Prolonged Atrial Fibrillation Duration Research Articles

Exosomes activate hippocampal microglia in atrial fibrillation through long-distance heart–brain communication

BackgroundThere is growing evidence that atrial fibrillation (AF) is a risk factor for cognitive impairment (CI) and dementia in the presence or absence of stroke. The purpose of this study was to explore the mechanism of CI caused by AF.MethodsEighteen male canines were randomly divided into a sham group, a pacing group, and a pacing + GW4869 group. An experimental model of AF was established by rapid atrial pacing (450 beats/min) for 2 weeks, and the sham group received pacemaker implantation without atrial pacing. The GW4869 group received an intravenous GW4869 injection (0.3 mg/kg, once a day) during pacing. All canines were locally injected with Ad-CD63-RFP in epicardial adipose tissue (EAT) to trace the exosomes. Ultracentrifugation was employed to isolate EAT-derived exosomes, followed by RNA sequencing and quantitative real-time PCR (qRT-PCR) to assess RNA in both exosomes and hippocampal tissue. The miRanda database was used to predict the targeting relationships between miRNA and mRNA, which were further validated by luciferase reporter assays. Western blot analysis was conducted to detect exosomal markers (CD63, CD81, TSG101) in EAT exosomes, while immunofluorescence was used to detect Ad-CD63-RFP signals in both EAT and hippocampal tissues, as well as microglial activation marker IBA-1. To further explore the effects of exosomes on microglial cells, in vitro experiments using brain microvascular endothelial cells (bEnd3) and microglial cells (BV2) were conducted. IBA-1 expression and RNA levels in BV2 cells were analyzed by immunofluorescence and qRT-PCR, respectively.ResultsAfter 14 days of pacing of the canine atrium, compared to the sham group, both the pacing and GW4869 groups exhibited an increased number of AF inductions, along with prolonged AF duration. The fluorescence intensity of Ad-CD63-RFP and the microglial activation marker IBA-1 were markedly greater in the hippocampus. RNA sequencing showed that the differentially expressed gene cfa-miR-22e in EAT exosomes was upregulated, and its target gene IL33 was downregulated in the hippocampus. qRT-PCR showed that the levels of cfa-miR-22e were increased in both EAT exosomes and the hippocampus, while the expression of IL-33, a target of cfa-miR-22e, was decreased in the hippocampus. The administration of GW4869 abolished these effects. The in vitro results from bEnd3 and BV2 cell experiments were consistent with the conclusions drawn from the in vivo studies.ConclusionOur study indicated that the exosomes secreted by EAT in canines with AF can penetrate the BBB and activate microglia in the hippocampus through the cfa-miR-22e/IL33 signalling pathway.

SIRT3/AMPK Signaling Pathway Regulates Lipid Metabolism and Improves Vulnerability to Atrial Fibrillation in Dahl Salt-Sensitive Rats.

Hypertension may result in atrial fibrillation (AF) and lipid metabolism disorders. The Sirtuins3 (SIRT3)/AMP-activated protein kinase (AMPK) signaling pathway has the capacity to regulate lipid metabolism disorders and the onset of AF. We hypothesize that the SIRT3/AMPK signaling pathway suppresses lipid metabolism disorders, thereby mitigating salt-sensitive hypertension (SSHT)-induced susceptibility to AF. The study involved 7-week-old male Dahl salt-sensitive that were fed either a high-salt diet (8% NaCl; DSH group) or a normal diet (0.3% NaCl; DSN group). Then DSH group was administered either oral metformin (MET, an AMPK agonist) or intraperitoneal injection of Honokiol (HK, a SIRT3 agonist). This experimental model allowed for the measurement of Systolic blood pressure (SBP), the expression levels of lipid metabolism-related biomarkers, pathological examination of atrial fibrosis, and lipid accumulation, as well as AF inducibility and AF duration. DSH decrease SIRT3, phosphorylation-AMPK, and very long-chain acyl-CoA dehydrogenase, (VLCAD) expression, increased FASN and FABP4 expression and concentrations of free fatty acid and triglyceride, atrial fibrosis and lipid accumulation in atrial tissue, enhanced level of SBP, promoted AF induction rate and prolonged AF duration, which are blocked by MET and HK. Our results also showed that the degree of atrial fibrosis was negatively correlated with VLCAD expression, but positively correlated with the expression of FASN and FABP4. We have confirmed that a high-salt diet can result in hypertension, and associated atrial tissue lipid metabolism dysfunction. This condition is linked to the inhibition of the SIRT3/AMPK signaling pathway, which plays a significant role in the progression of susceptibility to AF in SSHT rats.

