Pathophysiological mechanisms of atrial fibrillation: a translational appraisal

Impact of atrial fibrillation on left atrium haemodynamics: A computational fluid dynamics study

We analyse the haemodynamics of the left atrium, highlighting differences between healthy individuals and patients affected by atrial fibrillation. The computational study is based on patient-specific geometries of the left atria to simulate blood flow dynamics. We design a novel procedure to compute the boundary data for the 3D haemodynamic simulations, which are particularly useful in absence of data from clinical measurements. With this aim, we introduce a parametric definition of atrial displacement, and we use a closed-loop lumped parameter model of the whole cardiovascular circulation conveniently tuned on the basis of the patient's characteristics. We evaluate several fluid dynamics indicators for atrial haemodynamics, validating our numerical results in terms of clinical measurements; we investigate the impact of geometric and clinical characteristics on the risk of thrombosis. To highlight the correlation of thrombus formation with atrial fibrillation, according to medical evidence, we propose a novel indicator: age stasis. It arises from the combination of Eulerian and Lagrangian quantities. This indicator identifies regions where slow flow cannot properly rinse the chamber, accumulating stale blood particles, and creating optimal conditions for clots formation.

Premature atrial contractions: A predictor of atrial fibrillation and a relevant marker of atrial cardiomyopathy

An increased burden of premature atrial contractions (PACs) has long been considered a benign phenomenon. However, strong evidence of their involvement in the occurrence of atrial fibrillation (AF), ischemic stroke, and excess mortality suggests the need for management. The central question to be resolved is whether increased ectopic atrial rhythm is only a predictor of AF or whether it is a marker of atrial cardiomyopathy and therefore of ischemic stroke. After reviewing the pathophysiology of PACs and its impact on patient prognosis, this mini-review proposes to 1) detail the physiological and clinical elements linking PACs and AF, 2) present the evidence in favor of supraventricular ectopic activity as a marker of cardiomyopathy, and 3) outline the current limitations of this concept and the potential future clinical implications.

Cryoballoon catheter ablation or drug therapy to delay progression of atrial fibrillation: A single-center randomized trial

Background

Delaying atrial fibrillation (AF) progression is a key goal in cardiovascular treatment. However, numbers of previously published studies on delayed AF progression are relatively limited. The purpose of this study was to determine whether a cryoballoon catheter ablation (CA) strategy could delay AF progression compared to anti-arrhythmic drug (AAD) treatment in patients with paroxysmal AF.

Methods

A total of 204 subjects were enrolled in the trial, including 102 in the cryoballoon CA group and 102 in the AAD group. Participants were followed up with for 36 months. The primary study endpoint was the first occurrence of persistent atrial tachyarrhythmia, while secondary endpoints included the event rates of persistent atrial tachyarrhythmia at 1 and 2 years. The primary safety endpoint was serious adverse events.

Results

Overall, the 36-month follow-up was completed by 154 subjects (75.5%). At 3 years, documented progression from paroxysmal AF to persistent atrial tachyarrhythmia had occurred in 2 of the 102 patients assigned to undergo cryoballoon CA [2.203% (95% confidence interval (CI), 0.554–8.537)] and in 17 of the 102 patients assigned to receive AADs [20.223% (95% CI, 13.040–30.604)] [hazard ratio (HR), 0.107; 95% CI, 0.043–0.262; P < 0.001]. Lower rates of progression in the cryoballoon CA group compared to the AAD group were already obvious at 1 year [1.053% (95% CI, 0.149–7.238) vs. 5.284% (95% CI, 2.233–12.237)] [HR, 0.193; (95% CI, 0.039–0.956; P = 0.09)] and 2 years [2.203% (95% CI, 0.554–8.537) vs. 12.430% (95% CI, 7.066–21.371)] (HR, 0.169; 95% CI, 0.057–0.501, P < 0.001). Serious adverse events occurred in 7 of the 102 patients (6.9%) in the cryoballoon CA group and 9 of the 102 patients (8.8%) in the AAD group.

Conclusion

Cryoballoon CA was superior to AAD therapy in preventing the occurrence of persistent atrial tachyarrhythmia in patients with paroxysmal AF who had not received prior rhythm control therapy. Serious adverse events were rare.

Transcriptomic profile analysis of the left atrium in spontaneously hypertensive rats in the early stage

Left atrial remodeling, characterized by enlargement and hypertrophy of the left atrium and increased fibrosis, was accompanied by an increased incidence of atrial fibrillation. While before morphological changes at the early stage of hypertension, how overloaded hypertension influences the transcriptomic profile of the left atrium remains unclear. Therefore, RNA-sequencing was performed to define the RNA expressing profiles of left atrium in spontaneously hypertensive rats (SHRs) and normotensive Wistar-Kyoto (WKY) rats as a control group. We also compared the changes in the RNA expression profiles in SHRs treated with an angiotensin receptor blocker (ARB) and angiotensin receptor-neprilysin inhibitor (ARNI) to assess the distinct effects on the left atrium. In total, 1,558 differentially expressed genes were found in the left atrium between WKY rats and SHRs. Bioinformatics analysis showed that these mRNAs could regulate upstream pathways in atrial remodeling through atrial fibrosis, inflammation, electrical remodeling, and cardiac metabolism. The regulated transcripts detected in the left atrial tissue in both the ARB-treated and ARNI-treated groups were related to metabolism. In contrast to the ARB-treated rates, the transcripts in ARNI-treated rats were mapped to the cyclic guanosine monophosphate-protein kinase G signaling pathway.

The Predictive Value of Epicardial Fat Tissue Volume in the Occurrence and Development of Atrial Fibrillation: A Systematic Review and Meta-Analysis

Background

Atrial fibrillation (AF) is one of the most common arrhythmias in clinical practice. Although fat is currently considered to be a risk factor for AF and a pathogenic link between epicardial fat tissue (EFT) and AF has been speculated, there are currently few clinical studies and literature data domestically or abroad.

Objective

This study conducted a meta-analysis of observational case series studies to verify the relationship between atrial fibrillation and EFT and to strengthen the predictive value of EFT in the occurrence, development, and postablative recurrence of AF.

Methods

We conducted a systematic search of the literature in electronic databases until December 2021 and supplemented this through manual searches of individual studies, reviewed articles, and reference lists in conference proceedings. This study conducted a meta-analysis to compare the differences between different populations, such as healthy participants and AF patients, healthy subjects and AF subtype cases, and paroxysmal and persistent AF with AF recurrence and without AF recurrence after ablation.

Results

Following the retrieval of 828 articles, only 22 articles were selected as research results. Accordingly, the meta-analysis results show that the volume of EFT in AF is greater than that in healthy subjects (MD = 39.34 ml, 95% CI = 27.11, 51.58); persistent AF is greater than paroxysmal AF (MD = 14.37 ml, 95% CI = 7.46, 21.27); and recurrence after ablation is greater than without recurrence (MD = 14.37 ml, 95% CI = 7.46, 21.27).

Conclusion

The results of this study further confirm the connection between EFT and AF and that EFT has a certain predictive value for the occurrence and development of AF.

