Transforming growth factor-β1 level and outcome after catheter ablation for nonparoxysmal atrial fibrillation

Factors predicting the recurrence of atrial fibrillation after catheter ablation: A review

Atrial fibrillation (AF) is the most common and clinically significant type of cardiac arrhythmia. Although catheter ablation (CA) can restore sinus rhythm in patients with AF, some patients experience recurrence after the procedure. This requires us to find a simple and effective way to identify patients at a high risk of recurrence and to intervene early in the high-risk population to improve patient prognosis. The mechanism of AF recurrence is unclear, but it involves several aspects including patient history, inflammation, myocardial fibrosis, and genes. This article summarizes the current predictors of AF recurrence after CA, including myocardial fibrosis markers, inflammatory markers, MicroRNAs, Circular RNAs, AF recurrence scores, and imaging indicators. Each predictor has its own scope of application, and the predictive capacity and joint application of multiple predictors may improve the predictive power. In addition, we summarize the mechanisms involved in AF recurrence. We hope that this review will assist researchers understand the current predictors of AF recurrence and help them conduct further related studies.

Pathophysiology and clinical relevance of atrial myopathy

Atrial myopathy is a condition that consists of electrical, structural, contractile, and autonomic remodeling of the atria and is the substrate for development of atrial fibrillation, the most common arrhythmia. Pathophysiologic mechanisms driving atrial myopathy are inflammation, oxidative stress, atrial stretch, and neurohormonal signals, e.g., angiotensin-II and aldosterone. These mechanisms initiate the structural and functional remodeling of the atrial myocardium. Novel therapeutic strategies are being developed that target the pathophysiologic mechanisms of atrial myopathy. In this review, we will discuss the pathophysiology of atrial myopathy, as well as diagnostic and therapeutic strategies.

Comparing Inducibility of Re-Entrant Arrhythmia in Patient-Specific Computational Models to Clinical Atrial Fibrillation Phenotypes

BACKGROUND

Computational models of fibrosis-mediated, re-entrant left atrial (LA) arrhythmia can identify possible substrate for persistent atrial fibrillation (AF) ablation. Contemporary models use a 1-size-fits-all approach to represent electrophysiological properties, limiting agreement between simulations and patient outcomes.

OBJECTIVES

The goal of this study was to test the hypothesis that conduction velocity (ϴ) modulation in persistent AF models can improve simulation agreement with clinical arrhythmias.

METHODS

Patients with persistent AF (n = 37) underwent ablation and were followed up for ≥2 years to determine post-ablation outcomes: AF, atrial flutter (AFL), or no recurrence. Patient-specific LA models (n = 74) were constructed using pre-ablation and ≥90 days' post-ablation magnetic resonance imaging data. Simulated pacing gauged in silico arrhythmia inducibility due to AF-like rotors or AFL-like macro re-entrant tachycardias. A physiologically plausible range of ϴ values (±10 or 20% vs. baseline) was tested, and model/clinical agreement was assessed.

RESULTS

Fifteen (41%) patients had a recurrence with AF and 6 (16%) with AFL. Arrhythmia was induced in 1,078 of 5,550 simulations. Using baseline ϴ, model/clinical agreement was 46% (34 of 74 models), improving to 65% (48 of 74) when any possible ϴ value was used (McNemar's test, P = 0.014). ϴ modulation improved model/clinical agreement in both pre-ablation and post-ablation models. Pre-ablation model/clinical agreement was significantly greater for patients with extensive LA fibrosis (>17.2%) and an elevated body mass index (>32.0 kg/m2).

CONCLUSIONS

Simulations in persistent AF models show a 41% relative improvement in model/clinical agreement when ϴ is modulated. Patient-specific calibration of ϴ values could improve model/clinical agreement and model usefulness, especially in patients with higher body mass index or LA fibrosis burden. This could ultimately facilitate better personalized modeling, with immediate clinical implications.

Left Atrial Cardiomyopathy - A Challenging Diagnosis

Left atrial cardiomyopathy (LACM) has been an ongoing focus of research for several years. There is evidence that LACM is responsible for atrial fibrillation and embolic strokes of undetermined sources. Therefore, the correct diagnosis of LACM is of clinical importance. Various techniques, including electrocardiography, echocardiography, cardiac magnetic resonance imaging, computed tomography, electroanatomic mapping, genetic testing, and biomarkers, can both identify and quantify structural, mechanical as well as electrical dysfunction in the atria. However, the question arises whether these techniques can reliably diagnose LACM. Because of its heterogeneity, clinical diagnosis is challenging. To date, there are no recommendations for standardized diagnosis of suspected LACM. However, standardization could help to classify LACM more precisely and derive therapeutic directions to improve individual patient management. In addition, uniform diagnostic criteria for LACM could be important for future studies. Combining several parameters and relating them seems beneficial to approach the diagnosis of LACM. This review provides an overview of the current evidence regarding the diagnosis of LACM, in which several potential parameters are discussed and, consequently, a proposal for a diagnostic algorithm is presented.

