AbstractAtrial Fibrillation Patients Research Articles

HIPSC model reveals M1 macrophages cause atrial arrhythmia correlated to electrophysiological remodelling of atrial cardiomyocytes in 2D and 3D engineered heart tissue

Abstract Atrial fibrillation (AF) is the most common sustained arrhythmia with an estimated prevalence of 1.5–2%. Current treatments lack effectiveness and do not prevent recurrence. Inflammation is reported in AF patients, however, a causal connection remains elusive. In this study, we investigated the arrhythmic effects of pro-inflammatory macrophages (M1) on human induced pluripotent stem cell (hiPSC)-derived atrial cardiomyocytes (aCM), to better understand their role in AF. Macrophages are known to play a role in cardiac electrophysiology, but their role in arrhythmia is unclear. Three healthy hiPSC lines were differentiated to aCM and M1. Multi-electrode array recordings of isogenic, 2D cocultures of M1 and aCM showed a significant increase in beat rate irregularity compared to control conditions (P<0.001). Furthermore, spike amplitude of aCM and M1 cocultures was significantly decreased (P<0.001). Arrhythmias occurred only after activation of macrophages in the coculture. Addition of anti-inflammatory glucocorticoids significantly reduced beat irregularity in aCM and M1 cocultures compared to vehicle (1.9-fold decrease for Hydrocortisone, P<0.005) further supporting macrophage mediated inflammation to be the cause of the arrhythmia. RNA sequencing of aCM and M1 cocultures revealed aberrant expression of arrhythmia associated cardiac sodium and atrial potassium ion channels (SCN5A, KCNA5). Normal expression was restored through hydrocortisone addition. In addition, inflammation-induced arrhythmia was observed in 3D engineered heart tissues containing hiPSC derived aCM, M1 and cardiac fibroblasts. Tissues showed a significant increase in beating irregularity (P<0.005) compared to controls and had a significant, median reduction (>30%) of contraction amplitude (P<0.05). Our findings suggest a causal relationship between M1 and the occurrence of atrial arrhythmia. The reduction of arrhythmia using glucocorticoids correlates to clinical observations, that show their use being linked to reduced post operative AF burden. These results strongly support the relevance of the proposed hiPSC coculture model and elucidate a new potential AF mechanism.

P56 ROLE OF CARDIAC TROPONINS IN THE EMERGENCY DEPARTMENT IN PATIENTS WITH ATRIAL FIBRILLATION

Abstract Atrial fibrillation (AF) is the most frequent arrhythmia among those encountered in the emergency department. It’s well known that elevated values ​​of cardiac troponin in "stable” conditions is generally indicative of myocardial cytonecrosis and is associated with a worse prognosis in various clinical conditions. The role of cardiac biomarkers in the context of an AF episode has not yet been fully understood and is a source of debate in the cardiology community. Recent studies suggest the association of elevated troponin values in the context of an AF episode with an increased incidence of major cardiovascular events. Consequently, its measurement could be extensively taken into consideration also in the Emergency Department and implemented for risk stratification. There is currently insufficient evidence to support the dosing of cardiac troponins in all AF patients for risk stratification. The aim of this study is to investigate the significance of elevated troponin values ​​during AF and whether these are related to an increased cardiovascular risk. Methods and Results This is a retrospective and observational study and focuses on a population of patients who arrived in the Emergency Department of San Raffaele Hospital in Milan between the 1st of January 2018 and 22nd May 2021 with atrial fibrillation. Data were collected for 625 patients of whom 232 were enrolled for statistical analysis. The population was stratified based on cardiovascular risk factors and prior AF ablation. At 12–month follow–up we found that elevated troponin values ​​during atrial fibrillation in the Emergency Department do not correlate with an increase of deaths from any cause, major cardiovascular events or hospitalizations for heart failure. The presence of elevated cardiac troponin was not associated with an increased rate of CAD at coronary CT nor coronaru angiography. A weak association was seen between non–elevated cTnT–hs and higher rate of AF ablation. Conclusions Our data reject the hypothesis according to which elevated levels of highly sensitive cardiac troponin measured during an atrial fibrillation episode could be correlated with an higher incidence of major adverse cardiovascular events at 1–year follow up.

Expert Opinion on the Use of Novel Oral Anticoagulants for Stroke Prevention in Non-valvular Atrial Fibrillation for the Primary Care Setting in India: A Literature Review.