Exploring immune related gene signatures and mechanisms linking non alcoholic fatty liver disease to atrial fibrillation through transcriptome data analysis

Atrial fibrillation (AF) and related cardiovascular complications pose a heavy burden to patients and society. Mounting evidence suggests a close association between nonalcoholic fatty liver disease (NAFLD) and AF. NAFLD and AF transcriptomic datasets were obtained from GEO database and analyzed using several bioinformatics approaches. We established a NAFLD-AF associated gene diagnostic signature (NAGDS) using protein–protein interaction analysis and machine learning, which was further quantified through RT-qPCR. Potential miRNA targeting NAGDS were predicted. Gene modules highly correlated with NAFLD liver pathology or AF occurrence were identified by WGCNA. Enrichment analysis of the overlapped genes from key module revealed that T-cell activation plays essential roles in NAFLD and AF, which was further confirmed by immune infiltration. Furthermore, an integrated SVM-RFE and LASSO algorithm was used to identify CCL4, CD48, ITGB2, and RNASE6 as NAGDS, all of which were found to be upregulated in NAFLD and AF mouse tissues. Patients with higher NAGDS showed augmented T cell and macrophage immunity, more advanced liver pathological characteristics, and prolonged AF duration. Additionally, hsa-miR-26a-5p played a central role in the regulation of NAGDS. Our findings highlight the central role of T-cell immune response in linking NAFLD to AF, and established an accurate NAGDS diagnostic model, which could serve as potential targets for immunoregulatory therapy.

A Novel Tool for the Identification and Characterization of Repetitive Patterns in High-Density Contact Mapping of Atrial Fibrillation.

IntroductionElectrical contact mapping provides a detailed view of conduction patterns in the atria during atrial fibrillation (AF). Identification of repetitive wave front propagation mechanisms potentially initiating or sustaining AF might provide more insights into temporal and spatial distribution of candidate AF mechanism and identify targets for catheter ablation. We developed a novel tool based on recurrence plots to automatically identify and characterize repetitive conduction patterns in high-density contact mapping of AF.Materials and MethodsRecurrence plots were constructed by first transforming atrial electrograms recorded by a multi-electrode array to activation-phase signals and then quantifying the degree of similarity between snapshots of the activation-phase in the electrode array. An AF cycle length dependent distance threshold was applied to discriminate between repetitive and non-repetitive snapshots. Intervals containing repetitive conduction patterns were detected in a recurrence plot as regions with a high recurrence rate. Intervals that contained similar repetitive patterns were then grouped into clusters. To demonstrate the ability to detect and quantify the incidence, duration and size of repetitive patterns, the tool was applied to left and right atrial recordings in a goat model of different duration of persistent AF [3 weeks AF (3 wkAF, n = 8) and 22 weeks AF (22 wkAF, n = 8)], using a 249-electrode mapping array (2.4 mm inter-electrode distance).ResultsRecurrence plots identified frequent recurrences of activation patterns in all recordings and indicated a strong correlation between recurrence plot threshold and AF cycle length. Prolonged AF duration was associated with shorter repetitive pattern duration [mean maximum duration 3 wkAF: 74 cycles, 95% confidence interval (54–94) vs. 22 wkAF: 41 cycles (21–62), p = 0.03], and smaller recurrent regions within repetitive patterns [3 wkAF 1.7 cm2 (1.0–2.3) vs. 22 wkAF 0.5 cm2 (0.0–1.2), p = 0.02]. Both breakthrough patterns and re-entry were identified as repetitive conduction patterns.ConclusionRecurrence plots provide a novel way to delineate high-density contact mapping of AF. Dominant repetitive conduction patterns were identified in a goat model of sustained AF. Application of the developed methodology using the new generation of multi-electrode catheters could identify additional targets for catheter ablation of AF.