Serum periostin as a predictor of early recurrence of atrial fibrillation after catheter ablation

Catheter ablation is an effective method of rhythm therapy for atrial fibrillation (AF). AF recurrence is a common problem after catheter ablation. The aim of this study was to investigate influence factors of early recurrence after catheter ablation for AF. One hundred and three consecutive patients with AF were enrolled and underwent catheter ablation. Venous blood (Marked as A) was collected before ablation and left atrial blood (Marked as B) was collected after successful atrial septal puncture to detect serum periostin. After 3 months of follow-up, statistical analysis was made based on the recurrence of AF. 27 (26.2%) patients had a recurrence of atrial arrhythmia after catheter ablation. Patients with recurrent atrial arrhythmia had a larger left atrial volume (162.31 ± 47.76 vs. 141.98 ± 41.64,p = 0.039), and higher serum periostin levels (periostin A. 99.71 ± 16.475 vs. 90.36 ± 13.63, p = 0.005; periostin B. 103.95 ± 13.09 vs. 94.46 ± 15.85, p = 0.006) compared with the non-recurrent group. The numbers of patients with left atrial low-voltage areas (LVAs) were more in the recurrence group (p < 0.001). Left atrial volume, serum periostin and left atrial LVAs were included in univariate and multivariate COX regression analysis. It showed that left atrial LVAs (HR3.81; 95% CI 1.54 to 9.44; p = 0.004) and serum periostin A (HR1.07; 95% CI 1.02 to1.13; p = 0.008) were the independent predictors of AF recurrence. The cut-off value of serum periostin A was 87.95 ng/ ml (AUC, 0.681; sensitivity 88.9% and specificity 53.9%). Kaplan-Meier survival curve showed that the recurrence rate of AF was higher in patients with left atrial LVAs and higher serum periostin. The venous serum periostin level and left atrial LVAs were independent predictors of early recurrence of AF after catheter ablation.

Transforming growth factor-β in myocardial disease

Transforming growth factor-β (TGFβ) isoforms are upregulated and activated in myocardial diseases and have an important role in cardiac repair and remodelling, regulating the phenotype and function of cardiomyocytes, fibroblasts, immune cells and vascular cells. Cardiac injury triggers the generation of bioactive TGFβ from latent stores, through mechanisms involving proteases, integrins and specialized extracellular matrix (ECM) proteins. Activated TGFβ signals through the SMAD intracellular effectors or through non-SMAD cascades. In the infarcted heart, the anti-inflammatory and fibroblast-activating actions of TGFβ have an important role in repair; however, excessive or prolonged TGFβ signalling accentuates adverse remodelling, contributing to cardiac dysfunction. Cardiac pressure overload also activates TGFβ cascades, which initially can have a protective role, promoting an ECM-preserving phenotype in fibroblasts and preventing the generation of injurious, pro-inflammatory ECM fragments. However, prolonged and overactive TGFβ signalling in pressure-overloaded cardiomyocytes and fibroblasts can promote cardiac fibrosis and dysfunction. In the atria, TGFβ-mediated fibrosis can contribute to the pathogenic substrate for atrial fibrillation. Overactive or dysregulated TGFβ responses have also been implicated in cardiac ageing and in the pathogenesis of diabetic, genetic and inflammatory cardiomyopathies. This Review summarizes the current evidence on the role of TGFβ signalling in myocardial diseases, focusing on cellular targets and molecular mechanisms, and discussing challenges and opportunities for therapeutic translation.

Association between serum inflammatory biomarkers and atrial low voltage in patients with atrial fibrillation: A phase 1 FIB-MARK study

Background

The mechanisms leading to atrial fibrosis in patients with atrial fibrillation (AF), especially in relation to inflammation, remain unclear.

Methods and Results

Forty biomarkers were measured in peripheral blood samples collected prior to catheter ablation, and the association with left atrial (LVZ) was evaluated in 16 consecutive patients. The median %LVZ was 17%. In Pearson’s correlation analysis, interleukin(IL)-17A and interferon(IFN)-γ showed the most significant positive and negative correlations with %LVZ (R = 0.35 and 0.43, P < 0.001). Furthermore, the IL-17A/IFN-γ ratio was significantly associated with %LVZ (R = 0.65, P = 0.007), as was the macrophage inflammatory protein (MIP)-1δ/IFN-γ ratio (R = 0.73, P = 0.001). The area under the receiver operator characteristics curves of the IL-17A/IFN-γ and MIP-1δ/IFN-γ ratios for detecting severe LVZ (%LVZ ≥ 10% as a reference standard) were 0.88 and 0.90, respectively. The IL-17A/IFN-γ ratio was significantly higher in patients with severe LVZ than those without (1.41 versus 0.97, P = 0.01). Furthermore, the sensitivity, specificity, and accuracy for detecting severe LVZ were 60%, 100%, and 75.0%, respectively, at a cut-off value of 1.3.

Conclusions

Among inflammatory biomarkers, the serum IL-17A/IFN-γ ratio was associated with severe left atrial LVZ in patients with AF. However, further studies are needed to clarify the role of inflammatory biomarkers in the development and progression of atrial fibrosis in patients with AF.

