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Background/Objectives: The rate of recurrence after ablation for atrial fibrillation (AF) is considerable. Risk stratification for AF recurrence after ablation remains incompletely developed. Unsupervised clustering is a machine learning technique which might provide valuable insights in AF recurrence by identifying patient clusters using numerous clinical characteristics. We hypothesize that unsupervised clustering identifies patient clusters with different clinical phenotypes, including AF type and cardiovascular morbidities, and ablation outcomes. Methods: Baseline and procedural characteristics of 658 patients undergoing thoracoscopic ablation for advanced AF (persistent, with enlarged left atria, or with previous failed catheter ablation) between 2008 and 2021 were collected. Principal component analysis (PCA) was used as an unsupervised dimensionality reduction technique, followed by K-Means clustering for unsupervised data clustering. The silhouette score was used to determine the optimal number of clusters, resulting in the formation of three clusters. CHA2DS2-VASc score and AF recurrence were not included in the clustering, but were compared between clusters. Moreover, we compared the patients with and without previously established risk factors for AF recurrence for each cluster. Results: Unsupervised clustering resulted in three distinct clusters. Cluster I had a significantly lower rate of AF recurrence than Cluster II, which contained significantly more persistent AF patients than the other clusters. The CHA2DS2-VASc score in Cluster III was significantly higher than in the other clusters. In all clusters, but particularly in Cluster III, the recurrence risk was higher for persistent AF patients and female patients. In Cluster II, the recurrence risk was not influenced by an increased left atrial volume index, unlike other clusters. Conclusions: Using unsupervised clustering of clinical and procedural data, we identified three distinct advanced AF patient clusters with differences in AF type, CHA2DS2-VASc score, and AF recurrence. We found that established risk factors like BMI, AF type, and LAVI vary in importance across clusters.

The ability to record and analyse electrical behaviour across the heart using optical and electrode mapping has revolutionised cardiac research. However, wider uptake of these technologies is constrained by the lack of multi-functional and robustly characterised analysis and mapping software. We present ElectroMap, an adaptable, high-throughput, open-source software for processing, analysis and mapping of complex electrophysiology datasets from diverse experimental models and acquisition modalities. Key innovation is development of standalone module for quantification of conduction velocity, employing multiple methodologies, currently not widely available to researchers. ElectroMap has also been designed to support multiple methodologies for accurate calculation of activation, repolarisation, arrhythmia detection, calcium handling and beat-to-beat heterogeneity. ElectroMap implements automated signal segmentation, ensemble averaging and integrates optogenetic approaches. Here we employ ElectroMap for analysis, mapping and detection of pro-arrhythmic phenomena in silico, in cellulo, animal model and in vivo patient datasets. We anticipate that ElectroMap will accelerate innovative cardiac research and enhance the uptake, application and interpretation of mapping technologies leading to novel approaches for arrhythmia prevention.

Atrial fibrillation (AF) is the most common sustained arrhythmia and is associated with pronounced morbidity and mortality. Its prevalence, expected to further increase for the forthcoming years, and associated frequent hospitalizations turn AF into a major health problem. Structural and electrical atrial remodelling underlie the substrate for AF, but the exact mechanisms driving this remodelling remain incompletely understood. Recent studies have shown that microRNAs (miRNA), short non-coding RNAs that regulate gene expression, may be involved in the pathophysiology of AF. MiRNAs have been implicated in AF-induced ion channel remodelling and fibrosis. MiRNAs could therefore provide insight into AF pathophysiology or become novel targets for therapy with miRNA mimics or anti-miRNAs. Moreover, circulating miRNAs have been suggested as a new class of diagnostic and prognostic biomarkers of AF. However, the origin and function of miRNAs in tissue and plasma frequently remain unknown and studies investigating the role of miRNAs in AF vary in design and focus and even present contradicting results. Here, we provide a systematic review of the available clinical and functional studies investigating the tissue and plasma miRNAs in AF and will thereafter discuss the potential of miRNAs as biomarkers or novel therapeutic targets in AF.

