Atrial Electrical Remodeling Research Articles

Left atrial strain by reperfusion strategy as a predictor for MACE in patients after ST-elevation myocardial infarction

Abstract Background Left atrial electrical and mechanical remodelling (LAr) is a complex process attributable to multiple cardiovascular risk factors, it occurs as early as common cardiovascular risk factors are established and it’s a time-dependent response of the cardiomyocytes. Early reperfusion, the cornerstone in the STEMI management, prevents microvascular injury. Pharmacoinvasive strategy (PhI) via STEMI networks is rapidly gaining momentum to achieve optimal total ischemic time. Purpose To determine the importance of left atrial strain (LAS) as a marker of LAr and a predictor of MACE in patients after STEMI and (PhI). Methods Patients ≥18 years old diagnosed with STEMI at a single centre from April 2021 to February 2024 were included. Echocardiograms were performed by specialists within a month of the event. The main outcome was major adverse cardiovascular events, defined by reinfarction, heart failure, cardiogenic shock, major bleeding, or cardiovascular death. Events were prospectively recorded with a maximum follow-up of 900 days. Grouping was done according to two parameters: LAS below or above 25%, and reperfusion strategy, with 4 groups as a result. Baseline characteristics were analysed using an ANOVA test for normal variables, and Mann-Whitney test with a Kruskal-Wallis test for non-normal variables. Dichotomic variables were analysed using a Chi-square test. Survival analysis was done with a Kaplan-Meier Curve and Log-Rank test. All analyses were performed using StataMP 14.1. Results We included 144 patients, of which 87% (n=125) were male, and the median age was 60 years. The most common comorbidities were hypertension (52%), type 2 diabetes (40.3%), and tobacco use history (48%). The median total ischemic time was 283 minutes, with 12.7% having a total ischemic time <120 minutes. Median LVEF was 50%, whereas median global longitudinal strain was -15%. There was no difference among groups in any of the baseline characteristics. Group 1 (LAS <25% + PhI), had 35 patients, group 2 (LAS ≥25% + PhI) included 36 patients, group 3 (LAS<25% + PCI) had 18 patients, and group 4 (LAS ≥25% + PCI) had 55 patients. Composite of MACE was significantly increased in group 3 (p=0.005). The individual components of cardiovascular death (p=0.0035) and heart failure (p=0.036) were also increased in group 3. Conclusion Left atrial function has been widely recognized as a cardiac biomarker, due to its capability to predict the risk for heart failure and arrhythmias. Group 3 patients, who had a LAS below 25% and underwent a PCI strategy, had a significantly increased risk of MACE. This might be explained by delayed reperfusion in areas with sparse PCI centres. Prevention of microvascular damage and LAr might be achieved by early reperfusion either with pharmacoinvasive or primary coronary intervention. LAS, as a marker of LAr and microvascular injury, could be used as a predictor for MACE in STEMI patients. Table 1. Baseline Characteristics Figue 1. Kaplan-Meier Survival Curve

Inhibition of P2X7 receptor mitigates atrial fibrillation susceptibility in isoproterenol-induced rats.

Atrial fibrillation (AF) is a common cardiac arrhythmia that is characterized by atrial electrical remodeling. The P2X7 receptor (P2X7R), an ATP-gated ion channel, has been implicated in cardiovascular pathologies; however, its role in atrial electrical remodeling remains unclear. This study investigated whether inhibition of P2X7R could mitigate isoproterenol (ISO)-induced atrial electrical remodeling in rats and explored the underlying mechanisms. Two gene expression profiles related to AF (GSE79768 and GSE10598) were downloaded from the Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) were screened using GEO2R. Mendelian randomization (MR) investigated the causal relationship between P2X7R expression and AF. Enrichment analysis was also conducted. An animal model was established via intraperitoneal injection of ISO for 2 weeks. The rats were divided into three groups: control (CTL), ISO, and ISO+Brilliant Blue G (BBG). Cardiac electrophysiological parameters were assessed using programmed electrical stimulation. Myocardial fibrosis and hypertrophy were evaluated using Sirius Red and Wheat Germ Agglutinin staining, respectively. P2X7R abundance was assessed using immunofluorescence, and relevant proteins were detected by Western blotting. GEO2R and MR analyses indicated a correlation between P2X7R expression and AF. Rats in the ISO group exhibited increased P2X7R levels, abnormal cardiac electrophysiology, altered ion channel protein expression, myocardial hypertrophy, and fibrosis. Enrichment analysis indicated that oxidative stress responses might be involved, and Western blotting showed significantly elevated levels of NOX, CaMKII, and associated proteins. BBG (P2X7R inhibitor) treatment mitigated these effects. P2X7R was associated with AF, and inhibition of P2X7R curbed electrical and structural remodeling in ISO-induced AF, potentially via the NOX/CaMKII pathway.