Circulating S100A4 as a prognostic biomarker for patients with nonparoxysmal atrial fibrillation after catheter ablation

Background

Atrial fibrosis is involved in non-paroxysmal atrial fibrillation (NPAF) and is mainly mediated by the calcium-binding protein S100A4. This study aimed to verify the role of circulating S100A4 in the diagnosis of atrial fibrosis and the prognosis of NPAF.

Methods

Consecutive NPAF patients undergoing catheter ablation were selected. Patients with low voltage amplitudes (<0.40 mV) in the left atrium (LA), defined as low voltage zones (LVZs), were grouped in the scar group by electroanatomic mapping (EAM). Circulating S100A4 was detected by a human enzyme-linked immunosorbent assay (ELISA). The role of S100A4 in atrial fibrosis was further evaluated by Masson's trichrome staining and immunochemistry (IHC) in NPAF (atrial pacing) and control dogs. The prognostic value of the circulating S100A4 was evaluated by Cox regression analyses, the Kaplan-Meier (KM) method, and receiver operating characteristic (ROC) curves.

Results

We enrolled a total of 101 NPAF patients (age 60±8 years) who underwent EAM, including 53 patients with scars and 48 patients without scars at 1-year follow-up. The scar group showed a higher serum level of S100A4 (3.4±1.7 vs. 2.5±1.4 ng/mL, P<0.001) than the non-scar group. In the canine model, scar size matched the larger location of interstitial fibrosis in the NPAF group determined by Masson's trichrome staining. The expression of α-SMA and S100A4 was elevated in the NPAF group as determined by IHC compared to the control group (P<0.001). The clinical recurrence rate was markedly elevated in the scar group (27.1% vs. 8.9%, P<0.001), and the area under the ROC curve was high (0.865, 95% CI: 0.750-0.981) in predicting clinical recurrence of NPAF with the circulating S100A4 model.

Conclusions

Circulating S100A4 plays a role in atrial fibrosis in NPAF patients following ablation. The level of serum S100A4 can predict the clinical recurrence of NPAF.

Atrial fibrillation and cardiac fibrosis

The understanding of atrial fibrillation (AF) evolved from a sole rhythm disturbance towards the complex concept of a cardiomyopathy based on arrhythmia substrates. There is evidence that atrial fibrosis can be visualized using late gadolinium enhancement cardiac magnetic resonance imaging and that it is a powerful predictor for the outcome of AF interventions. However, a strategy of an individual and fibrosis guided management of AF looks promising but results from prospective multicentre trials are pending. This review gives an overview about the relationship between cardiac fibrosis and AF focusing on translational aspects, clinical observations, and fibrosis imaging to emphasize the concept of personalized paths in AF management taking into account the individual amount and distribution of fibrosis.

Cardiovascular magnetic resonance-determined left ventricular myocardium impairment is associated with C-reactive protein and ST2 in patients with paroxysmal atrial fibrillation

BACKGROUND

Myocardial strain assessed with cardiovascular magnetic resonance (CMR) feature tracking can detect early left ventricular (LV) myocardial deformation quantitatively in patients with a variety of cardiovascular diseases, but this method has not yet been applied to quantify myocardial strain in patients with atrial fibrillation (AF) and no coexistent cardiovascular disease, i.e., the early stage of AF. This study sought to compare LV myocardial strain and T1 mapping indices in AF patients and healthy subjects, and to investigate the associations of a portfolio of inflammation, cardiac remodeling and fibrosis biomarkers with LV myocardial strain and T1 mapping indices in AF patients with no coexistent cardiovascular disease.

METHODS

The study consisted of 80 patients with paroxysmal AF patients and no coexistent cardiovascular disease and 20 age- and sex-matched healthy controls. Left atrial volume (LAV), LV myocardial strain and native T1 were assessed with CMR, and compared between the AF patients and healthy subjects. Biomarkers of C-reactive protein (CRP), transforming growth factor beta-1 (TGF-β1), collagen III N-terminal propeptide (PIIINP), and soluble suppression of tumorigenicity 2 (sST2) were obtained with blood tests, and compared between the AF patients and healthy controls. Associations of these biomarkers with those CMR-measured parameters were analyzed for the AF patients.

RESULTS

For the CMR-measured parameters, the AF patients showed significantly larger LAV and LV end-systolic volume, and higher native T1 than the healthy controls (max P = 0.027). The absolute values of the LV peak systolic circumferential strain and its rate as well as the LV diastolic circumferential strain rate were all significantly reduced in the AF patients (all P < 0.001). For the biomarkers, the AF patients showed significantly larger CRP (an inflammation biomarker) and sST2 (a myocardium stiffness biomarker) than the controls (max P = 0.007). In the AF patients, the five CMR-measured parameters of LAV, three LV strain indices and native T1 were all significantly associated with these two biomarkers of CRP and sST2 (max P = 0.020).

CONCLUSIONS

In patients with paroxysmal AF and no coexistent cardiovascular disease, LAV enlargement and LV myocardium abnormalities were detected by CMR, and these abnormalities were associated with biomarkers that reflect inflammation and myocardial stiffness.

How transforming growth factor contributes to atrial fibrillation?