Atrial fibrillation (AF), the most prevalent cardiac arrhythmia encountered in clinical practice, is linked with substantial morbidity and mortality due to accompanying risk of stroke and thromboembolism. Patients with AF are at a five-fold higher risk of suffering from a stroke. Anticoagulation therapy, with either vitamin K antagonists or novel oral anticoagulants (NOACs), is a standard approach to reduce the risk. Consultant physicians (CPs) in India are the primary point of contact for the majority of patients before they approach a specialist. The CPs may face challenges in screening and diagnosing AF patients. The apprehensions associated with managing AF patients with anticoagulants, further add to the challenges of a CP. This review aimed to identify the key decision points for the CPs to diagnose AF and initiate anticoagulation in patients with non-valvular AF (NVAF) and bring to the table a simplified recommendation supported by expert opinion and guidelines for stroke prevention in NVAF patients.

Machine Learning Using a Single-Lead ECG to Identify Patients With Atrial Fibrillation-Induced Heart Failure

AimsAtrial fibrillation (AF) and heart failure often co-exist. Early identification of AF patients at risk for AF-induced heart failure (AF-HF) is desirable to reduce both morbidity and mortality as well as health care costs. We aimed to leverage the characteristics of beat-to-beat-patterns in AF to prospectively discriminate AF patients with and without AF-HF.MethodsA dataset of 10,234 5-min length RR-interval time series derived from 26 AF-HF patients and 26 control patients was extracted from single-lead Holter-ECGs. A total of 14 features were extracted, and the most informative features were selected. Then, a decision tree classifier with 5-fold cross-validation was trained, validated, and tested on the dataset randomly split. The derived algorithm was then tested on 2,261 5-min segments from six AF-HF and six control patients and validated for various time segments.ResultsThe algorithm based on the spectral entropy of the RR-intervals, the mean value of the relative RR-interval, and the root mean square of successive differences of the relative RR-interval yielded an accuracy of 73.5%, specificity of 91.4%, sensitivity of 64.7%, and PPV of 87.0% to correctly stratify segments to AF-HF. Considering the majority vote of the segments of each patient, 10/12 patients (83.33%) were correctly classified.ConclusionBeat-to-beat-analysis using a machine learning classifier identifies patients with AF-induced heart failure with clinically relevant diagnostic properties. Application of this algorithm in routine care may improve early identification of patients at risk for AF-induced cardiomyopathy and improve the yield of targeted clinical follow-up.

A Heart Rate Variability-Based Paroxysmal Atrial Fibrillation Prediction System

Atrial fibrillation (AF) is characterized by totally disorganized atrial depolarizations without effective atrial contraction. It is the most common form of cardiac arrhythmia, affecting more than 46.3 million people worldwide and its incidence rate remains increasing. Although AF itself is not life-threatening, its complications, such as strokes and heart failure, are lethal. About 25% of paroxysmal AF (PAF) patients become chronic for an observation period of more than one year. For long-term and real-time monitoring, a PAF prediction system was developed with four objectives: (1) high prediction accuracy, (2) fast computation, (3) small data storage, and (4) easy medical interpretations. The system takes a 400-point heart rate variability (HRV) sequence containing no AF episodes as the input and outputs whether the corresponding subject will experience AF episodes in the near future (i.e., 30 min). It first converts an input HRV sequence into four image matrices via extended Poincaré plots to capture inter- and intra-person features. Then, the system employs a convolutional neural network (CNN) to perform feature selection and classification based on the input image matrices. Some design issues of the system, including feature conversion and classifier structure, were formulated as a binary optimization problem, which was then solved via a genetic algorithm (GA). A numerical study involving 6085 400-point HRV sequences excerpted from three PhysioNet databases showed that the developed PAF prediction system achieved 87.9% and 87.2% accuracy on the validation and the testing datasets, respectively. The performance is competitive with that of the leading PAF prediction system in the literature, yet our system is much faster and more intensively tested. Furthermore, from the designed inter-person features, we found that PAF patients often possess lower (~60 beats/min) or higher (~100 beats/min) heart rates than non-PAF subjects. On the other hand, from the intra-person features, we observed that PAF patients often exhibit smaller variations (≤5 beats/min) in heart rate than non-PAF subjects, but they may experience short bursts of large heart rate changes sometimes, probably due to abnormal beats, such as premature atrial beats. The other findings warrant further investigations for their medical implications about the onset of PAF.