Isoproterenol Increases Left Atrial Fibrosis and Susceptibility to Atrial Fibrillation by Inducing Atrial Ischemic Infarction in Rats

Left atrial (LA) fibrosis is a major arrhythmogenic substrate for atrial fibrillation (AF). The purpose of this study was to assess whether isoproterenol (ISO) induces LA fibrosis and increases susceptibility to AF, exploring the underlying mechanisms. Male Sprague-Dawley rats were subcutaneously injected ISO once per day for 2 days. Five weeks after injection, the ISO group had higher susceptibility AF and prolonged AF duration compared with the control group. ISO decreased LA conduction velocity (CV) and increased LA conduction heterogeneity. ISO increased fibrosise areas and the protein levels of collagen types I and III in the left atrium. Antifibrosis drug pirfenidone decreased AF occurrence and reduced LA fibrosis in ISO treated rats. ISO injection induced atrial ischemia infarction by increasing heart rate and decreasing diastolic and systolic blood pressures. These findings demonstrated that ISO increases susceptibility to AF by increasing LA fibrosis and LA conduction abnormalities 5 weeks after injection. ISO injection induces atrial ischemic injury is the main cause of fibrosis. Rats with ISO-induced LA fibrosis may be used in further AF research.

Fisetin Alleviates Atrial Inflammation, Remodeling, and Vulnerability to Atrial Fibrillation after Myocardial Infarction.

Atrial inflammation and fibrosis are the critical processes involved in atrial fibrillation (AF) after myocardial infarction (MI). Fisetin is a dietary flavonoid that has shown forceful anti-inflammatory and anti-proliferative properties in diverse models of disease. However, fisetin's role in atrial inflammation, fibrosis, and AF vulnerability post-MI remains completely unknown.Rats were subjected to MI surgery, by left anterior descending coronary artery ligation or sham operation, and treated with DMSO or fisetin via intraperitoneal injection. After 28 days, echocardiographic parameters were performed, and AF inducibility was tested. We further evaluated the inflammation, fibrosis of left atria (LA), and related signal pathways by RT-PCR, Western blot, and staining analysis.Compared to the MI group, fisetin treatment improved cardiac function, inhibited macrophage recruitment into the LA and production of IL-1β and TNF-α, and attenuated adverse atrial fibrosis following acute myocardial infarction (AMI). Electrophysiological recordings, using an isolated perfused heart, showed that MI-induced higher inducibility of AF and prolonged AF duration, interatrial conduction time (IACT), atrial effective refractory period (AERP) were significantly alleviated by fisetin. Mechanistically, fisetin markedly increased phosphorylated AMPK (p-AMPK) levels and suppressed NF-κB p65, p38MAPK, and smad3 phosphorylation in the LA post-MI.We demonstrate that fisetin improves LA expansion, cardiac function, atrial inflammation, fibrosis, and vulnerability to AF following MI by possibly regulating AMPK/NF-κB p65 and p38MAPK/smad3 signaling pathways.

Mechanism of electrical remodeling of atrial myocytes and its influence on susceptibility to atrial fibrillation in diabetic rats

AimsTo explore the atrial electrical remodeling and the susceptibility of atrial fibrillation (AF) in diabetic rats. Materials and methodsZucker diabetic fatty (ZDF) rats were chosen as diabetic animal model, and age-matched non-diabetic littermate Zucker lean (ZL) rats as control. AF susceptibility was determined by electrophysiological examination. The current density of Ito, IKur and ICa-L were detected by whole-cell patch-clamp technique, and ion channel protein expression in atrial tissue and HL-1 cells treated with advanced glycation end products (AGE) was analyzed by western blotting. Key findingsDiabetic rats had significantly enlarged left atria and evenly thickened ventricular walls, hypertrophied cells and interstitial fibrosis in atrial myocardium, increased AF susceptibility, and prolonged AF duration after atrial burst stimulation. Compared with atrial myocytes isolated from ZL controls, atrial myocytes isolated from ZDF rats had prolonged action potential duration, decreased absolute value of resting membrane potential level and current densities of Ito, IKur and ICa-L. The ion channel protein (Kv4.3, Kv1.5 and Cav1.2) expression in atrium tissue of ZDF rats and HL-1 cells treated with high concentration AGE were significantly down-regulated, compared with controls. SignificanceThe atrial electrical remodeling induced by hyperglycemia contributed to the increased AF susceptibility in diabetic rats.