Atrial fibrillation (AF) is the most common clinically significant arrhythmia. There are four fundamental pathophysiological mechanisms of AF including: electrical remodeling, structural remodeling, autonomic nervous system changes, and Ca2+ handling abnormalities. The transforming growth factor-β (TGF-β) superfamily are cytokines that have the ability to regulate numerous cell functions including proliferation, differentiation, apoptosis, epithelial-mesenchymal transition, and production of extracellular matrix. During the last decade numerous studies have demonstrated that TGF-β affects the architecture of the heart. TGF-β1 has been shown to be involved in the development and propagation of atrial fibrillation (AF). Investigators have studied TGF-β signaling in AF with the aim of discovering potential therapeutic agents. In this review we discuss the role of TGF-β in atrial fibrillation and specifically its role in atrial structural and electrical remodeling.

Platelets Promote Ang II (Angiotensin II)-Induced Atrial Fibrillation by Releasing TGF-β1 (Transforming Growth Factor-β1) and Interacting With Fibroblasts

Hypertension is a risk factor of atrial fibrillation (AF), and a certain number of patients with hypertension were found with an enlarged left atrium. Platelet activation is found in patients with hypertension or pressure overload/Ang II (angiotensin II)-induced hypertensive animal models and contribute to ventricular fibrosis. Whether hypertension-induced atrial fibrosis is mediated by platelets remains unknown. Our previous experimental data showed that platelet-derived TGF-β1 (transforming growth factor-β1) was reduced in patients with hypertensive AF. The present study is to investigate whether platelet-derived TGF-β1 promotes Ang II-induced atrial fibrosis and AF. Platelet activation and atrial platelet accumulation were measured in sinus rhythm controls, normotensive AF, and patients with hypertensive AF. Ang II (1500 ng/kg per minute, 3 weeks) infused mice with pharmacological (clopidogrel) and genetic platelet inhibition (TGF-β1 deletion in platelets) were used. Platelet activation, atrial structural remodeling, atrial electrical transmission, AF inducibility, inflammation, and fibrosis were measured in mice. We found that circulating platelets were activated in patients with hypertensive AF. A large amount of platelet was accumulated in the atriums of patients with hypertensive AF. Both clopidogrel treatment and platelet-specific deletion of TGF-β1 attenuated Ang II-induced structural remodeling, atrial electrical transmission, AF inducibility, as well as atrial inflammation and fibrosis than mice without interventions. Furthermore, clopidogrel blocked atrial platelet accumulation and platelet-fibroblast conjugation. Platelets promoted atrial fibroblast differentiation in cell culture. Profibrotic actions of platelets are largely via activation of atrial fibroblasts by releasing TGF-β1 and inducing platelet-fibroblast conjugation, and platelet inhibition is sufficient to inhibit atrial fibrosis and AF inducibility.

Atrial Myopathy Underlying Atrial Fibrillation

While AF most often occurs in the setting of atrial disease, current assessment and treatment of patients with AF does not focus on the extent of the atrial myopathy that serves as the substrate for this arrhythmia. Atrial myopathy, in particular atrial fibrosis, may initiate a vicious cycle in which atrial myopathy leads to AF, which in turn leads to a worsening myopathy. Various techniques, including ECG, plasma biomarkers, electroanatomical voltage mapping, echocardiography, and cardiac MRI, can help to identify and quantify aspects of the atrial myopathy. Current therapies, such as catheter ablation, do not directly address the underlying atrial myopathy. There is emerging research showing that by targeting this myopathy we can help decrease the occurrence and burden of AF.

Chromosome 4q25 variants and biomarkers of myocardial fibrosis in patients with atrial fibrillation

INTRODUCTION

Little is known about how genetic predisposition and fibrosis relate in atrial fibrillation (AF). Hence, we sought to determine whether the genetic variants and biomarkers for fibrosis enhance prediction of outcomes after catheter ablation.

METHODS AND RESULTS

Consecutive patients who underwent catheter ablation of AF (paroxysmal, 158; nonparoxysmal, 137) or supraventricular tachycardia without AF (n = 70) were studied retrospectively. Plasma levels of transforming growth factor β1 (TGF-β1), tissue inhibitor of metalloproteinase 1 (TIMP-1), and 4q25 single-nucleotide polymorphisms (SNPs) (rs10033464 and rs220073) were measured. Mean plasma levels of both TGF-β1 and TIMP-1 were higher in patients with AF than in the control (all P < .001). Plasma levels of TIMP-1 were higher in patients with recurrence compared with those without recurrence (P = .039). Patients with variant alleles of rs10033464 showed increased recurrence after catheter ablation in patients with paroxysmal AF including after adjustment (P = .027). Patients with TIMP-1 < 107 ng/mL and no variant allele (GG) at rs10033464 had lower recurrence rates compared with other groups in those with paroxysmal AF (logrank; P = .007), whereas there was no significant difference among those patients with persistent forms of AF. Inclusion of biomarkers and genotype improved discrimination of AF recurrence in patients with paroxysmal AF (C-statistic .499 vs .600).

