heart tissue and isolated cardiac fibroblasts (CFs).

Results

EPS analysis revealed that AF was significantly less inducible in SacVal-treated mice than in vehicle-treated mice. Optical mapping of the atrium showed that SacVal-treated and valsartan-treated mice restored the prolonged action potential duration (APD); however, only SacVal-treated mice showed the restoration of decreased conduction velocity (CV) compared to vehicle-treated mice. In addition, the electrophysiological distribution analysis demonstrated that heterogeneous electrophysiological properties were rate-dependent and increased heterogeneity was closely related to the susceptibility to AF. SacVal attenuated the increased heterogeneity of CV at short pacing cycle length in atria, whereas Val could not. Histological and molecular evaluation showed that SacVal exerted the anti-fibrotic effect on the atria. An in vitro study of CFs treated with natriuretic peptides and LBQ657, the metabolite and active form of sacubitril, revealed that C-type natriuretic peptide (CNP) combined with LBQ657 had an additional anti-fibrotic effect on CFs.

Conclusions

Our results demonstrated that SacVal can improve the conduction disturbance and heterogeneity through the attenuation of fibrosis in murine atria and reduce the susceptibility of AF in heart failure with pressure overload, which might be attributed to the enhanced function of CNP.

Small molecules as modulators of the proteostasis machinery: Implication in cardiovascular diseases

With the escalating prevalence of cardiovascular diseases, the substantial socioeconomic burden on healthcare systems is intensifying. Accumulating empirical evidence underscores the pivotal role of the proteostasis network in regulating cardiac homeostasis and function. Disruptions in proteostasis may contribute to the loss of protein function or the acquisition of toxic functions, which are intricately linked to the development of cardiovascular ailments such as atrial fibrillation, heart failure, atherosclerosis, and cardiac aging. It is widely acknowledged that the proteostasis network encompasses molecular chaperones, autophagy, and the ubiquitin proteasome system (UPS). Consequently, the proteostasis network emerges as an appealing target for therapeutic interventions in cardiovascular diseases. Numerous small molecules, acting as modulators of the proteostasis machinery, have exhibited therapeutic efficacy in managing cardiovascular diseases. This review centers on elucidating the role of the proteostasis network in various cardiovascular diseases and explores the potential of small molecules as therapeutic agents.