Atrial Remodeling Research Articles

Integrating single-cell sequencing and genetic lineage tracing reveals endothelial plasticity during atrial remodeling

Abstract Background Atrial fibrillation (AF), as the most burdensome cardiac arrhythmia, could lead to the significant mortality and morbidity. Atrial fibrosis is a well-recognized pathophysiological factor of the development and progression of AF, which also hampers its treatment. However, the underlying mechanisms of this intricate process remain largely unknown. Purpose This study sought to reveal the cellular composition of AF substrate and investigate the vital contributors to atrial structural remodeling. Methods Left atrial appendages from three patients with AF undergoing surgical ablation and three individuals with sinus rhythm undergoing heart transplantation were subjected to 10X single-cell RNA sequencing (scRNA-seq). Another five public scRNA-seq or snRNA-seq datasets of potentially remodeled right or left appendages were retrieved across three publications. The vital contributors of atrial structural remodeling and their characteristics were identified by intercellular communication analysis and trajectory inference. Transverse aortic constriction (TAC) was used to induce atrial remodeling in Cdh5-CreERT2;RFP mice, followed by scRNA-seq of endothelial cells (ECs). Human primary atrial ECs and fibroblasts were isolated for cell-cell interaction experiments. ECs-specific mouse models of Transforming growth factor beta 1 (TGFB1) (knockout and overexpression) were generated. Electrophysiological and histology analyses were performed to determine the consequences of ECs-derived TGFB1 gain and loss of function in the atrium. Results The comprehensive analysis of different scRNA-seq datasets revealed that ECs played an important regulatory role in the homeostasis of atrial substrate and displayed remarkable mesenchymal activation during atrial remodeling, which was further confirmed by TAC mice. Immunofluorescence staining and high-content screening suggested that the complete transition from ECs to mesenchymal cells slightly contributed to atrial remodeling. However, TGFB1 secreted from mesenchymal activated ECs significantly promoted activation, proliferation, and collagen secretion of fibroblasts. We discovered that overexpression of TGFB1 in ECs of mice significantly increased atrial fibrosis, and thus prolonging AF duration. Besides, knockout of TGFB1 in ECs of mice underwent TAC significantly attenuated the atrial fibrosis and decreased the rate of AF. Conclusion Our work demonstrates that mesenchymal ECs-derived Tgfb1 plays an important role in atrial remodeling by regulating the fibroblast function. EC-specific interventions were suggested to facilitate the development of novel strategies for mitigating AF substrate remodeling.

BA6b9, a novel sk4 K + channel blocker, attenuates atrial fibrillation substrate in rats with reduced ejection fraction

Abstract Background 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 novel druggable targets for efforts to treat AF. Methods and Findings 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 post-myocardial 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. Interpretation 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.

Effect of selective renal denervation guided by renal nerve stimulation on atrial remodeling

Abstract Background The renal nerves play a crucial role in regulating blood pressure (BP), and the parasympathetic nervous has been confirmed as one of the components of the renal nerves, with close connections to the central solitary nucleus. Renal nerve stimulation (RNS) can activate not only the sympathetic nerves, leading to an elevation in BP, but also the parasympathetic nerves, resulting in a reduction in BP. Multiple clinical studies have demonstrated that compared to pulmonary vein isolation (PVI), renal denervation (RDN) combined with PVI significantly increased the likelihood of freedom from atrial fibrillation, but its mechanism remains unclear. Purpose Exploring the effects of renal sympathetic denervation and renal parasympathetic denervation on atrial neural remodeling and structural remodeling from a histological perspective of atrial myocardium. Methods 24 adult healthy Kunming dogs were randomly divided into three groups: (1) RNS-guided reduced BP response sites ablation (RRA group, n=8), (2) RNS-guided elevated BP response sites ablation (ERA group, n=8), and (3) RNS only, no ablation (RSC group, n=8). Left atrial samples were obtained after a 4-week follow-up period. Results Compared to the RSC group, the ERA group showed a significant decrease in tyrosine hydroxylase (TH), while the RRA group showed a significant decrease in choline acetyltransferase (CHAT) and muscarinic acetylcholine receptor 2 (CM2) (Fig. 1A-1C). Histological results indicated that compared to the RSC group, the ERA group exhibited orderly arrangement of myocardial cells, with a significant reduction in the degree of mitochondrial swelling and a decrease in average myocardial cell area. In contrast, the RRA group showed disordered arrangement of myocardial cells, with some myofibril dissolution, noticeable swelling of cell nuclei and mitochondria, and an increase in average myocardial cell area (Fig. 1D). Further evaluation of left atrial fibrosis degree revealed that compared to the RSC group, the ERA group showed a significant decrease in Collagen I, with a reduction in interstitial fibrosis degree, while the RRA group showed a significant increase in Collagen I expression, with an increase in myocardial interstitial fibrosis degree (Fig.2). Conclusion Renal sympathetic denervation can reduce atrial sympathetic nerve, improve atrial macrostructure, ultrastructure, and fibrosis levels, which may be one of the reasons why RDN combined with PVI is more effective in maintaining sinus rhythm compared to PVI. Renal parasympathetic denervation can decrease atrial parasympathetic nerve, leading to deterioration of atrial tissue structure and exacerbation of fibrosis. This emphasizes the importance of electrical stimulation guidance during the RDN procedure to avoid "side effects" caused by renal parasympathetic nerves ablation.Figure 1Figure 2

Ablation strategy for patients with atrial fibrillation and heart failure - a Danish nationwide cohort study