CONCLUSIONS

The combination of plasma TIMP-1 concentrations less than 107 ng/mL and the absence of a variant allele at rs10033464 was associated with lower recurrence rates in patients with paroxysmal AF. This study suggests that 4q25 SNPs and biomarkers for fibrosis may provide additive value in risk stratification for AF recurrence after catheter ablation.

Immunopathogenesis and biomarkers of recurrent atrial fibrillation following ablation therapy in patients with preexisting atrial fibrillation

INTRODUCTION

Recurrent atrial fibrillation (RAF) following ablation therapy occurs in about 50% of patients. The pathogenesis of RAF is unknown, but is believed to be driven by atrial remodeling in the setting of background inflammation. Structural, electrophysiological and mechanical remodeling has been associated with atrial fibrillation (AF). Inflammation and fibrotic remodeling are the major factors perpetuating AF, as mediators released from the atrial tissues and cardiomyocytes due to mechanical and surgical injury could initiate the inflammatory process. In this article, we have critically reviewed the key mediators that may serve as potential biomarkers to predict RAF. Areas covered: Damage associated molecular patterns, heat shock proteins, inflammatory cytokines, non-inflammatory markers, markers of inflammatory cell activity, and markers of collagen deposition and metabolism are evaluated as potential biomarkers with molecular treatment options in RAF. Expert commentary: Establishing biomarkers to predict RAF could be useful in reducing morbidity and mortality. Investigations into the role of DAMPs participating in a sterile immune response may provide greater insight into the pathogenesis of RAF. Markers evaluating immune cell activity, collagen deposition, and levels of heat shock proteins show the greatest promise as potential biomarkers to predict RAF and develop novel therapies.

Noninvasive assessment of left atrial fibrosis. Correlation between echocardiography, biomarkers, and electroanatomical mapping

AIM

Left atrial (LA) fibrosis promotes atrial fibrillation (AF), may predict poor radiofrequency catheter ablation (RFCA) outcome, and may be assessed invasively using electroanatomical mapping (EAM). Speckle tracking echocardiography (STE) enables quantitative assessment of LA function. The aim was to assess the relationship between LA fibrosis derived from EAM and LA echocardiographic parameters as well as biomarkers of fibrosis in patients with AF.

METHODS

Sixty-six patients (64% males, mean age 56 ± 10) with nonvalvular AF treated with first RFCA were prospectively studied. Seventy-three percent of patients were in sinus rhythm at the time of examination. LA geometry, systolic, and diastolic function were assessed. In STE global, peak atrial longitudinal (PALS) and contractile (PACS) strain were calculated. LA stiffness index (LAs) - the ratio of E/e' to PALS - was assessed. The EAM of LA was build using Carto System before RFCA. Low amplitude potentials area (LAPA) was quantitatively analyzed and expressed as a percentage of LA surface using the cut-off <0.5 mV to detect potential sites of fibrosis. The serum concentrations of MMP-9, PIIINP, and TGFβ1were estimated before RFCA.

RESULTS

Pearson correlation analysis showed a significant correlation between LA diastolic function parameters: PALS (-0.54, P < .001), LAs (0.65, P < .001), and LAPA in patients who were in sinus rhythm. Also LA volume significantly correlated with LAPA (0.44, P < .002). None of biomarkers correlated with LAPA.

CONCLUSION

Left atrial diastolic parameters derived from STE correlate well with the extent of LA fibrosis. Thus, STE may be useful in the noninvasive assessment of LA fibrosis and selection of candidates for RFCA.

[Biomarkers and atrial fibrillation : Prediction of recurrences and thromboembolic events after rhythm control management]

Atrial fibrillation (AF) is the most common arrhythmia in clinical praxis and is associated with an increased risk for cardio- and cerebrovascular complications leading to an increased mortality. Catheter ablation represents one of the most important and efficient therapy strategies in AF patients. Nevertheless, the high incidence of arrhythmia recurrences after catheter ablation leads to repeated procedures and higher treatment costs. Recently, several scores had been developed to predict rhythm outcomes after catheter ablation. Biomarker research is also of enormous interest. There are many clinical and blood biomarkers pathophysiologically associated with AF occurrence, progression and recurrences. These biomarkers-including different markers in blood (e. g. von Willebrand factor, D‑dimer, natriuretic peptides) or urine (proteins, epidermal grown factor receptor) but also cardiac imaging (echocardiography, computed tomography, magnetic resonance imaging)-could help to improve clinical scores and be useful for individualized AF management and optimized patients' selection for different AF treatment strategies. In this review, the role of diverse biomarkers and their predictive value related to AF-associated complications are discussed.

