Cardiac Fibrosis in Patients With Atrial Fibrillation: Mechanisms and Clinical Implications

Sex-based differences and risk of recurrence in patients with atrial fibrillation undergoing pulmonary vein isolation

INTRODUCTION

Studies suggest increased likelihood of atrial fibrillation (AF) recurrence after catheter ablation (CA) in women than in men, indicating that sex may be an independent risk factor for recurrence. Nevertheless, the influence of sex on AF recurrence and underlying mechanisms remains unclear.

METHODS

Retrospective, single-centre study including patients undergoing AF CA between 2017 and 2021. Late recurrence (LR) was defined as AF recurrence ≥90 days after ablation, whereas early recurrence (ER) occurred within 90 days.

RESULTS

656 patients (32% women) were included, with a median follow-up period of 26 months. Compared to men, women undergoing CA were older, had higher body mass indexes, and had higher rates of hypertension, thyroid dysfunction, and valvular disease. Women also had increased LR risk after CA (HR 1.76, 95% CI [1.19, 2.59]). A time-split multivariable analysis at one year of follow-up showed no difference in LR risk during the first 12 months after CA (HR 1.19, 95% CI [0.73, 1.94]); however, LR risk increased in women (HR 2.90, 95% CI [1.68, 5.01]) after 12 months. In a sex-stratified analysis, coronary calcium score (CCS) >100 was associated with increased LR risk in men (HR 1.81, 95% CI [1.06, 3.08]), but not in women. Cardiac adipose tissue volume was not associated with increased LR risk.

CONCLUSIONS

Fewer women underwent CA than men and LR was more frequent in women, particularly one year after the procedure. CCS was associated with increased LR risk in men.

Ventricular late gadolinium enhancement by cardiac MRI as a predictor of atrial fibrillation in hypertrophic cardiomyopathy

BACKGROUND

Atrial fibrillation (AF) increases stroke and mortality in patients with hypertrophic cardiomyopathy (HCM). Cardiac MRI (CMR) is increasingly used to detect late gadolinium enhancement (LGE) as a reliable indicator of left ventricular fibrosis, a potential predisposing factor of AF. Our research explored the correlation between left ventricular LGE and AF prevalence in HCM.

METHODS

This retrospective study involved 351 HCM patients who underwent CMR. LGE percentages (0%, 1-5%, 6-14%, ≥15%) on CMR were compared with AF prevalence in HCM patients. Demographic, comorbidity, and imaging data were analyzed using appropriate univariate and multivariate analyses assessing for significant differences in AF prevalence. The predetermined significance level was p < 0.05.

RESULTS

CMR demonstrated increased LGE in those with AF (p = 0.004). Increased LGE correlated with increased AF rates: 27.6% (0% LGE), 38.5% (1-5% LGE), 44.4% (6-14% LGE), and 54.7% (≥15% LGE) (p = 0.101, p = 0.043, p = 0.002, respectively, vs. 0% LGE). Adjusted for age, differences persisted and were most evident for LGE >15% (p = 0.001). Multivariate analysis, factoring age, gender, BMI, RVSP, and LVEF, supported LGE (odds ratio of 1.20, p = 0.036) and LAVI (odds ratio 1.05, 1.02-1.07, p < 0.001) as predictive markers for AF prevalence.

CONCLUSIONS

Our study suggests a correlation between ventricular LGE and AF in patients with HCM. LGE exceeding 15% was associated with a significant increase in AF prevalence. These patients may require more frequent AF monitoring.

Modified mRNA-Mediated CCN5 Gene Transfer Ameliorates Cardiac Dysfunction and Fibrosis without Adverse Structural Remodeling

Modified mRNAs (modRNAs) are an emerging delivery method for gene therapy. The success of modRNA-based COVID-19 vaccines has demonstrated that modRNA is a safe and effective therapeutic tool. Moreover, modRNA has the potential to treat various human diseases, including cardiac dysfunction. Acute myocardial infarction (MI) is a major cardiac disorder that currently lacks curative treatment options, and MI is commonly accompanied by fibrosis and impaired cardiac function. Our group previously demonstrated that the matricellular protein CCN5 inhibits cardiac fibrosis (CF) and mitigates cardiac dysfunction. However, it remains unclear whether early intervention of CF under stress conditions is beneficial or more detrimental due to potential adverse effects such as left ventricular (LV) rupture. We hypothesized that CCN5 would alleviate the adverse effects of myocardial infarction (MI) through its anti-fibrotic properties under stress conditions. To induce the rapid expression of CCN5, ModRNA-CCN5 was synthesized and administrated directly into the myocardium in a mouse MI model. To evaluate CCN5 activity, we established two independent experimental schemes: (1) preventive intervention and (2) therapeutic intervention. Functional analyses, including echocardiography and magnetic resonance imaging (MRI), along with molecular assays, demonstrated that modRNA-mediated CCN5 gene transfer significantly attenuated cardiac fibrosis and improved cardiac function in both preventive and therapeutic models, without causing left ventricular rupture or any adverse cardiac remodeling. In conclusion, early intervention in CF by ModRNA-CCN5 gene transfer is an efficient and safe therapeutic modality for treating MI-induced heart failure.

A New Hope for the Treatment of Atrial Fibrillation: Application of Pulsed-Field Ablation Technology

In recent years, the prevalence of and mortality associated with cardiovascular diseases have been rising in most countries and regions. AF is the most common arrhythmic condition, and there are several treatment options for AF. Pulmonary vein isolation is an effective treatment for AF and is the cornerstone of current ablation techniques, which have one major limitation: even when diagnosed and treated at a facility that specializes in ablation, patients have a greater chance of recurrence. Therefore, there is a need to develop better ablation techniques for the treatment of AF. This article first compares the current cryoablation (CBA) and radiofrequency ablation (RFA) techniques for the treatment of AF and discusses the utility and advantages of the development of pulsed-field ablation (PFA) technology. The current research on PFA is summarized from three perspectives, namely, simulation experiments, animal experiments, and clinical studies. The results of different stages of experiments are summarized, especially during animal studies, where pulmonary vein isolation was carried out effectively without causing injury to the phrenic nerve, esophagus, and pulmonary veins, with higher safety and shorter incision times. This paper focuses on a review of various a priori and clinical studies of this new technique for the treatment of AF.

Ziprasidone triggers inflammasome signaling via PI3K-Akt-mTOR pathway to promote atrial fibrillation

BACKGROUND

Second-generation antipsychotics increase the risk of atrial fibrillation. This study explores whether the atypical antipsychotic ziprasidone triggers inflammasome signaling, leading to atrial arrhythmia.

METHODS

Electromechanical and pharmacological assessments were conducted on the rabbit left atria (LA). The patch-clamp technique was used to measure ionic channel currents in single cardiomyocytes. Detection of cytosolic reactive oxygen species production was performed in atrial cardiomyocytes.

RESULTS

The duration of action potentials at 50 % and 90 % repolarization was dose-dependently shortened in ziprasidone-treated LA. Diastolic tension in LA increased after ziprasidone treatment. Ziprasidone-treated LA showed rapid atrial pacing (RAP) triggered activity. PI3K inhibitor, Akt inhibitor and mTOR inhibitor abolished the triggered activity elicited by ziprasidone in LA. The NLRP3 inhibitor MCC950 suppressed the ziprasidone-induced post-RAP-triggered activity. MCC950 treatment reduced the reverse-mode Na+/Ca2+ exchanger current in ziprasidone-treated myocytes. Cytosolic reactive oxygen species production decreased in ziprasidone-treated atrial myocytes after MCC950 treatment. Protein levels of inflammasomes and proinflammatory cytokines, including NLRP3, caspase-1, IL-1β, IL-18, and IL-6 were observed to be upregulated in myocytes treated with ziprasidone.

CONCLUSIONS

Our findings suggest ziprasidone induces atrial arrhythmia, potentially through upregulation of the NLRP3 inflammasome and enhancement of reactive oxygen species production via the PI3K/Akt/mTOR pathway.

New-onset hypertension as a contributing factor to the incidence of atrial fibrillation in the elderly

Hypertension and atrial fibrillation are closely related. However, hypertension is already prevalent in young adults, but atrial fibrillation usually occurs in the elderly. In the present analysis, we investigated incident atrial fibrillation in relation to new-onset hypertension in an elderly Chinese population. Our study participants were elderly (≥65 years) hypertensive residents, recruited from community health centers in the urban Shanghai (n = 4161). Previous and new-onset hypertension were defined as the use of antihypertensive medication or elevated systolic/diastolic blood pressure (≥140/90 mmHg), respectively, at entry and during follow-up on ≥ 2 consecutive clinic visits. Atrial fibrillation was detected by a 30-s single-lead electrocardiography (ECG, AliveCor® Heart Monitor) and further evaluated with a regular 12-lead ECG. During a median of 2.1 years follow-up, the incidence rate of atrial fibrillation was 7.60 per 1000 person-years in all study participants; it was significantly higher in patients with new-onset hypertension (n = 368) than those with previous hypertension (n = 3793, 15.76 vs. 6.77 per 1000 person-years, P = 0.02). After adjustment for confounding factors, the hazard ratio for the incidence of atrial fibrillation was 2.21 (95% confidence interval 1.15-4.23, P = 0.02) in patients with new-onset hypertension versus those with previous hypertension. The association was even stronger in those aged ≥ 75 years (hazard ratio 2.70, 95% confidence interval 1.11-6.56, P = 0.03). In patients with previous hypertension, curvilinear association (P for non-linear trend = 0.04) was observed between duration of hypertension and the risk of incident atrial fibrillation, with a higher risk in short- and long-term than mid-term duration of hypertension. Our study showed a significant association between new-onset hypertension and the incidence of atrial fibrillation in elderly Chinese. In an elderly Chinese population with previous and new-onset hypertension, we found that the new-onset hypertension during follow-up, compared with previous hypertension, was associated with a significantly higher risk of incident atrial fibrillation. In patients with previous hypertension, curvilinear association was observed between duration of hypertension and the risk of incident atrial fibrillation, with a higher risk in short- and long-term than mid-term duration of hypertension.

Associations of the fibrosis-4 index with left atrial low-voltage areas and arrhythmia recurrence after catheter ablation: cardio-hepatic interaction in patients with atrial fibrillation

Background

The relationship between liver fibrosis and left atrial (LA) remodeling in atrial fibrillation (AF) remains uncertain. We examined the associations between the fibrosis-4 (FIB4) index, an indicator of liver fibrosis, and both LA low-voltage areas (LVAs) on electroanatomic mapping and AF recurrence postablation.