Association between reactive hyperemia peripheral arterial tonometry index and atrial fibrillation recurrence after catheter ablation

BackgroundVascular endothelial function has recently been recognized as an independent predictor of cardiovascular events. However, studies investigating its association with atrial fibrillation (AF) are lacking. This study aimed to examine association with AF recurrence and vascular endothelial function as assessed using natural logarithmic transformation of reactive hyperemia peripheral arterial tonometry index (LnRHI). MethodsNinety-nine consecutive AF patients who underwent catheter ablation (CA) at Shinshu University Hospital between September 2015 and April 2017 were enrolled. LnRHI was measured 48 to 72 h before CA using the EndoPAT system. The primary outcome was AF recurrence beyond 3 months post-ablation. ResultsA total of 30 (30.3%) patients experienced AF recurrence after CA over a median follow-up period of 210 days (range: 93–764 days). Female sex and low LnRHI were significantly associated with AF recurrence. In multivariate analysis, LnRHI was an independent predictor of AF recurrence (hazard ratio: 0.087, 95% confidence interval 0.015–0.51, p = 0.007). In comparison in Kaplan-Meier analysis of high LnRHI (LnRHI ≥0.52, n = 52) and low LnRHI (LnRHI ≪0.52, n = 47) groups, AF recurrence rate was significantly higher in the low LnRHI group (log-rank test, p = 0.043). A negative correlation was observed between LnRHI and AF duration, whereby LnRHI was significantly decreased when the duration of AF events exceeded 1 year. ConclusionDecreased LnRHI was associated with AF recurrence after CA and prolonged AF duration.

Edoxaban suppresses the progression of atrial fibrosis and atrial fibrillation in a canine congestive heart failure model.

Coagulation factor Xa activates the protease-activated receptor 2 (PAR2) and causes tissue fibrosis; however, the effects of Xa inhibitor edoxaban on atrial fibrosis and atrial fibrillation (AF) have not been investigated. We examined the effect of edoxaban on the progression of atrial fibrosis in a canine congestive heart failure (CHF) model. Beagle dogs were assigned to sham, placebo, and edoxaban groups (n = 6/group). Dogs of the placebo or edoxaban groups received 19days of medication with daily oral placebo or edoxaban, respectively, followed by 14days of ventricular tachypacing. Dogs of the sham group had no medication or pacing. Ventricular tachypacing prolonged AF duration in dogs of the placebo group (159 ± 41s, p < 0.01 vs. sham); however, this effect was suppressed by edoxaban treatment. Compared with the sham group, tachypacing alone also significantly increased the atrial fibrotic area (2.9 ± 0.1% vs. 7.8 ± 0.4%, p < 0.01), PAR2 expression (1.0 ± 0.1 vs. 1.8 ± 0.3, p < 0.05), and atrial fibronectin expression (1.0 ± 0.2 vs. 2.0 ± 0.2, p < 0.01). These responses were suppressed by edoxaban treatment (area 5.9 ± 0.4%, p < 0.01; PAR2 1.1 ± 0.1, p < 0.05; fibronectin 1.2 ± 0.2, p < 0.05 vs. placebo). Edoxaban showed suppressive effects on atrial remodeling, AF progression, and excessive expressions of PAR2 and fibronectin in a canine CHF model. The suppression of the Xa/PAR2 pathway might be a potential pharmacological target of edoxaban.