Clinical outcome of pulmonary vein isolation (PVI) has been predominantly focused on the reoccurrence of atrial fibrillation (AF) and the maintenance of sinus rhythm. However, there has been a limited intermediate follow-up on health-related quality-of-life (HRQoL) of patients. Given the relatively high recurrence rate of persistent AF after PVI treatment, it is important to follow up with clinical outcomes on symptom improvement as well as health-related quality-of-life. This study was designed to investigate the recurrence rate of atrial tachyarrhythmia (ATa), AF-related symptoms and HRQoL after PVI in patients with persistent AF who were treated with the second generation cryoballoon. Total 148 patients participated in the study who were treated by PVI between 2013 and 2017 for persistent AF. All patients visited the out-patient clinic 2-5 years after PVI. During this visit all patients filled-out an AF Effect on Quality-of-life (AFEQT) questionnaire and a seven-day Holter was applied. All rhythm recordings acquired post ablation were collected and analysed, and the modified European Heart Rhythm Association score (mEHRA) scores were calculated before and after the ablation. The average age of patients was 63±9 year old and 44 (27.9%) were female. Mean CHA2DS2 VASc score was 1.9±1.4, and moderate and severe left atrial (LA) dilation was present in 53 (36.1%) and 15 (10.2%) patients, respectively. After a follow-up of 3.7±1.0 years, 81 (54.7%) patients had an ATa recurrence and 35 (23.6%) patients underwent a repeat LA ablation. However, the mEHRA score significantly improved in 80.4% of the patients (p <0.001), with the median overall AFEQT score of 88.9 [70.4-97.2]. There is a considerable ATa recurrence rate after PVI of persistent AF at intermediate-term follow-up. However, our data indicate that PVI significantly improved AF-related symptoms and resulted in a high HRQoL for 2-5 years in patients with persistent AF.

Atrial fibrosis serves as an arrhythmogenic substrate in atrial fibrillation (AF) and contributes to AF persistence. Treating atrial fibrosis is challenging because atrial fibroblast activity is multifactorial. We hypothesized that the primary cilium regulates the profibrotic response of AF atrial fibroblasts, and explored therapeutic potentials of targeting primary cilia to treat fibrosis in AF. We included 25 patients without AF (non-AF) and 26 persistent AF patients (AF). Immunohistochemistry using a subset of the patients (non-AF: n = 10, AF: n = 10) showed less ciliated fibroblasts in AF versus non-AF. Acetylated α-tubulin protein levels were decreased in AF, while the gene expressions of AURKA and NEDD9 were highly increased in AF patients’ left atrium. Loss of primary cilia in human atrial fibroblasts through IFT88 knockdown enhanced expression of ECM genes, including FN1 and COL1A1 . Remarkably, restoration or elongation of primary cilia by an AURKA selective inhibitor or lithium chloride, respectively, prevented the increased expression of ECM genes induced by different profibrotic cytokines in atrial fibroblasts of AF patients. Our data reveal a novel mechanism underlying fibrotic substrate formation via primary cilia loss in AF atrial fibroblasts and suggest a therapeutic potential for abrogating atrial fibrosis by restoring primary cilia.