Methods

We recruited 343 patients who underwent radiofrequency catheter ablation (RFCA) or cryoballoon ablation (CBA) for AF. First, the association between the FIB4 index and LA LVAs (<0.5 mV) was evaluated in RFCA using electroanatomic mapping (n = 214). Next, the utility of a FIB4 index ≥1.3, recommended cut-off value of liver fibrosis, was verified to assess the risk for AF recurrence in CBA without additional LVA ablation (n = 129).

Results

Patients with a FIB4 index ≥1.3 had a higher prevalence of LA LVAs (>5 cm2) compared to those without. Additionally, the quantitative size of LVAs showed a positive correlation with the FIB4 index (R = .642, p < .001). In multivariate logistic models, a FIB4 index ≥1.3 was related to the presence of LVAs after adjusting for LA diameter, right atrial end-systolic area, and nonparoxysmal AF (odds ratio 2.508; p = 0.039). In CBA, AF recurrence rate was 13.1% during 3-12 months postablation. In multivariate Cox models, a FIB4 index ≥1.3 was an important predictor of AF recurrence (hazard ratio 3.796; p = .037), suggesting that LVAs might be associated with AF recurrence after CBA.

Conclusion

The FIB4 index was a novel predictor of the existence of LA LVAs on electroanatomic mapping and AF recurrence after CBA.

Astragaloside IV inhibits angiotensin II-induced atrial fibrosis and atrial fibrillation by SIRT1/PGC-1α/FNDC5 pathway

Aims and objectives

Astragaloside IV (AS-IV) has been found to possess anti-oxidative, anti-inflammatory, and anti-apoptotic properties, but its effect on atrial fibrosis is yet to be determined. This research investigates the protective role of AS-IV in angiotensin II (Ang II)-induced atrial fibrosis and atrial fibrillation (AF).

Methods

C57BL/6 male mice aged 8-10 weeks (n = 40) were subcutaneously administered Ang II (2.0 mg/kg/day) or saline, with AS-IV (80 mg/kg) intraperitoneally administered 2 h before Ang II infusion for 4 weeks. Biochemical, histological, and morphological analyses were carried out. Using transesophageal burst pacing, AF was generated in vivo.

Results

Here, we report that AS-IV treatment inhibited Ang II-induced AF development in mice (58 ± 5.86 vs 15.13 ± 2.16 %, p < 0.001). Ang II + AS-IV therapy was effective in reducing the atrial fibrotic area and decreasing the increase in smooth muscle alpha-actin (α-SMA)-positive myofibroblasts brought on by Ang II treatment (fibrotic area: 26.25 ± 3.81 vs 8.62 ± 1.83 %, p < 0.001 and α-SMA: 65.62 ± 10.63 vs 17.25 ± 1.78 %, p < 0.001). The reactive oxygen species (ROS) production was reduced by pretreatment with Ang II + AS-IV (9.20 ± 0.92 vs 2.63 ± 0.22 %/sec, p < 0.001). In addition, Ang II + AS-IV treatment suppressed oxidative stress in Ang II-induced atrial fibrosis (malondialdehyde: 701.78 ± 85.01 vs 504.07 ± 25.62 pmol/mg protein, p < 0.001; superoxide dismutase: 13.82 ± 1.25 vs 29.54 ± 2.45 U/mg protein, p < 0.001 and catalase: 11.43 ± 1.19 vs 20.83 ± 3.29 U/mg protein, p < 0.001, respectively). Moreover, Ang II + AS-IV decreased the expression of α-SMA, collagen III and collagen I (3.32 ± 0.53 vs 1.41 ± 0.20 fold, p < 0.001; 3.41 ± 0.55 vs 1.48 ± 0.18 fold, p < 0.001; 2.34 ± 0.55 vs 0.99 ± 0.17 fold, p < 0.001, respectively) while increasing the protein expression of sirtuin 1 (SIRT1), peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (PGC-1α), and fibronectin type III domain-containing protein 5 (FNDC5) in Ang II-treated mice (0.22 ± 0.02 vs 0.57 ± 0.08 fold, p < 0.001; 0.28 ± 0.04 vs 0.72 ± 0.05 fold, p < 0.001; 0.38 ± 0.03 vs 0.68 ± 0.06 fold, p < 0.001, respectively).

Conclusion

Our data led us to speculate that AS-IV may protect against Ang II-induced atrial fibrosis and AF via upregulation of the SIRT1/PGC-1α/FNDC5 pathway.

Cardioembolic Stroke: Past Advancements, Current Challenges, and Future Directions

Cardioembolic stroke accounts for over 20% of ischemic strokes and is associated with worse outcomes than other types of strokes. Atrial fibrillation (AF) is the most common risk factor for cardioembolic stroke. In this narrative review, we present an update about cardioembolic stroke mainly related to AF and atrial cardiopathy. Direct oral anticoagulants (DOACs) have revolutionized stroke prevention in patients with AF; however, their efficacy in preventing recurrent embolic stroke of unknown source remains uncertain. Various cardiac monitoring methods are used to detect AF, which is crucial for preventing stroke recurrence. DOACs are preferred over warfarin for AF-related stroke prevention; however, the timing of initiation after acute ischemic stroke is debated. Resuming anticoagulation after intracerebral hemorrhage in AF patients requires careful assessment of the risks. While catheter ablation may reduce the incidence of cardiovascular events, its effect on stroke prevention is unclear, especially in heart failure patients. Atrial cardiopathy is the emerging cause of embolic stroke of unknown source, which indicates atrial structural and functional disorders that can precede AF. Future research should focus on refining stroke risk prediction models, optimizing AF detection, understanding the roles of ablation and anticoagulation in stroke prevention, and establishing atrial cardiopathy as a therapeutic target, which could significantly reduce the burden of stroke.

The role of cellular senescence in profibrillatory atrial remodelling associated with cardiac pathology

AIMS

Cellular senescence is a stress-related or aging response believed to contribute to many cardiac conditions; however, its role in atrial fibrillation (AF) is unknown. Age is the single most important determinant of the risk of AF. The present study was designed to (i) evaluate AF susceptibility and senescence marker expression in rat models of aging and myocardial infarction (MI), (ii) study the effect of reducing senescent-cell burden with senolytic therapy on the atrial substrate in MI rats, and (iii) assess senescence markers in human atrial tissue as a function of age and the presence of AF.

METHODS AND RESULTS

AF susceptibility was studied with programmed electrical stimulation. Gene and protein expression was evaluated by immunoblot or immunofluorescence (protein) and digital polymerase chain reaction (PCR) or reverse transcriptase quantitative PCR (messenger RNA). A previously validated senolytic combination, dasatinib and quercetin, (D+Q; or corresponding vehicle) was administered from the time of sham or MI surgery through 28 days later. Experiments were performed blinded to treatment assignment. Burst pacing-induced AF was seen in 100% of aged (18-month old) rats, 87.5% of young MI rats, and 10% of young control (3-month old) rats (P ≤ 0.001 vs. each). Conduction velocity was slower in aged [both left atrium (LA) and right atrium (RA)] and young MI (LA) rats vs. young control rats (P ≤ 0.001 vs. each). Atrial fibrosis was greater in aged (LA and RA) and young MI (LA) vs. young control rats (P < 0.05 for each). Senolytic therapy reduced AF inducibility in MI rats (from 8/9 rats, 89% in MI vehicle, to 0/9 rats, 0% in MI D + Q, P < 0.001) and attenuated LA fibrosis. Double staining suggested that D + Q acts by clearing senescent myofibroblasts and endothelial cells. In human atria, senescence markers were upregulated in older (≥70 years) and long-standing AF patients vs. individuals ≤60 and sinus rhythm controls, respectively.

CONCLUSION

Our results point to a potentially significant role of cellular senescence in AF pathophysiology. Modulating cell senescence might provide a basis for novel therapeutic approaches to AF.

Incremental value of diastolic wall strain in predicting heart failure events in patients with atrial fibrillation

Diastolic wall strain (DWS), an echocardiographic index based on linear elasticity theory, has been identified as a predictor of heart failure (HF) in patients with sinus rhythm. However, its effectiveness in atrial fibrillation (AF) patients remains uncertain. This study aims to assess DWS as a predictor of HF in AF patients with preserved ejection fraction. We analysed a prospective database of AF patients undergoing transthoracic echocardiography. AF patients with reduced left ventricular ejection fraction (< 50%), posterior wall motion abnormality, hypertrophic cardiomyopathy, valvular heart disease, pericardial disease, congenital heart disease, or history of pacemaker/implantable cardioverter-defibrillator implantation or cardiac surgery were excluded. The study followed patients until HF development, death, or last visit. Follow-up for patients who underwent catheter ablation was censored on the date of their procedure. HF was ascertained based on the Framingham criteria. DWS was calculated using a validated formula: DWS = (PWs -PWd)/PWs, where PWs is the posterior wall thickness at end-systole and PWd is the posterior wall thickness at end-diastole. Among 411 study patients (mean age 69.6 years, 66% men), 20 (5%) was underwent catheter ablation and 57 (14%) developed HF during a mean follow-up of 82 months. Cox-proportional hazards demonstrated that low DWS (≤ 0.33) significantly predicted HF events (hazard ratio [HR] 3.28, 95% confidence interval [CI]) 1.81-5.94, P < 0.0001), independent of age (per 10 years; HR 1.99, 95% CI 1.35-2.93, P < 0.001), indexed left ventricular mass (per 10 g/m2; HR 1.16, 95% CI 1.05-1.27, P < 0.01), and indexed left atrial volume (per 10 mL/m2; HR 1.14, 95% CI 1.04-1.24, P < 0.01). Additionally, global log-likelihood ratio chi-square statistics indicated that DWS incrementally predicts HF development beyond age, indexed left ventricular mass, and left atrial volume (P < 0.001).

Arrhythmias and cardiac MRI associations in patients with established cardiac dystrophinopathy

AIMS

Some patients with cardiac dystrophinopathy die suddenly. Whether such deaths are preventable by specific antiarrhythmic management or simply indicate heart failure overwhelming medical therapies is uncertain. The aim of this prospective, cohort study was to describe the occurrence and nature of cardiac arrhythmias recorded during prolonged continuous ECG rhythm surveillance in patients with established cardiac dystrophinopathy and relate them to abnormalities on cardiac MRI.

METHODS AND RESULTS

A cohort of 10 patients (36.3 years; 3 female) with LVEF<40% due to Duchenne (3) or Becker muscular (4) dystrophy or Duchenne muscular dystrophy-gene carrying effects in females (3) were recruited, had cardiac MRI, ECG signal-averaging and ECG loop-recorder implants. All were on standard of care heart medications and none had prior history of arrhythmias.No deaths or brady arrhythmias occurred during median follow-up 30 months (range 13-35). Self-limiting episodes of asymptomatic tachyarrhythmia (range 1-29) were confirmed in 8 (80%) patients (ventricular only 2; ventricular and atrial 6). Higher ventricular arrhythmia burden correlated with extent of myocardial fibrosis (extracellular volume%, p=0.029; native T1, p=0.49; late gadolinium enhancement, p=0.49), but not with LVEF% (p=1.0) on MRI and atrial arrhythmias with left atrial dilatation. Features of VT episodes suggested various underlying arrhythmia mechanisms.