The Complex Relation between Atrial Cardiomyopathy and Thrombogenesis

Heart disease, as well as systemic metabolic alterations, can leave a ‘fingerprint’ of structural and functional changes in the atrial myocardium, leading to the onset of atrial cardiomyopathy. As demonstrated in various animal models, some of these changes, such as fibrosis, cardiomyocyte hypertrophy and fatty infiltration, can increase vulnerability to atrial fibrillation (AF), the most relevant manifestation of atrial cardiomyopathy in clinical practice. Atrial cardiomyopathy accompanying AF is associated with thromboembolic events, such as stroke. The interaction between AF and stroke appears to be far more complicated than initially believed. AF and stroke share many risk factors whose underlying pathological processes can reinforce the development and progression of both cardiovascular conditions. In this review, we summarize the main mechanisms by which atrial cardiomyopathy, preceding AF, supports thrombogenic events within the atrial cavity and myocardial interstitial space. Moreover, we report the pleiotropic effects of activated coagulation factors on atrial remodeling, which may aggravate atrial cardiomyopathy. Finally, we address the complex association between AF and stroke, which can be explained by a multidirectional causal relation between atrial cardiomyopathy and hypercoagulability.

Cellular heterogeneity and repolarisation across the atria: an in silico study

Mechanisms of atrial fibrillation and the susceptibility to reentries can be impacted by the repolarization across the atria. Studies into atrial fibrillation ignore cell-to-cell heterogeneity due to electrotonic coupling. Recent studies show that cellular variability may have a larger impact on electrophysiological behaviour than assumed. This paper aims to determine the impact of cellular heterogeneity on the repolarization phase across the AF remodelled atria. Using a population of models approach, 10 anatomically identical atrial models were created to include cellular heterogeneity. Atrial models were compared with an equivalent homogenous model. Activation, APD90, and repolarization maps were used to compare models. The impact of electrotonic coupling in the tissue was determined through a comparison of RMP, APD20, APD50, APD90, and triangulation between regional atrial tissue and the single cell populations. After calibration, cellular heterogeneity does not impact atrial depolarization. Repolarization patterns were significantly impacted by cellular heterogeneity, with the APD90 across the LA increasing due to heterogeneity and the reverse occurring in the RA. Electrotonic coupling caused a reduction in variability across all biomarkers but did not fully remove variability. Electrotonic coupling resulted in an increase in APD20 and APD50, and reduced triangulation compared to isolated cell populations. Heterogeneity also caused a reduction in triangulation compared with regionally homogeneous atria.

Pathomechanism of oxidative stress in cardiovascularrenal remodeling and therapeutic strategies

The high prevalence of cardiovascular disease in patients with chronic kidney disease indicates significant interactions between pathogenic pathways operating in the kidney and heart. These interactions involve all cell types (endothelial cells, smooth muscle cells, macrophages, and others), components of the vasculature, glomeruli, and heart that are susceptible to oxidative damage and structural alterations. A vicious cycle occurs whereby harmful factors such as reactive oxygen species and inflammation damage of vascular structures that themselves become sources of additional dangerous/toxic components released into the local environment. The evidence of this vicious cycle in chronic kidney disease should therefore lead to add other factors to both traditional and nontraditional risk factors. This review will examine the processes occurring during progressive kidney dysfunction with regard to vascular injury, renal remodeling, cardiac hypertrophy, and the transversal role of oxidative stress in the development of these complications.

Atrial Fibrillation among Patients Admitted to the Department of Internal Medicine in a Tertiary Care Centre: A Descriptive Cross-sectional Study

INTRODUCTION

Atrial fibrillation is one of the commonest arrhythmias with an overall prevalence estimated to be 0.4-1% in the general population. The objective of this study was to find out the prevalence of atrial fibrillation among patients admitted to the Department of Internal Medicine in a tertiary care centre.

METHODS

A descriptive cross-sectional study was conducted among patients admitted to the Department of Internal Medicine of a tertiary care centre from 01 March 2021 to 01 March 2022. Ethical approval was obtained from the Institutional Review Committee (Reference number: IRC-478/2021). Convenience sampling method was used. Data were collected from the hospital records using a semi-structured study proforma including demography, clinical presentation, laboratory investigations, electrocardiogram, 2-dimension echocardiography, and CHA2DS2VASc score. Point estimate and 95% Confidence Interval were calculated.

RESULTS

Among 27,980 patients, atrial fibrillation was found in 185 (0.66%) (0.58-0.77, 95% Confidence Interval). Among them 66 (35.67%) were in the age group of 61-70 years and 97 (52.43%) were females. Dyspnea was present in 149 (80.54%), palpitation in 137 (74.05%) and pedal edema in 117 (63.27%). Valvular atrial fibrillation was seen in 101 (54.59%) and non-valvular atrial fibrillation was seen in 84 (45.41%) patients.

CONCLUSIONS

The prevalence of atrial fibrillation was found to be similar when compared to other studies conducted in similar settings.

Effects of cGMP/Akt/GSK-3β signaling pathway on atrial natriuretic peptide secretion in rabbits with rapid atrial pacing

Atrial natriuretic peptide (ANP) plays a pivotal role in the regulation of the cardiovascular system. The ANP level increases during atrial fibrillation (AF), suggesting that AF may provoke ANP secretion, but its potential mechanism is still unclear. In the present study, the potential mechanisms of rapid atrial pacing (RAP) regulating ANP secretion was explored. Rabbits were subjected to burst RAP, ANP secretion increased whereas cyclic guanosine monophosphate (cGMP) concentrations decreased during RAP. The p-Akt and p-GSK-3β levels decreased in atrial tissues. Natriuretic peptide receptor A (NPR-A) protein and particulate guanylate cyclase (PGC) activity were detected. The sensitivity of NPR-A to ANP decreased, leading to the decrease of PGC activity. Also, the isolated atrial perfusion system were made in the rabbit model, cGMP was shown to inhibit ANP secretion, and the Akt inhibitor LY294002 (LY) and GSK-3β inhibitor SB216763 (SB) attenuated the inhibitory effects of cGMP on ANP secretion and enhanced the inhibitory effects of cGMP on atrial dynamics. In conclusion, NPR-A interacts with ANP to regulate PGC expression, and influence the expression of cGMP during RAP, which involves in the Akt/GSK-3β signaling pathway. From the aforementioned points we conclude that cGMP regulates ANP secretion by the Akt/GSK-3β signaling pathway during atrial pacing.

Colchicine: Emerging therapeutic effects on atrial fibrillation by alleviating myocardial fibrosis in a rat model

Although many research have found that colchicine has general therapeutic effect in cardiovascular disease, the therapeutic mechanism in atrial fibrillation has not been clearly studied. To explore whether colchicine plays a role in the treatment of AF by reducing myocardial fibrosis, we performed a series of studies. Rat models of AF were induced by Ach-CaCl₂ to assess the therapeutic effect of colchicine at doses of 0.8 mg/kg on the duration of AF rhythm, degree of myocardial fibrosis, and secretion of inflammatory factors in the serum. RNA-Seq was also performed to elucidate the possible mechanisms by which colchicine might reduce the alleviation of myocardial fibrosis associated with AF. These studies showed that colchicine reduced the duration of AF and the degree of fibrosis in the left atrium and that it significantly reduced the secretion of TGFβ1, activin A, collagen I, and collagen III. These results suggest that colchicine may reduce myocardial fibrosis by (1) inhibiting the TGFβ1/ALK5 and activin A/ALK4 fibrosis pathways; (2) inhibiting the activation, phenotypic transformation, and apoptosis resistance of myocardial fibroblasts; and (3) reducing the synthesis of inflammatory factors and collagen.