Abstract 13619: Obese Patients With New Onset Atrial Fibrillation/Flutter Have Higher Rates of Hospitalization, Cardioversion, and Ablation

Atrial fibrillation (AF) is the most common arrhythmia and can lead to frequent healthcare encounters. Obesity is a rapidly growing epidemic, and greater than one third of all adults in the USA are obese. Additionally, obese patients have over twice the prevalence of AF compared to the non-obese. Despite the frequency of these conditions, there is limited research assessing the relationship between obesity and healthcare resource utilization (HRU) in AF patients. We hypothesized that obese patients with new onset atrial fibrillation/flutter (AFL) would have higher AF/AFL related hospitalizations and procedures compared to non-obese patients. We utilized MarketScan® claims data to select patients with new onset atrial fibrillation or atrial flutter in 2017 and 2018 and classified them according to diagnosis codes as obese or non-obese. We then stratified by the diagnosis of obesity. There were 95,314 patients with new onset atrial fibrillation/flutter, which included 72,218 (76%) who were non-obese and 23,096 (24%) who were obese. There were significantly more males than females (64.4% vs. 35.6%). The average age was similar at 54.4 (+/- 0.04) in the non-obese and 54.6 (+/- 0.06) in the obese cohort. The rate of hospitalizations (35.9% vs. 24.8%, p<0.001), cardioversions (16% vs. 10%, p<0.001), and ablation procedures (10% vs. 7%, p<0.0001) were significantly higher in the obese versus non-obese cohort. Obese patients with new onset AF/AFL had significantly higher HRU than non-obese patients. This increased health resource utilization increases the cost of care in such patients and future studies should concentrate on understanding the reasons for this difference.

Emergency Department capacity to initiate thromboprophylaxis in patients with atrial fibrillation and thrombotic risk after discharge: URGFAICS cohort analysis.

Atrial fibrillation (AF) is the most prevalent heart rhythm disorder in the general population. Stroke prevention is one of the leading management objectives in the treatment of AF patients. The variables associated with the non-initiation of thromboprophylaxis in patients with thrombotic risk consulting for an episode of AF in Emergency Departments (ED) were investigated. This was a multipurpose, analytical, non-interventionist, multicenter Spanish study with a prospective 30-day follow-up. All patients ≥ 18years of age consulting to the ED for the casual finding of AF in an electrocardiogram (ECG) performed 12h prior to the consultation or with symptoms related to AF were enrolled from September 1, 2016 to February 28, 2017. Patients not previously received thromboprophylaxis were selected. Multivariate analysis was performed to calculate the odds ratio (OR) and the 95% confidence interval (CI). A total of 634 patients, not received thromboprophylaxis and at high thrombotic risk, were included. Of these, 251 (39.6%) did not receive thromboprophylaxis at ED discharge. In the multivariate analysis, non-initiation of anticoagulation at discharge from the ED was mostly related to cognitive impairment (OR 3.95; (95% CI 2.02-7.72), cancer history (OR 2.12; (95%CI 1.18-3.81), AF duration < 48h (OR 2.49; (95% CI 1.48-4.21) and patients with re-establishment of sinus rhythm (OR 3.65; (95% CI 1.47-9.06). Reinforcement of the use of CHA2DS2-VASC as a stroke risk scale and empowerment of ED physicians is a must to improve this gap in care.

Practical aspects of antithrombotic therapy in patients with atrial fibrillation and coronary artery disease

Atrial fibrillation (AF) is the most common cardiac arrhythmia, which is associated with an increased risk of cardiovascular death. The latter is partly due to the common combination with coronary artery disease (CAD). If indicated, patients with AF need continuous direct oral anticoagulant therapy to prevent thromboembolic events. In addition, patients with CAD who require urgent or elective percutaneous coronary intervention require dual antiplatelet therapy. Therefore, physicians often face a dilemma when choosing the most appropriate antithrombotic therapy regimen for AF patients undergoing percutaneous coronary intervention. Integrating two medication approaches to treat a single patient with a combination of AF and CAD is challenging and must strike a balance between high efficacy and safety. This article provides an overview of studies on this issue.