CONCLUSIONS

The overall prevalence of arrhythmias was low. Even in such a small sample size, higher arrhythmia counts occurred in those with larger scar burden and greater ventricular volume, suggesting key roles for myocardial stretch as well as disease progression in arrhythmogenesis. These features overlap with the stage of left ventricular dysfunction when heart failure also becomes overt. The findings of this pilot study should help inform the design of a definitive study of specific antiarrhythmic management in dystrophinopathy.

TRIAL REGISTRATION NUMBER

ISRCTN15622536.

Atrial fibrosis heterogeneity is a risk for atrial fibrillation in pigs with ischaemic heart failure

BACKGROUND

Atrial fibrillation (AF) is the most common arrhythmia and is associated with considerable morbidity and mortality. Ischaemic heart failure (IHF) remains one of the most common causes of AF in clinical practice. However, ischaemia-mediated mechanisms leading to AF are still incompletely understood, and thus, current treatment approaches are limited. To improve our understanding of the pathophysiology, we studied a porcine IHF model.

METHODS

In pigs, IHF was induced by balloon occlusion of the left anterior descending artery for 90 min. After 30 days of reperfusion, invasive haemodynamic measurements and electrophysiological studies were performed. Masson trichrome and immunofluorescence staining were conducted to assess interstitial fibrosis and myofibroblast activation in different heart regions.

RESULTS

After 30 days of reperfusion, heart failure with significantly reduced ejection fraction (left anterior obique 30°, 34.78 ± 3.29% [IHF] vs. 62.03 ± 2.36% [control], p < .001; anterior-posterior 0°, 29.16 ± 3.61% vs. 59.54 ± 1.09%, p < .01) was observed. These pigs showed a significantly higher susceptibility to AF (33.90% [IHF] vs. 12.98% [control], p < .05). Histological assessment revealed aggravated fibrosis in atrial appendages but not in atrial free walls in IHF pigs (11.13 ± 1.44% vs. 5.99 ± .86%, p < .01 [LAA], 8.28 ± .56% vs. 6.01 ± .35%, p < .01 [RAA]), which was paralleled by enhanced myofibroblast activation (12.09 ± .65% vs. 9.00 ± .94%, p < .05 [LAA], 14.37 ± .60% vs. 10.30 ± 1.41%, p < .05 [RAA]). Correlation analysis indicated that not fibrosis per se but its cross-regional heterogeneous distribution across the left atrium was associated with AF susceptibility (r = .6344, p < .01).

CONCLUSION

Our results suggest that left atrial cross-regional fibrosis difference rather than overall fibrosis level is associated with IHF-related AF susceptibility, presumably by establishing local conduction disturbances and heterogeneity.

Epicardial adipose tissue in obesity with heart failure with preserved ejection fraction: Cardiovascular magnetic resonance biomarker study

BACKGROUND

Obesity has become a serious public health issue, significantly elevating the risk of various complications. It is a well-established contributor to Heart failure with preserved ejection fraction (HFpEF). Evaluating HFpEF in obesity is crucial. Epicardial adipose tissue (EAT) has emerged as a valuable tool for validating prognostic biomarkers and guiding treatment targets. Hence, assessing EAT is of paramount importance. Cardiovascular magnetic resonance (CMR) imaging is acknowledged as the gold standard for analyzing cardiac function and morphology. We hope to use CMR to assess EAT as a bioimaging marker to evaluate HFpEF in obese patients.

AIM

To assess the diagnostic utility of CMR for evaluating heart failure with preserved ejection fraction [HFpEF; left ventricular (LV) ejection fraction ≥ 50%] by measuring the epicardial adipose tissue (EAT) volumes and EAT mass in obese patients.

METHODS

Sixty-two obese patients were divided into two groups for a case-control study based on whether or not they had heart failure with HFpEF. The two groups were defined as HFpEF+ and HFpEF-. LV geometry, global systolic function, EAT volumes and EAT mass of all subjects were obtained using cine magnetic resonance sequences.

RESULTS

Forty-five patients of HFpEF- group and seventeen patients of HFpEF+ group were included. LV mass index (g/m2) of HFpEF+ group was higher than HFpEF- group (P < 0.05). In HFpEF+ group, EAT volumes, EAT volume index, EAT mass, EAT mass index and the ratio of EAT/[left atrial (LA) left-right (LR) diameter] were higher compared to HFpEF- group (P < 0.05). In multivariate analysis, Higher EAT/LA LR diameter ratio was associated with higher odds ratio of HFpEF.

CONCLUSION

EAT/LA LR diameter ratio is highly associated with HFpEF in obese patients. It is plausible that there may be utility in CMR for assessing obese patients for HFpEF using EAT/LA LR diameter ratio as a diagnostic biomarker. Further prospective studies, are needed to validate these proof-of-concept findings.

Cardiac arrhythmogenesis: roles of ion channels and their functional modification

Cardiac arrhythmias cause significant morbidity and mortality and pose a major public health problem. They arise from disruptions in the normally orderly propagation of cardiac electrophysiological activation and recovery through successive cardiomyocytes in the heart. They reflect abnormalities in automaticity, initiation, conduction, or recovery in cardiomyocyte excitation. The latter properties are dependent on surface membrane electrophysiological mechanisms underlying the cardiac action potential. Their disruption results from spatial or temporal instabilities and heterogeneities in the generation and propagation of cellular excitation. These arise from abnormal function in their underlying surface membrane, ion channels, and transporters, as well as the interactions between them. The latter, in turn, form common regulatory targets for the hierarchical network of diverse signaling mechanisms reviewed here. In addition to direct molecular-level pharmacological or physiological actions on these surface membrane biomolecules, accessory, adhesion, signal transduction, and cytoskeletal anchoring proteins modify both their properties and localization. At the cellular level of excitation-contraction coupling processes, Ca2+ homeostatic and phosphorylation processes affect channel activity and membrane excitability directly or through intermediate signaling. Systems-level autonomic cellular signaling exerts both acute channel and longer-term actions on channel expression. Further upstream intermediaries from metabolic changes modulate the channels both themselves and through modifying Ca2+ homeostasis. Finally, longer-term organ-level inflammatory and structural changes, such as fibrotic and hypertrophic remodeling, similarly can influence all these physiological processes with potential pro-arrhythmic consequences. These normal physiological processes may target either individual or groups of ionic channel species and alter with particular pathological conditions. They are also potentially alterable by direct pharmacological action, or effects on longer-term targets modifying protein or cofactor structure, expression, or localization. Their participating specific biomolecules, often clarified in experimental genetically modified models, thus constitute potential therapeutic targets. The insights clarified by the physiological and pharmacological framework outlined here provide a basis for a recent modernized drug classification. Together, they offer a translational framework for current drug understanding. This would facilitate future mechanistically directed therapeutic advances, for which a number of examples are considered here. The latter are potentially useful for treating cardiac, in particular arrhythmic, disease.

Association of left atrial enlargement with heart failure events in non-valvular atrial fibrillation patients with preserved left ventricular ejection fraction

Aims

Atrial fibrillation (AF) increases the risk of heart failure (HF); however, little is known regarding the risk stratification for incident HF in AF patients, especially with preserved left ventricular ejection fraction (LVEF).

Methods and results

The Fushimi AF Registry is a community-based prospective survey of AF patients. From the registry, 3002 non-valvular AF patients with preserved LVEF and with the data of antero-posterior left atrial diameter (LAD) at enrolment were investigated. Patients were stratified by LAD (<40, 40-44, 45-49, and ≥50 mm) with backgrounds and HF hospitalization incidences compared between groups. Of 3002 patients [mean age, 73.5 ± 10.7 years; women, 1226 (41%); paroxysmal AF, 1579 (53%); and mean CHA2DS2-VASc score, 3.3 ± 1.7], the mean LAD was 43 ± 8 mm. Patients with larger LAD were older and less often paroxysmal AF, with a higher CHA2DS2-VASc score (all P < 0.001). Heart failure hospitalization occurred in 412 patients during the median follow-up period of 6.0 years. Larger LAD was independently associated with a higher HF hospitalization risk [LAD ≥ 50 mm: hazard ratio (HR), 2.36; 95% confidence interval (CI), 1.75-3.18; LAD 45-49 mm: HR, 1.84; 95% CI, 1.37-2.46; and LAD 40-44 mm: HR, 1.34; 95% CI, 1.01-1.78, compared with LAD < 40 mm) after adjustment by age, sex, AF type, and CHA2DS2-VASc score. These results were also consistent across major subgroups, showing no significant interaction.

Conclusion

Left atrial diameter is significantly associated with the risk of incident HF in AF patients with preserved LVEF, suggesting the utility of LAD regarding HF risk stratification for these patients.

Mediterranean diet and epicardial adipose tissue in patients with atrial fibrillation treated with ablation: a substudy of the 'PREDIMAR' trial

AIMS

To analyse the relationship between Mediterranean diet (MedDiet) adherence and epicardial adipose tissue (EAT) in patients with atrial fibrillation (AF) and the association between EAT or MedDiet adherence at baseline with AF recurrence after ablation.

METHODS AND RESULTS

We included 199 patients from the PREDIMAR trial (PREvención con DIeta Mediterránea de Arritmias Recurrentes), in a single centre in this substudy. All of them had a computed tomography with EAT measurement. Lifestyle and clinical characteristics were obtained at baseline. The traditional MedDiet pattern was defined according to the MedDiet Adherence Screener (MEDAS). Any documented AF > 30 s after ablation was considered a recurrence. Multivariable-adjusted linear and logistic regression models were run to assess the cross-sectional association of MedDiet with EAT, and of EAT with the AF type at baseline. Also, Cox regression models were used to prospectively assess the associations of MedDiet adherence and EAT with AF recurrences after ablation. Median EAT was 135 g (interquartile range: 112-177), and the mean MedDiet score was 7.75 ± 2 points. A higher MEDAS ≥ 7 that was associated with lower odds of an EAT ≥ 135 g [multivariable odds ratio (mOR) = 0.45; 95% CI = 0.22-0.91; P = 0.025] was significantly associated with persistent AF after adjusting for traditional risk factors (mOR: 2.22; 95% CI: 1.03-4.79; P = 0.042). No significant associations were observed between EAT ≥ 135 g and the risk of atrial tachyarrhythmia recurrences after ablation [multivariable-adjusted hazard ratio (mHR) = 1.18; 95% CI: 0.72-1.94; P = 0.512], or between MEDAS ≥ 7 and AF recurrence (mHR = 0.78; 95% CI: 0.47-1.31; P = 0.344).