Presenting Pattern of Atrial Fibrillation and Outcomes of Early Rhythm Control Therapy

BACKGROUND

Whether atrial fibrillation (AF) pattern or timing of AF therapy modifies the effectiveness of early rhythm control (ERC) is not known.

OBJECTIVES

This study sought to compare clinical characteristics and outcomes in patients presenting with different AF patterns on ERC vs usual care.

METHODS

The effects of ERC were compared in first-diagnosed AF (FDAF), paroxysmal AF (paroxAF), and persistent AF (persAF) in this prespecified analysis of the EAST-AFNET 4 (Early treatment of atrial fibrillation for stroke prevention) trial. Associations between AF pattern and primary outcomes (first primary outcome: cardiovascular death, stroke, and hospitalization for heart failure and acute coronary syndrome; second primary outcome: nights spent in hospital per year) were compared over a mean follow-up of 5.1 years. Changes in health-related quality of life were assessed by the EQ-5D.

RESULTS

FDAF patients (n = 1,048, enrolled 7 days after diagnosing AF) were slightly older (71 years of age, 48.0% female) than patients with paroxAF (n = 994, 70 years of age, 50.0% female) and persAF (n = 743, 70 years of age, 38.0% female). ERC reduced the primary outcome in all 3 AF patterns. Hospitalizations for acute coronary syndrome were highest in FDAF (incidence rate ratio [IRR]: 1.50; 95% CI: 0.83-2.69; P for interaction = 0.032) compared with paroxAF (IRR: 0.64; 95% CI: 0.32-1.25) and persAF (IRR: 0.50; 95% CI: 0.25-1.00). FDAF patients spent more nights in hospital (IRR: 1.38; 95% CI: 1.12-1.70; P for interaction = 0.004) than paroxAF (IRR: 0.84; 95% CI: 0.67-1.03), and persAF (IRR: 1.02; 95% CI: 0.80-1.30) patients. ERC improved health-related quality of life (EQ-5D score) in patients with paroxAF and persAF but not in patients with FDAF (P = 0.019).

CONCLUSIONS

ERC reduces the first primary composite outcome in all AF patterns. Patients with FDAF are at high risk for hospitalization and acute coronary syndrome, particularly on ERC. (Early treatment of atrial fibrillation for stroke prevention trial; ISRCTN04708680; Early Treatment of Atrial Fibrillation for Stroke Prevention Trial [EAST]; NCT01288352; Early treatment of Atrial fibrillation for Stroke prevention Trial [EAST]; EudraCT2010-021258-20).

A New Hope: Sodium-Glucose Cotransporter-2 Inhibition to Prevent Atrial Fibrillation

Atrial arrhythmias are common in patients with diabetes mellitus (DM), and despite recent advances in pharmaceutical and invasive treatments, atrial fibrillation (AF) and atrial flutter (AFl) are still associated with substantial mortality and morbidity. Clinical trial data imply a protective effect of sodium-glucose cotransporter-2 inhibitors (SGLT2is) on the occurrence of AF and AFl. This review summarizes the state of knowledge regarding DM-mediated mechanisms responsible for AF genesis and recurrence but also discusses the recent data from experimental studies, published trials and metanalyses.

Epicardial Adipose Tissue and Cardiac Arrhythmias: Focus on Atrial Fibrillation

Atrial Fibrillation (AF) is the most frequent cardiac arrhythmia and its prevalence increases with age. AF is strongly associated with an increased risk of stroke, heart failure and cardiovascular mortality. Among the risk factors associated with AF onset and severity, obesity and inflammation play a prominent role. Numerous recent evidence suggested a role of epicardial adipose tissue (EAT), the visceral fat depot of the heart, in the development of AF. Several potential arrhythmogenic mechanisms have been attributed to EAT, including myocardial inflammation, fibrosis, oxidative stress, and fat infiltration. EAT is a local source of inflammatory mediators which potentially contribute to atrial collagen deposition and fibrosis, the anatomical substrate for AF. Moreover, the close proximity between EAT and myocardium allows the EAT to penetrate and generate atrial myocardium fat infiltrates that can alter atrial electrophysiological properties. These observations support the hypothesis of a strong implication of EAT in structural and electrical atrial remodeling, which underlies AF onset and burden. The measure of EAT, through different imaging methods, such as echocardiography, computed tomography and cardiac magnetic resonance, has been proposed as a useful prognostic tool to predict the presence, severity and recurrence of AF. Furthermore, EAT is increasingly emerging as a promising potential therapeutic target. This review aims to summarize the recent evidence exploring the potential role of EAT in the pathogenesis of AF, the main mechanisms by which EAT can promote structural and electrical atrial remodeling and the potential therapeutic strategies targeting the cardiac visceral fat.

An Efficient Hybrid Methodology for Local Activation Waves Detection under Complex Fractionated Atrial Electrograms of Atrial Fibrillation

Local activation waves (LAWs) detection in complex fractionated atrial electrograms (CFAEs) during catheter ablation (CA) of atrial fibrillation (AF), the commonest cardiac arrhythmia, is a complicated task due to their extreme variability and heterogeneity in amplitude and morphology. There are few published works on reliable LAWs detectors, which are efficient for regular or low fractionated bipolar electrograms (EGMs) but lack satisfactory results when CFAEs are analyzed. The aim of the present work is the development of a novel optimized method for LAWs detection in CFAEs in order to assist cardiac mapping and catheter ablation (CA) guidance. The database consists of 119 bipolar EGMs classified by AF types according to Wells' classification. The proposed method introduces an alternative Botteron's preprocessing technique targeting the slow and small-ampitude activations. The lower band-pass filter cut-off frequency is modified to 20 Hz, and a hyperbolic tangent function is applied over CFAEs. Detection is firstly performed through an amplitude-based threshold and an escalating cycle-length (CL) analysis. Activation time is calculated at each LAW's barycenter. Analysis is applied in five-second overlapping segments. LAWs were manually annotated by two experts and compared with algorithm-annotated LAWs. AF types I and II showed 100% accuracy and sensitivity. AF type III showed 92.77% accuracy and 95.30% sensitivity. The results of this study highlight the efficiency of the developed method in precisely detecting LAWs in CFAEs. Hence, it could be implemented on real-time mapping devices and used during CA, providing robust detection results regardless of the fractionation degree of the analyzed recordings.

Association between Anemia and New-Onset Atrial Fibrillation in Critically Ill Patients in the Intensive Care Unit: A Retrospective Cohort Analysis

New-onset atrial fibrillation (NOAF) is one of the leading causes of morbidity and mortality, especially in older patients in the intensive care unit (ICU). Although many comorbidities are associated with NOAF, the effect of anemia on the onset of atrial fibrillation is still unknown. This study aimed to test the hypothesis that anemia is associated with an increased risk of developing NOAF in critically ill patients in intensive care. We performed a retrospective analysis of critically ill patients who underwent routine hemoglobin and electrocardiography monitoring in the ICU. Receiver operating characteristics analysis determined the hemoglobin (Hb) value that triggered NOAF formation. Bivariate correlation was used to determine the relationship between anemia and NOAF. The incidence of NOAF was 9.9% in the total population, and 12.8% in the patient group with anemia. Analysis of 1931 patients revealed a negative association between anemia and the development of NOAF in the ICU. The stimulatory Hb cut-off value for the formation of NOAF was determined as 9.64 g/dL. Anemia is associated with the development of NOAF in critically ill patients in intensive care.