Oroxin B Resembles Bisoprolol in Attenuating Beta1-Adrenergic Receptor Autoantibody-Induced Atrial Remodelling via the PTEN/AKT/mTOR Signalling Pathway.

Beta1-adrenergic receptor autoantibodies (β1-AAbs) promote atrial remodelling and ultimately lead to the development of atrial fibrillation (AF). Oroxin B is a natural flavonoid glycoside with a variety of biological activities, including anti-inflammatory and autophagy-promoting effects, and has therapeutic benefits for a variety of diseases. The aim of this study was to investigate the potential therapeutic role of Oroxin B in the development of β1-AAb-induced atrial fibrillation and to elucidate the underlying mechanisms involved. We established a rat model of β1-AAb-induced atrial fibrillation via active immunisation. The first stage was divided into three groups: the control group, the β1-AAb group and the β1-AAb + bisoprolol group. The second stage was divided into three groups: the control group, the β1-AAb group and the β1-AAb + Oroxin B group. Serum levels of β1-AAbs, atrial tissue levels of cyclic monophosphate (cAMP), atrial electrophysiological parameters, cardiac structure and function, mitochondrial structure, autophagy levels, cardiomyocyte apoptosis and myocardial fibrosis were examined. The results showed that bisoprolol, a β1-blocker, improved β1-AAb-induced atrial electrical remodelling, reduced atrial collagen deposition, ameliorated the increase in LAD and regulated the balance of autophagy and apoptosis in atrial myocytes through the PTEN/AKT/mTOR signalling pathway. Oroxin B, a PTEN agonist, can improve the impairment of autophagy homeostasis and apoptosis in atrial tissue by activating the PTEN/AKT/mTOR signalling pathway, thereby improving atrial structure and electrical remodelling. Moreover, Oroxin B may play a therapeutic role in β1AAb-induced atrial fibrillation. In conclusion, our results demonstrate the potential therapeutic role of Oroxin B in β1AAb-induced atrial fibrillation and the underlying mechanisms, suggesting that Oroxin B may be an effective antiarrhythmic medication.

The gut microbial metabolite phenylacetylglutamine increases susceptibility to atrial fibrillation after myocardial infarction through ferroptosis and NLRP3 inflammasome.

Myocardial infarction (MI) is an important risk factor for the development of atrial fibrillation (AF), and the gut microbial metabolite phenylacetylglutamine (PAGln) is strongly associated with the prognosis of MI patients. However, whether PAGln is involved in the regulation of AF after MI is currently unknown. Therefore, the present study aimed to explore the effect of PAGln on the susceptibility to AF after MI.MI model was constructed by surgically ligating the left anterior descending branch of the coronary artery. PAGln was administered by intraperitoneal injection for 7 consecutive days starting after surgery and then investigated by histopathologic, molecular biological, and electrophysiologic studies.Myocardial ischemia resulted in intestinal barrier dysfunction and significantly increased circulating levels of PAGln. Compared with the myocardial ischemia group, administration of PAGln significantly exacerbated atrial fibrosis and atrial electrical remodeling in mice after myocardial ischemia, as evidenced by shortening of the ERP (at varying pacing cycle lengths of 40, 60, 80, and 100), ion channel remodeling (Nav1.5, Cav1.2, and Kv1.5), and decreased expression of CX40, which led to an increase in the susceptibility to AF (54.5% vs. 90.9%, P < 0.05). In addition, administration of PAGln further exacerbated MI-induced intestinal barrier dysfunction compared with the MI group. Mechanistically, PAGln may affect atrial remodeling and AF susceptibility after MI by modulating ferroptosis and NLRP3 inflammasome.The present study preliminarily reveals that the gut microbial metabolite PAGln exacerbates post-MI AF remodeling and AF susceptibility, possibly through ferroptosis and activation of NLRP3 inflammasome.

Abstract 4144530: IL-37 promotes resolution of Right Heart Disease-induced inflammation and atrial fibrillation.