CONCLUSION

In patients with AF, higher adherence to MedDiet is associated with a significantly lower amount of EAT. Epicardial adipose tissue ≥ 135 g was significantly associated with persistent AF.

The effects of daily dose of intense exercise on cardiac responses and atrial fibrillation

Atrial fibrillation (AF) is a supraventricular tachyarrhythmia that is strongly associated with cardiovascular (CV) disease and sedentary lifestyles. Despite the benefits of exercise on overall health, AF incidence in high-level endurance athletes rivals that of CV disease patients, suggesting a J-shaped relationship with AF. To investigate the dependence of AF vulnerability on exercise, we varied daily swim durations (120, 180 or 240 min day-1 ) in 7-week-old male CD1 mice. We assessed mice after performing equivalent amounts of cumulative work during swimming (i.e. ∼700 L O2  kg-1 ), as determined from O2 consumption rates (V ̇ O 2 ${\dot V_{{{\mathrm{O}}_2}}}$ ). The meanV ̇ O 2 ${\dot V_{{{\mathrm{O}}_2}}}$ during exercise increased progressively throughout the training period and was indistinguishable between the swim groups. Consistent with similar improvements in aerobic conditioning induced by swimming, skeletal muscle mitochondria content increased (P = 0.027) indistinguishably between exercise groups. Physiological ventricular remodelling, characterized by mild hypertrophy and left ventricular dilatation, was also similar between exercised mice without evidence of ventricular arrhythmia inducibility. By contrast, prolongation of daily swim durations caused progressive and vagal-dependent heart rate reductions (P = 0.008), as well as increased (P = 0.005) AF vulnerability. As expected, vagal inhibition prolonged (P = 0.013) atrial refractoriness, leading to reduced AF vulnerability, although still inducible in the 180 and 240 min swim groups. Accordingly, daily swim dose progressively increased atrial hypertrophy (P = 0.003), fibrosis (P < 0.001) and macrophage accumulation (P = 0.006) without differentially affecting the ventricular tissue properties. Thus, increasing daily exercise duration drives progressively adverse atrial-specific remodelling and vagal-dependent AF vulnerability despite robust and beneficial aerobic conditioning and physiological remodelling of ventricles and skeletal muscle. KEY POINTS: Previous studies have suggested that a J-shaped dose-response relationship exists between physical activity and cardiovascular health outcomes, with moderate exercise providing protection against many cardiovascular disease conditions, whereas chronic endurance exercise can promote atrial fibrillation (AF). We found that AF vulnerability increased alongside elevated atrial hypertrophy, fibrosis and inflammation as daily swim exercise durations in mice were prolonged (i.e. ≥180 min day-1 for 6 weeks). The MET-h week-1 (based on O2  measurements during swimming) needed to induce increased AF vulnerability mirrored the levels linked to AF in athletes. These adverse atria effects associated with excessive daily exercise occurred despite improved aerobic conditioning, skeletal muscle adaptation and physiological ventricular remodelling. We suggest that atrial-specific changes observed with exercise arise from excessive elevations in venous filling pressures during prolonged exercise bouts, which we argue has implications for all AF patients because elevated atrial pressures occur in most cardiovascular disease conditions as well as ageing which are linked to AF.

Aging and atrial fibrillation: A vicious circle

Atrial fibrillation (AF) is the commonest sustained cardiac arrhythmia observed in clinical practice. Its prevalence increases dramatically with advancing age. This review article discusses the recent advances in studies investigating the relationship between aging and AF and the possible underlying mechanisms.

Left atrial strain analysis in the realm of pediatric cardiology: Advantages and implications

BACKGROUND

Left atrial (LA) strain analysis has emerged as a noninvasive technique for assessing LA function and early detection of myocardial deformation. Recently, its application has also shown promise in the pediatric population, spanning diverse cardiac conditions that demand accurate and sensitive diagnostic measures.

OBJECTIVE

This research article endeavors to explore the role of LA strain parameters and contribute to the growing body of knowledge in pediatric cardiology, paving the way for more effective and tailored approaches to patient care.

METHODS

A comprehensive literature review was conducted to gather evidence from studies using echocardiographic strain imaging techniques across pediatric populations.

RESULTS

LA strain parameters exhibited greater sensitivity than conventional atrial function indicators, with early detection of diastolic dysfunction and LA remodeling in pediatric cardiomyopathy, children with multisystem inflammatory syndrome, rheumatic heart disease, as well as childhood renal insufficiency and obesity offering prognostic relevance as potential markers in these pediatric subpopulations. However, there remains a paucity of evidence concerning pediatric mitral valve pathology, justifying further exploration.

CONCLUSION

LA strain analysis carries crucial clinical and prognostic implications in pediatric cardiac conditions, with reliable accuracy and sensitivity to early functional changes.

Stroke in Patients with Atrial Fibrillation: Epidemiology, Screening, and Prognosis

Atrial fibrillation (AF) is the most common sustained arrythmia and one of the strongest risk factors and causal mechanisms of ischemic stroke (IS). Acute IS due to AF tends to be more severe than with other etiology of IS and patients with treated AF have reported to experience worse outcomes after endovascular treatment compared with patients without AF. As cardioembolism accounts for more than a fifth of ISs and the risk of future stroke can be mitigated with effective anticoagulation, which has been shown to be effective and safe in patients with paroxysmal or sustained AF, the screening of patients with cryptogenic IS (CIS) for AF is paramount. Embolic stroke of undetermined source (ESUS) is a subtype of CIS with a high likelihood of cardioembolism. The European Stroke Organization and European Society of Cardiology guidelines recommend at least 72 h of screening when AF is suspected. The longer the screening and the earlier the time point after acute IS, the more likely the AF paroxysm is found. Several methods are available for short-term screening of AF, including in-hospital monitoring and wearable electrocardiogram recorders for home monitoring. Implantable loop monitors provide an effective long-term method to screen patients with high risk of AF after IS and artificial intelligence and convolutional neural networks may enhance the efficacy of AF screening in the future. Direct oral anticoagulants (DOACs) are preferred over vitamin K antagonists in both primary and secondary prevention of IS in AF patients. Recent data from the randomized controlled trials (RCT) also suggest that early initiation of DOAC treatment after acute IS is safe compared to later initiation. Anticoagulation treatment may still predispose for intracranial bleeding, particularly among patients with prior cerebrovascular events. Left atrial appendix closure offers an optional treatment choice for patients with prior intracranial hemorrhage and may offer an alternative to oral anticoagulation even for patients with IS, but these indications await validation in ongoing RCTs. There are still controversies related to the association of found AF paroxysms in CIS patients with prolonged screening, pertaining to the optimal duration of screening and screening strategies with prolonged monitoring techniques in patients with ESUS. In this review, we summarize the current knowledge of epidemiology, screening, and prognosis in AF patients with stroke.

Cardiomyocyte and endothelial cells play distinct roles in the tumour necrosis factor (TNF)-dependent atrial responses and increased atrial fibrillation vulnerability induced by endurance exercise training in mice

AIMS

Endurance exercise is associated with an increased risk of atrial fibrillation (AF). We previously established that adverse atrial remodelling and AF susceptibility induced by intense exercise in mice require the mechanosensitive and pro-inflammatory cytokine tumour necrosis factor (TNF). The cellular and mechanistic basis for these TNF-mediated effects is unknown.

METHODS AND RESULTS

We studied the impact of Tnf excision, in either atrial cardiomyocytes or endothelial cells (using Cre-recombinase expression controlled by Nppa or Tie2 promoters, respectively), on the cardiac responses to six weeks of intense swim exercise training. TNF ablation, in either cell type, had no impact on the changes in heart rate, autonomic tone, or left ventricular structure and function induced by exercise training. Tnf excision in atrial cardiomyocytes did, however, prevent atrial hypertrophy, fibrosis, and macrophage infiltration as well as conduction slowing and increased AF susceptibility arising from exercise training. In contrast, endothelial-specific excision only reduced the training-induced atrial hypertrophy. Consistent with these cell-specific effects of Tnf excision, inducing TNF loss from atrial cardiomyocytes prevented activation of p38MAPKinase, a strain-dependent downstream mediator of TNF signalling, without affecting the atrial stretch as assessed by atrial pressures induced by exercise. Despite TNF's established role in innate immune responses and inflammation, neither acute nor chronic exercise training caused measurable NLRP3 inflammasome activation.

CONCLUSIONS

Our findings demonstrate that adverse atrial remodelling and AF vulnerability induced by intense exercise require TNF in atrial cardiomyocytes whereas the impact of endothelial-derived TNF is limited to hypertrophy modulation. The implications of the cell autonomous effects of TNF and crosstalk between cells in the atria are discussed.

Patchy fibrosis promotes trigger-substrate interactions that both generate and maintain atrial fibrillation

Fibrosis has been mechanistically linked to arrhythmogenesis in multiple cardiovascular conditions, including atrial fibrillation (AF). Previous studies have demonstrated that fibrosis can create functional barriers to conduction which may promote excitation wavebreak and the generation of re-entry, while also acting to pin re-entrant excitation in stable rotors during AF. However, few studies have investigated the role of fibrosis in the generation of AF triggers in detail. We apply our in-house computational framework to study the impact of fibrosis on the generation of AF triggers and trigger-substrate interactions in two- and three-dimensional atrial tissue models. Our models include a reduced and efficient description of stochastic, spontaneous cellular triggers as well as a simple model of heterogeneous inter-cellular coupling. Our results demonstrate that fibrosis promotes the emergence of focal excitations, primarily through reducing the electrotonic load on individual fibre strands. This enables excitation to robustly initiate within these single strands before spreading to neighbouring strands and inducing a full tissue focal excitation. Enhanced conduction block can allow trigger-substrate interactions that result in the emergence of complex, re-entrant excitation patterns. This study provides new insight into the mechanisms by which fibrosis promotes the triggers and substrate necessary to induce and sustain arrhythmia.

Pinocembrin attenuates susceptibility to atrial fibrillation in rats with pulmonary arterial hypertension

BACKGROUND

Pulmonary arterial hypertension (PAH) is a disease characterized by pulmonary vascular remodeling that triggers fibrosis and excessive myocardium apoptosis, ultimately facilitating atrial fibrillation (AF). In various rat models, Pinocembrin has anti-fibrotic and anti-apoptotic effects, reducing arrhythmia vulnerability. However, whether pinocembrin alleviates to AF in a PAH model remains unclear. The experiment aims to investigate how pinocembrin affects AF susceptibility in PAH rats and the possible mechanisms involved.

METHODS

The PAH model was induced by monocrotaline (MCT; i. p. 60 mg/kg). Concurrently, rats received pinocembrin (i.p.50 mg/kg) or saline. Hemodynamics parameters, electrocardiogram parameters, lung H.E. staining, atrial electrophysiological parameters, histology, Western blot, and TUNEL assay were detected.