Abstract Introduction Atrial fibrillation (AF) patients with heart failure (HF) face increased risks of AF recurrence and HF admission. Catheter ablation (CA) is a recognized treatment option. Due to observed atrial remodelling and fibrosis associated with ventricular remodelling in HF patients, it could be suggested that a more comprehensive ablation strategy should be applied for these patients. Purpose To examine the risk of AF recurrence and HF admission by ablation strategy for patients with AF and HF. Method This nationwide cohort study was conducted using real-life data from Danish healthcare registries. All patients above 18 years of age, with a diagnosis of AF and HF that underwent first-time CA from January 1st 2010 to December 31st 2018, were identified and included at the date of ablation. Exposure of interest was ablation strategy - pulmonary vein isolation (PVI) or additional ablation to PVI (PVI plus). PVI plus was defined as either roofline, mitral linear ablation, posterior wall isolation, complex fractionated atrial electrograms or ganglionated plexi ablation. Primary endpoint was HF admission and AF recurrence after a 3-months blanking period. AF recurrence was defined by a composite endpoint of first-reached endpoint of either use of antiarrhythmic drugs, AF admission, electrical cardioversions, or AF re-ablation. The relative rates of recurrent AF and HF admission by ablation strategy (PVI or PVI plus) were examined by Cox proportional models using PVI as reference. The analyses were adjusted for clinically important baseline characteristics including age, sex, AF type (paroxysmal or persistent), diagnosis-to-ablation time, procedural year, body mass index, size of left atrium, as well as co-morbidities such as ischemic heart disease, chronic obstructive pulmonary disease, chronic kidney disease, hypertension, and diabetes. Results The study cohort consisted of 1,270 patients diagnosed with AF and HF undergoing first-time CA, of which 1,119 (88%) received PVI and 151 (12%) received PVI plus. 80% where males in both groups. Median age was 62 for the PVI group and 64 for the PVI plus group. Severely enlarged left atrium, ischemic heart disease and use of amiodarone were more prevalent in the PVI plus group compared to the PVI group (Table 1). The relative risk of recurrent AF showed a hazard ratio of 1.02 (95% CI: 0.77-1.37) for the PVI plus group compared to the PVI group, and for HF admission the hazard ratio was 0.95 (95% CI: 0.55-1.65) for the PVI plus group compared to the PVI group (Figure 1). Conclusion No significant differences in AF recurrence and HF admission were observed between PVI and PVI plus strategy in AF and HF patients in this observational study. With a diagnosis-to-ablation time exceeding 3 years, it could be argued that advanced atrial remodelling may diminish the impact of reverse atrial remodelling after catheter ablation, irrespective of the ablation strategy employed.Table 1Figure 1

Prognostic impact of left atrial reverse remodeling in patients with ADHF-HFpEF regardless of atrial fibrillation -PURSUIT-HFpEF Registry-

Abstract Background Left atrial (LA) dilatation is associated with increased mortality in patients with cardiovascular disease including heart failure (HF) and LA reverse remodeling (LARR) was reported to be associated with favorable outcomes in patients with HF. However, it remains to be clarified whether LARR could have prognostic value in patients with HF with preserved ejection fraction (HFpEF). Purpose The purpose of this study is to elucidate whether LARR is associated with clinical outcome in patients with HFpEF in relation to the presence of atrial fibrillation (AF). Methods We prospectively studied 492 patients with acute decompensated heart failure with preserved ejection fraction (ADHF-HFpEF) without the poor outcome during the first year postdischarge. Echocardiography was performed just before discharge and at 1 year after discharge. LARR was defined as the reduction of 15% or more in left atrial end-systolic volume (LAV). The primary outcome was rehospitalization for worsening heart failure. Results All study patients were divided into 2 groups according to the presence of AF at discharge (AF group, n=182 and non-AF group, n=310). During a mean follow-up period of 1.4±1.2 years, 78 patients were rehospitalized for worsening heart failure (37 patients in AF group and 41 in non-AF group). ΔLAV, the degree of reduction in LAV during the first year postdischarge, was significantly independently associated with primary outcome after multivariable adjustment both in AF group (p=0.033, HR 0.992 [0.984-0.999]) and non-AF group (p=0.021, HR 0.986 [0.974-0.998]). Kaplan-Meier analysis revealed that patients with LARR had significantly lower risk for primary outcome than those without LARR not only in the whole study patients (8% vs 20%, p=0.001) but also both in AF group (9% vs 24% p=0.013) and in non-AF group (8% vs 16% p=0.043). Among clinical characteristics during the index hospitalization, the presence of AF and prior HF hospitalization were significantly independently associated with LARR at multivariate Cox logistic regression analysis (p=0.006, OR 0.554 [0.364-0.843] and p=0.007, OR 0.491 [0.292-0.826], respectively). Conclusion(s) The left atrial reverse remodeling could have the prognostic impact in patients with ADHF-HFpEF regardless of the presence of atrial fibrillation.Kaplan-Meier curves in AF and non-AF

Proteomic biomarkers and biological mechanisms associated with atrial fibrillation in heart failure patients

Abstract Background Atrial fibrillation (AF) and heart failure (HF) are intertwined conditions with high mortality rates and large impact on quality of life, and their coexistence is increasingly prevalent. Both conditions influence each other’s development and progression, and share many risk-factors—such as hypertension, obesity, diabetes mellitus and ischaemic heart disease. Moreover, their combined presence further increases the risk of hospitalization and mortality. The biological mechanisms at play in HF patients with AF may therefore differ from those in HF patients without AF. Purpose We aimed to describe the differences in pathophysiological pathways in HF patients with versus without AF, by identifying biomarkers associated with AF from a panel of 4210 circulating proteins and subsequently examining biological mechanisms related to these biomarkers. Methods We examined 377 ambulant HF patients with reduced ejection fraction from a longitudinal cohort study. We measured 4210 circulating proteins in baseline blood samples using an aptamer-based multiplex proteomic approach. Associations between AF (known AF history or AF on the baseline ECG) and the proteins were assessed using linear regression models adjusted for age, sex, kidney function and duration of HF at baseline. Associations of proteins significantly related to AF, with biological processes, were assessed using network-based clustering and subsequent enrichment analysis. Results The median [25th, 75th percentile] age was 64 [55, 72], 73% [274/377] were male, 28% [104/375] had NYHA-class III or IV, and 37% [139/377] had AF (either AF history: 36% [137/377] or AF on baseline ECG: 8% [30/374]). We found 71 proteins significantly associated with AF (FDR<0.05), including well-studied (e.g. troponin T, IGFBP7, MFAP4, BMP10, angiopoietin 2) and lesser studied (e.g. olfactomedin−like protein 3, keratocan, basigin) proteins in the AF domain. Our pathway analysis revealed clusters of proteins related to various underlying mechanisms, such as axon guidance, elastic fibre assembly, macrophage derived foam cell differentiation, ether lipid metabolism and amyloid-beta binding. Overviews of the significantly associated proteins and related biological mechanisms are provided in Figures 1 and 2. Conclusion HF patients with AF have distinct proteomic profiles and these differences are related to various biological mechanisms, many of which can be associated with atrial remodelling. This study provides an overview of the biological mechanisms behind AF in HF, confirms prior findings regarding AF-related proteins, and could guide future research in novel treatment targets and HF-AF management.Figure 1:Proteins associated with AFFigure 2:Biological mechanisms