Role of serum TGF-β1 level in atrial fibrosis and outcome after catheter ablation for paroxysmal atrial fibrillation

This study aimed to evaluate the relationship between serum transforming growth factor-β1 (TGF-β1) concentration and atrial fibrosis and to determine whether plasma TGF-β1 concentration is an independent predictor of atrial fibrillation (AF) recurrence after catheter ablation.We included 98 consecutive patients who underwent catheter ablation, including 38 with paroxysmal AF (AF group) and 60 with paroxysmal supraventricular tachycardia (control group). We compared their preablation serum concentration of biomarkers and clinical and echocardiographic findings.Serum TGF-β1 concentrations, type-III procollagen N-terminal peptides (PIIINP), type-IV procollagen (IV-C), and laminin (LN) were significantly higher in the AF group than in the control group; however, there was no correlation between their concentrations and left atrial diameter (LAD). The area of the low-voltage zone positively correlated with TGF-β1 and PIIINP concentrations, but not with LAD. Atrial tachyarrhythmia (AF and AFL/AT) recurrence was observed in 15 patients (39.4%) at mean 241.4 ± 68.5 days of follow-up 12 months after ablation. Regression analysis revealed that TGF-β1 was a major risk factor for AF recurrence (odds ratio, 1.14; 95% confidence interval, 1.11-1.17; P = .02).Serum TGF-β1 concentration is an independent predictor of AF recurrence in patients with paroxysmal AF and may help identify patients likely to have better outcomes after catheter ablation.

Association of pre-ablation level of potential blood markers with atrial fibrillation recurrence after catheter ablation: a meta-analysis

Aims

The meta-analysis was aimed to search for candidate blood markers whose pre-ablation level was associated with atrial fibrillation (AF) recurrence after radiofrequency catheter ablation (RFCA).

Methods and results

A systematic literature search of PubMed, EMBASE, Springer Link, Web of Science, Wiley-Cochrane library, and supplemented with Google scholar search engine was performed. Thirty-six studies covering 11 blood markers were qualified for this meta-analysis. Compared with the nonrecurrence group, the recurrence group had increased pre-ablation level of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), N-terminal pro-brain natriuretic peptide (NT-pro-BNP), interleukin-6 (IL-6), C-reactive protein, low density lipoprotein (LDL), and tissue inhibitor of metal loproteinase-2 (TIMP-2) [standardized mean difference (95% confidence interval): 0.37 (0.13-0.61), 0.77 (0.40-1.14), 1.25 (0.64-1.87), 0.37 (0.21-0.52), 0.35 (0.10-0.60), 0.24 (0.07-0.42), 0.17 (0.00-0.34), respectively], while no statistical difference of pre-ablation level of white blood cell, total cholesterol, triglyceride, and transforming growth factor-β1 was found. Subgroup analysis demonstrated that ANP was associated with AF recurrence in participants who had no concomitant structural heart diseases (SHD); however, not in participants who had SHD, C-reactive protein was associated with AF recurrence in Asian studies, whereas not in European studies.

Conclusion

Increased pre-ablation level of ANP, BNP, NT-pro-BNP, IL-6, C-reactive protein, LDL, and TIMP-2 was associated with greater risk of AF recurrence after RFCA.

Concomitant Obesity and Metabolic Syndrome Add to the Atrial Arrhythmogenic Phenotype in Male Hypertensive Rats

Background

Besides hypertension, obesity and the metabolic syndrome have recently emerged as risk factors for atrial fibrillation. This study sought to delineate the development of an arrhythmogenic substrate for atrial fibrillation in hypertension with and without concomitant obesity and metabolic syndrome.

Methods and Results

We compared obese spontaneously hypertensive rats (SHR‐obese, n=7–10) with lean hypertensive controls (SHR‐lean, n=7–10) and normotensive rats (n=7–10). Left atrial emptying function (MRI) and electrophysiological parameters were characterized before the hearts were harvested for histological and biochemical analyses. At the age of 38 weeks, SHR‐obese, but not SHR‐lean, showed increased body weight and impaired glucose tolerance together with dyslipidemia compared with normotensive rats. Mean blood pressure was similarly increased in SHR‐lean and SHR‐obese when compared with normotensive rats (178±9 and 180±8 mm Hg [not significant] versus 118±5 mm Hg, P<0.01 for both), but left ventricular end‐diastolic pressure was more increased in SHR‐obese than in SHR‐lean. Impairment of left atrial emptying function, increase in total atrial activation time, and conduction heterogeneity, as well as prolongation of inducible atrial fibrillation durations, were more pronounced in SHR‐obese as compared with SHR‐lean. Histological and biochemical examinations revealed enhanced triglycerides and more pronounced fibrosis in the left atrium of SHR‐obese. Besides increased expression of profibrotic markers in SHR‐lean and SHR‐obese, the profibrotic extracellular matrix protein osteopontin was highly upregulated only in SHR‐obese.

Conclusions

In addition to hypertension alone, concomitant obesity and metabolic syndrome add to the atrial arrhythmogenic phenotype by impaired left atrial emptying function, local conduction abnormalities, interstitial atrial fibrosis formation, and increased propensity for atrial fibrillation.