RESULTS

Compared to the control rats, MCT-induced PAH rats possessed prominently enhancive mPAP (mean pulmonary artery pressure), pulmonary vascular remodeling, AF inducibility, HRV, right atrial myocardial fibrosis, apoptosis, atrial ERP, APD, and P-wave duration. Additionally, there were lowered protein levels of Cav1.2, Kv4.2, Kv4.3, and connexin 40 (CX40) in the MCT group in right atrial tissue. However, pinocembrin reversed the above pathologies and alleviated the activity of the Rho A/ROCKs signaling pathway, including the expression of Rho A, ROCK1, ROCK2, and its downstream MYPT-1, LIMK2, BCL-2, BAX, cleaved-caspase3 in right atrial and HL-1 cells.

CONCLUSION

Present data exhibited pinocembrin attenuated atrial electrical, ion-channel, and autonomic remodeling, diminished myocardial fibrosis and apoptosis levels, thereby reducing susceptibility to AF in the MCT-induced PAH rats. Furthermore, we found that pinocembrin exerted inhibitory action on the Rho A/ROCK signaling pathway, which may be potentially associated with its anti-AF effects.

MicroRNAs in atrial fibrillation target genes in structural remodelling

We aim to elucidate how miRNAs regulate the mRNA signature of atrial fibrillation (AF), to gain mechanistic insight and identify candidate targets for future therapies. We present combined miRNA-mRNA sequencing using atrial tissues of patient without AF (n = 22), with paroxysmal AF (n = 22) and with persistent AF (n = 20). mRNA sequencing previously uncovered upregulated epithelial to mesenchymal transition, endothelial cell proliferation and extracellular matrix remodelling involving glycoproteins and proteoglycans in AF. MiRNA co-sequencing discovered miRNAs regulating the mRNA expression changes. Key downregulated miRNAs included miR-135b-5p, miR-138-5p, miR-200a-3p, miR-200b-3p and miR-31-5p and key upregulated miRNAs were miR-144-3p, miR-15b-3p, miR-182-5p miR-18b-5p, miR-4306 and miR-206. MiRNA expression levels were negatively correlated with the expression levels of a multitude of predicted target genes. Downregulated miRNAs associated with increased gene expression are involved in upregulated epithelial and endothelial cell migration and glycosaminoglycan biosynthesis. In vitro inhibition of miR-135b-5p and miR-138-5p validated an effect of miRNAs on multiple predicted targets. Altogether, the discovered miRNAs may be explored in further functional studies as potential targets for anti-fibrotic therapies in AF.

Salidroside attenuates atrial fibrosis and atrial fibrillation vulnerability induced by angiotensin-II through inhibition of LOXL2-TGF-β1-Smad2/3 pathway

Aims and objectives

Salidroside (SAL), an active component isolated from the Chinese plant Rose Rhodiola, has anti-inflammatory, antioxidant, anti-cancer, neuroprotective, and renal protective properties. Atrial fibrosis developed due to angiotensin II (Ang II) plays a crucial function in developing atrial fibrillation (AF). This research investigates the involvement of SAL in AF, its vulnerability to AF, and Ang II-induced inflammatory atrial fibrosis.

Methods

Ang II (2 mg/kg/day) was infused underneath the skin into male C57BL/6 mice (8-10 weeks old, n = 40) for four weeks to create the AF model. SAL (50 mg/kg/day) was given intraperitoneally once per day for 28 days. Analyses of morphology, histology, and biochemical were carried out. Transesophageal burst pacing was used in vivo to induce AF.

Results

Ang II injection increased mice's heart rate and systolic blood pressure (SBP), whereas SAL treatment was significantly reduced. Ang II infusion increased left atrial diameter (LAD) in mice, which was attenuated after SAL treatment. SAL alone did not affect AF inducibility, but SAL therapy markedly decreased Ang II-induced AF inducibility. Additionally, the expression levels of interleukin-1 beta (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) were inhibited with SAL therapy in mice. Compared to the Ang II group, Ang II infusion raised malondialdehyde (MDA) levels and reduced superoxide dismutase (SOD) and catalase (CAT) activity, but SAL therapy altered all of these effects. SAL treatment significantly reduced LOXL2, TGF-β1, p-Smad2 and p-Smad3 protein expression than the Ang II group mice.

Conclusion

SAL inhibits atrial fibrosis and potentially attenuates increased susceptibility to AF by suppressing the LOXL2-TGF-β1-Smad2/3 pathway.

Inflammation and Coagulation are Two Interconnected Pathophysiological Pathways in Atrial Fibrillation Pathogenesis

Introduction

Atrial fibrillation (AF) is associated with elevated levels of clotting factors such as tissue factor (TF) and factor XII (FXII). Various inflammation markers, such as interleukin-6 (IL-6), tumor necrosis factor-α (TNF- α), and high-sensitive C-reactive protein (hs-CRP), have also been associated with AF. This study explores the relationship between inflammation markers and coagulation activity, including their impact on heart structural changes in these patients.

Methods

We observed 283 patients with nonvalvular AF who underwent a complete examination at admission, but only 183 patients have successful cardioversion. As a control group, similar patients without AF were examined. The markers of the coagulation and inflammation were studied by ELISA on the analyzer "Stat Fax 303 Plus". Studies were conducted using l statistical package SPSS 13.0.

Results

It was revealed that patients with AF had significantly higher levels of hs-CRP, IL-6, and TNF-α and had elevated levels of TF and FXII compared with control group. The moderate correlations were observed between IL-6 and left atrial diameter (LAD), IL-6 and LA stiffness, hs-CRP and left atrial volume (LAV), TF and LAV.

Conclusion

We have demonstrated that patients with AF have the relationship between elevated levels of inflammatory markers and coagulation activity, which contributes to structural atrial remodeling.

Regular exercise delays microvascular endothelial dysfunction by regulating antioxidant capacity and cellular metabolism

Aging is the basis for several unfavorable conditions, including cardiovascular diseases (CVDs). In this sense, regular physical activity (regular PA) has been proven to delay cellular aging and prevent endothelial dysfunction related to CVDs. Despite numerous studies involving athletes, little is known about cellular and molecular mechanisms of regular PA among master athletes. The present study aimed at evaluating the effects of regular PA on local microcirculatory functions in elderly athletes as compared to age-matched sedentary controls. Moreover, molecular/epigenetic mechanisms (nitric oxide, oxidative stress, PGC-1α, SIRT1 and miR29) were also assessed. The results of the present study showed that regular PA significantly increased local blood flow in post-ischemia and post-heating conditions, as well as NO plasma concentrations, denoting a better endothelial function/microcirculatory efficiency. Moreover, athletes presented a greater plasma antioxidant and increased transcriptional levels of the metabolism regulator PGC-1α. Finally, regular PA enhanced plasma level of SIRT1 and miR29, suggested as epigenetic regulators of redox balance and cellular metabolism. In addition, stimulated local blood flow was directly related to plasma antioxidant capacity, and SIRT1 and miR29 levels. Overall, our data confirm the beneficial effects of regular PA on the cardiovascular profile in elderly athletes and shed light on molecular signals involved in the positive adaptations to exercise.

COMP Improves Ang-II-Induced Atrial Fibrillation via TGF-β Signaling Pathway

Cartilage oligomeric matrix protein (COMP) regulates transforming growth factor-β (TGF-β) signaling pathway, which has been proved to be associated with skin fibrosis and pulmonary fibrosis. Atrial fibrosis is a major factor of atrial fibrillation (AF). Nevertheless, the interaction between COMP and TGF-β as well as their role in AF remains undefined. The purpose of this study is to clarify the role of COMP in AF and explore its potential mechanism. The hub gene of AF was identified from two datasets using bioinformatics. Furthermore, it was verified by the downregulation of COMP in angiotensin-II (Ang-II)-induced AF in mice. Moreover, the effect on AF was examined using CCK8 assay, ELISA, and western blot. The involvement of TGF-β pathway was further discussed. The expression of COMP was the most significant among all these hub genes. Our experimental results revealed that the protein levels of TGF-β1, phosphorylated Smad2 (P-Smad2), and phosphorylated Smad3 (P-Smad3) were decreased after silencing COMP, which indicated that COMP knockdown could inhibit the activation of TGF-β pathway in AF cells. However, the phenomenon was reversed when the activator SRI was added. COMP acts as a major factor and can improve Ang-II-induced AF via TGF-β signaling pathway. Thus, our research enriches the understanding of the interaction between COMP and TGF-β in AF, and provides reference for the pathogenesis and diagnosis of AF.

Construction and validation of a cuproptosis-related diagnostic gene signature for atrial fibrillation based on ensemble learning

BACKGROUND

Atrial fibrillation (AF) is the most common type of cardiac arrhythmia. Nonetheless, the accurate diagnosis of this condition continues to pose a challenge when relying on conventional diagnostic techniques. Cell death is a key factor in the pathogenesis of AF. Existing investigations suggest that cuproptosis may also contribute to AF. This investigation aimed to identify a novel diagnostic gene signature associated with cuproptosis for AF using ensemble learning methods and discover the connection between AF and cuproptosis.

RESULTS

Two genes connected to cuproptosis, including solute carrier family 31 member 1 (SLC31A1) and lipoic acid synthetase (LIAS), were selected by integration of random forests and eXtreme Gradient Boosting algorithms. Subsequently, a diagnostic model was constructed that includes the two genes for AF using the Light Gradient Boosting Machine (LightGBM) algorithm with good performance (the area under the curve value > 0.75). The microRNA-transcription factor-messenger RNA network revealed that homeobox A9 (HOXA9) and Tet methylcytosine dioxygenase 1 (TET1) could target SLC31A1 and LIAS in AF. Functional enrichment analysis indicated that cuproptosis might be connected to immunocyte activities. Immunocyte infiltration analysis using the CIBERSORT algorithm suggested a greater level of neutrophils in the AF group. According to the outcomes of Spearman's rank correlation analysis, there was a negative relation between SLC31A1 and resting dendritic cells and eosinophils. The study found a positive relationship between LIAS and eosinophils along with resting memory CD4+ T cells. Conversely, a negative correlation was detected between LIAS and CD8+ T cells and regulatory T cells.

CONCLUSIONS

This study successfully constructed a cuproptosis-related diagnostic model for AF based on the LightGBM algorithm and validated its diagnostic efficacy. Cuproptosis may be regulated by HOXA9 and TET1 in AF. Cuproptosis might interact with infiltrating immunocytes in AF.