INTRODUCTION: Atrial Fibrillation (AF) is the most common cardiac arrhythmia. Hypertension, obesity, diabetes or right heart disease (RHD) are important risk factors for AF. Inflammation stands as a common denominator among most AF risk factors. Studies have shown that patients with AF present high levels of circulating IL-18. Our group recently described that inflammation-resolution may prevent AF in RHD, however, the mechanism remains unclear. To inhibit IL-18-induced inflammation, IL37, a specific antagonist of IL-18-receptor was shown to attenuate cardiac fibrosis in a mice model of myocardial infarction, but little is known about its efficacy to prevent AF. HYPOTHESIS: IL-37 curbs RHD-induced atrial inflammation and AF vulnerability. METHODS: To induce right-sided cardiac hypertrophy and dilation, pulmonary artery banding (PAB) was performed in male and female Wistar rats (250-300g). Sham animals did not receive the ligation. Animals were randomized into four groups: Sham and PAB treated or not with IL37 (100 ng/ml/kg). Electrophysiological studies and echocardiography were performed in vivo before sacrifices at day (D)0, D7, D14 and D21. To analyze the atrial conduction, right atrial (RA) optical mapping was performed on Langendorff-perfused hearts. Histology, western blot, and qPCR were performed to study the expression of proteins and genes involved in atrial inflammation, fibrosis, and electrical remodeling. RESULTS: Twenty-one days after surgery, PAB rats were more vulnerable to AF and developed severe right-sided hypertrophy and dilation compared to Sham. Reliable to clinical evidence, female rats might be more resistant to AF than males. AF was associated with increased RA levels of inflammatory biomarkers including IL18, IL1β, and IL6. IL37 treatment was associated with decreased atrial expression of inflammatory markers. CONCLUSION: IL37 is a potential new therapeutic strategy to reduce atrial inflammation and prevent AF vulnerability in RHD.

The connection site of the Bachmann bundle to the left atrium affects atrial electrical and anatomical remodeling

Abstract Background A common route for the propagation of the conduction system from the right atrium to the left atrium (LA) is via the Bachmann bundle (BB) which is a parallel-aligned muscular structure. It is empirically known that the site of conduction from BB to LA differs depending on the patient. Purposes To clear the clinical significance of differences in the BB conduction sites in patients with atrial fibrillation (AF). Methods We studied 182 patients (90 non-paroxysmal AF, 121 males, and 68.2 ± 10.0 years) who received catheter ablation for AF. Clinical data, echocardiographic data, and blood samples were evaluated. High-density LA mapping during high right atrial pacing was constructed. The site of conduction from BB to LA, the global activation time, LA mean voltage, the abnormal conduction zone (ACZ), and the conduction block (CBZ) were evaluated. The conduction from BB was connected to the region surrounded by the left atrial roof line, the carina of the right pulmonary vein, and the base of the left atrial appendage in all patients (Figure 1). This area was divided into four regions (right-roof, mid-roof, right-anterior, and mid-anterior area), and BB conduction sites were classified into each area by three independent observers who did not know clinical data. Global activation time for the LA was calculated by subtracting the earliest from the latest activation within the LA. Isochronal activation maps were created at a 5-ms interval setting, and ACZ (Figure 2) and CBZ were identified on the activation map by locating a site with isochronal crowding of ≥3 isochrones and ≥8 isochrones, which were calculated as ≤27 cm/s and ≤10 cm/s. Results The conduction from BB was observed in 45 patients in the right-roof area, 24 in the mid-roof, 76 in the right-anterior, 23 cases in the mid-anterior, and 14 in multiple sites. Global activation time (right-roof 108±20, mid-roof 107±16, right-anterior 105±19, and mid-anterior 117±20ms, P=0.0781) was more prolonged and left atrium diameter was larger (42.1±6.6, 42.6±8.5, 42.5±6.6, and 46.4±6.6mm, P=0.0718) in patients with mid-anterior BB connections. LA mean voltage (4.90±1.94, 5.72±2.62, 4.13±1.58, and 4.88±1.96mV, P=0.0032) was higher and plasma brain natriuretic peptide level (139±138, 67±59, 128±139, and 164±197pg/mL, P=0.0861) was lower in patients with mid-roof BB connections. ACZ (41/45 91%, 20/24 83%, 73/76 96%, and 23/23 100%, P=0.0904) and CBZ (1/45 2%, 0/24 0%, 8/76 11%, and 2/23 9%, P=0.0850) appearance rates were lower in patients with mid-roof BB connections. Conclusion The connection site of the Bachmann bundle to the left atrium may affect atrial electrical and anatomical remodeling in patients with atrial fibrillation.

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

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

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

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

M6A reader YTHDF2 governs the onset of atrial fibrillation by modulating Cacna1c translation.