Percutaneous Retrieval of Left Atrial Appendage Closure Devices in Patients With Atrial Fibrillation: A Case Report

Left atrial appendage closure (LAAC) devices can be inadvertently released into unfavorable locations, which may allow them to migrate to a different position within the left atrial appendage or embolize from the heart into the aorta. In such instances, it can be challenging to remove the LAAC device. Here, we present two cases in which patients with atrial fibrillation experienced LAAC device exposure at an inappropriate site because of interventional operator error and device mismatch: (a) the LAAC device was dislodged into the aortic arch and retrieved percutaneously from the femoral artery route, and (b) in the left atrium, which was dislodged into the left atrium and retrieved via atrial transseptal puncture of the femoral vein.

The Atrium in Atrial Fibrillation - A Clinical Review on How to Manage Atrial Fibrotic Substrates

Atrial fibrillation (AF) is the most common sustained arrhythmia in the population and is associated with a significant clinical and economic burden. Rigorous assessment of the presence and degree of an atrial arrhythmic substrate is essential for determining treatment options, predicting long-term success after catheter ablation, and as a substrate critical in the pathophysiology of atrial thrombogenesis. Catheter ablation of AF has developed into an essential rhythm-control strategy. Nowadays is one of the most common cardiac ablation procedures performed worldwide, with its success inversely related to the extent of atrial structural disease. Although atrial substrate evaluation remains complex, several diagnostic resources allow for a more comprehensive assessment and quantification of the extent of left atrial structural remodeling and the presence of atrial fibrosis. In this review, we summarize the current knowledge on the pathophysiology, etiology, and electrophysiological aspects of atrial substrates promoting the development of AF. We also describe the risk factors for its development and how to diagnose its presence using imaging, electrocardiograms, and electroanatomic voltage mapping. Finally, we discuss recent data regarding fibrosis biomarkers that could help diagnose atrial fibrotic substrates.

Angiotensin II Mediates Cardiomyocyte Hypertrophy in Atrial Cardiomyopathy via Epigenetic Transcriptional Regulation

Aims

European Heart Rhythm Association established an expert consensus to define, characterize, and classify atrial cardiomyopathy into four subgroups based on their histopathological features. The predominant pathological feature of classes I and III is the hypertrophy of atrial cardiomyocytes. Here, we aim to investigate the mechanism of epigenetic transcriptional regulation of cardiomyocyte hypertrophy in atrial cardiomyopathy.

Methods and Results

Compared with that of sinus rhythm control individuals, the myocardium of patients with atrial fibrillation exhibited increased levels of angiotensin II (AngII), chromatin-bound myocyte enhancer factor 2 (MEF2), acetylated histone H4 (H4ac), and H3K27ac; upregulation of hypertrophy-related genes; and decreased levels of histone deacetylase (HDAC) 4 and HDAC5 bound to the promoters of hypertrophy-related genes. Furthermore, incubation of atrial cardiomyocytes with AngII increased their cross-sectional area and improved the expression of hypertrophy-related genes. AngII also promoted the phosphorylation of HDAC4 and HDAC5 and induced their nuclear export. RNA sequencing analyses revealed that AngII significantly upregulated genes associated with cardiac hypertrophy. Chromatin immunoprecipitation showed that this correlated with increased levels of chromatin-bound MEF2, H4ac, and H3K27ac and decreased HDAC4 and HDAC5 enrichment in the promoters of hypertrophy-related genes. Moreover, these AngII-induced prohypertrophic effects could be partially reverted by treatment with the AngII receptor blocker losartan.

Conclusions

AngII had a prohypertrophic effect on atrial cardiomyopathy which was epigenetic-dependent. Patients with atrial fibrillation manifest an increased susceptibility to hypertrophy and exhibit epigenetic characteristics that are permissive for the transcription of hypertrophy-related genes. AngII induces histone acetylation via the cytoplasmic-nuclear shuttling of HDACs, which constitutes a novel mechanism of atrial hypertrophy regulation and might provide a promising therapeutic strategy for atrial cardiomyopathy.

Large and Small Animal Models of Heart Failure With Reduced Ejection Fraction

Heart failure (HF) describes a heterogenous complex spectrum of pathological conditions that results in structural and functional remodeling leading to subsequent impairment of cardiac function, including either systolic dysfunction, diastolic dysfunction, or both. Several factors chronically lead to HF, including cardiac volume and pressure overload that may result from hypertension, valvular lesions, acute, or chronic ischemic injuries. Major forms of HF include hypertrophic, dilated, and restrictive cardiomyopathy. The severity of cardiomyopathy can be impacted by other comorbidities such as diabetes or obesity and external stress factors. Age is another major contributor, and the number of patients with HF is rising worldwide in part due to an increase in the aged population. HF can occur with reduced ejection fraction (HF with reduced ejection fraction), that is, the overall cardiac function is compromised, and typically the left ventricular ejection fraction is lower than 40%. In some cases of HF, the ejection fraction is preserved (HF with preserved ejection fraction). Animal models play a critical role in facilitating the understanding of molecular mechanisms of how hearts fail. This review aims to summarize and describe the strengths, limitations, and outcomes of both small and large animal models of HF with reduced ejection fraction that are currently used in basic and translational research. The driving defect is a failure of the heart to adequately supply the tissues with blood due to impaired filling or pumping. An accurate model of HF with reduced ejection fraction would encompass the symptoms (fatigue, dyspnea, exercise intolerance, and edema) along with the pathology (collagen fibrosis, ventricular hypertrophy) and ultimately exhibit a decrease in cardiac output. Although countless experimental studies have been published, no model completely recapitulates the full human disease. Therefore, it is critical to evaluate the strength and weakness of each animal model to allow better selection of what animal models to use to address the scientific question proposed.

The Increasing Role of Rhythm Control in Patients With Atrial Fibrillation: JACC State-of-the-Art Review

The considerable mortality and morbidity associated with atrial fibrillation (AF) pose a substantial burden on patients and health care services. Although the management of AF historically focused on decreasing AF recurrence, it evolved over time in favor of rate control. Recently, more emphasis has been placed on reducing adverse cardiovascular outcomes using rhythm control, generally by using safe and effective rhythm-control therapies (typically antiarrhythmic drugs and/or AF ablation). Evidence increasingly supports early rhythm control in patients with AF that has not become long-standing, but current clinical practice and guidelines do not yet fully reflect this change. Early rhythm control may effectively reduce irreversible atrial remodeling and prevent AF-related deaths, heart failure, and strokes in high-risk patients. It has the potential to halt progression and potentially save patients from years of symptomatic AF; therefore, it should be offered more widely.