Glucagon-like Peptide-1 Receptor Activation Reduces Pulmonary Vein Arrhythmogenesis and Regulates Calcium Homeostasis

Glucagon-like peptide-1 (GLP-1) receptor agonists are associated with reduced atrial fibrillation risk, but the mechanisms underlying this association remain unclear. The GLP-1 receptor agonist directly impacts cardiac Ca2+ homeostasis, which is crucial in pulmonary vein (PV, the initiator of atrial fibrillation) arrhythmogenesis. This study investigated the effects of the GLP-1 receptor agonist on PV electrophysiology and Ca2+ homeostasis and elucidated the potential underlying mechanisms. Conventional microelectrodes and whole-cell patch clamp techniques were employed in rabbit PV tissues and single PV cardiomyocytes before and after GLP-1 (7-36) amide, a GLP-1 receptor agonist. Evaluations were conducted both with and without pretreatment with H89 (10 μM, an inhibitor of protein kinase A, PKA), KN93 (1 μM, an inhibitor of Ca2+/calmodulin-dependent protein kinase II, CaMKII), and KB-R7943 (10 μM, an inhibitor of Na+/Ca2+ exchanger, NCX). Results showed that GLP-1 (7-36) amide (at concentrations of 1, 10, and 100 nM) reduced PV spontaneous activity in a concentration-dependent manner without affecting sinoatrial node electrical activity. In single-cell experiments, GLP-1 (7-36) amide (at 10 nM) reduced L-type Ca2+ current, NCX current, and late Na+ current in PV cardiomyocytes without altering Na+ current. Additionally, GLP-1 (7-36) amide (at 10 nM) increased sarcoplasmic reticulum Ca2+ content in PV cardiomyocytes. Furthermore, the antiarrhythmic effects of GLP-1 (7-36) amide on PV automaticity were diminished when pretreated with H89, KN93, or KB-R7943. This suggests that the GLP-1 receptor agonist may exert its antiarrhythmic potential by regulating PKA, CaMKII, and NCX activity, as well as modulating intracellular Ca2+ homeostasis, thereby reducing PV arrhythmogenesis.

Evaluation of left atrial and ventricular remodeling in atrial fibrillation subtype by using speckle tracking echocardiography

Background

Atrial fibrillation (AF) is associated with cardiac structural and functional remodeling. We investigated the left atrial (LA) and left ventricular (LV) changes in AF subtypes by using two-dimensional echocardiography strain techniques.

Methods

The study population consisted of 102 subjects with sinus rhythm (control group) and 463 patients with AF, among which 284 patients had paroxysmal AF (PAF) and 179 patients had persistent AF (PerAF). A speckle tracking automatic functional imaging software was used to perform the strain analysis.

Results

Patients with AF had dilated LA maximum and minimum volume, decreased LA reservoir strain, lower LV ejection fraction (LVEF), and impaired global longitudinal strain (GLS) compared to those of the sinus rhythm control group. In patients with PerAF, the LA maximum and minimum volumes were larger, and the LA reservoir strain [PAF vs. PerAF, 28% (21,33) vs. 19% (14, 28), P < 0.05], LVEF, and absolute GLS value (PAF vs. PerAF, -16.9 ± 3.3 vs. -14.1 ± 3.5%) were lower than those in patients with PAF. Patients with AF regardless of LA enlargement had decreased LA reservoir strain and lower LVEF and absolute GLS value than those in the sinus rhythm control group.

Conclusion

Compared with those with normal sinus rhythm, patients with AF had dilated LA volume and impaired LA function, which were further worsened in patients with PerAF than those in patients with PAF. LA functional impairment occurred before LA enlargement. Left atrioventricular remodeling happened across different stages of AF development.

The inter-chamber differences in the contractile function between left and right atrial cardiomyocytes in atrial fibrillation in rats

Introduction

The left and right atria (LA, RA) work under different mechanical and metabolic environments that may cause an intrinsic inter-chamber diversity in structure and functional properties between atrial cardiomyocytes (CM) in norm and provoke their different responsiveness to pathological conditions. In this study, we assessed a LA vs. RA difference in CM contractility in paroxysmal atrial fibrillation (AF) and underlying mechanisms.

Methods

We investigated the contractile function of single isolated CM from LA and RA using a 7-day acetylcholine (ACh)-CaCl2 AF model in rats. We compared auxotonic force, sarcomere length dynamics, cytosolic calcium ([Ca2+]i) transients, intracellular ROS and NO production in LA and RA CM, and analyzed the phosphorylation levels of contractile proteins and actin-myosin interaction using an in vitro motility assay.

Results

AF resulted in more prominent structural and functional changes in LA myocardium, reducing sarcomere shortening amplitude, and velocity of sarcomere relengthening in mechanically non-loaded LA CM, which was associated with the increased ROS production, decreased NO production, reduced myofibrillar content, and decreased phosphorylation of cardiac myosin binding protein C and troponin I. However, in mechanically loaded CM, AF depressed the auxotonic force amplitude and kinetics in RA CM, while force characteristics were preserved in LA CM.

Discussion

Thus, inter-atrial differences are increased in paroxysmal AF and affected by the mechanical load that may contribute to the maintenance and progression of AF.

Relationship Between Fibrosis, Endocardial Endothelial Damage, and Thrombosis of Left Atrial Appendage in Atrial Fibrillation

BACKGROUND

Left atrial appendage (LAA) thrombus (LAAT) and ischemic stroke are considered important in atrial cardiomyopathy with progressive atrial fibrosis and endocardial endothelial damage.

OBJECTIVES

This study aimed to obtain histological evidence to clarify the association between LAA fibrosis and endocardial endothelial damage with LAAT, ischemic stroke, and clinical risk factors.

METHODS

Ninety-six patients with atrial fibrillation (AF) scheduled to undergo LAA excision during surgery were enrolled. They underwent transesophageal echocardiography before the surgery to validate the LAA function/morphology and LAAT presence or absence. The resected LAAs were subjected to Azan-Mallory staining and CD31 immunohistochemistry to quantify the degree of fibrosis and endocardial endothelial damage staged as F1-F4 and E1-E4 per the quantiles.

RESULTS

Patients with an LAAT and/or ischemic stroke history had higher fibrosis degrees (18.4% ± 9.9% vs 10.4% ± 7.0%, P < 0.0001) and lower CD31 expressions (0.27 [IQR: 0.05-0.57] vs 1.02 [IQR: 0.49-1.65]; P < 0.0001). Also, higher CHADS₂ was associated with a higher degree of fibrosis and lower CD31 expression. Multivariate logistic regression analysis revealed that endothelial damage (E4) was associated with an LAAT and/or ischemic stroke history independent of AF type (paroxysmal or nonparoxysmal) with an OR of 3.47. Among patients with nonparoxysmal AF, fibrosis (F4, OR: 3.66), endothelial damage (E4, OR: 4.62), and LAA morphology (non-chicken-wing, OR: 3.79) were independently associated with LAAT and/or stroke. The degree of fibrosis correlated significantly with endothelial damage (R = -0.38, P = 0.0001).

CONCLUSIONS

These histological findings may be essential in considering the pathophysiology of LAAT and stroke within the atrial cardiomyopathy context.

Alcohol and Atrial Fibrillation: A Pathophysiologic Perspective

Atrial fibrillation (AF) is the most common cardiac arrhythmia responsible for significant morbidity and mortality. Its burden on patients and the health care system is only expected to increase. Several studies have established a dose-response relationship between the amount and frequency of alcohol consumption and the incidence of new onset AF independent of sex, age, and other risk factors. This causal relationship is mediated by the impact alcohol consumption has on conduction properties of the atrium, structural and cellular effect on cardiac myocytes, and dysregulation of the autonomic nervous system. This article reviews the current literature supporting the link between alcohol consumption and AF while attempting to provide an insight into pathophysiological mechanisms.

Multiplatform modeling of atrial fibrillation identifies phospholamban as a central regulator of cardiac rhythm

Atrial fibrillation (AF) is a common and genetically inheritable form of cardiac arrhythmia; however, it is currently not known how these genetic predispositions contribute to the initiation and/or maintenance of AF-associated phenotypes. One major barrier to progress is the lack of experimental systems to investigate the effects of gene function on rhythm parameters in models with human atrial and whole-organ relevance. Here, we assembled a multi-model platform enabling high-throughput characterization of the effects of gene function on action potential duration and rhythm parameters using human induced pluripotent stem cell-derived atrial-like cardiomyocytes and a Drosophila heart model, and validation of the findings using computational models of human adult atrial myocytes and tissue. As proof of concept, we screened 20 AF-associated genes and identified phospholamban loss of function as a top conserved hit that shortens action potential duration and increases the incidence of arrhythmia phenotypes upon stress. Mechanistically, our study reveals that phospholamban regulates rhythm homeostasis by functionally interacting with L-type Ca2+ channels and NCX. In summary, our study illustrates how a multi-model system approach paves the way for the discovery and molecular delineation of gene regulatory networks controlling atrial rhythm with application to AF.

Cardiomyocyte electrophysiology and its modulation: current views and future prospects

Normal and abnormal cardiac rhythms are of key physiological and clinical interest. This introductory article begins from Sylvio Weidmann's key historic 1950s microelectrode measurements of cardiac electrophysiological activity and Singh & Vaughan Williams's classification of cardiotropic targets. It then proceeds to introduce the insights into cardiomyocyte function and its regulation that subsequently emerged and their therapeutic implications. We recapitulate the resulting view that surface membrane electrophysiological events underlying cardiac excitation and its initiation, conduction and recovery constitute the final common path for the cellular mechanisms that impinge upon this normal or abnormal cardiac electrophysiological activity. We then consider progress in the more recently characterized successive regulatory hierarchies involving Ca2+ homeostasis, excitation-contraction coupling and autonomic G-protein signalling and their often reciprocal interactions with the surface membrane events, and their circadian rhythms. Then follow accounts of longer-term upstream modulation processes involving altered channel expression, cardiomyocyte energetics and hypertrophic and fibrotic cardiac remodelling. Consideration of these developments introduces each of the articles in this Phil. Trans. B theme issue. The findings contained in these articles translate naturally into recent classifications of cardiac electrophysiological targets and drug actions, thereby encouraging future iterations of experimental cardiac electrophysiological discovery, and testing directed towards clinical management. This article is part of the theme issue 'The heartbeat: its molecular basis and physiological mechanisms'.

Trends in worldwide research on cardiac fibrosis over the period 1989-2022: a bibliometric study

Background

Cardiac fibrosis is a hallmark of various end-stage cardiovascular diseases (CVDs) and a potent contributor to adverse cardiovascular events. During the past decades, extensive publications on this topic have emerged worldwide, while a bibliometric analysis of the current status and research trends is still lacking.

Methods

We retrieved relevant 13,446 articles on cardiac fibrosis published between 1989 and 2022 from the Web of Science Core Collection (WoSCC). Bibliometrix was used for science mapping of the literature, while VOSviewer and CiteSpace were applied to visualize co-authorship, co-citation, co-occurrence, and bibliographic coupling networks.