Atrial fibrillation (AF) is the most common arrhythmia, which is tightly associated with the abnormal expression and function of ion channels in the atrial cardiomyocytes. N6-methyladenosine (m6A), a widespread chemical modification in eukaryotic mRNA, is known to play a significant regulatory role in the pathogenesis of heart disease. However, the significance of m6A regulatory proteins in the onset of AF remains unclear. Here, we demonstrate that the m6A reader protein YTHDF2 regulates atrial electrical remodeling and AF onset by modulating the Cav1.2 expression. Firstly, YTHDF2 expression was selectively upregulated in rat atrial cardiomyocytes with AF. Secondly, YTHDF2 knockout reduced AF susceptibility in mice. Thirdly, the knockout of YTHDF2 increased Cav1.2 protein levels in an m6A-in-dependent manner, ultimately prolonging the atrial myocardial refractory period, a critical electrophysiological substrate for the onset of AF. Fourthly, the N-terminal domain of YTHDF2 was identified as critical for Cacna1c mRNA translation regulation. Overall, our findings unveil that YTHDF2 can alter Cav1.2 protein expression in an m6A-independent manner, thereby facilitating the onset of AF. Our study suggests that YTHDF2 may be a potential intervention target for AF.

Inhibition of TREM-1 ameliorates angiotensin II-induced atrial fibrillation by attenuating macrophage infiltration and inflammation through the PI3K/AKT/FoxO3a signaling pathway

Inflammation and infiltration of immune cells are intricately linked to the pathogenesis of atrial fibrillation (AF). Triggering receptor expressed on myeloid cells-1 (TREM-1), an enhancer of inflammation, is implicated in various cardiovascular disorders. However, the precise role and potential mechanisms of TREM-1 in the development of AF remain ambiguous. Atrial samples from patients with AF were used to assess the expression levels of TREM-1. An angiotensin II (Ang II)-induced AF mouse model was established to assess the functionality of TREM-1. Cardiac function and AF inducibility were assessed through echocardiography, programmed transvenous cardiac pacing, and atrial electrophysiological mapping. Peripheral blood and atrial inflammatory cells were assessed using flow cytometry. Using histology, bulk RNA sequencing, biochemical analyses, and cell cultures, the mechanistic role of TREM-1 in AF was elucidated. TREM-1 expression was upregulated and co-localized with macrophages in the atria of patients with AF. Pharmacological inhibition of TREM-1 decreased Ang II-induced atrial enlargement and electrical remodeling. TREM-1 inhibition also ameliorated Ang II-induced NLRP3 inflammasome activation, inflammatory factor release, atrial fibrosis, and macrophage infiltration. Transcriptomic analysis revealed that TREM-1 modulates Ang II-induced inflammation through the PI3K/AKT/FoxO3a signaling pathway. In vitro studies further supported these findings, demonstrating that TREM-1 activation exacerbates Ang II-induced inflammation, while overexpression of FoxO3a counteracts this effect. This study discovered the critical role of TREM-1 in the pathogenesis of AF and its underlying molecular mechanisms. Inhibition of TREM-1 provides a new therapeutic strategy for the treatment of AF.

Persistent hypertension induces atrial remodeling and atrial fibrillation through DNA damage and ATM/CHK2/p53 signaling pathway

Atrial fibrillation (AF) is the most prevalent arrhythmia in clinical practice, with hypertension emerging as an independent risk factor. Previous literature has established associations between DNA damage response (DDR) and autophagy in relation to the pathogenesis of AF. The aim of this study was to evaluate the effect of atrial DNA damage response in persistent hypertension-induced atrial electrical and structural remodeling, and to further explore the potential therapeutic targets. Patient samples, spontaneous hypertensive rats (SHR) and angiotensin II (Ang II)-challenged HL-1 cells were employed to elucidate the detailed mechanisms. Bioinformatics analysis and investigation on human atrial samples revealed a critical role of DDR in the pathogenesis of AF. The markers of atrial DNA damage, DDR, autophagy, inflammation and fibrosis were detected by western blot, immunofluorescence, monodansyl cadaverine (MDC) assay and transmission electron microscopy. Compared with the control group, SHR exhibited significant atrial electrical and structural remodeling, abnormal increase of autophagy, inflammation, and fibrosis, which was accompanied by excessive activation of DDR mediated by the ATM/CHK2/p53 pathway. These detrimental changes were validated by in vitro experiments. Ang II-challenged HL-1 cells also exhibited significantly elevated γH2AX expression, and markers related to autophagy, inflammation as well as structural remodeling. Additionally, inhibition of ATM with KU55933 (a specific ATM inhibitor) significantly reversed these effects. Collectively, these data demonstrate that DNA damage and the subsequently overactivated ATM/CHK2/p53 pathway play critical roles in hypertension-induced atrial remodeling and the susceptibility to AF. Targeting ATM/CHK2/p53 signaling may serve as a potential therapeutic strategy against AF.