Impact of epicardial adipose tissue and atrial functional impairment in patients with severe aortic stenosis undergoing transcatheter aortic valve replacement

Abstract Background Recent studies outlined the additional prognostic value of atrial function in patients with severe aortic stenosis (AS) undergoing transcatheter aortic valve replacement (TAVR). At the same time, increased epicardial adipose tissue (EAT) volumes have proven impact on atrial functional impairment in cardiovascular disease by nurturing adverse atrial remodelling. Purpose To explore the impact of increased EAT volumes as a potential pathomechanistic factor of atrial functional impairment in patients with severe AS undergoing TAVR. Methods 146 patients with severe AS underwent cardiac magnetic resonance (CMR) within 48h prior to TAVR between January 2017 and June 2021. Image analyses included myocardial volume quantification as well as CMR-feature-tracking derived strain. EAT volumes were manually delineated on short axis stacks in end-diastolic cardiac phases and indexed to body surface area. Functional and morphological parameters were compared between patients with high and low EAT volumes. Associations between morphological and functional parameters and EAT were tested using a multivariable linear regression model including patient specific parameters. Results After dichotomization at the median of 46.5ml/m2 total EAT volume, patients were assigned to high- and low-EAT groups accordingly. There was comparable age and body mass index and similar rates of co-morbidities such as hypertension, diabetes and atrial fibrillation in both groups. We observed a higher number of male patients in the high-EAT group (36 [53%] vs. 50 [72%], p=0.018). Regarding left and right ventricular dimensions and function, no differences could be shown. Left atrial (LA) end-systolic volumes were significantly higher in the high-EAT group (29.4ml/ml² [19.7-39.4] vs. 40.9ml/ml² [30.2-59.3], p=0.008), while there were no significant differences in end-diastolic volumes. Furthermore, LA reservoir strain was significantly lower in the high-EAT group compared to the low-EAT group (18.0% [11.7-21.0] vs. 11.8% [7.7-16.4], p=0.008) and was independently associated with higher EAT volumes (p=0.018) irrespective of cardiovascular risk factors and left ventricular (LV) systolic function in a multivariable regression model. Conclusion In patients with severe AS undergoing TAVR, increased EAT volumes are associated with both, morphological and functional changes of the atria. As impaired atrial function was previously shown to be an important predictor of mortality in TAVR patients, those results potentially render EAT as an additional pathomechanistic link between atrial remodelling and worse outcome in TAVR patients.

Left atrial remodeling and novel biomarkers in obese patients with heart failure with preserved ejection fraction compared to type-2-diabetics and obese controls: a cardiac magnetic resonance study

Abstract Background Elevated filling pressures and subsequent left atrial (LA) dilation are common findings in heart failure with preserved ejection fraction (HFpEF), reflecting a chronic state of the disease and holding prognostic value. HFpEF is thought to develop through a long-term pro-inflammatory state triggered by comorbidities, such as obesity and type 2 diabetes mellitus (T2DM). Emerging biomarkers have shown associations with structural remodeling, but also increased myocardial stiffness. Purpose To elucidate the relationship between LA volume and function, and prognostic biomarkers (NT-proBNP, BNP-32, IL1R1, Galectin-3, and Pentraxin-3) in an obese cohort with T2DM or HFpEF and T2DM, versus healthy obese controls. Methods We conducted a prospective cohort study of 35 obese participants, divided into three groups: T2DM (n=16), HFpEF with T2DM (NYHA II-III, n=13), and healthy obese controls (n=6). Each subject underwent comprehensive CMR at a 3T scanner to assess LA strain and volume. Atrial strain was assessed on 2- and 4-chamber view cine images by experienced CMR investigators using dedicated software. Routine labs and serum levels of biomarkers were measured. If labs or images were repeated, the average was calculated. Statistical significance was determined through ANOVA and student’s t-test for group comparisons and Pearson correlation for associations between LA parameters and biomarker levels. Results Cohorts were evenly matched in terms of demographics, vital signs, and ventricular volumes and functions, as depicted in Table 1. Only one patient in the HFpEF subgroup reported history of atrial fibrillation. Both minimum and maximum LA volumes were significantly elevated in the HFpEF group compared to the T2DM and control groups (p < 0.018). LA strain (conduit, reservoir, and booster) was notably compromised in the HFpEF cohort, contrasting with the obese T2DM group where LA strain values did not differ significantly from those observed in obese controls (Figure 1). Biomarker analysis revealed a marked increase of NT-proBNP, BNP-32, Galectin-3, and Pentraxin-3 in the HFpEF cohort. In the HFpEF cohort, IL1R1 was the only biomarker that was strongly associated with higher left ventricular enddiastolic (r=0.69, p=0.003) and endsystolic volumes (r=0.75, p=0.009). Moreover, IL1R1 was the only biomarker associated with atrial functional changes (booster strain, r=-0.57, p=0.043) in the HFpEF patients. Our findings indicate that ILR1 plays a crucial role in the cardiometabolic (obesity-T2DM) HFpEF phenotype, with its activation leading to advanced cardiac remodeling. Conclusion Obese HFpEF patients with T2DM showed severely altered left atrial morphology and function compared to those that are only obese or obese with T2DM. Moreover, our findings revealed that atrial remodeling in this population is driven by pro-fibrotic inflammatory pathways.Characteristics of the study cohortLeft atrial strain analysis