Effects of atrial fibrillation on ventricular remodeling in the human heart

Abstract Atrial fibrillation (AF) is often found in patients with heart failure (HF). Clinical data indicated that the arrhythmic component of AF alone could contribute to left-ventricular (LV) dysfunction. However, the effects of non-tachycardic AF with arrhythmic excitation of the human LV, are unknown. We investigated human LV myocardium from patients with sinus rhythm (SR) or normofrequent AF (mean EF&amp;gt;50%, matched clinical data, derived from septal resections during AVR). In histological analysis we detected no difference between SR (n=17 patients) and AF patients (n=18) regarding the amount and distribution of fibrosis. We isolated human LV cardiomyocytes (CM) and studied cellular Ca-handling (Fura-2). Systolic Ca-transient amplitude of LV CM was reduced in patients suffering from AF (n=8 AF patients vs. 11 SR), while diastolic Ca-levels and Ca-transient kinetics were not significantly changed. These results were confirmed in LV CM from non-failing donors (NF) with AF (n=4 AF patients vs. 8 SR). For the standardized investigation of a normofrequent arrhythmia, we simulated AF in vitro by using arrhythmic (60 bpm, 40% beat-to-beat variability) or rhythmic (60 bpm) field stimulation. Human LV CM from NF SR patients (n=8) showed an impaired Ca-transient amplitude after 24h arrhythmic culture pacing without changes in diastolic Ca and Ca-transient kinetics. For studying a model suitable for more standardized chronic pacing, we utilized human iPSC cardiomyocytes (iPSC-CM) from healthy donors (n=6). After 7 days, arrhythmically paced iPSC-CM exhibited a reduced systolic Ca-transient amplitude, a trend towards a prolonged Ca-elimination time and a reduced sarcoplasmic reticulum Ca-load. Confocal line-scans of arrhythmically paced cells (Fluo-4 AM) showed an increased diastolic Ca-leak from the sarcoplasmic reticulum, possibly underlying the reduced Ca-load. Coupled with the Ca changes, cytosolic Na was elevated after arrhythmia. We found an increased late INa, which could explain the detrimentally altered Ca/Na-interplay. Accordingly, Patch-clamp experiments revealed a prolonged action potential duration after arrhythmia. We further elucidated the underlying mechanisms of this electrophysiological remodeling by showing that oxidative stress (H2O2, LPO) is increased in the LV of patients suffering from AF (n=6 AF patients vs. 6 SR), which was associated with an enhanced NOX2/-4 activity. Consecutively, Ca2+/calmodulin-dependent protein kinase IIδ (CaMKII) was found to be more oxidized (CaMKII-Met281/282) in the LV of AF patients (n=7 AF patients vs. 7 SR) leading to an increased CaMKII activity, which adversely regulated EC-coupling protein phosphorylation including RyR2 hyperphosphorylation. Normofrequent arrhythmia/AF impairs human ventricular EC-coupling via increased oxidative stress and enhanced CaMKII. Thus, this translational study provides the first mechanistic characterization and the potential negative impact of isolated AF on the human LV. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): Else Kröner-Fresenius-Stiftung (EKFS) and Deutsche Gesellschaft für Innere Medizin

Non-valvular Atrial Fibrillation in CKD: Role of Vitamin K Antagonists and Direct Oral Anticoagulants. A Narrative Review.

Atrial fibrillation (AF) is the most common arrhythmia in chronic kidney disease (CKD), with a close bidirectional relationship between the two entities. The presence of CKD in AF increases the risk of thromboembolic events, mortality and bleeding. Vitamin K antagonists (VKA) have been the mainstay of treatment for the prevention of thromboembolic events in AF until recently, with confirmed benefits in AF patients with stage 3 CKD. However, the risk-benefit profile of VKA in patients with AF and stages 4–5 CKD is controversial due to the lack of evidence from randomized controlled trials. Treatment with VKA in CKD patients has been associated with conditions such as poorer anticoagulation quality, increased risk of bleeding, faster progression of vascular/valvular calcification and higher risk of calciphylaxis. Direct oral anticoagulants (DOACs) have shown equal or greater efficacy in stroke/systemic embolism prevention, and a better safety profile than VKA in post-hoc analysis of the pivotal randomized controlled trials in patients with non-valvular AF and stage 3 CKD, yet evidence of its risk-benefit profile in more advanced stages of CKD is scarce. Observational studies associate DOACs with a good safety/effectiveness profile compared to VKA in non-dialysis CKD patients. Further, DOACs have been associated with a lower risk of acute kidney injury and CKD development/progression than VKA. This narrative review summarizes the evidence of the efficacy and safety of warfarin and DOACs in patients with AF at different CKD stages, as well as their effects on renal function, vascular/valvular calcification and bone health.