Results

We identified four major research trends: (1) pathophysiological mechanisms; (2) treatment strategies; (3) cardiac fibrosis and related CVDs; (4) early diagnostic methods. The most recent and important research themes such as left ventricular dysfunction, transgenic mice, and matrix metalloproteinase were generated by burst analysis of keywords. The reference with the most citations was a contemporary review summarizing the role of cardiac fibroblasts and fibrogenic molecules in promoting fibrogenesis following myocardial injury. The top 3 most influential countries were the United States, China, and Germany, while the most cited institution was Shanghai Jiao Tong University, followed by Nanjing Medical University and Capital Medical University.

Conclusions

The number and impact of global publications on cardiac fibrosis has expanded rapidly over the past 30 years. These results are in favor of paving the way for future research on the pathogenesis, diagnosis, and treatment of cardiac fibrosis.

Phosphatidylethanolamine aggravates Angiotensin II-induced atrial fibrosis by triggering ferroptosis in mice

As atrial fibrosis is the main feature of atrial structural remodeling, inhibiting atrial fibrosis is crucial to the prevention of atrial fibrillation (AF) progression. Research has shown the correlation between abnormal lipid metabolism and AF progression. However, the effect of specific lipids on atrial fibrosis remains unclear. In the present study, we applied ultra-high-performance lipidomics to analyze the lipid profiles in patients with AF and identify phosphatidylethanolamine (PE) as the differential lipid associated with AF. To detect the effect of the differential lipid on atrial fibrosis, we performed the intraperitoneal injection of Angiotensin II (Ang II) to mice to induce atrial fibrosis and supplemented PE in diets. We also treated atrial cells with PE to evaluate the cellular effect of PE. We found that PE supplementation aggravated atrial fibrosis and increased the expression of the fibrosis-related protein in vitro and in vivo. Moreover, we detected the effect of PE on the atrium. We found that PE increased oxidation products and regulated the expression of ferroptosis-related proteins, which could be alleviated by a ferroptosis inhibitor. PE increased peroxidation and mitochondrial damage in vitro, which promoted cardiomyocyte death induced by Ang II. Examination of protein expression in cardiomyocytes indicated that PE triggered ferroptosis and caused cell death to participate in myocardium fibrosis. In summary, our findings demonstrated the differential lipid profiles of AF patients and revealed the potential effect of PE on atrial remodelling, suggesting that inhibition of PE and ferroptosis might serve as a potential therapy to prevent AF progression.

Long-Term Sports Practice and Atrial Fibrillation: An Updated Review of a Complex Relationship

Atrial fibrillation (AF) is the most common sustained arrhythmia in clinical practice, and it is an enormous burden worldwide because of its high morbidity, disability and mortality. It is generally acknowledged that physical activity (PA) is strongly associated with a significant reduction in the risk of cardiovascular (CV) disease and all-cause mortality. Moreover, it has been observed that moderate and regular physical activity has the potential to reduce the risk of AF, in addition to improving overall well-being. Nevertheless, some studies have associated intense physical activity with an increased risk of AF. This paper aims to review the main related literature to investigate the association between PA and AF incidence and draw pathophysiological and epidemiological conclusions.

The role and implications of left atrial fibrosis in surgical mitral valve repair as assessed by CMR: the ALIVE study design and rationale

Background

Patients with mitral regurgitation (MR) commonly suffer from left atrial (LA) remodeling. LA fibrosis is considered to be a key player in the LA remodeling process, as observed in atrial fibrillation (AF) patients. Literature on the presence and extent of LA fibrosis in MR patients however, is scarce and its clinical implications remain unknown. Therefore, the ALIVE trial was designed to investigate the presence of LA remodeling including LA fibrosis in MR patients prior to and after mitral valve repair (MVR) surgery.

Methods

The ALIVE trial is a single center, prospective pilot study investigating LA fibrosis in patients suffering from MR in the absence of AF (identifier NCT05345730). In total, 20 participants will undergo a CMR scan including 3D late gadolinium enhancement (LGE) imaging 2 week prior to MVR surgery and at 3 months follow-up. The primary objective of the ALIVE trial is to assess the extent and geometric distribution of LA fibrosis in MR patients and to determine effects of MVR surgery on reversed atrial remodelling.

Implications

This study will provide novel insights into the pathophysiological mechanism of fibrotic and volumetric atrial (reversed) remodeling in MR patients undergoing MVR surgery. Our results may contribute to improved clinical decision making and patient-specific treatment strategies in patients suffering from MR.

A possible new cardiac heterogeneity as an arrhythmogenic driver

Atrial fibrillation (AF) is the commonest cardiac arrhythmia, affecting 3 million people in the USA and 8 million in the EU (according to the European Society of Cardiology). So, why is it that even with the best medical care, around a third of the patients are treatment resistant. Extensive research of its etiology showed that AF and its mechanisms are still debatable. Some of the AF origins are ascribed to functional and ionic heterogeneities of the heart tissue and possibly to additional triggering agents. But, have all AF origins been detected? Are all accepted origins, in fact, arrhythmogenic? In order to study these questions and specifically to check our new idea of intermittency as an arrhythmogenesis agent, we chose to employ a mathematical model which was as simple as possible, but which could still be used to observe the basic network processes of AF development. At this point we were not interested in the detailed ionic propagations nor in the actual shapes of the induced action potentials (APs) during the AF outbreaks. The model was checked by its ability to exactly recapture the basic AF developmental stages known from experimental cardiac observations and from more elaborate mathematical models. We use a simple cellular automata 2D mathematical model of N × N matrices to elucidate the field processes leading to AF in a tissue riddled with randomly distributed heterogeneities of different types, under sinus node operation, simulated by an initial line of briefly stimulated cells inducing a propagating wave, and with or without an additional active ectopic action potential pulse, in turn simulated by a transitory operation of a specific cell. Arrhythmogenic contributions, of three different types of local heterogeneities in myocytes and their collaborations, in inducing AF are examined. These are: a heterogeneity created by diffuse fibrosis, a heterogeneity created by myocytes having different refractory periods, and a new heterogeneity type, created by intermittent operation of some myocytes. The developmental stages (target waves and spirals) and the different probabilities of AF occurring under each condition, are shown. This model was established as being capable of reproducing the known AF origins and their basic development stages, and in addition has shown: (1) That diffuse fibrosis on its own is not arrhythmogenic but in combination with other arrhythmogenic agents it can either enhance or limit AF. (2) In general, combinations of heterogeneities can act synergistically, and, most importantly, (3) The new type of intermittency heterogeneity proves to be extremely arrhythmogenic. Both the intermittency risk and the fibrosis role in AF generation were established. Knowledge of the character of these arrhythmogenesis agents can be of real importance in AF treatment.

Thoracoscopic ablation delays progression from paroxysmal to persistent atrial fibrillation

OBJECTIVE

The study objective was to determine whether mini-invasive transthoracoscopic atrial fibrillation ablation can delay the progression of atrial fibrillation from paroxysmal to persistent.

METHODS

Patients aged 18 to 80 years with paroxysmal nonvalvular atrial fibrillation and a history of stroke or systemic thromboembolism were consecutively enrolled from September 2014 to June 2019. In the treatment group, patients underwent transthoracoscopic atrial fibrillation ablation plus left atrial appendage excision (atrial fibrillation ablation plus left atrial appendage excision group). Patients unwilling to receive surgical intervention were treated with antiarrhythmic drugs and oral anticoagulants and recruited as a control group (atrial fibrillation plus antiarrhythmic drugs group). The primary end point was the progression of atrial fibrillation from paroxysmal to persistent.

RESULTS

This study included 49 patients in the atrial fibrillation plus antiarrhythmic drugs group (29 men) and 77 patients in the atrial fibrillation ablation plus left atrial appendage excision group (48 men). In the atrial fibrillation ablation plus left atrial appendage excision group, after a median follow-up of 951 days (interquartile range, 529-1366 days), 8 patients (10.4%) progressed to persistent atrial fibrillation. In the atrial fibrillation plus antiarrhythmic drugs group, after a median follow-up of 835 days (interquartile range, 548-1214 days), 14 patients (28.6%) progressed to persistent atrial fibrillation. The atrial fibrillation ablation plus left atrial appendage excision group had a significantly lower incidence of atrial fibrillation progression than the atrial fibrillation plus antiarrhythmic drugs group during follow-up (3.9 vs 12.3 per 100 person-years, log-rank 8.6, P = .003).

CONCLUSIONS

Patients with paroxysmal nonvalvular atrial fibrillation who chose to undergo transthoracoscopic atrial fibrillation ablation had a lower incidence of progression to persistent atrial fibrillation than patients who chose conservative therapy. This strategy might be especially suitable for patients with paroxysmal nonvalvular atrial fibrillation at high risk of stroke and high risk of bleeding.

CircCAMTA1 facilitates atrial fibrosis by regulating the miR-214-3p/TGFBR1 axis in atrial fibrillation

Circular RNAs (circRNAs) have been shown to be associated with cardiac fibrosis. Atrial fibrosis is an important pathophysiological event in the progression of atrial fibrillation (AF). Although a novel circRNA calmodulin binding transcription activator 1 (circCAMTA1) has been reported to be related with the development of AF, the detailed molecular mechanisms remain largely unknown. In this study, we found that circCAMTA1 was upregulated in atrial muscle tissues of AF patients and angiotensin-II (Ang-II)-treated human atrial fibroblasts (HAFs). Moreover, circCAMTA1 expression was positively correlated with the expression of collagen (I and III) and α-SMA in atrial muscle tissues of AF patients. In vitro experiments, knockdown of circCAMTA1 significantly suppressed Ang-II-induced HAFs proliferation and reduced the expression of atrial fibrosis-associated genes, but overexpression of circCAMTA1 exhibited opposite results. In vivo experiments, circCAMTA1 knockdown ameliorated Ang-II-induced atrial fibrosis by reducing AF incidence, AF duration, and collagen synthesis. Functionally, circCAMTA1 facilitated Ang-II-induced atrial fibrosis in vitro and in vivo via downregulating the inhibitory effect of miR-214-3p on transforming growth factor β receptor 1 (TGFBR1) expression. In conclusions, circCAMTA1 knockdown alleviated atrial fibrosis through downregulating TGFBR1 expression intermediated by miR-214-3p in AF, suggesting circCAMTA1/miR-214-3p/TGFBR1 axis may be a novel therapeutic target for AF treatment in clinic.