How different types of cardiomyopathy with hypertrophic phenotype affect left atrial remodeling and function

Abstract Background Left atrial (LA) dysfunction is a common feature in hypertrophic cardiomyopathies. How the underlying etiology and pathophysiology of different cardiomyopathies affects LA remodeling and function remains unexplored. Purpose The aim of our study is to investigate the influence of various cardiomyopathies with hypertrophic phenotype on LA remodeling and function. Methods Patients with left ventricular (LV) hypertrophic phenotype who underwent cardiac magnetic resonance (CMR) were included. A group of patients with a normal CMR was included as a control group. CMR acquisitions used for clinical indication of heart failure diagnosis and etiology were retrospectively analyzed to obtain LA reservoir, conduit, and booster strain, left atrioventricular coupling index (LACI) and LA sphericity. Differences between groups were assessed. To investigate the independent clinical associates of LA reservoir, conduit and booster strain, multivariable linear regression analyses were performed. Results A total of 375 individuals were analyzed including 321 patients diagnosed with LV hypertrophy and 54 patients with a normal CMR. Of the 321 patients with LV hypertrophy, 148 were diagnosed with hypertrophic cardiomyopathy (HCM), 35 with cardiac amyloidosis (CA), 41 with hypertensive cardiomyopathy (HTN) and 97 with severe asymptomatic aortic stenosis (AS). CMR LA characteristic and strain analysis results are summarized in Figure 1. The indexed LA end-systolic volume (iLAVmax), indexed LA end-diastolic volume (iLAVmin) and LA sphericity were larger in patients with CA when compared to other groups (all p<0.05). CA patients displayed more left atrioventricular uncoupling (lower LACI) when compared to individuals with HCM, HTN, AS, and controls (all p<0.001), while no significant differences were observed across other groups. CA patients exhibited lower LA reservoir and booster strains compared to the other groups (all p<0.05), whereas no significant differences were observed across other hypertrophic phenotype diseases. Age, iLAVMax and LACI were independently associated with all the three LA strain components (Figure 2, all p<0.05). Conclusions LA remodeling and function are affected differently across the various etiologies of LV hypertrophy. CA patients exhibit more pronounced atrial involvement, whereas those with HCM, asymptomatic AS, and HTN display similar patterns of atrial dysfunction and remodeling. Additionally, CMR-derived iLAVmax and LACI are independently correlated with LA function.

Impact of adjacent thoracic structures in negative left atrial remodelling in atrial fibrillation

Abstract Background Previous work has suggested that compression from external structures can promote negative atrial remodelling in atrial fibrillation (AF) [1]. This is mechanistically plausible, with many recognised risk factors in developing AF (age, hypertension, obesity, obstructive sleep apnoea, etc.) related through activation of the autonomic nervous system with an associated increase in atrial pressure and chronic elevation in wall stress [2,3]. Such negative remodelling contributes to the existence of arrhythmogenic atrial substrate [4]. This is highly significant when we consider catheter ablation of extrapulmonary vein targets. Purpose This study aims to investigate the relationship between abnormal conduction patterns indicative of potential AF drivers and their proximity to structures adjacent to the left atrium (LA). Methods Eight patients with paroxysmal or persistent AF, scheduled for an elective catheter ablation procedure using a charge density mapping (CDM) system [5] underwent pre-procedural cardiac MRI. 3D surface mesh reconstructions of individuals’ LA and adjacent structures (ascending aorta [AoA], descending aorta [AoD], and spine) were produced from 2D MRI slices using a proprietary graphical interface tool developed in MATLAB (Figure 1A & B) [6]. MRI derived LA geometries were registered with their CDM counterparts by the Iterative Closest Point algorithm (Figure 1C); this enabled integration of MRI LA geometries into the CDM system. Subsequently, non-contact intrachamber voltage measurements from individuals’ procedures were used to derive cardiac activation directly onto MRI LA geometries. Abnormal conduction patterns representing possible AF drivers (focal firing, rotational propagation, and pivoting propagation) [5] were quantified as occurrences per second at each vertex of MRI LA geometries (Figure 1D). These conduction patterns could then be visualised and assessed in the context of adjacent structures (Figure 1E), with the Euclidean distance between each vertex of the MRI LA geometries and the closest point to their adjacent structures being calculated. Results Mean age was 65±9 years; 4 patients (50%) were male; AF was paroxysmal in 3 (37%) and persistent in 5 (63%); median time since AF diagnosis was 1 (1-3.8) years; ablation type was de novo in 5 (63%) and retreatment in 3 (38%). Frequencies of pivoting and rotational propagation were notably higher in regions of the LA closer to the AoA, and lower near the AoD and spine (Figure 2A & B). Conversely, focal firing showed a less prominent trend, being more frequent in LA regions nearer the AoD and distant from the AoA (Figure 2C). Conclusions Compression from the ascending aorta may promote anterior LA remodelling in AF, leading to increased pivoting and rotational AF drivers. Clinically, this suggests a potential target for ablation therapy with an anterior seatbelt line connecting the right superior pulmonary vein to the mitral annulus.