Usefulness of Preoperative Transforming Growth Factor-Beta to Predict New Onset Atrial Fibrillation After Surgical Ventricular Septal Myectomy in Patients With Obstructive Hypertrophic Cardiomyopathy

Postoperative atrial fibrillation (AF) occurs frequently after cardiac surgery and contributes significantly to mortality. Transforming growth factor-beta (TGF-β) is associated with postoperative AF after coronary artery bypass grafting and valve surgery. We performed a prospective study to evaluate the role of TGF-β as a predictor of AF after myectomy. A total of 109 consecutive obstructive hypertrophic cardiomyopathy patients without previous AF who underwent myectomy were identified. We measured plasma TGF-β levels before surgery, monitored heart rhythm until discharge, and followed patients for a mean of 36 ± 10 months. AF was documented in 19 patients (17%). AF patients were older (50 ± 10 vs 43 ± 15 years, p = 0.037). Patients who developed AF had higher plasma TGF-β levels (1,695 ± 2,011 vs 1,099 ± 2,494 pg/ml, p = 0.011), more major adverse cardiac events (32% vs 7%, p = 0.006), and more strokes (16% vs 0%, p = 0.005) than patients who did not. TGF-β level ≥358 pg/ml predicted AF with sensitivity and specificity of 58% and 77% (p = 0.011), respectively. Higher TGF-β levels were associated with pulmonary hypertension (25% vs 8%, p = 0.033). In multivariable regression analysis, age (odds ratio 1.05, 95% confidence interval 1.00 to 1.11, p = 0.041) and TGF-β levels (odds ratio 2.42, 95% confidence interval 1.30 to 4.50, p = 0.005) predicted AF independently. In conclusion, elevated preoperative TGF-β value is an independent predictor of postoperative AF in hypertrophic cardiomyopathy patients after surgical ventricular septal myectomy.

Association of SCN10A Polymorphisms with the Recurrence of Atrial Fibrillation after Catheter Ablation in a Chinese Han Population

The nonsynonymous SCN10A single nucleotide polymorphism (SNP) rs6795970 has been reported to associate with PR interval and atrial fibrillation (AF) and in strong linkage disequilibrium (LD) with the AF-associated SNP rs6800541. In this study, we investigated whether rs6795970 polymorphisms are associated with AF recurrence after catheter ablation. A total of 502 consecutive patients with AF who underwent catheter ablation were included. AF recurrence was defined as a documented episode of any atrial arrhythmias lasting ≥30 s after a blanking period of 3 months. AF recurrence was observed between 3 and 12 months after catheter ablation in 24.5% of the patients. There was a significant difference in the allele distribution (p = 7.86 × 10⁻⁵) and genotype distribution (p = 1.42 × 10⁻⁵) of rs6795970 between the AF recurrence and no recurrence groups. In a multivariate analysis, we identified the following independent predictors of AF recurrence: the rs6795970 genotypes in an additive model (OR 0.36, 95%CI 0.22~0.60, p = 7.04 × 10⁻⁵), a history of AF ≥36 months (OR 3.57, 95%CI 2.26~5.63, p = 4.33 × 10⁻⁸) and left atrial diameter (LAD) ≥40 mm (OR 1.85, 95%CI 1.08~3.19, p = 0.026). These data suggest that genetic variation in SCN10A may play an important role in predicting AF recurrence after catheter ablation in the Chinese Han population.

Transforming Growth Factor-β1 T869C Gene Polymorphism Is Associated with Acquired Sick Sinus Syndrome via Linking a Higher Serum Protein Level

Background

Familial sick sinus syndrome is associated with gene mutations and dysfunction of ion channels. In contrast, degenerative fibrosis of the sinus node tissue plays an important role in the pathogenesis of acquired sick sinus syndrome. There is a close relationship between transforming growth factor-β1 mediated cardiac fibrosis and acquired arrhythmia. It is of interest to examine whether transforming growth factor-β1 is involved in the pathogenesis of acquired sick sinus syndrome.

Methods

Overall, 110 patients with acquired SSS and 137 age/gender-matched controls were screened for transforming growth factor-β1 and cardiac sodium channel gene polymorphisms using gene sequencing or restriction fragment length polymorphism methods. An enzyme-linked immunosorbent assay was used to determine the serum level of transforming growth factor-β1.

Results

Two transforming growth factor-β1 gene polymorphisms (C-509T and T+869C) and one cardiac sodium channel gene polymorphism (H588R) have been identified. The C-dominant CC/CT genotype frequency of T869C was significantly higher in acquired sick sinus syndrome patients than in controls (OR 2.09, 95% CI 1.16–3.75, P = 0.01). Consistently, the level of serum transforming growth factor-β1 was also significantly greater in acquired sick sinus syndrome group than in controls (5.3±3.4 ng/ml vs. 3.7±2.4 ng/ml, P = 0.01). In addition, the CC/CT genotypes showed a higher transforming growth factor-β1 serum level than the TT genotype (4.25 ± 2.50 ng/ml vs. 2.71± 1.76 ng/ml, P = 0.028) in controls.

Conclusion

Transforming growth factor-β1 T869C polymorphism, correlated with high serum transforming growth factor-β1 levels, is associated with susceptibility to acquired sick sinus syndrome.

Association of Plasma Transforming Growth Factor-β1 Levels and the Risk of Atrial Fibrillation: A Meta-Analysis

Introduction

Numerous studies have demonstrated that plasma transforming growth factor-β1 (TGF-β1) may be involved in the pathogenesis of atrial fibrillation (AF), but some discrepancy remained. We performed a meta-analysis to evaluate the association between the plasma level of TGF-β1 and the risk of AF.