The Properties of the Transient Outward, Inward Rectifier and Acetylcholine-Sensitive Potassium Currents in Atrial Myocytes from Dogs in Sinus Rhythm and Experimentally Induced Atrial Fibrillation Dog Models.

Atrial fibrillation (AF) is the most common chronic/recurrent arrhythmia, which significantly impairs quality of life and increases cardiovascular morbidity and mortality. Therefore, the aim of the present study was to investigate the properties of three repolarizing potassium currents which were shown to contribute to AF-induced electrical remodeling, i.e., the transient outward (Ito), inward rectifier (IK1) and acetylcholine-sensitive (IK,ACh) potassium currents in isolated atrial myocytes obtained from dogs either with sinus rhythm (SR) or following chronic atrial tachypacing (400/min)-induced AF. Atrial remodeling and AF were induced by chronic (4-6 weeks of) right atrial tachypacing (400/min) in dogs. Transmembrane ionic currents were measured by applying the whole-cell patch-clamp technique at 37 °C. The Ito current was slightly downregulated in AF cells when compared with that recorded in SR cells. This downregulation was also associated with slowed inactivation kinetics. The IK1 current was found to be larger in AF cells; however, this upregulation was not statistically significant in the voltage range corresponding with atrial action potential (-80 mV to 0 mV). IK,ACh was activated by the cholinergic agonist carbachol (CCh; 2 µM). In SR, CCh activated a large current either in inward or outward directions. The selective IK,ACh inhibitor tertiapin (10 nM) blocked the outward CCh-induced current by 61%. In atrial cardiomyocytes isolated from dogs with AF, the presence of a constitutively active IK,ACh was observed, blocked by 59% with 10 nM tertiapin. However, in "AF atrial myocytes", CCh activated an additional, significant ligand-dependent and tertiapin-sensitive IK,ACh current. In our dog AF model, Ito unlike in humans was downregulated only in a slight manner. Due to its slow inactivation kinetics, it seems that Ito may play a more significant role in atrial repolarization than in ventricular working muscle myocytes. The presence of the constitutively active IK,ACh in atrial myocytes from AF dogs shows that electrical remodeling truly developed in this model. The IK,ACh current (both ligand-dependent and constitutively active) seems to play a significant role in canine atrial electrical remodeling and may be a promising atrial selective drug target for suppressing AF.

Calcium-mediated DAD in membrane potentials and triggered activity in atrial myocytes of ETV1f / fMyHCCre /+ mice.

The E-twenty-six variant 1 (ETV1)-dependent transcriptome plays an important role in atrial electrical and structural remodelling and the occurrence of atrial fibrillation (AF), but the underlying mechanism of ETV1 in AF is unclear. In this study, cardiomyocyte-specific ETV1 knockout (ETV1f/fMyHCCre/+, ETV1-CKO) mice were constructed to observe the susceptibility to AF and the underlying mechanism in AF associated with ETV1-CKO mice. AF susceptibility was examined by intraesophageal burst pacing, induction of AF was increased obviously in ETV1-CKO mice than WT mice. Electrophysiology experiments indicated shortened APD50 and APD90, increased incidence of DADs, decreased density of ICa,L in ETV1-CKO mice. There was no difference in VINACT,1/2 and VACT,1/2, but a significantly longer duration of the recovery time after inactivation in the ETV1-CKO mice. The recording of intracellular Ca2+ showed that there was significantly increased in the frequency of calcium spark, Ca2+ transient amplitude, and proportion of SCaEs in ETV1-CKO mice. Reduction of Cav1.2 rather than NCX1 and SERCA2a, increase RyR2, p-RyR2 and CaMKII was reflected in ETV1-CKO group. This study demonstrates that the increase in calcium spark and SCaEs corresponding to Ca2+ transient amplitude may trigger DAD in membrane potential in ETV1-CKO mice, thereby increasing the risk of AF.

Inhibition of α-Amino-3-Hydroxy-5-Methyl-4-Isoxazolepropionic Acid Receptors Ameliorates Atrial Inflammation and Vulnerability to Atrial Fibrillation in Rats with Anxiety Disorders.