Dysfunctional atrial fibroblast processing of filamin A in atrial fibrillation

Abstract Background/Introduction Atrial fibrillation (AF), the most common sustained cardiac arrhythmia, is associated with atrial structural remodelling, hallmarked by fibrosis. Atrial fibrosis is instigated by atrial fibroblasts (AFBs). It was previously uncovered the hormone calcitonin (CT) is produced in the heart and, via binding to the CT-receptors (CTR), inhibits atrial fibrogenesis and fibroblast profibrotic activity. [1] In AF, abnormally increased CTR internalisation causes loss of physiological surface CTR and prevents fibroblast activation by CT. The molecular mechanisms of this phenomenon in ACFs are unknown. Aim To explore the role of filamin A (FLNa), an actin cross-linking protein that was previously shown to interact with CTR, [2] in the regulation of CTR trafficking. Methods AFBs were enzymatically isolated from left atrial appendage biopsies collected from 30 patients in persistent AF or normal sinus rhythm (SR, controls) undergoing elective heart surgery. Immunostaining assessed the localisation of CTR and its overlap with the nucleus (stained with DAPI) and FLNa in AFBs. Co-localisation was quantified by the JACoP BIOP plugin for ImageJ. Target mRNA expression was assessed by RT-qPCR and protein levels by immunoblot. Immunoprecipitation (IP) then immunoblot (IB) validated protein-protein interactions. Calpain activity was assessed with a fluorescence-based assay. The effects of calpains on FLNa proteolytic processing was examined with calpain inhibitor calpeptin (10nM–100nM vs DMSO loading control). Results Immunostaining revealed aberrant, intracellular localisation of CTR in AF-AFBs (A) with increased nuclear localisation (p=0.03) and reduced co-localisation with FLNa (p=0.03). FLNa gene expression showed a trend towards reduction in AF (by 36%, p=0.06; B). Meanwhile, although full-length FLNa protein was unaltered in AF, there was a striking 67% reduction (p=0.02) in the expression of FLNa’s c-terminal fragment (FLNaCT), which contains the CTR binding domain (C). Co-immunoprecipitation confirmed a physical interaction between CTR and FLNaCT (D) in both SR and AF AFBs. FLNaCT is typically generated when FLNa is cleaved by the protease calpain 1, whose protein (F) but not mRNA (E), was significantly downregulated (71%, p<0.001) in AF. Puzzlingly, a ~70% loss of calpain 1 protein was associated with unchanged calpain activity (G) and FLNaCT levels in AFBs treated with calpain inhibitor calpeptin (H). Conclusions Persistent AF is associated with an aberrant CTR localisation and FLNa proteolytic processing, not attributable to altered calpain activity. Further characterisation of the molecular determinants of the altered CTR localisation may uncover novel and potentially druggable facets of structural remodelling in AF.

Duration of sinus rhythm after direct current cardioversion does not predict recurrence of atrial fibrillation after subsequent catheter ablation: a multicentre study

Abstract Background Catheter ablation (CA) for persistent atrial fibrillation (PsAF) is associated with high rates of AF recurrence. DC cardioversion (DCCV) is often performed before CA, with wide variation in duration of maintenance of sinus rhythm (SR) post-DCCV. Factors associated with short duration of SR after DCCV, such as raised body mass index, prior duration of AF, prolonged p wave duration on the 12-lead ECG, and indexed left atrial volume, are either associated with or indicative of atrial electrical and structural remodelling, suggesting that shorter duration of SR after DCCV reflects a more advanced substrate for AF, which could in turn also influence the likelihood of success after CA. Objective To determine if post-DCCV SR duration is associated with AF recurrence after subsequent CA. Methods We performed a multicentre retrospective study of patients undergoing first-time CA for PsAF between 2015-2018 with prior DCCV. SR duration after the last DCCV prior to CA was recorded. The primary outcome was the first recurrence of atrial arrhythmia post-CA (after a 90-day post-CA blanking period). We also performed a pre-specified sensitivity analysis for amiodarone use at DCCV, by performing repeat analysis after excluding all such patients across the three groups. Results A total of 331 patients were identified across five centres and categorised by post-DCCV SR duration: <7 days (group 1); 7-31 days (group 2); >31 days (group 3; Table 1). Over median post-CA follow-up of 591 days, 207 patients (62.5%) met the primary outcome. There was no significant between-group difference in the time to primary outcome (log rank p=0.82; Figure 1). There were significantly more blanking period arrhythmias in groups 1 and 2 than group 3 after post hoc Bonferroni correction (pairwise p=0.001, 0.002 respectively; Table 1). After exclusion of patients on amiodarone at time of DCCV, there remained no significant between-group difference in the time to primary outcome (log rank p=0.85). Conclusion Shorter duration of SR post-DCCV is associated with blanking period arrhythmia after CA, but crucially does not predict long-term AF recurrence. Early AF recurrence after DCCV should not influence decisions on CA suitability or be used to predict long-term CA success.

Effects of cardiac resynchronization therapy and physiologicaL pacing on left atrioventricular coupling index: the REPHYL-LACI study