BACKGROUNDGenomic and experimental studies suggest a role for PITX2 in atrial fibrillation (AF). To assess if this association is relevant for recurrent AF in patients, we tested whether left atrial PITX2 affects recurrent AF after AF ablation.METHODSmRNA concentrations of PITX2 and its cardiac isoform, PITX2c, were quantified in left atrial appendages (LAAs) from patients undergoing thoracoscopic AF ablation, either in whole LAA tissue (n = 83) or in LAA cardiomyocytes (n = 52), and combined with clinical parameters to predict AF recurrence. Literature suggests that BMP10 is a PITX2-repressed, atrial-specific, secreted protein. BMP10 plasma concentrations were combined with 11 cardiovascular biomarkers and clinical parameters to predict recurrent AF after catheter ablation in 359 patients.RESULTSReduced concentrations of cardiomyocyte PITX2, but not whole LAA tissue PITX2, were associated with AF recurrence after thoracoscopic AF ablation (16% decreased recurrence per 2-(ΔΔCt) increase in PITX2). RNA sequencing, quantitative PCR, and Western blotting confirmed that BMP10 is one of the most PITX2-repressed atrial genes. Left atrial size (HR per mm increase [95% CI], 1.055 [1.028, 1.082]); nonparoxysmal AF (HR 1.672 [1.206, 2.318]), and elevated BMP10 (HR 1.339 [CI 1.159, 1.546] per quartile increase) were predictive of recurrent AF. BMP10 outperformed 11 other cardiovascular biomarkers in predicting recurrent AF.CONCLUSIONSReduced left atrial cardiomyocyte PITX2 and elevated plasma concentrations of the PITX2-repressed, secreted atrial protein BMP10 identify patients at risk of recurrent AF after ablation.TRIAL REGISTRATIONClinicalTrials.gov NCT01091389, NL50069.018.14, Dutch National Registry of Clinical Research Projects EK494-16.FUNDINGBritish Heart Foundation, European Union (H2020), Leducq Foundation.

Recent studies have demonstrated that primary cilia not only play a role in cardiovascular development, but also in the progression of acquired heart disease. Their role in atrial fibrillation (AF) is incompletely understood. We hypothesize that there is a causal link between primary cilia genes and the occurrence of AF. We integrated AF GWAS data with various multi-omic datasets—including data on gene expression, DNA methylation, and protein expression quantitative trait loci (eQTL, mQTL, and pQTL)—from human left atrial appendage (LAA) tissues and blood. Genetic variants linked to primary cilia-related genes were used as instrumental variables to explore their causal links to AF, through summary-data-based Mendelian randomization (SMR) and Bayesian colocalization. Single-cell sequencing data were used to analyze the expression of the selected genes across different cell types. The mechanisms by which the selected genes exert their effects were explored using RNA sequencing data, clinical indicators, and immunohistochemical markers from 22 patients without AF from the PREDICT-AF cohort, and 21 patients with paroxysmal AF and 19 patients with persistent AF from the MARK-AF cohort. Through SMR analyses, we established significant associations between predicted CEP68 expression and AF in both blood (OR 1.25; 95% CI 1.18–1.33; false discovery rate (FDR) = 1.81 × 10−9) and LAA tissue (OR 1.12; 95% CI 1.08–1.16; FDR = 6.18 × 10−9). Moreover, predicted methylation of CEP68 showed an inverse relationship with AF risk (OR 0.87; 95% CI 0.84–0.90; FDR = 2.55 × 10−15). Colocalization results for CEP68 in both blood and the LAA indicated strong evidence of a shared causal variant. Within single-cell data, compared to the control group, AF patients had higher levels of CEP68 in fibroblasts (p = 0.046). In bulk RNA-seq data, CEP68 expression showed no significant differences among the no AF, paroxysmal AF, and persistent AF groups. CEP68 was positively correlated with the cardiac remodeling marker Thrombospondin-2 in 22 patients without AF from the PREDICT-AF cohort (r = 0.45, p = 0.03). In AF patients from the MARK-AF study, CEP68 was also positively associated with LAVI (r = 0.34, p = 0.03). Collectively, our results support a model in which genetically predicted CEP68 regulation is linked to AF liability and is consistent with fibroblast activation and remodeling-related pathways as potential mediators.