Relationship of endothelin-1 expression and the changes in collagen fiber distribution in canine chronic atrial fibrillation by rapid left atrial pacing

Objective To detect the expression of endothelin-1(ET-1)and the changes in collagen fiber distribution in left and right atrium in a canine model of chronic atrial fibrillation(AF), in order to investigate the relationship of ET-1 and atrial fibrosis in atrial fibrillation. Methods A total of 16 male canines were randomized into 4 groups: Sham group, AF lasting 1 week group(1W group), AF lasting 2 weeks group(2W group)and AF lasting 4 weeks group(4W group)(n=4, each). A canine model of chronic AF was made by rapid left atrial pacing. The mRNA and protein expression levels of ET-1 and collagen type I(COL1)in left and right atrium of canines were measured by real-time quantitative polymerase chain reaction(PCR)and Western Blotting respectively in each group. Collagen fiber deposit in left and right atrium of canines in each group was assessed by Masson's staining. Results Along with prolonged AF duration, the mRNA and protein expression levels of COL1 and ET-1 as well as collagen volume fraction(CVF)in left and right atriums were gradually increased in chronic AF groups of 1-, 2-, 4-weeks duration versus the sham group.CVF: left atrium(5.64±0.63)%, (11.45±1.98)%, (16.71±1.59)% vs. (3.25±0.51)%, right atrium(6.46±0.73)%, (15.01±2.11)%, (20.70±2.37)% vs. (2.72±0.70)%, all P 0.05). Conclusions The distribution of collagen fibers in left and right atriums is anisotropic in a canine model of chronic AF. ET-1 may play an important role in the development of AF by promoting atrial fibrosis. Key words: Atrial fibrillation; Collagen type I; Tachycarclia, ectopic atrial

Prerequisites for Exploring Predictors of Chronic Atrial Fibrillation Recurrence After Ablation.

The ablation treatment for the atrial fibrillation extends to the persistent atrial fibrillation now. However, the cure rate of persistent atrial fibrillation by Radiofrequency Ablation is lower than paroxysmal atrial fibrillation and we really want to know is the information that what kind of persistent atrial fibrillation ablation therapy is effective for. Therefore, it is wished the predictors of recurrence after the ablation for the persistent atrial fibrillation is confirmed, but does not yet confirm. The cause that is not confirmed seems to be present in many factors including the gene which the atrial fibrillation occurs in and persist, the change of pathology into remodeling according to progression of atrial fibrillation and strategy of the ablation corresponding to them. Left atrium diameter, Duration of atrial fibrillation and Cardiac Function that are involved deeply in atrial muscle and electric remodeling, and Ablation strategy corresponding to them are considered based on the conventional report. It can be stated now, however, that persistent atrial fibrillation patients with some degree (although this "some degree" has not been clearly defined) of enlarged left atrium diameter, prolonged atrial fibrillation duration, or decreased cardiac function may also revert to sinus rhythm with Radiofrequency Ablation, more efficient treatment may be developed in the future and reversion to sinus rhythm may increase the benefit to patients. In summary, RF ablation for persistent AF is currently required with further study of the predictors of recurrence after the ablation for the persistent atrial fibrillation.

Inducibility of Atrial Fibrillation After GP Ablations and “Autonomic Blockade”: Evidence for the Pathophysiological Role of the Nonadrenergic and Noncholinergic Neurotransmitters

Recent clinical reports that used cholinergic and adrenergic blockade (CAB) as an alternative to ganglionated plexi (GP) ablation to terminate atrial fibrillation (AF) showed mixed results. We investigated the role of other neurotransmitters in AF inducibility. In 23 pentobarbital anesthetized dogs, a left and right thoracotomy allowed the attachment of electrode catheters to the left and right pulmonary veins and atrial appendages (AA). Programmed stimulation was used to determine the effective refractory periods (ERP) and AF inducibility, measured by the window of vulnerability (WOV). AF duration in response to acetylcholine (Ach; 100 mM) applied to the AA was measured before and after GP ablation + CAB and with vagus nerve stimulation (VNS). After GP ablation + CAB, Ach induced AF duration was determined in response to vasoactive intestinal peptide (VIP) and its specific antagonist ([Ac-Tyr1,D-phe2]-VIP). GP ablation + CAB significantly prolonged ERP, eliminated WOV, and suppressed the duration of Ach induced AF (P ≤ 0.01 for all). Also slowing of the heart rate by VNS was essentially blocked; however, with Ach 100 mM applied to the AA, VNS, and VIP applied to the AA markedly prolonged AF duration. This effect was blocked by the VIP antagonist. Neither GP ablation nor CAB can fully suppress AF inducibility arising from the atrial neural network. Our findings suggest that other neurotransmitters, such as VIP released during VNS, can promote sustained AF despite GP ablation and "autonomic blockade," which may further define the substrate for AF outside the pulmonary vein-atrial junctions.