Emerging Antiarrhythmic Drugs for Atrial Fibrillation

Atrial fibrillation (AF), the most common cardiac arrhythmia worldwide, is driven by complex mechanisms that differ between subgroups of patients. This complexity is apparent from the different forms in which AF presents itself (post-operative, paroxysmal and persistent), each with heterogeneous patterns and variable progression. Our current understanding of the mechanisms responsible for initiation, maintenance and progression of the different forms of AF has increased significantly in recent years. Nevertheless, antiarrhythmic drugs for the management of AF have not been developed based on the underlying arrhythmia mechanisms and none of the currently used drugs were specifically developed to target AF. With the increased knowledge on the mechanisms underlying different forms of AF, new opportunities for developing more effective and safer AF therapies are emerging. In this review, we provide an overview of potential novel antiarrhythmic approaches based on the underlying mechanisms of AF, focusing both on the development of novel antiarrhythmic agents and on the possibility of repurposing already marketed drugs. In addition, we discuss the opportunity of targeting some of the key players involved in the underlying AF mechanisms, such as ryanodine receptor type-2 (RyR2) channels and atrial-selective K⁺-currents (I_K2P and I_SK) for antiarrhythmic therapy. In addition, we highlight the opportunities for targeting components of inflammatory signaling (e.g., the NLRP3-inflammasome) and upstream mechanisms targeting fibroblast function to prevent structural remodeling and progression of AF. Finally, we critically appraise emerging antiarrhythmic drug principles and future directions for antiarrhythmic drug development, as well as their potential for improving AF management.

Atrial Fibrillation Mechanisms Before and After Pulmonary Vein Isolation Characterized by Non-Contact Charge Density Mapping

BACKGROUND

The interaction of pulmonary vein and putative non-pulmonary triggers of atrial fibrillation (AF) remains unclear, and has yet to translate into patient tailored ablation strategies.

OBJECTIVE

To use non-contact mapping to detail the global conduction patterns in paroxysmal and persistent AF and how they are modified during pulmonary vein ablation.

METHODS

40 patients at atrial fibrillation ablation underwent mapping using a non-contact catheter (AcQMap, Acutus Medical Inc) before and after pulmonary vein isolation (PVI). Propagation history maps were analysed post-procedure for each patient to categorise conduction patterns into Focal, Organised reentrant and Disorganized patterns.

RESULTS

Activation patterns identified by using a non-contact mapping system can be sub-classified from three main patterns into subtypes (MacroReentrant and LocalisedReentrant subtypes, Disorganized 1 and Disorganized 2 subtypes). Persistent AF demonstrated more D-Patterns, and less O-Patterns and F-Patterns than paroxysmal AF. In addition, PAF patients inducible after PVI demonstrated a greater number and higher prevalence of MR subtypes than those non-inducible. PVs remained the critical region and included almost one third of all patterns across any AF-types. PVI was effective to eliminate PV-related functional phenotypes, and impacted on recurrence with other patterns.

CONCLUSION

Activation patterns identified using AcQMap can be classified into three main patterns (F-Patterns, O-Patterns and D-Patterns) as well as subtypes (MR and LR subtype, D1 and D2 subtype). PerAF was different from PAF in demonstrating a greater region number and prevalence of D-Patterns, but lower region number and prevalence of O-Patterns and F-Patterns.

The effects of apixaban on clot characteristics in atrial fibrillation: A novel pharmacodynamic biomarker

Atrial fibrillation (AF) is a major risk factor for stroke. We aim to characterize AF patients and the effects of apixaban therapy in terms of clot microstructure using gel point analysis, a novel biomarker. Seventy-eight patients were included in the study, 50 Stroke with AF (AF-S), and 28 AF without stroke (AF). Pre- and post-anticoagulation samples were collected: gel point (GP) analysis was performed to obtain (i) TGP (the time taken to reach the GP or the clot formation time) and (ii) d_{f ,} the fractal dimension of the clot, a quantification of clot fibrin microstructure at the GP. At baseline, the AF-S group had a d_f  = 1.70 (±0.05) and TGP = 306 (±73 s). The AF group had a df = 1.70 ± 0.05 and TGP = 346 ± 78 s, showing a significantly shortened TGP in the stroke group (p = .008). For both groups, apixaban significantly prolonged TGP, p = .005, but resulted in no change in df. Apixaban prolonged clotting time while having no significant impact on the blood's ability to form stable clots (no change in d_f ). This indicates that apixaban provides protection from the formation of thrombi by reducing clotting kinetics.

Cardiovascular Complications of Interatrial Conduction Block: JACC State-of-the-Art Review

Interatrial block (IAB) is an electrocardiographic pattern describing the conduction delay between the right and left atria. IAB is classified into 3 degrees of block that correspond to decreasing conduction in the region of Bachmann's bundle. Although initially considered benign in nature, specific subsets of IAB have been associated with atrial arrhythmias, elevated thromboembolic stroke risk, cognitive impairment, and mortality. As the pathophysiologic relationships between IAB and stroke are reinforced, investigation has now turned to the potential benefit of early detection, atrial imaging, cardiovascular risk factor modification, antiarrhythmic pharmacotherapy, and stroke prevention with oral anticoagulation. This review provides a contemporary overview of the epidemiology, pathophysiology, diagnosis, and management of IAB, with a focus on future directions.

Endomysial fibrosis, rather than overall connective tissue content, is the main determinant of conduction disturbances in human atrial fibrillation

Aims

Although in persistent atrial fibrillation (AF) a complex AF substrate characterized by a high incidence of conduction block has been reported, relatively little is known about AF complexity in paroxysmal AF (pAF). Also, the relative contribution of various aspects of structural alterations to conduction disturbances is not clear. In particular, the contribution of endomysial fibrosis to conduction disturbances during progression of AF has not been studied yet.

Methods and results

During cardiac surgery, epicardial high-density mapping was performed in patients with acutely induced (aAF, n = 11), pAF (n = 12), and longstanding persistent AF (persAF, n = 9) on the right atrial (RA) wall, the posterior left atrial wall (pLA) and the LA appendage (LAA). In RA appendages, overall and endomysial (myocyte-to-myocyte distances) fibrosis and connexin 43 (Cx43) distribution were quantified. Unipolar AF electrogram analysis showed a more complex pattern with a larger number of narrower waves, more breakthroughs and a higher fractionation index (FI) in persAF compared with aAF and pAF, with no differences between aAF and pAF. The FI was consistently higher at the pLA compared with the RA. Structurally, Cx43 lateralization increased with AF progression (aAF = 7.5 ± 8.9%, pAF = 24.7 ± 11.1%, persAF = 35.1 ± 11.4%, P < 0.001). Endomysial but not overall fibrosis correlated with AF complexity (r = 0.57, P = 0.001; r = 0.23, P = 0.20; respectively).

Conclusions

Atrial fibrillation complexity is highly variable in patients with pAF, but not significantly higher than in patients with acutely induced AF, while in patients with persistent AF complexity is higher. Among the structural alterations studied, endomysial fibrosis, but not overall fibrosis, is the strongest determinant of AF complexity.