Diminished α7 nicotinic acetylcholine receptor (α7nAChR) rescues amyloid-β induced atrial remodeling by oxi-CaMKII/MAPK/AP-1 axis-mediated mitochondrial oxidative stress

The potential coexistence of Alzheimer's disease (AD) and atrial fibrillation (AF) is increasingly common as aging-related diseases. However, little is known about mechanisms responsible for atrial remodeling in AD pathogenesis. α7 nicotinic acetylcholine receptors (α7nAChR) has been shown to have profound effects on mitochondrial oxidative stress in both organ diseases. Here, we investigate the role of α7nAChR in mediating the effects of amyloid-β (Aβ) in cultured mouse atrial cardiomyocytes (HL-1 cells) and AD model mice (APP/PS1). In vitro, apoptosis, oxidative stress and mitochondrial dysfunction induced by Aβ long-term (72h) in HL-1 cells were prevented by α-Bungarotoxin(α-BTX), an antagonist of α7nAChR. This cardioprotective effect was due to reinstating Ca²⁺ mishandling by decreasing the activation of CaMKII and MAPK signaling pathway, especially the oxidation of CaMKII (oxi-CaMKII). In vivo studies demonstrated that targeting knockdown of α7nAChR in cardiomyocytes could ameliorate AF progression in late-stage (12 months) APP/PS1 mice. Moreover, α7nAChR deficiency in cardiomyocytes attenuated APP/PS1-mutant induced atrial remodeling characterized by reducing fibrosis, atrial dilation, conduction dysfunction, and inflammatory mediator activities via suppressing oxi-CaMKII/MAPK/AP-1. Taken together, our findings suggest that diminished α7nAChR could rescue Aβ-induced atrial remodeling through oxi-CaMKII/MAPK/AP-1-mediated mitochondrial oxidative stress in atrial cells and AD mice.

Chronic catestatin treatment reduces atrial fibrillation susceptibility via improving calcium handling in post-infarction heart failure rats

BACKGROUND

Abnormal Ca²⁺ handling is a pivotal element of atrial fibrillation (AF) substrates. Catestatin (CST) modulates intracellular Ca²⁺ handling in cardiomyocytes (CMs). We investigated the effects of CST administration on atrial Ca²⁺ handling and AF susceptibility in rats with post-infarction heart failure (HF).

METHODS

Myocardial infarction (MI) was established by ligation of the left anterior descending coronary artery in rats. Two-week later, rats with post-infarction HF were randomly treated with saline (MI group) or CST (MI + CST group) for 4-week. Cellular Ca²⁺ imaging was performed by incubating atrial CMs with Fura-2 AM. An in vitro electrophysiological study was performed to assess the vulnerability to action potential duration (APD) alternans and AF. Ca²⁺ handling proteins expression was determined using western blotting.

RESULTS

In atrial CMs, compared with the sham group, the sarcoplasmic reticulum (SR) Ca²⁺ load, Ca²⁺ transient (CaT) amplitude, and threshold for Ca²⁺ alternans were significantly decreased, but the diastolic intracellular Ca²⁺ level, SR Ca²⁺ leakage, and spontaneous Ca²⁺ events were markedly increased in the MI group. However, CST attenuated these Ca²⁺-handling abnormalities induced by post-infarction HF. Moreover, vulnerability to atrial APD alternans and AF was significantly increased in isolated hearts from the MI group compared to the sham group, whereas all effects were prevented by CST. CST treatment also preserved SR Ca²⁺-ATPase protein expression but decreased the protein levels of phosphorylated-ryanodine receptor 2 and phosphorylated-Ca²⁺/calmodulin-dependent protein kinase II in atria from post-infarction HF rats.

CONCLUSION

Chronic CST treatment reduces AF vulnerability in rats with MI-induced HF by improving Ca²⁺ handling.

Atrial fibrillation episode status and incidence of coronary slow flow: A propensity score-matched analysis

Background

Previous studies have shown that patients with a history of atrial fibrillation (AF) have a higher risk of developing coronary slow flow (CSF). However, whether AF episode status affects the incidence of CSF has not been confirmed. This study investigated the correlation between AF episode status and the incidence of CSF.

Methods

We enrolled patients with AF who underwent coronary angiography for symptoms of myocardial ischemia between January 1, 2017, and April 30, 2022, at our institution and classified them according to whether they had an episode of AF in the perioperative period. The outcomes were defined the occurrence of CSF overall and in each of the three coronary arteries. The analysis was repeated after adjusting the baseline information by the propensity score matching method in a 1:1 ratio.

Results

214 patients who met the inclusion and exclusion criteria were included in the study (AF episode group: 100 patients, AF non-episode group: 114 patients). Before matching, age, left atrial size, ejection fraction, heart rate, CSF incidence, and mean corrected thrombolysis in myocardial infarction frame counts were higher in patients with intraoperative AF episodes than in patients without episodes. To prevent the dependent variable (CSF incidence) from being confounded by confounding factors, we matched the two groups for age, left atrial size, and ejection fraction. In the logistic regression analysis, the incidence of CSF was significantly higher in the intraoperative AF episode group (P = 0.010, OR = 2.327, 95% CI: 1.226-4.416) than in the non-episode group.

Conclusion

In patients with AF, AF episode status is significantly correlated with an increased overall incidence of CSF.

Relationship Between Periodontitis and Atrial Fibrosis in Atrial Fibrillation: Histological Evaluation of Left Atrial Appendages

BACKGROUND

Atrial fibrosis contributes to the onset and persistence of atrial fibrillation (AF) and AF-related stroke. Periodontitis, a common infectious and inflammatory disease, aggravates some systemic diseases. However, the association of periodontitis with AF and with atrial fibrosis has remained unclarified.

OBJECTIVES

The authors aimed to elucidate the relationship between periodontitis and atrial fibrosis by studying resected left atrial appendages (LAAs).

METHODS

Seventy-six patients with AF (55 with nonparoxysmal AF, 25 with mitral valve regurgitation, 18 with LAA thrombus) who were scheduled to undergo LAA excision during cardiac surgery were prospectively enrolled. All patients underwent an oral examination, and the remaining number of teeth, bleeding on probing, periodontal probing depth, and periodontal inflamed surface area (PISA) were evaluated as parameters of periodontitis. The degree of fibrosis in each LAA was quantified by Azan-Mallory staining.

RESULTS

Bleeding on probing (R = 0.48; P < 0.0001), periodontal probing depth of ≥4 mm (R = 0.26; P = 0.02), and PISA (R = 0.46; P < 0.0001) were positively correlated with atrial fibrosis. Among patients with >10 remaining teeth, PISA was positively and strongly correlated with atrial fibrosis (R = 0.57; P < 0.0001). After adjustments for age, AF duration, BMI, mitral valve regurgitation, and CHADS₂ (congestive heart failure, hypertension, age, diabetes, previous stroke/transient ischemic attack) score, PISA was significantly associated with atrial fibrosis (β = 0.016; P = 0.0002).

CONCLUSIONS

The authors histologically revealed the association of periodontitis with atrial fibrosis. This indicates that periodontitis, which is modifiable, is likely a risk factor for AF.

Analysis of infiltrated immune cells in left atriums from patients with atrial fibrillation and identification of circRNA biomarkers for postoperative atrial fibrillation

Background: Atrial fibrillation (AF) increases the risk of stroke and heart failure. Postoperative AF (POAF) increases the risk of mortality after cardiac surgery. This study aims to explore mechanisms underlying AF, analyze infiltration of immune cells in left atrium (LA) from patients with AF, and identify potential circular RNA (circRNA) biomarkers for POAF. Methods: Raw data of GSE797689, GSE115574, and GSE97455 were downloaded and processed. AF-related gene co-expression network was constructed using weighted gene correlation network analysis and enrichment analysis of genes in relevant module was conducted. Gene set enrichment analysis (GSEA) and gene set variation analysis (GSVA) were applied to investigate pathways significantly enriched in AF group. Infiltration of immune cells was analyzed using single-sample GSEA. Differentially expressed genes (DEGs) between patients with or without AF were identified and competing endogenous RNA (ceRNA) networks of DEGs were constructed. To screen biomarkers for POAF, differentially expressed circRNAs (DEcircRNAs) between patients with or without POAF were identified. Intersection between DEcircRNAs and circRNAs in ceRNA networks of DEGs were extracted and circRNAs in the intersection were further screened using support vector machine, random forest, and neural network to identify biomarkers for POAF. Results: Three modules were found to be relevant with AF and enrichment analysis indicated that genes in these modules were enriched in synthesis of extracellular matrix and inflammatory response. The results of GSEA and GSVA suggested that inflammatory response-related pathways were significantly enriched in AF group. Immune cells like macrophages, mast cells, and neutrophils were significantly infiltrated in LA tissues from patients with AF. The expression levels of immune genes such as CHGB, HLA-DRA, LYZ, IGKV1-17 and TYROBP were significantly upregulated in patients with AF, which were correlated with infiltration of immune cells. ceRNA networks of DEGs were constructed and has_circ_0006314 and hsa_circ_0055387 were found to have potential predictive values for POAF. Conclusion: Synthesis of extracellular matrix and inflammatory response were main processes involved in development and progression of AF. Infiltration of immune cells was significantly different between patients with or without AF. Has_circ_0006314 and hsa_circ_0055387 were found to have potential predictive values for POAF.

Acetyltransferase p300 regulates atrial fibroblast senescence and age-related atrial fibrosis through p53/Smad3 axis

Atrial fibrosis induced by aging is one of the main causes of atrial fibrillation (AF), but the potential molecular mechanism is not clear. Acetyltransferase p300 participates in the cellular senescence and fibrosis, which might be involved in the age-related atrial fibrosis. Four microarray datasets generated from atrial tissue of AF patients and sinus rhythm (SR) controls were analyzed to find the possible relationship of p300 (EP300) with senescence and fibrosis. And then, biochemical assays and in vivo electrophysiological examination were performed on older AF patients, aging mice, and senescent atrial fibroblasts. The results showed that (1) the left atrial tissues of older AF patients, aging mouse, and senescence human atrial fibroblasts had more severe atrial fibrosis and higher protein expression levels of p300, p53/acetylated p53 (ac-p53)/p21, Smad3/p-Smads, and fibrosis-related factors. (2) p300 inhibitor curcumin and p300 knockdown treated aging mouse and senescence human atrial fibroblasts reduced the senescence ratio of atrial fibroblasts, ameliorated the atrial fibrosis, and decreased the AF inducibility. In contrast, over-expression of p300 can lead to the senescence of atrial fibroblasts and atrial fibrosis. (3) p53 knockdown decreased the expression of aging and fibrosis-related proteins. (4) Co-immunoprecipitation and immunofluorescence showed that p53 forms a complex with smad3 and directly regulates the expression of smad3 in atrial fibroblasts. Our findings suggest that the mechanism of atrial fibrosis induced by aging is, at least, partially dependent on the regulation of p300, which provides new sights into the AF treatment, especially for the elderly.