Abstract P382: Transcriptomic Analysis Of Human Left Atrial Tissue Reveals Mitochondrial Gene Co-expression

Atrial fibrillation (AF) risk is heritable. High rate electrical activity in AF requires increased energy. Atrial mitochondrial structure and function are altered in AF patients in an effort to generate adequate ATP through oxidative phosphorylation. Genomic studies have identified putative AF risk genes, but the association of AF risk genes with expression of mitochondrial genes is unclear. We tested the hypothesis that putative AF risk genes are co-expressed with mitochondrial genes that play a role in atrial energy production. RNA-seq was performed on left atrial appendage (LAA) tissues obtained from 251 cardiac surgery patients. RNA coexpression profiles were evaluated for 222 putative AF risk genes. Genes encoding proteins that localize to the mitochondria were identified using MitoCarta 2.0. Changes in metabolic pathways were detected using Ingenuity Pathway Analysis (IPA). Our analysis identified 128 AF risk genes that coexpressed with at least one mitochondrial gene. The highest level of mitochondrial gene coexpression was evident with PCCB, in which 30% (253 of 848) of coexpressed genes were mitochondrial. CASQ2 (24%, 104 of 431) and ASAH1 (20%, 37 of 182) also showed high levels of mitochondrial gene coexpression. The IPA Oxidative Phosphorylation Pathway was significantly altered (p&lt;0.05) for 26 AF risk genes, with CASQ2 (9.42E-79), MYH6 (4.73E-78), YWHAE (4.96E-75), and TTN (4.30E-71) the most strongly associated (Table). Additionally, 12 AF risk genes coexpressed with genes encoded by mitochondrial DNA (mtDNA) (Table). ASAH1, CASQ2, MYH6, NACA, NUCKS1, PLN, TTN, and YWHAE coexpressed with all 13 mtDNA encoded components of the electron transport chain. Many AF risk genes show significant coexpression with mitochondrial genes. We propose that genetic risk scores based on these AF risk genes may identify a subset of AF patients that would benefit from AF therapies that enhance metabolic activity.

Long noncoding RNA and atrial fibrillation.

Atrial fibrillation (AF), a common arrhythmia that usually occurs in patients with heart disease, is one of the leading causes for mortality and disability worldwide. Current drug therapy for AF patients lacks sufficient efficacy and has side effects. Radiofrequency ablation is more effective than traditional drug therapy, but this invasive procedure is associated with potential risks and postoperative recurrence, limiting the clinical benefits for AF patients. Therefore, it is necessary to expand our understanding about the underlying molecular mechanism of AF and to explore the new therapeutic strategies. Long noncoding RNA (lncRNA) is a set of noncoding RNA longer than 200 nucleotides. Growing evidence indicates that lncRNA is involved in numerous pathophysiological processes of AF, such as structural remodeling, electrical remodeling, renin-angiotensin system, abnormal calcium regulation, etc. In addition, lncRNA involved in structural remodeling and electrical remodeling has the potential to be a novel target for the diagnosis and treatment of AF, and lncRNA involved in autonomic nerve remodeling may bring new enlightenment for the prognosis and recurrence of AF.

The impact of chronic heart failure on heart remodeling in patients with atrial fibrillation

Atrial fibrillation (AF) and chronic heart failure (CHF) often coexist due to common pathophysiological mechanisms and risk factors. However, the effect of CHF on heart remodeling in patients with permanent AF has been insufficiently studied. The aim: to study the influence of CHF on changes in structural and geometric parameters and diastolic function of the heart in patients with permanent AF. Materials and methods. The study included 100 patients (men – 60 % (n = 60); women – 40 % (n = 40)) with CHF of ischemic origin and AF, stage II AB, NYHA II-IV FC, and 16 coronary heart disease patients (men – 62.5 % (n = 10), women – 37.5 % (n = 6)) with AF without signs of CHF. Patients were comparable in age (P = 0.267), height (p = 0.406), weight (P = 0.518), body surface area (P = 0.388). Doppler echocardiography was performed on the device Esaote MyLab Eight (Italy) according to standard methods. Results. Patients with AF and signs of CHF were dominated by individuals with eccentric hypertrophy (49 % vs. 19 %; P = 0.0270), and patients with AF without signs of CHF – with eccentric remodeling (0 % vs. 25 %; P = 0.0001). Patients with AF and signs of CHF had significantly higher systolic pressure in the pulmonary artery (54.85 ± 14.23 mm Hg vs. 42.99 ± 11.94 mm Hg; P = 0.028) and pulmonary capillary wedge pressure (PCWP) (12.18 (9.80; 15.33) mm Hg vs. 8.92 (7.62; 10.50) mm Hg; P = 0.005) than patients with AF without signs of CHF, indicating more pronounced pulmonary hypertension and a more significant increase in left atrium pressure. AF patients with signs of CHF demonstrated significantly higher left ventricle end-diastolic pressure (LVEDP), as evidenced by the parameters: E\E’ medial (9.87 ± 5.24 vs. 6.15 ± 1.39; P = 0.001), E/E’ mean (8.38 ± 4.21 vs. 6.06 ± 1.97; P = 0.005), e’ medial (9.96 ± 3.79 cm/s vs. 12.81 ± 3.60 cm/s; P = 0.004). AF patients with signs of CHF had decreased LV EF (55.58 ± 14.65 % vs. 65.44 ± 10.87 %; P = 0.006), systolic velocity of the medial fibrous ring of the mitral valve S (6.92 ± 2.41 cm/s vs. 8.40 ± 2.03 cm/s; P = 0.015), and significantly higher values of TEI RV (0.58 ± 0.16 c. u. vs. 0.48 ± 0.11 c. u.; P = 0.011), but decreased TAPSE values (16.22 ± 4.60 mm vs. 19.54 ± 5.00 mm; P = 0.067), indicating more pronounced systolic dysfunction of both ventricles. Conclusions. Comorbidity of CHF and AF in patients is accompanied by the increased percentage of eccentric hypertrophy (49 %; P = 0.027), more pronounced systolic dysfunction of the left and right ventricles, increased LVEDP, PCWP, systolic pressure in the pulmonary artery, dilation of the inferior vena cava.