Previous studies have found that anxiety disorders may increase the incidence of atrial fibrillation (AF). More and more studies have shown that α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) are involved in the occurrence and development of cardiovascular diseases. However, the role of AMPARs in AF associated with anxiety disorder remains unclear. The aim of this study was to investigate the effect of AMPARs on AF susceptibility in rats with anxiety disorder and its possible mechanism. The anxiety disorder rat model was established by unpredictable empty bottle stimulation and was treated with AMPARs agonist and antagonist. Our results showed that AMPARs antagonist treatment significantly reduced sympathetic activity, improved heart rate variability, shortened action potential duration, prolonged effective refractory period, reduced AF induction rate, and improved cardiac electrical remodeling and the expression of inflammatory factors. In addition, inhibition of AMPARs reduced the phosphorylation of IκBα and p65. Our experimental results suggest that inhibition of AMPARs can reduce autonomic remodeling, improve atrial electrical remodeling, and suppress myocardial inflammation, which provides a potential therapeutic strategy for the treatment of AF associated with anxiety disorder.

Chronic angiotensin-converting enzyme inhibition attenuates frailty and protects against atrial fibrillation in aging mice

BackgroundAging is a major risk factor for atrial fibrillation (AF); however, not all individuals age at the same rate. Frailty, which is a measure of susceptibility to adverse health outcomes, can be quantified with a frailty index (FI). ObjectiveThis study aimed to determine the effects of angiotensin-converting enzyme (ACE) inhibition on AF and atrial remodeling in aging and frail mice. MethodsAging mice were treated with the ACE inhibitor enalapril for 6 months beginning at 16.5 months of age and frailty was quantified. AF susceptibility and atrial structure and function were assessed by intracardiac electrophysiology in anesthetized mice, high-resolution optical mapping in intact atrial preparations, patch clamping in isolated atrial myocytes, and histology and molecular biology in atrial tissues. ResultsEnalapril attenuated frailty in aging mice with larger effects in females. AF susceptibility was increased in aging mice but attenuated by enalapril. AF susceptibility and duration also increased as a function of FI score. P-wave duration was increased and atrial conduction velocity was reduced in aging mice and improved after enalapril treatment. Furthermore, P-wave duration and atrial conduction velocity were strongly correlated with FI score. Atrial action potential upstroke velocity (Vmax) and Na+ current (INa) were reduced whereas atrial fibrosis was increased in aging mice. Action potential Vmax, INa, and fibrosis were improved by enalapril and also correlated with FI scores. ConclusionACE inhibition with enalapril attenuates frailty and reduces AF susceptibility in aging mice by preventing atrial electrical and structural remodeling.

Dapagliflozin: A sodium–glucose cotransporter 2 inhibitor, attenuates angiotensin II-induced atrial fibrillation by regulating atrial electrical and structural remodeling

AimAtrial fibrillation (AF), the most common arrhythmia, is characterized by atrial electrical and structural remodeling. Previous studies have found that sodium–glucose cotransporter 2 inhibitor (SGLT2i) can protect myocardium in a glucose independent mechanism. But the role of SGLT2i in regulating AF remains largely unknown. This study, we aimed to investigate the effect of Dapagliflozin (DAPA) in reducing AF susceptibility via inhibiting electrical and structural remodeling. MethodThe mouse model was established by Angiotensin II (2000 ng/kg/min) infusion for 3 weeks, and an in vitro model was generated by stimulating HL-1 and primary mouse fibroblast with Ang II (1 μM) for 24 h. Programmed electrical stimulation, ECG and whole-cell patch clamp were used to detect DAPA effect on atrial electrical remodeling induced by Ang II. To observe DAPA effect on atrial structural remodeling induced by Ang II, we used echocardiographic, H&E and Masson staining to evaluate atrial dilation. To further explore the protective mechanism of DAPA, we adopt in silico molecular docking approaches to investigate the binding affinity of Ang II and CaMKII at Met-281 site. Western blot was to detect expression level of CaMKII, ox-CaMKII, Nav1.5, Kv4.3, Kv4.2, Kchip2, Kir2.1 and Cx40. ResultsAng II induced AF, atrial dilatation and fibrosis, led to atrial electrical and structural remodeling. However, these effects were markedly abrogated by DAPA treatment, a specific SGLT2i. Our observation of atrial electrical activity in mice revealed that DAPA could rescue the prolonged action potential duration (APD) and the abnormal currents of IK1, Ito and INaL triggered by Ang II infusion. DAPA could reduce the binding affinity of Ang II and CaMKII at Met-281 site, which indicated that DAPA may directly alleviate the activation of CaMKII caused by Ang II. DAPA could reduce the upregulation of ox-CaMKII caused by Ang II infusion in atrial tissues. Moreover, DAPA also ameliorated the aberrant expression levels of electrical activity related proteins (Nav1.5, Kv4.3, Kv4.2, Kchip2, Kir2.1 and Cx40) and fibrosis related signal pathways (TGF-β1, p-smad/smad) caused by Ang II. Furthermore, we confirmed that DAPA, as well as other SGLT2i (EMPA, CANA), could reverse these abnormalities caused by Ang II incubation in HL-1 cells and primary mouse fibroblasts, respectively. ConclusionOverall, our study identifies DAPA, a widely used SGLT2i, contributes to inhibiting Ang II-induced ox-CaMKII upregulation and electrical and structural remodeling to reduce AF susceptibility, suggesting that DAPA may be a potential therapy of treating AF.