Paroxysmal Atrial Fibrillation in Horses: Pathophysiology, Diagnostics and Clinical Aspects

Atrial fibrillation (AF) is the most common arrhythmia in horses causing poor performance. As in humans, the condition can be intermittent in nature, known as paroxysmal atrial fibrillation (pAF). This review covers the literature relating to pAF in horses and includes references to the human literature to compare pathophysiology, clinical presentation, diagnostic tools and treatment. The arrhythmia is diagnosed by auscultation and electrocardiography (ECG), and clinical signs can vary from sudden loss of racing performance to reduced fitness or no signs at all. If left untreated, pAF may promote electrical, functional and structural remodeling of the myocardium, thus creating a substrate that is able to maintain the arrhythmia, which over time may progress into permanent AF. Long-term ECG monitoring is essential for diagnosing the condition and fully understanding the duration and frequency of pAF episodes. The potential to adapt human cardiac monitoring systems and computational ECG analysis is therefore of interest and may benefit future diagnostic tools in equine medicine.

Extended ECG Improves Classification of Paroxysmal and Persistent Atrial Fibrillation Based on P- and f-Waves

Background

The standard 12-lead ECG has been shown to be of value in characterizing atrial conduction properties. The added value of extended ECG recordings (longer recordings from more sites) has not been systematically explored yet.

Objective

The aim of this study is to employ an extended ECG to identify characteristics of atrial electrical activity related to paroxysmal vs. persistent atrial fibrillation (AF).

Methods

In 247 participants scheduled for AF ablation, an extended ECG was recorded (12 standard plus 3 additional leads, 5 min recording, no filtering). For patients presenting in sinus rhythm (SR), the signal-averaged P-wave and the spatiotemporal P-wave variability was analyzed. For patients presenting in AF, f-wave properties in the QRST (the amplitude complex of the ventricular electrical activity: Q-, R-, S-, and T-wave)-canceled ECG were determined.

Results

Significant differences between paroxysmal (N = 152) and persistent patients with AF (N = 95) were found in several P-wave and f-wave parameters, including parameters that can only be calculated from an extended ECG. Furthermore, a moderate, but significant correlation was found between echocardiographic parameters and P-wave and f-wave parameters. There was a moderate correlation of left atrial (LA) diameter with P-wave energy duration (r = 0.317, p < 0.001) and f-wave amplitude in lead A3 (r = -0.389, p = 0.002). The AF-type classification performance significantly improved when parameters calculated from the extended ECG were taken into account [area under the curve (AUC) = 0.58, interquartile range (IQR) 0.50-0.64 for standard ECG parameters only vs. AUC = 0.76, IQR 0.70-0.80 for extended ECG parameters, p < 0.001].

Conclusion

The P- and f-wave analysis of extended ECG configurations identified specific ECG features allowing improved classification of paroxysmal vs. persistent AF. The extended ECG significantly improved AF-type classification in our analyzed data as compared to a standard 10-s 12-lead ECG. Whether this can result in a better clinical AF type classification warrants further prospective study.

Restoring Ravaged Heart: Molecular Mechanisms and Clinical Application of miRNA in Heart Regeneration

Human heart development is a complex and tightly regulated process, conserving proliferation, and multipotency of embryonic cardiovascular progenitors. At terminal stage, progenitor cell type gets suppressed for terminal differentiation and maturation. In the human heart, most cardiomyocytes are terminally differentiated and so have limited proliferation capacity. MicroRNAs (miRNAs) are non-coding single-stranded RNA that regulate gene expression and mRNA silencing at the post-transcriptional level. These miRNAs play a crucial role in numerous biological events, including cardiac development, and cardiomyocyte proliferation. Several cardiac cells specific miRNAs have been discovered. Inhibition or overexpression of these miRNAs could induce cardiac regeneration, cardiac stem cell proliferation and cardiomyocyte proliferation. Clinical application of miRNAs extends to heart failure, wherein the cell cycle arrest of terminally differentiated cardiac cells inhibits the heart regeneration. The regenerative capacity of the myocardium can be enhanced by cardiomyocyte specific miRNAs controlling the cell cycle. In this review, we focus on cardiac-specific miRNAs involved in cardiac regeneration and cardiomyocyte proliferation, and their potential as a new clinical therapy for heart regeneration.

Identification of Atrial Fibrillation-Related lncRNA Based on Bioinformatic Analysis

BACKGROUND

Atrial fibrillation (AF) is the most common arrhythmia in the world. Long noncoding RNA (lncRNA) has been found to play an important role in cardiovascular diseases including heart failure, myocardial infarction, and atherosclerosis. However, the role of lncRNA in AF has rarely been studied. The purpose of this study is to identify the expression profile of lncRNA in AF patients, explore the function of lncRNA in AF, and provide a potential scientific basis for the treatment of AF in the future.

METHODS

The lncRNA and mRNA expression profiles were obtained from the atrial appendage samples of GSE31821, GSE411774, GSE79768, and GSE115574 in the Gene Expression Omnibus (GEO) database. Functional analysis was performed via Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Gene Set Variation Analysis (GSVA). The "CIBERSORT" R kit was used to analyze 22 immune cell infiltrates in AF and sinus rhythm (SR) patients. The "CORRPLOT" R package was used to analyze the immune correlation between lncRNA and immune cells.

RESULTS

A total of 6 differentially expressed lncRNAs and 45 differentially expressed mRNAs were identified in the AF and SR groups. GO, KEGG, and GSVA results showed that abnormally expressed lncRNAs were involved in signaling pathways related to the atrium, including the Toll-like receptor signaling pathway and calcium signaling pathway. Immune cell infiltration analysis revealed that native B cells, follicular helper T cells, and resting dendritic cells may be involved in the AF process. In addition, LINC00844 was negatively correlated with resting dendritic cells.

CONCLUSION

The expression profile of lncRNA in AF patients was different from that in normal controls. The physiological functions of these differentially expressed lncRNAs may be related to the pathogenesis of AF, which provide a scientific basis for the prognosis and treatment of patients with AF.

Postoperative atrial fibrillation and atrial epicardial fat: Is there a link?

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Detailed local EAT analysis does not differ between POAF and non-POAF.

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General rather than local effects of EAT play a role in the onset of early POAF.

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The dominance of surgical induced factors may obscure the potential role of EAT.

Background

Atrial Epicardial Adipose Tissue (EAT) is presumably involved in the pathogenesis of atrial fibrillation (AF). The transient nature of postoperative AF (POAF) suggests that surgery-induced triggers provoke an unmasking of a pre-existent AF substrate. The aim is to investigate the association between the volume of EAT and the occurrence of POAF. We hypothesise that the likelihood of developing POAF is higher in patients with high compared to low left atrial (LA) EAT volumes.

Methods

Quantification of LA EAT based on the Hounsfield Units using custom made software was performed on pre-operative coronary computed tomography angiography scans of patients who underwent cardiac surgery between 2009 and 2019. Patients with mitral valve disease were excluded.

Results

A total of 83 patients were included in this study (CABG = 34, aortic valve = 33, aorta ascendens n = 7, combination n = 9), of which 43 patients developed POAF. The EAT percentage in the LA wall nor indexed EAT volumes differed between patients with POAF and with sinus rhythm (all P > 0.05). In multivariable analysis, age and LA volume index (LAVI) were the only independent predictors for early POAF (OR: 1.076 and 1.056, respectively).