A programme for early diagnosis of atrial fibrillation: a multi-centre study in primary care.

Atrial fibrillation (AF) is a morbid disease whose complications can be prevented if prompt and correctly treated. To assess the usefulness of an early AF diagnosis programme in at-risk individuals in primary care centres. In an open-label, multi-centre, controlled interventional study, individuals with one or more risk factors for AF but without known AF were enrolled. They were allocated to intervention and control groups in a 1:2 ratio. Participants in the intervention group had three clinical and educational visits (0, 6 and 12 months). In intervention subgroup A, an electrocardiogram (ECG) was performed at each visit and in subgroup B, only if arrhythmia was detected on auscultation. After 2 years, the medical records of all participants were reviewed. Participants diagnosed with AF were followed for two additional years. Of the total 2231 participants enrolled, 1503 (67.36%) were allocated to the control group and 728 (32.63%) to the intervention groups (355 in subgroup A, 373 subgroup B). The groups showed similar clinical characteristics. New-onset AF was diagnosed in 38 patients. Early detection in subgroup B was similar to subgroup A and superior to control group (3.2% versus 1.2%, hazard ratio 3.149, 95% confidence interval 1.503-6.597, P = 0.002). AF patients in subgroups A and B had similar long-term complications and a tendency for fewer complications than AF patients in the control group. An intervention programme consisting of health education, systematic auscultation and opportunistic ECG by a primary care provider is a useful method for the early diagnosis of AF.

Large extracellular vesicles in the left atrial appendage in patients with atrial fibrillation\u2014the missing link?

Atrial fibrillation (AF) is the most frequent arrhythmic disease in humans, which leads to thrombus formation in the left atrial appendage and stroke through peripheral embolization. Depending on their origin, large extracellular vesicles (lEVs) can exert pro-coagulant functions. In the present study, we investigated how different types of AF influence the levels of large EV subtypes in three distinct atrial localizations. Blood samples were collected from the right and left atrium and the left atrial appendage of 58 patients. 49% of the patients had permanent AF, 34% had non-permanent AF, and 17% had no history of AF. Flow cytometric analysis of the origin of the lEVs showed that the proportion of platelet-derived lEVs in the left atrial appendage was significantly higher in permanent AF patients compared to non-permanent AF. When we grouped patients according to their current heart rhythm, we also detected significantly higher levels of platelet-derived lEVs in the left atrial appendage (LAA) in patients with atrial fibrillation. In vitro studies revealed, that platelet activation with lipopolysaccharide (LPS) leads to higher levels of miR-222-3p and miR-223-3p in platelet-derived lEVs. Treatment with lEVs from LPS- or thrombin-activated platelets reduces the migration of endothelial cells in vitro. These results suggest that permanent atrial fibrillation is associated with increased levels of platelet-derived lEVs in the LAA, which are potentially involved in LAA thrombus formation.