Abstract Aims Non-vitamin K oral anticoagulants are safe and effective for stroke prevention in patients with atrial fibrillation (AF). Data on the safety and efficacy of edoxaban in routine care are limited in Europe. We report 1-year outcomes in patients with AF treated with edoxaban in routine care. Methods and results ETNA-AF-Europe is a prospective, multicentre, post-authorization, observational study enrolling patients treated with edoxaban in 10 European countries, the design of which was agreed with the European Medicines Agency as part of edoxaban’s post-approval safety plan. Altogether 13 092 patients in 852 sites completed the 1-year follow-up [mean age: 73.6 ± 9.5 years; 57% male, mean follow-up: 352 ± 49 days (median: 366 days)]. Most patients had associated comorbidities (mean CHA2DS2-VASc score: 3.1 ± 1.4). Stroke or systemic embolism was reported in 103 patients (annualized event rate: 0.82%/year), and major bleeding events were reported in 132 patients (1.05%/year). Rates of intracranial haemorrhage were low [30 patients (0.24%/year)]. Death occurred in 442 patients (3.50%/year); cardiovascular (CV) death occurred in 206 patients (1.63%/year). The approved dosing of edoxaban was chosen in 83%. All-cause and CV mortality were higher in patients receiving edoxaban 30 mg vs. 60 mg, in line with the higher age and more frequent comorbidities of the 30 mg group. Major bleeding was also numerically more common in patients receiving edoxaban 30 mg vs. 60 mg. Conclusion The rates of stroke, systemic embolism, and major bleeding are low in this large unselected cohort of high-risk AF patients routinely treated with edoxaban.

Introduction: Atrial fibrillation (AF) is the most common cardiac arrhythmia. Consequently, novel therapies are being developed. Ultimately, the impact of compounds on the action potential (AP) needs to be tested in freshly isolated human atrial myocytes. However, the frequent depolarized state of these cells upon isolation seriously hampers reliable AP recordings. Purpose: We assessed whether AP recordings from single human atrial myocytes could be improved by providing these cells with a proper inward rectifier K + current (I K1 ), and consequently with a regular, non-depolarized resting membrane potential (RMP), through “dynamic clamp”. Methods: Single myocytes were enzymatically isolated from left atrial appendage tissue obtained from patients with paroxysmal AF undergoing minimally invasive surgical ablation. APs were elicited at 1 Hz and measured using perforated patch-clamp methodology, injecting a synthetic I K1 to generate a regular RMP. The injected I K1 had strong or moderate rectification. For comparison, a regular RMP was forced through injection of a constant outward current. A wide variety of ion channel blockers was tested to assess their modulatory effects on AP characteristics. Results: Without any current injection, RMPs ranged from −9.6 to −86.2 mV in 58 cells. In depolarized cells (RMP positive to −60 mV), RMP could be set at −80 mV using I K1 or constant current injection and APs could be evoked upon stimulation. AP duration differed significantly between current injection methods ( p < 0.05) and was shortest with constant current injection and longest with injection of I K1 with strong rectification. With moderate rectification, AP duration at 90% repolarization (APD 90 ) was similar to myocytes with regular non-depolarized RMP, suggesting that a synthetic I K1 with moderate rectification is the most appropriate for human atrial myocytes. Importantly, APs evoked using each injection method were still sensitive to all drugs tested (lidocaine, nifedipine, E-4031, low dose 4-aminopyridine, barium, and apamin), suggesting that the major ionic currents of the atrial cells remained functional. However, certain drug effects were quantitatively dependent on the current injection approach used. Conclusion: Injection of a synthetic I K1 with moderate rectification facilitates detailed AP measurements in human atrial myocytes. Therefore, dynamic clamp represents a promising tool for testing novel antiarrhythmic drugs.

Despite our expanding knowledge about the mechanism underlying atrial fibrillation (AF), the interplay between the biological events underlying AF remains incompletely understood. This study aimed to identify the functionally enriched gene-sets in AF and capture their interconnection via pivotal factors, that may drive or be driven by AF. Global abundance of the proteins in the left atrium of AF patients compared to control patients (n = 3/group), and the functionally enriched biological processes in AF were determined by mass-spectrometry and gene set enrichment analysis, respectively. The data were validated in an independent cohort (n = 19–20/group). In AF, the gene-sets of innate immune system, metabolic process, cellular component disassembly and ion homeostasis were up-regulated, while the gene-set of ciliogenesis was down-regulated. The innate immune system was over-represented by neutrophil degranulation, the components of which were extensively shared by other gene-sets altered in AF. In the independent cohort, an activated form of neutrophils was more present in the left atrium of AF patients with the increased gene expression of neutrophil granules. MYH10, required for ciliogenesis, was decreased in the atrial fibroblasts of AF patients. We report the increased neutrophil degranulation appears to play a pivotal role, and affects multiple biological processes altered in AF.