Abstract Introduction Cardiac dyssynchrony and right ventricular pacing are associated with left atrial (LA) remodeling and atrioventricular uncoupling. Cardiac resynchronization therapy -CRT and conduction system pacing –CSP are important therapeutic options. Left atrioventricular coupling index (LACI) is a novel imaging parameter useful to describe the relationship between LA and left ventricle (LV). It could be measured as the ratio between LA end-diastolic volume (EDV) and the LV EDV or, alternatively, as the LA volume indexed for body surface area (LAVi) divided for a’ measured by tissue Doppler imaging (TDI) at medial mitral annulus level. Higher values indicate greater impairment of atrioventricular coupling. However, LACI has not been investigated in patients treated with CRT or CSP, and there is no comparison data about the two different measurement methodologies with echocardiography. Purpose To study the effects of CRT/CSP on LACI. Methods We retrospectively collected clinical, ECG and echocardiographic data of patients treated with standard CRT or CSP. Changes between baseline and follow-up (i.e. before and after CRT/CSP) were tested for significance. Baseline features were compared with these of a control group of patients without established major cardiovascular diseases. Results We enrolled fifty-six patients (median age at first echo 78[72.5-82]years; males 70%) and 56 controls (median age 77[72.5-83]years, p=0.974; males 57%, p= 0.170). Main clinical/instrumental data are shown in Table 1 and 2. In patients treated with CRT/CSP baseline LACIv (LAVid/LV EDV) was significantly lower than in controls (31[21-44]%vs34[29-48]%, p=0.040), despite higher LAVi and LV volumes in the first group (p<0.0001 for both). Conversely, LACId (LAVi/TDI-a’) was significantly higher in the CRT/CSP (4.48[2.81-8.28]vs2.89[2.36-3.67]mlxsecond/cm-1, p<0.0001). After a median follow-up of 515[282-1326]days, patients treated with CRT/CSP showed a significant increase of both LACIv (40[29-50]%, p=0.004) and LACId (4.95[3.77-9.89], p<0.0001). This worsening of atrioventricular coupling was accompanied by a trending LA dilatation with significant reduction of its reservoir function compared to baseline (expansion index 0.58[0.38-1.30]vs0.43[0.29-0.58], p=0.0002), despite a tendency toward stability or improvement of LV size and systolic/diastolic parameters. Conclusions In patients treated with CRT/CSP there is a worsening of LACI over time. We can speculate that the detrimental effects of artificial pacing might not be adequately counterbalanced by CRT/CSP, or that LV and LA pathology follow alternative trajectories with different responses to treatments. Moreover, the measurement of LACId should be probably avoided in patients with conduction disorders or paced. Further larger case-control studies are needed to clarify the usefulness of LACI as a valid parameter to assess atrioventricular coupling and its changes over time in patients treated with CRT/CSP.

Comparison of pulsed field ablation versus cryoballon and radiofrequency ablation for pulmonary vein isolation in atrial fibrillation patients with heart failure

Abstract Background Pulmonary vein isolation (PVI) is the gold standard for atrial fibrillation (AF) ablation and can be achieved by a variety of technical methodes. While thermal ablation modalities (TA), such as cryoballon (CB) and radiofrequency ablation (RF) have been established as the standard approaches, PFA has been introduced as a nvel non-thermal modality showing comparable safety and procedural efficiency. Despite the high incidence of AF in heart failure (HF) patients, data comparing outcomes of HF patients undergoing PVI by either PFA or thermal ablation (RFA/CB) are limited. Purpose This study’s aim was to compare the efficacy and safety of PFA for AF ablation versus CB/RFA in HF patients. Methods Consecutive HF patients with preserved (HFpEF), mildly reduced (HFmrEF) and reduced (HFrEF) ejection fraction undergoing PVI for AF by either PFA or CB/RFA at our institution were included. The primary end-point was time to death or recurrence of AF. Secondary end-points were periprocedural complications and clinical and echocardiographic parameters. Results We included 140 HF patients who underwent PVI either by PFA (PFA group, 76 patients) or thermal ablation approaches (TA group, 64 patients). Our patients had a mean age of 69 years and were predominantly male (62%). There was no significant difference in the baseline characteristics and in the type of AF between both groups (42% with ParAF, 45% with PersAF) and 13% LSPersAF). The distribution of heart failure types was similar between both groups: HFpEF (PFA: 71%, TA: 75%), HFmrEF (PFA: 21%, TA: 20%) and HFrEF (PFA: 8 %, TA: 5%). After the 365-days follow-up period we observed no significant difference for the primary end-point between both groups (HR: 0.79, 95% CI 0.35-1.78; p=0.575). In total 58% of the PFA patients and 59% of the TA group were still free from AF. While symptom improvement was documented in both groups, patients in the PFA group showed significant improvement of left atrial volume index (p = 0.014), NT-pro BNP levels (p = 0.046), and left ventricular ejection fraction (LVEF) (p = 0.005). Conclusion In this study, PFA and thermal ablation modalities showed comparable results in terms of safety and procedural efficiency in patients with heart failure. Since previous studies have shown that HF patients with AF benefit from PVI using thermal ablation modalities, our results suggest that PFA might also be a promising ablation method in this vulnerable population, inducing left atrial reverse remodeling and thereby contributing to improvement of left ventricular systolic function.

Prognostic value of left atrial strain in patients with moderate to severe mitral stenosis

Abstract Background Mitral stenosis causes an inflow restriction during diastole and is characterized by an increase in left atrial (LA) pressure with reduced cardiac output. Pressure overload of the LA can lead to atrial fibrosis and remodeling, resulting in a loss of LA reservoir and compliance capacity that can lead to backward load on the pulmonary circulation. To date, there are limited studies evaluating the impact of LA strain on prognosis of mitral stenosis patients. Purpose The aim of this study was to assess the prognostic value of LA strain in patients with moderate to severe mitral stenosis using two-dimensional (2D) strain imaging. Methods This was a single-center retrospective study, 237 patients with moderate or severe mitral stenosis were enrolled from January 2010 to December 2022. Baseline clinical and echocardiographic parameters were collected, LA strain measurements with reference time point at end diastole for reservoir strain (LASr), conduit strain (LAScd) and contraction strain (LASct) were analyzed using TOMTEC software. The endpoint was a composite outcome of all-cause mortality, heart failure hospitalization and valve intervention (percutaneous transvenous mitral commissurotomy and surgical intervention). All the LA parameters were analyzed separately to avoid collinearity. Results A total of 237 patients were included in the study. The patients had a mean age was 66.56 ± 13.61 years-old and were predominantly female (67.9%) with median follow up duration is 4.54 years (IQR 1.44 – 6.44). Mean left ventricular ejection fraction (LVEF) was 56.86 ± 10.51%, mean left atrium volume index (LAVI) was 73.94 ± 55.46 ml/m2, mean for LASr, LAScd and LASct were 11.81 ± 8.89%, -6.19 ± 4.50%, and -5.58 ± 6.05% respectively. LASr with a cut-off < 15.8% was independently associated with the composite outcome of all-cause mortality, heart failure hospitalization and valve intervention on multivariable Cox regression analysis (HR 2.51, 95% CI 1.54 - 4.10, p < 0.001). LAScd, LASct and LA volume index did not demonstrate any significant association with the endpoint. Conclusion LASr was independently associated with all-cause mortality, heart failure hospitalization and valve intervention in patients with moderate to severe mitral stenosis.