Conclusions

As expected, advanced age and LAVI were independent predictors of POAF. However, the amount of local EAT was not associated with the occurrence of AF after cardiac surgery. This suggests that the role of EAT in POAF is rather limited, or that the association of EAT in the early phase of POAF is obscured by the dominance of surgical-induced triggers.

Recent advances in the tools available for atrial fibrillation ablation

INTRODUCTION

Atrial fibrillation (AF) is the commonest arrhythmia in clinical practice with significant detrimental health impacts. Much effort has been spent in mapping AF, determine its triggers and drivers, and how to develop tools to eliminate these triggers.

AREAS COVERED

In this state of-the-art review article, we aim to highlight the recent techniques in catheter-based management of Atrial Fibrillation; including new advancements either in the catheter design or the software used. This includes a comprehensive summary of the most recent tools used in AF mapping and subsequent ablation.

EXPERT OPINION

Electrical isolation of the pulmonary veins has been developed and established as the cornerstone in AF ablation with good results in patients with paroxysmal AF (PAF) whilst new ablation tools are aimed at streamlining the procedure. However, the quest for persistent AF (PeAF) remains. The future of AF ablation, we believe, lies in identifying AF drivers by means of the new developing mapping tools and altering their electrical properties in a safe, reproducible, and effective manner.

Clinical characteristics and prognostic factors of atrial fibrillation at a tertiary center of Pakistan - From a South-Asian perspective - A cross-sectional study

Background

There is lack of large data from South-Asian region on atrial fibrillation and it is imperative that clinical presentation, prognostic factors, management pursued, and outcomes are known for this part of the world. Once collective evidence for the region is known, region-specific guidelines can be laid forward.

Objectives

To evaluate clinical characteristics and prognostic factors of atrial fibrillation at a tertiary care center of Pakistan.

Methods

This was a retrospective study conducted at a tertiary care center of Pakistan. Period of study ranged from July–December 2018. All hospitalized patients who were admitted with atrial fibrillation as a primary or associated diagnosis were enrolled.

Results

A total of 636 patients were enrolled. The mean age was 68.5 ± 12 years and 49.5% (315) were male. 90.6% of the patients were admitted via emergency room. Majority (59.9%) had previously known AF and 40% developed new-onset AF during the hospital stay. Hypertension was the most common co-morbid condition (85.4%) followed by Diabetes Mellitus (40.1%). At least 9% had rheumatic heart disease. The median CHA₂DS₂VASc and HASBLED scores were 4 and 2 respectively. More than one-third of patients had sepsis as a primary diagnosis (36.8%). The in-hospital mortality of patients with atrial fibrillation was 6.7%. Patients with new-onset AF had higher mortality. Sepsis and stroke were independently associated with a higher mortality. There was no significant difference in median CHA₂DS₂VASc and HASBLED scores for patients with new-onset and previously known AF. On discharge, 83% of the eligible patients received oral anticoagulation.

Conclusion

There was higher prevalence of chronic co-morbid conditions in the studied population leading to a higher CHA₂DS₂VASC Score. Sepsis and stroke were independently associated with higher in-hospital mortality.

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Sepsis and stroke are independently associated with higher in-hospital mortality in patients with atrial fibrillation.

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There is higher prevalence of chronic co-morbid conditions in the studied population.

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Hypertension is the most common co-morbid condition associated with atrial fibrillation.

Cardiac fibrosis and atrial fibrillation

Cardiac fibrosis is characterized by the imbalance of production and degradation of the extracellular matrix. The result of this process is an accumulation of scar tissue, which is associated with many pathological processes such as excessive mechanical stress on the heart, inflammation, ischemia, oxidative stress, or excessive neurohormonal activation. Fibrotic response results in damaged heart architecture and dysfunction of the heart. Cardiac fibrosis leads to increased stiffness of the left ventricle and arteries, promotes disorders of contraction and relaxation of the heart, disrupts electrophysiology of heart cells, and induces arrhythmias.

Atrial fibrillation is one of the most common arrhythmias. It is associated with a deterioration in the quality of life and more frequent use of medical assistance. It is also an instantaneous risk factor for many diseases, including stroke. The underlying cause of this arrhythmia is electrical and structural remodeling induced by cardiac fibrosis. Therefore, much attention is paid to the search for biochemical markers that would allow non-invasive determination of the degree of this fibrosis.

The promising markers include galectin-3, human epididymis protein 4 (HE4), serum soluble ST2, and adipose triglyceride lipase (ATGL). Studies have shown that plasma concentrations of these substances reflect the degree of myocardial fibrosis and are indirectly associated with AF.

There are high hopes for the use of these markers in patients undergoing arrhythmia ablation. More research is needed to confirm that these markers can be used to estimate the chance of maintaining sinus rhythm in patients after ablation.

Renal denervation reduces atrial remodeling in hypertensive rats with metabolic syndrome

Atrial fibrillation (AF) is highly prevalent in hypertensive patients with metabolic syndrome and is related to inflammation and activation of the sympathoadrenergic system. The multi-ligand Receptor-for-Advanced-Glycation-End-products (RAGE) activates inflammation-associated tissue remodeling and is regulated by the sympathetic nervous system. Its counterpart, soluble RAGE (sRAGE), serves as anti-inflammatory decoy receptor with protective properties. We investigated the effect of sympathetic modulation by renal denervation (RDN) on atrial remodeling, RAGE/sRAGE and RAGE ligands in metabolic syndrome. RDN was performed in spontaneously hypertensive obese rats (SHRob) with metabolic syndrome compared with lean spontaneously hypertensive rats (SHR) and with normotensive non-obese control rats. Blood pressure and heart rate were measured by telemetry. The animals were killed 12 weeks after RDN. Left atrial (LA) and right atrial (RA) remodeling was assessed by histological analysis and collagen types. Sympathetic innervation was measured by tyrosine hydroxylase staining of atrial nerve fibers, RAGE/sRAGE, RAGE ligands, cytokine expressions and inflammatory infiltrates were analyzed by Western blot and immunofluorescence staining. LA sympathetic nerve fiber density was higher in SHRob (+44%) versus controls and reduced after RDN (-64% versus SHRob). RAGE was increased (+718%) and sRAGE decreased (- 62%) in SHRob as compared with controls. RDN reduced RAGE expression (- 61% versus SHRob), significantly increased sRAGE levels (+162%) and induced a significant decrease in RAGE ligand levels in SHRob (- 57% CML and - 51% HMGB1) with reduced pro-inflammatory NFkB activation (- 96%), IL-6 production (- 55%) and reduced inflammatory infiltrates. This led to a reduction in atrial fibrosis (- 33%), collagen type I content (- 72%), accompanied by reduced LA myocyte hypertrophy (- 21%). Transfection experiments on H9C2 cardiomyoblasts demonstrated that RAGE is directly involved in fibrosis formation by influencing cellular production of collagen type I. In conclusion, suppression of renal sympathetic nerve activity by RDN prevents atrial remodeling in metabolic syndrome by reducing atrial sympathetic innervation and by modulating RAGE/sRAGE balance and reducing pro-inflammatory and pro-fibrotic RAGE ligands, which provides a potential therapeutic mechanism to reduce the development of AF.