Laboratory predictors of clinical outcomes in patients with atrial fibrillation

Atrial fibrillation (AF) is the most common cardiac arrhythmia in clinical practice that affects intracardiac hemodynamics and is accompanied by increased mortality due to the risk of stroke and systemic thromboembolism. In recent years, numerous studies, evaluating the use of biomarkers in AF patients, have been conducted to expand the possibility of stratification the complications risks.The aim of the review is to evaluate the possible isolated and combined predictive significance of NT-proBNP, troponin T (TnT) and D-dimer levels in the development and progression of AF and its thromboembolic complications according to published data. Determining the level of NT-proBNP can be used to diagnose cardioembolic stroke in latent forms of AF. Patients with a cardioembolic stroke have been shown to have higher BNP/NT-proBNP levels than patients with an atherothrombotic stroke and venous thromboembolism. Elevated TnT level is independently associated with AF detection as a cause of stroke. The assessment on the CHADS2 scale significantly correlates with the level of troponin I (TnI). However, it is equally important to take into account TnI level even with a low score of CHADS2. Patients with the level of TnI ≥ 0.040 pg/L are considered to be prescribed anticoagulants in the same way as the patients with high CHADS2 score. Similar results were obtained analyzing high-sensitivity cardiac troponin T (hs-cTnT) data. The level of D-dimer 0.315 mg/L was determined to be the optimal limit level for predicting the adverse functional outcome of stroke owing to AF. Patients with a high level of D-dimer have shown a high risk of developing thromboembolic and cardiovascular complications despite their taking anticoagulant drugs. D-dimer levels positively correlate with the CHA2DS2 and CHA2DS2-VASC scales of stroke risk stratification. The analysis of the biomarkers combination has revealed the increase of hs-cTnT and BNP associated with stroke in AF patients (p&lt;0.05). However, ABC scale, including hs-cTnT and NT- pro BNP, hasn't given more accurate result in stroke predicting than CHA2DS2-VASc scale. The integration of biomarkers in predicting the risk of AF occurrence, progression and appearance of thromboembolic complications is a promising direction. An isolated level of biomarkers (hs-cTnT, NT-proBNP, D-dimer) and their combination with clinical risk factors can improve the quality of cardioembolic strokes prognosis.

Abstract P780: Myosin Light Chain Dephosphorylation by Ppp1r12c Promotes Atrial Hypocontractility in Atrial Fibrillation

Atrial fibrillation (AF) is the most common sustained arrhythmia, with an estimated prevalence in the U.S.of 6.1 million. AF increases the risk of a thromboembolic stroke in five-fold. Although atrial hypocontractility contributes to stroke risk in AF, the molecular mechanisms reducing myofilament contractile function in AF remains unknown. We have recently identified protein phosphatase 1 subunit 12c (PPP1R12C) as a key molecule targeting myosin light-chain phosphorylation in AF. Objective: We hypothesize that the overexpression of PPP1R12C causes hypophosphorylation of atrial myosin light-chain 2 (MLC2a), thereby decreasing atrial contractility in AF. Methods and Results: Left and right atrial appendage tissues were isolated from AF patients versus sinus rhythm (SR). To evaluate the role of the PP1c-PPP1R12C interaction in MLC2a de-phosphorylation, we utilized Western blots, co-immunoprecipitation, and phosphorylation assays. In patients with AF, PPP1R12C expression was increased 3.5-fold versus SR controls with an 88% reduction in MLC2a phosphorylation. PPP1R12C-PP1c binding and PPP1R12C-MLC2a binding were significantly increased in AF. In vitro studies of either pharmacologic (BDP5290) or genetic (T560A), PPP1R12C activation demonstrated increased PPP1R12C binding with both PP1c and MLC2a, and dephosphorylation of MLC2a. Additionally, to evaluate the role of PPP1R12C expression in cardiac function, mice with lentiviral cardiac-specific overexpression of PPP1R12C (Lenti-12C) were evaluated for atrial contractility using echocardiography, versus wild-type and Lenti-controls. Lenti-12C mice demonstrated a 150% increase in left atrium size versus controls, with reduced atrial strain and atrial ejection fraction. Also, programmed electrical stimulation was performed to evaluate AF inducibility in vivo. Pacing-induced AF in Lenti-12C mice was significantly higher than controls. Conclusion: The overexpression of PPP1R12C increases PP1c targeting to MLC2a and provokes dephosphorylation, associated with a reduction in atrial contractility and an increase in AF inducibility. All these discoveries suggest that PP1 regulation of sarcomere function at MLC2a is a main regulator of atrial contractility in AF.