Associations between biomarkers and P-wave indices in patients with heart failure

Abstract Background Atrial structural abnormalities linked to the risk of atrial fibrillation (AF), as indicated by P-wave indices on surface ECG, are associated with the fibrotic transformation of the atrial myocardium. To what extent incident AF can be predicted by ECG characteristics in patients with advanced atrial structural remodeling, such as patients with heart failure (HF), is less well studied. Purpose To evaluate the association between P-wave indices and biomarkers implicated in cardiac fibrosis, and incident AF in patients with HF. Methods Patients with new-onset or worsening of HF were prospectively recruited in a observational study (n=501) and followed-up for 5 years. Blood samples were collected for analysis using proximity extension assay that included a subset of biomarkers that were associated with fibrosis development (TIMP-2, MMP-2, MMP-3, MMP-9, ST-2, GDF-15, Gal-3). All ECGs ever recorded in the hospital catchment area were exported in digital format and processed using Glasgow algorithm for calculation of the P-wave indices (P-wave duration [PWD], P-wave terminal force in V1 [PTFV1] and P-wave axis [Paxis]) and rhythm identification. AF diagnosis was ascertained by manual ECG review. Only patients who did not have AF reported or ECG documented at enrolment were included in the analysis. Of those subjects, 121 patients also had biomarkers of fibrosis analyzed. Cox-regression analyses were used to assess biomarkers’ and p-wave indices’ associations with incident AF. Results After exclusion of patients with prevalent AF (n=317), 184 patients comprised the study group (mean age of 71 years, 33.2% women, 121 patients with biomarker data available). During follow-up, incident AF was observed in 39 patients. At enrolment, PWD>120 ms was observed in 38.7%, abnormal PTFV1>40 mm*ms in 24.5% and Paxis<0° in 5.4%. Among the seven biomarkers assessed, five demonstrated significant associations with incident AF in adjusted analyses: TIMP4 (HR 1.78; 95%CI 1.03-3.05; p=0.037); MMP2 (HR 1.97; 95%CI 1.03-3.80; p=0.042), MMP3 (HR 1.39; 95%CI 1.03-1.88; p=0.031); ST2 (HR 1.91; 95%CI 1.29-2.83; p=0.001) and GDF-15 (HR 2.56; 95%CI 1.50-4.35; p=0.001) (Figure 1). However, none of the tested P-wave variables (P-wave duration, P-wave terminal force, and P-wave axis) were associated to incident AF. Conclusions In this prospective long-term follow-up study of patients admitted for acute HF, biomarkers with proven associations to fibrosis were strongly associated with incident AF. P-wave indices used for prediction of AF in epidemiological cohorts appear to have limited value in patients with HF who have high prevalence of ECG atrial abnormalities at baseline.

Effects of mineralocorticoid receptor antagonists on new-onset or recurrent atrial fibrillation: a Bayesian and frequentist network meta-analysis of randomized trials

Abstract Aims Clinical and translational research suggests that mineralocorticoid receptor antagonists (MRAs) may prevent atrial fibrosis and electrical remodeling associated with atrial fibrillation (AF). This study aimed to consolidate existing evidence from randomized controlled trials (RCTs) evaluating the effect of MRAs on incident or recurrent AF. Methods Medline, Cochrane Library and Scopus were searched until February 12, 2024. Triple-independent study selection, data extraction and quality assessment were performed. Evidence was pooled using both pairwise and Bayesian and frequentist network meta-analyses. Results Twenty-three RCTs (13,358 participants) were identified. Based on the pairwise random effects meta-analysis, MRAs were associated with a significant reduction in AF events compared to placebo or usual care (risk ratio {RR}= 0.75; 95% confidence interval {CI}= [0.66, 0.87]; P< 0.001; I2= 3%). This protective effect was robust both for new-onset and recurrent AF episodes (subgroup p-value= 0.69), while the baseline HF status was not a significant effect modifier (subgroup p-value= 0.58). MRAs demonstrated a significantly higher reduction in AF events for patients with chronic renal disease compared to placebo (RR= 0.78; 95% CI= [0.62, 0.98]; P= 0.03; I2= 0%). The network meta-analyses revealed that only spironolactone was associated with a significant reduction in AF events (Bayesian RR= 0.76; 95% CI= [0.65, 0.89]; P< 0.001; level of evidence moderate; SUCRA 0.731), while eplerenone and finerenone showed a neutral effect. Conclusion MRAs confer a significant benefit in terms of reducing incident or recurrent AF episodes, irrespective of HF status. In this context, spironolactone may be preferable compared to eplerenone or finerenone.

Cocoa flavanols alleviate early diastolic dysfunction by decreasing left atrial volume in healthy elderly individuals

Abstract Background Enlargement of the left atrium (LA) predicts future cardiovascular events. Current guidelines recommend cocoa flavanol (CF) intake as it provides cardiovascular and metabolic benefits, although underlying mechanisms are not fully revealed. In this study, we hypothesized that CF intake reverses LA enlargement as a surrogate marker for diastolic dysfunction in elderly individuals without cardiovascular diseases. Methods and Results In a randomized, double-blinded trial, we investigated the effects of CF on systolic and diastolic heart function in healthy elderly individuals. Precise assessment of left-atrial and left-ventricular volume as well as strain rates, all together as emblems of early subclinical cardiac impairment, and markers of systolic function were measured by high-resolution cardiac magnetic resonance (CMR) imaging before and after CF intake. Sixty-three participants (59% male) aged ≥ 55 years received either 500 mg CF (n=30) or a placebo (n=33) twice daily for 30 days. CF counteracted subclinical cardiac dysfunction, evidenced by a reduction in maximal LA volume and LA volume index by 12.6±3.5% (p=0.0063 and p=0.0067) and LV end-diastolic volume (LVEDV) and LVEDV index by ~4.9±1.9% (p=0.049 and p=0.0413). CF intake did not influence strain, strain rate, and systolic function parameters, while the systolic blood pressure decreased by 7 mmHg [~4.7±1.9% (p=0.04)]. Conclusion We provide evidence that CF intake mitigates early changes of diastolic dysfunction and improves cardiovascular health by reversing left atrial and left ventricular remodeling. Cocoa flavanol consumption may prevent age-related cardiac changes in healthy elderly individuals and promote a health span free from cardiovascular diseases.