ECG signal classification based on deep CNN and BiLSTM

Background

Currently, cardiovascular disease has become a major disease endangering human health, and the number of such patients is growing. Electrocardiogram (ECG) is an important basis for {medical doctors to diagnose the cardiovascular disease, which can truly reflect the health of the heart. In this context, the contradiction between the lack of medical resources and the surge in the number of patients has become increasingly prominent. The use of computer-aided diagnosis of cardiovascular disease has become particularly important, so the study of ECG automatic classification method has a strong practical significance.

Methods

This article proposes a new method for automatic identification and classification of ECG.We have developed a dense heart rhythm network that combines a 24-layer Deep Convolutional Neural Network (DCNN) and Bidirectional Long Short-Term Memory (BiLSTM) to deeply mine the hierarchical and time-sensitive features of ECG data. Three different sizes of convolution kernels (32, 64 and 128) are used to mine the detailed features of the ECG signal, and the original ECG is filtered using a combination of wavelet transform and median filtering to eliminate the influence of noise on the signal. A new loss function is proposed to control the fluctuation of loss during the training process, and convergence mapping of the tan function in the range of 0–1 is employed to better reflect the model training loss and correct the optimization direction in time.

Results

We applied the dataset provided by the 2017 PhysioNet/CINC challenge for verification. The experiment adopted ten-fold cross validation,and obtained an accuracy rate of 89.3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\%$$\end{document}% and an F1 score of 0.891.

Conclusions

This article proposes its own method in the aspects of ECG data preprocessing, feature extraction and loss function design. Compared with the existing methods, this method improves the accuracy of automatic ECG classification and is helpful for clinical diagnosis and self-monitoring of atrial fibrillation.

Long-term mortality and cardiovascular outcomes in patients with atrial flutter after catheter ablation

AIMS

For patients with typical and atypical atrial flutter (AFL) but without history of atrial fibrillation (AF), the long-term cardiovascular (CV) outcomes after catheter ablation for AFL remain unclear. We compared the long-term all-cause mortality and CV outcomes in patients with AFL receiving catheter ablation compared with the results with medical therapy.

METHODS AND RESULTS

Atrial flutter patients receiving catheter ablation for typical AFL were identified using the Health Insurance Database, and constituted the 'AFL ablation group'. Patients with typical and atypical AFL but without ablation (AFL without ablation group) were propensity matched to the AFL ablation group. Patients with prior AF diagnosis were excluded. Primary outcomes included all-cause and CV mortality, heart failure (HF) hospitalization, and stroke. The multivariable cox hazards regression model was used to evaluate the hazard ratio (HR) for study outcomes. A total of 3784 AFL patients (1892 patients in each group) was studied. Their mean follow-up durations were 7.85 ± 2.57 years (AFL without ablation group) and 8.31 ± 4.53 years (AFL ablation group). Atrial flutter with ablation patients had lower risks of all-cause mortality (HR: 0.68, P < 0.001), CV deaths (HR: 0.78, P = 0.001), HF hospitalization (HR: 0.84, P = 0.01), and stroke (HR: 0.80, P = 0.01).

CONCLUSIONS

Catheter ablation for AFL in patients without prior AF was associated with lower risks of all-cause mortality and CV events compared with AFL patients without ablation during long-term follow-ups.

Investigating the association between P wave duration and atrial fibrillation recurrence after radiofrequency ablation in early persistent atrial fibrillation patients

BACKGROUND

In the present study, we aimed to explore the association between P wave duration, as the measured time from the start point of the P wave to the end point, and atrial fibrillation recurrence after transcatheter radiofrequency ablation in patients with early persistent atrial fibrillation.

METHODS

Patients with early persistent atrial fibrillation who underwent the first radiofrequency ablation procedure were retrospectively analyzed. The electrocardiographic, echocardiographic and clinical data of the enrolled patients before and after operation were collected and recorded. After adjusting confounding factors and performing stratified analysis, the association between the P wave duration and the atrial fibrillation recurrence of patients with early persistent atrial fibrillation after radiofrequency ablation was explored.

RESULTS

The proportions of atrial fibrillation recurrence of the low, medium, and high P wave duration groups were 6.4%, 19.7%, and 47.0%, respectively. After potential confounding factors were adjusted, the risk of atrial fibrillation recurrence gradually increased with the increase of P wave duration (odds ratio: 1.093, 95% confidence interval: 1.063-1.124, p < 0.001). This trend was statistically significant (odds ratio: 1.099, 95% confidence interval: 1.052-1.149, p < 0.001), especially in comparison of high vs. low (odds ratio: 16.99, 95% confidence interval: 4.75-60.78, p < 0.001). Curve fitting showed that there was a linear and positive association between the P wave duration and the risk of atrial fibrillation recurrence. This association was consistent in different subgroups based on gender, drinking, history of smoking, hypertension, diabetes mellitus, peripheral artery disease, stroke or transient ischemia attack, hyperlipidemia, heart failure, and heart rate, suggesting that there was no significant interaction between different grouping parameters and the association (p for interaction range = 0.217-0.965).

CONCLUSIONS

In patients with early persistent atrial fibrillation who underwent radiofrequency ablation procedure for the first time and converted to sinus rhythm, the P wave duration within 72 h after the procedure was independently associated with the risk of atrial fibrillation recurrence, and such association was linear and positive.

Applications of multimodality imaging for left atrial catheter ablation

Atrial arrhythmias, including atrial fibrillation and atrial flutter, may be treated through catheter ablation. The process of atrial arrhythmia catheter ablation, which includes patient selection, pre-procedural planning, intra-procedural guidance, and post-procedural assessment, is typically characterized by the use of several imaging modalities to sequentially inform key clinical decisions. Increasingly, advanced imaging modalities are processed via specialized image analysis techniques and combined with intra-procedural electrical measurements to inform treatment approaches. Here, we review the use of multimodality imaging for left atrial ablation procedures. The article first outlines how imaging modalities are routinely used in the peri-ablation period. We then describe how advanced imaging techniques may inform patient selection for ablation and ablation targets themselves. Ongoing research directions for improving catheter ablation outcomes by using imaging combined with advanced analyses for personalization of ablation targets are discussed, together with approaches for their integration in the standard clinical environment. Finally, we describe future research areas with the potential to improve catheter ablation outcomes.

Device-Based Sympathetic Nerve Regulation for Cardiovascular Diseases

Sympathetic overactivation plays an important role in promoting a variety of pathophysiological processes in cardiovascular diseases (CVDs), including ventricular remodeling, vascular endothelial injury and atherosclerotic plaque progression. Device-based sympathetic nerve (SN) regulation offers a new therapeutic option for some CVDs. Renal denervation (RDN) is the most well-documented method of device-based SN regulation in clinical studies, and several large-scale randomized controlled trials have confirmed its value in patients with resistant hypertension, and some studies have also found RDN to be effective in the control of heart failure and arrhythmias. Pulmonary artery denervation (PADN) has been clinically shown to be effective in controlling pulmonary hypertension. Hepatic artery denervation (HADN) and splenic artery denervation (SADN) are relatively novel approaches that hold promise for a role in cardiovascular metabolic and inflammatory-immune related diseases, and their first-in-man studies are ongoing. In addition, baroreflex activation, spinal cord stimulation and other device-based therapies also show favorable outcomes. This review summarizes the pathophysiological rationale and the latest clinical evidence for device-based therapies for some CVDs.