Minor allele of GJA1 gene polymorphism is associated with higher heart rate during atrial fibrillation

Atrial fibrillation (AF) tachycardia causes heart failure and requires more attention. The genetic background of individual heart rate (HR) variations during AF are unclear. We hypothesized that HR-associated single nucleotide polymorphisms (SNPs) reported in Genome-Wide Association Studies (GWAS) are also associated with HR during AF. We enrolled patients with persistent AF (311 for screening and 146 for replication) who underwent AF ablation and were genotyped for the 21 h-associated SNPs reported in GWAS. The patients underwent 24-h Holter monitoring before AF ablation and electrophysiological study after AF ablation during sinus rhythm. Only the GJA1 SNP rs1015451 (T>C) was significantly associated with total HR (TT 110,643 ± 17,542 beats/day, TC 116,350 ± 19,060 beats/day, CC 122,163 ± 25,684 beats/day, P = 8.5 × 10−4). We also confirmed this significant association in the replication set. The intra-atrial conduction was faster in AF patients with the GJA1 minor allele than in those without it. Multivariate analysis revealed the presence of a GJA1 SNP rs1015451 additive model, female gender, lower left ventricular ejection fraction, and higher 1:1 atrioventricular nodal conduction were independently associated with higher HR during AF. The GJA1 SNP might be a new genetic marker for AF tachycardia.

Interpretation of clinical studies in electrophysiology: statistical considerations for the clinician.

Atrial fibrillation (AF) outcome studies play an essential role in the development of clinical evidence to improve the management of AF patients. Understanding the statistical considerations involved in study design and interpretation is crucial if electrophysiologists are to change practice. In this review, with the guidance of a medical statistician and a clinical trialist we provide an overview of important statistical issues for the clinician, with a focus on clinical studies in AF ablation. Various types of study designs including randomized controlled trials, superiority, and non-inferiority studies are described, along with their implications and limitations. Appropriate sample size calculation is fundamental to ensure statistical power and efficient resource use. Multiplicity in study endpoints is useful to encapsulate the varied effects of an intervention/treatment, although statistical adjustments are required to account for this. Finally, we discuss the limitations with the current primary endpoint used in AF ablation studies, namely, freedom from atrial tachyarrhythmia of >30 seconds, and propose AF burden as a more relevant primary endpoint, based on findings from recent clinical studies. However, technical challenges need to be overcome before AF burden can be routinely adopted, especially the need for non-invasive, long-term monitoring. The emergence of newer technologies, particularly wearable technology, offers significant promise in filling this gap.

Abstract 13383: The Vascular Endothelial Barrier: A Novel Therapeutic Target for Preventing Atrial Fibrillation

Atrial fibrillation (AF), the most common arrhythmia, is associated with inflammation and vascular dysfunction. AF patients have elevated levels of vascular endothelial growth factor (VEGF; 90-580 pg/ml), which promotes vascular leak and edema. We have previously identified edema-induced disruption of sodium channel (Na V 1.5) -rich intercalated disk (ID) nanodomains as a novel arrhythmia mechanism. We hypothesized that (i) elevated VEGF levels promote AF by disrupting ID nanodomains, and slowing atrial conduction, and (ii) protection of the vascular barrier can prevent these arrhythmias. Clinically-relevant VEGF levels (500 pg/ml, 60 minutes) increased FITC-dextran extravasation (99.3% vs. 24.3% in vehicle controls) in WT mouse hearts, consistent with increased vascular leak. Electron microscopy revealed ID nanodomain swelling, near both gap junctions (perinexi; 64±9nm vs 17±1nm) and mechanical junctions (63±4nm vs 27±2nm) in VEGF-treated hearts relative to controls. Super-resolution STORM microscopy revealed Na V 1.5 enrichment at perinexi (9±2 fold) and N-cadherin-rich sites (7±1 fold) relative to non-junctional ID sites in control hearts. VEGF reduced Na V 1.5 enrichment at both sites (6±1 and 4±1 fold, respectively), consistent with Na V 1.5 translocation from ID nanodomains. Atrial conduction, assessed by optical mapping, was slowed by VEGF (10±0.4 cm/s vs 21.3±1.3 cm/s at baseline). VEGF increased atrial arrhythmia burden both ex vivo (80% vs 0% in vehicle controls) and in vivo (70% vs 20% in vehicle controls). Next, we tested two strategies shown to prevent vascular barrier breakdown. Blocking connexin43 hemichannels (αCT11 peptide) decreased both incidence (40%) and duration (1.45±3.42s) of VEGF-induced arrhythmias. Likewise, blocking pannexin1 channels (Panx1-IL2 peptide) shortened VEGF-induced arrhythmias (2.48±0.83s). Mefloquine and spironolactone, which are small molecules that respectively inhibit Cx43 hemichannels and pannexin channels, were also found to effectively prevent VEGF-induced atrial arrhythmias. These results highlight VEGF-induced vascular leak as a novel mechanism for AF, and suggest vascular barrier protection as an anti-arrhythmic strategy.