Intermittent hypoxia is significantly associated with low-voltage areas in patients with atrial fibrillation complicated by obstructive sleep apnea

Abstract Background Obstructive sleep apnea (OSA) is one of risk factors for atrial fibrillation (AF); however, how OSA affects the structural and electrical atrial remodeling is not well described. This study aimed to determine the association of OSA with left atrial (LA) size and LA low-voltage area (LVA), a known arrhythmogenic substrate for AF. Methods Eighty-three patients undergoing catheter ablation of AF (forty-nine with OSA [apnea–hypopnea index: AHI ≥ 5/h] and thirty-four control patients without OSA by full polysomnography or portable monitor) were studied. In all cases, LA maps were created using a three-dimensional electro-anatomical mapping system in sinus rhythm or pacing from the right atrium. LVA was defined as a bipolar voltage &amp;lt; 0.5 mV. %LVA is defined as ratio of LVA to LA area. Results LVA and %LVA were larger in OSA group as compared to Control group (6.0 ± 6.6 vs. 2.6 ± 3.2 cm2, P = 0.003 and 7.5 ± 8.5 vs. 3.5 ± 4.6 %, P = 0.008, respectively). On the other hand, there was no difference in LA size between the two groups. In addition, 3% oxygen desaturation index (ODI) was significantly correlated with %LVA (r = 0.282, P = 0.010), but not with LA size (r = 0.053, P = 0.637). Multiple regression analysis demonstrated that 3%ODI ≥ 30 (3.088, 1.078-8.851, P = 0.036) was significantly associated with %LVA after adjustment. Conclusion In patients with AF complicated by OSA, significant enlargement of the LVA was observed, but there was no evidence of enlargement in LA size. Intermittent hypoxia may be one of the mechanisms of this atrial electro-anatomical remodeling.figure 1figure 2

No Detectable Differences in microRNA Plasma Levels between Diabetic Hypertensive Patients with and without Incident Subclinical Atrial Fibrillation.

Background: Long-term rhythm monitoring (LTRM) can detect undiagnosed atrial fibrillation (AF) in patients at risk of AF and stroke. Circulating microRNAs (miRNAs), which have been shown to play a role in atrial electrical and structural remodelling, could help to select patients who would benefit most from LTRM. The aim of this study was to investigate whether patients with diabetes mellitus (DM) and hypertension and screen-detected subclinical AF (SCAF) using an insertable cardiac monitor (ICM) have significantly different plasma baseline levels of five selected miRNAs playing a role in the modulation of atrial electrical and structural remodelling (miR-21-5p, miR-29b-3p, miR-150-5p, miR-328-3p, and miR-432-5p) compared to those without SCAF. Methods: This study was performed at the outpatient clinic of a secondary academic teaching hospital between December 2013 and November 2015. Eligible patients were ≥65 years of age with DM and hypertension but without known heart diseases. All patients received an ICM. On the day of ICM implantation, blood samples for the measurement of plasma levels of the five miRNAs were drawn. In this post hoc analysis, we investigated their expression by reverse transcription-quantitative polymerase chain reaction. MiRNA plasma levels in patients with and without newly detected SCAF were compared. Results: We included 82 consecutive patients (median age of 71.3 years (IQR 67.4-75.1)), who were followed for a median of 588 days (IQR: 453-712 days). Seventeen patients (20.7%) had ICM-detected SCAF. Plasma levels of miR-328-3p, miR-29b-3p, miR-21-5p, miR-432-5p, and miR-150-5p were slightly but not significantly different in patients with incident SCAF compared with patients without. Conclusions: In patients with hypertension and DM, newly detected SCAF was not significantly associated with changes in expression levels of miR-21-5p, miR-29b-3p, miR-150-5p, miR-328-3p, and miR-432-5p.