Persistent atrial fibrillation in a goat model of chronic left atrial overload

Atrial dilatation predisposes to atrial fibrillation. Although several animal models focus on the initiating mechanisms of atrial fibrillation in dilated atria, a model of left atrial overload resulting in persistent atrial fibrillation in nonanesthetized animals has not been presented thus far. In 24 goats a vascular shunt was implanted between the aorta and the left atrium through a left thoracotomy. In 6 animals the shunt was ligated immediately (control group). Ultrasonic crystals were implanted to monitor atrial dilatation. Bipolar electrodes were positioned epicardially on the left atrium for measurement of the atrial effective refractory period, conduction times, and atrial fibrillation duration. Four weeks of overload resulted in an increase of left atrial pressure (23.1 +/- 6.8 mm Hg in the open-shunt group vs 7.0 +/- 1.9 mm Hg in the control group, P = .002) and a progressive dilatation of the left atrium (135% +/- 20% in the open-shunt group vs 98% +/- 8.0% in the control group, P = .002). Among the open-shunt group's long-term survivors (n = 12), 9 animals showed prolonged atrial fibrillation (>1 hour), and of these, 6 were in persistent atrial fibrillation (>1 week). The atrial effective refractory period increased during the first week and remained prolonged until death (182 +/- 11 ms in the open-shunt group vs 161 +/- 15 ms, P = .03). The conduction time did not change. An increase in collagen formation was noticed in both groups, without a significant difference between them. A chronic aortic to left atrial shunt is a feasible model in the goat. It induces progressive left atrial dilatation with an increased atrial fibrillation duration up to hours in the majority of animals. Prolonged atrial fibrillation duration could not be explained by a shortening of atrial effective refractory period or increase in fibrosis.

Effects of acetyl strophanthidin on duration of atrial fibrillation in the neurally-intact and blockaded dog.

Although the inotropic and dromotropic effects of cardiac glycosides in atrial fibrillation (AF) are well recognized, their action on AF itself is not clear. Accordingly, to determine whether cardiac glycosides prolong AF, the duration of electrically induced AF, atrioventricular conduction, and left ventricular function were assessed for 30 minutes before and for 30 minutes following intravenous administration of acetyl strophanthidin (AS), 20 micrograms/kg, in neurally intact, beta-blocked, and beta-blocked and vagotomized dogs. In the intact dog, AS, 20 micrograms/kg, increased peak dp/dt by 132 +/- 35 mmHg.sec-1, p less than 0.05, and slowed ventricular response by 16 +/- 7 min-1, p less than 0.05, but had a variable effect on AF duration. While the increased left ventricular peak dp/dt persisted for 15 minutes after AS, an increased duration of AF was evident only at 20 minutes, when the effects of AS on left ventricular (LV) inotropy were no longer apparent. Moreover, the subset of dogs that did not demonstrate prolongation of average duration of AF after AS had a greater increment of peak dp/dt than those that showed prolongation, 237 +/- 52 versus 53 +/- 31 mmHg.sec-1, p less than 0.05. An additional 20 micrograms/kg, which produced ventricular extrasystoles, prolonged AF duration when compared to both control and 30-minute measurements. Acetyl strophanthidin, 20 micrograms/kg, had a variable effect on duration of AF with beta-blockade but prolonged duration by 114 +/- 34%, p less than 0.05, with both vagotomy and beta-blockade.(ABSTRACT TRUNCATED AT 250 WORDS)