Risk of atrial fibrillation recurrence after new-onset transient episode during ST-elevation myocardial infarction

Abstract Background Atrial fibrillation (AF) often complicates ST-elevation myocardial infarction (STEMI) and is associated with major in-hospital complications and increased mortality. The data on AF recurrence after new-onset transient STEMI-associated AF is scarce, and electrocardiographic (ECG) predictors of AF recurrence are unknown. Purpose Our aim was to assess the risk of AF recurrence and to find out the predictors of AF recurrence after transient STEMI-associated AF. Methods STEMI patients admitted during 2007-2010 for primary percutaneous coronary interventions (PCI) were followed up until 2018. All ECGs ever recorded before, during or after STEMI (n=58907) were exported from regional database in digital format and processed using Glasgow algorithm. Clinical characteristics and mortality status were retrieved from the Swedish national registries. Information regarding AF was obtained from the national registries and the regional ECG database. STEMI-associated AF was defined as first-ever AF episode occurring between symptom onset and hospital discharge. Patients with pre-existing AF, AF after acute coronary artery bypass surgery and patients discharged with ongoing AF were excluded from analysis. P-wave indexes were assessed from the latest sinus rhythm ECG before discharge. The primary endpoint was the first documented AF episode after discharge. The secondary endpoints were total mortality and ischemic stroke. Cox regression analysis was adjusted for relevant clinical covariates. Results 1) 1956 patients who were discharged alive on sinus rhythm were included in the analysis (age 65±12, 70% males), 127(6.5%) of them had transient STEMI-associated AF. 2) Patients with STEMI-associated AF were more likely to develop AF during follow-up (n=74 [58.3%]) than patients without AF before or during STEMI (No AF) (n=56 [3.1%], HR=4.80 95%CI 3.93-5.97) (Figure 1). 3) None of the clinical and demographic characteristics was associated with AF recurrence. P-wave duration, P-terminal force in V1 and P-voltage in lead I were associated with AF recurrence, however only reduced P-wave voltage in lead I <93 µV (75th percentile) (HR=2.29 95% CI 1.21-4.35, p=0.011) remained independently associated with AF recurrence in adjusted analysis (Figure 2). 4) During follow-up, 134 patients had an ischemic stroke and 522 died. STEMI-associated AF was associated with higher long-term mortality risk comparing to No AF (HR=1.18 95%CI 1.02-1.36). The risk of stroke was not associated with STEMI-associated AF (HR=1.08 95%CI 0.79-1.49). In patients with STEMI-associated AF, occurrence of stroke did not differ between patients with and without AF recurrence (5[7%] vs 8 [15%] respectively, p=0.147). Conclusion STEMI-associated transient AF is associated with a 4.8-fold increased risk of AF after discharge, reaching 28% by 1 year after discharge. ECG-based P-wave indexes reflecting atrial remodeling can be used for the prediction of AF recurrence after discharge.

Serum exosomal long non-coding RNA H19 as a theragnostic target for atrial fibrillation

Abstract Background/Introduction Exosomes are membrane vesicles of 30- to 150-nm secreted by most cell types that can mediate intercellular communication by transmitting various forms of RNAs. Long non-coding RNAs (lncRNAs, ≥ 200 nucleotides length) have been reported to play important roles in the pathophysiological processes that promote the development and progression of many diseases. Interestingly, recent studies have shown that exosomal lncRNAs exhibit different expression profiles in various diseases and are being extensively studied in the medical field as an ideal target for the diagnosis and treatment. However, there is still little known about their role in atrial fibrillation (AF). Purpose The aim of this study was to identify a novel theragnostic target exosomal lncRNA for AF. Methods First, serum exosomes from controls and patients with persistent AF were isolated and characterized by transmission electron microscopy, nanoparticle tracking analysis, and western blot. Next, serum exosomal lncRNA expression profiles were explored using RNA-sequencing analysis. In addition, the expression levels of candidate exosomal lncRNAs were confirmed using qRT-PCR (n = 50 per group). Finally, AF-related pathophysiological mechanisms of exosomal lncRNA were investigated in angiotensin II (Ang II)-treated human induced pluripotent stem cell-derived atrial cardiomyocytes (iPSC-atrial CMs). Results After RNA-sequencing analysis, we identified 27 differentially expressed lncRNAs (i.e., 4 upregulated and 23 downregulated lncRNAs with a |fold change| ≥ 2 and p < 0.05) in serum exosomes from patients with persistent AF compared with the controls. In fact, qRT-PCR reveled that exosomal lncRNA H19 was consistently downregulated in the serum of patients with persistent AF compared with the controls (p < 0.01). In addition, exosomal lncRNA H19 exhibited significant diagnostic validity for AF. Notably, we confirmed that exosomal lncRNA H19 was involved in AF-related pathophysiological mechanisms. In Ang II-treated iPSC-atrial CMs, inhibition of lncRNA H19 significantly aggravated Ang II-induced increases in levels of hypertrophic markers (ANP, BNP and β-MHC), cell surface area and inflammation (p < 0.05). Mechanistically, we found that loss of lncRNA H19 weakens the inhibition of its direct target microRNAs, miR-141-3p and miR-200a-3p, leading to downregulation of their target PTEN, thereby promoting the atrial remodeling and the consequent AF. Conclusion In conclusion, serum-derived exosomal lncRNA H19 could serve as a potential target for the diagnosis and treatment of AF.