Synergistic Effects of Weight Loss and Catheter Ablation: Can microRNAs Serve as Predictive Biomarkers for the Prevention of Atrial Fibrillation Recurrence?

In atrial fibrillation (AF), multifactorial pathologic atrial alterations are manifested by structural and electrophysiological changes known as atrial remodeling. AF frequently develops in the context of underlying cardiac abnormalities. A critical mechanistic role played by atrial stretch is played by abnormal substrates in a number of conditions that predispose to AF, including obesity, heart failure, hypertension, and sleep apnea. The significant role of overweight and obesity in the development of AF is known; however, the differential effect of overweight, obesity, cardiovascular comorbidities, lifestyle, and other modifiable risk factors on the occurrence and recurrence of AF remains to be determined. Reverse remodeling of the atrial substrate and subsequent reduction in the AF burden by conversion into a typical sinus rhythm has been associated with weight loss through lifestyle changes or surgery. This makes it an essential pillar in the management of AF in obese patients. According to recently published research, microRNAs (miRs) may function as post-transcriptional regulators of genes involved in atrial remodeling, potentially contributing to the pathophysiology of AF. The focus of this review is on their modulation by both weight loss and catheter ablation interventions to counteract atrial remodeling in AF. Our analysis outlines the experimental and clinical evidence supporting the synergistic effects of weight loss and catheter ablation (CA) in reversing atrial electrical and structural remodeling in AF onset and in recurrent post-ablation AF by attenuating pro-thrombotic, pro-inflammatory, pro-fibrotic, arrhythmogenic, and male-sex-associated hypertrophic remodeling pathways. Furthermore, we discuss the promising role of miRs with prognostic potential as predictive biomarkers in guiding approaches to AF recurrence prevention.

Reduced plakoglobin increases the risk of sodium current defects and atrial conduction abnormalities in response to androgenic anabolic steroid abuse.

Androgenic anabolic steroids (AAS) are commonly abused by young men. Male sex and increased AAS levels are associated with earlier and more severe manifestation of common cardiac conditions, such as atrial fibrillation, and rare ones, such as arrhythmogenic right ventricular cardiomyopathy (ARVC). Clinical observations suggest a potential atrial involvement in ARVC. Arrhythmogenic right ventricular cardiomyopathy is caused by desmosomal gene defects, including reduced plakoglobin expression. Here, we analysed clinical records from 146 ARVC patients to identify that ARVC is more common in males than females. Patients with ARVC also had an increased incidence of atrial arrhythmias and Pwave changes. To study desmosomal vulnerability and the effects of AAS on the atria, young adult male mice, heterozygously deficient for plakoglobin (Plako+/-), and wild type (WT) littermates were chronically exposed to 5α-dihydrotestosterone (DHT) or placebo. The DHT increased atrial expression of pro-hypertrophic, fibrotic and inflammatory transcripts. In mice with reduced plakoglobin, DHT exaggerated Pwave abnormalities, atrial conduction slowing, sodium current depletion, action potential amplitude reduction and the fall in action potential depolarization rate. Super-resolution microscopy revealed a decrease in NaV1.5membrane clustering in Plako+/- atrial cardiomyocytes after DHT exposure. In summary, AAS combined with plakoglobin deficiency cause pathological atrial electrical remodelling in young male hearts. Male sex is likely to increase the risk of atrial arrhythmia, particularly in those with desmosomal gene variants. This risk is likely to be exaggerated further by AAS use. KEY POINTS: Androgenic male sex hormones, such as testosterone,might increase the risk of atrial fibrillation in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC), which is often caused by desmosomal gene defects (e.g. reduced plakoglobin expression). In this study, we observed a significantly higher proportion of males who had ARVC compared with females, and atrial arrhythmias and Pwave changes represented a common observation in advanced ARVC stages. In mice with reduced plakoglobin expression, chronic administration of 5α-dihydrotestosterone led to Pwave abnormalities, atrial conduction slowing, sodium current depletion and a decrease in membrane-localized NaV1.5 clusters. 5α-Dihydrotestosterone, therefore, represents a stimulus aggravating the pro-arrhythmic phenotype in carriers of desmosomal mutations and can affect atrial electrical function.