Methods

Published clinical studies evaluating the association between the plasma level of TGF-β1 and the risk of AF were retrieved from PubMed and EMBASE databases. Two reviewers independently evaluated the quality of the included studies and extracted study data. Subgroup analysis and sensitivity analysis were performed to evaluate for heterogeneity between studies.

Results

Of the 395 studies identified initially, 13 studies were included into our analysis, with a total of 3354 patients. Higher plasma level of TGF-β1 was associated with increased risk of AF when evaluated as both a continuous variable (SMD 0.67; 95%CI 0.29–1.05) and a categorical variable (OR 1.01, 95% CI 1.01–1.02).

Conclusions

This meta-analysis suggests an association between elevated plasma TGF-β1 and new onset AF. Additional studies with larger sample sizes are needed to further investigate the relationship between plasma TGF-β1 and the occurrence of AF.

The potential role of atrial natriuretic peptide in the effects of Angiotensin-(1-7) in a chronic atrial tachycardia canine model

Objective:

The objective of this article is to investigate the possible role of atrial natriuretic peptide (ANP) in Angiotensin-(1–7) (Ang-(1–7)) signaling pathway on atrial electrical and structural remodeling in a chronic rapid atrial pacing canine model.

Methods:

Twenty-four dogs were randomly assigned to four groups: a sham group, paced control group, a paced + Ang-(1–7) group and a paced + Ang-(1–7) + A-71915 group. Atrial rapid pacing (ARP) at 600 bpm was maintained for 14 days except in the animals from the sham group. During the pacing, Ang-(1–7) (6 μg•kg-1•h-1) or Ang-(1–7) (6 μg•kg-1•h-1) + A-71915 (ANP receptor antagonist, 0.30 μg•kg-1•h-1) were given intravenously, respectively. After pacing, it was measured that electrophysiological parameters including atrial effective refractory periods (ERPs), inducibility and duration of atrial fibrillation (AF), I_CaL and I_Na changed, where I_CaL refers to voltage-dependent L-type Ca²⁺ current and I_Na refers to cardiac sodium current. Then, the fibrosis and the expression of Cav1.2, I_Nav1.5α subunit, TGF-β₁ and ANP in atria were assessed.

Results:

After ARP, compared with the sham group, the atrial ERPs at six sites in each dog were shortened with the increasing in inducibility and duration of AF in the paced control group. The density of I_CaL, I_Na and the expression of Cav1.2, I_Nav1.5α subunit mRNA were decreased. Atrial tissue from the paced dogs showed significant interstitial fibrosis. The expression of TGF-β₁ and ANP in mRNA and protein levels were increased. Compared with the paced control group, the shortening of atrial ERPs, and the increasing of inducibility and duration of AF induced by ARP were alleviated by Ang-(1–7) treatment (p < 0.05). The density of I_CaL and I_Na and the expression of Cav1.2 and I_Nav1.5α subunit mRNA were slightly decreased. Atrial tissue showed less interstitial fibrosis after Ang-(1–7) treatment. The increasing of ANP expression was improved by Ang-(1–7), while the increasing of TGF-β₁ expression was alleviated by Ang-(1–7) (p < 0.05). A-71915 treatment blocked the beneficial effects of Ang-(1–7) on the aforementioned electrophysiological parameters and atrial fibrosis. And A-71915 treatment blocked Ang-(1–7), improving the expression of TGF-β₁.

Conclusion:

Ang-(1–7) prevented atrial structural and electrical remodeling induced by ARP. Furthermore, Ang-(1–7) promoted ANP secretion, and ANP played a crucial role in the cardiac protection of the former.

Electrophysiological Perspectives on Hybrid Ablation of Atrial Fibrillation

To overcome limitations of minimally invasive surgical ablation as a standalone procedure in eliminating atrial fibrillation (AF), hybrid approaches incorporating adjunctive endovascular catheter ablation have been proposed in recent years. The endovascular component targets residual conduction gaps and identifies additional electrophysiological targets with the goal of minimizing recurrent atrial arrhythmia. We performed a systematic review of published studies of hybrid AF ablation, analyzing 432 pooled patients (19% paroxysmal, 29% persistent, 52% long-standing persistent) treated using three different approaches: A. bilateral thoracoscopy with bipolar radiofrequency (RF) clamp-based approach; B. right thoracoscopic suction monopolar RF catheter-based approach; and C. subxiphoid posterior pericardioscopic ("convergent") approach. Freedom from recurrence off antiarrhythmic medications at 12 months was seen in 88.1% [133/151] for A, 73.4% [47/64] for B, and 59.3% [80/135] for C, with no significant difference between paroxysmal (76.9%) and persistent/long-standing persistent AF (73.4%). Death and major surgical complications were reported in 8.5% with A, 0% with B and 8.6% with C. A critical appraisal of hybrid ablation is presented, drawing from experiences and insights published over the years on catheter ablation of AF, with a discussion of the rationale underlying hybrid ablation, its strengths and limitations, where it may have a unique role in clinical management of patients with AF, which questions remain unanswered and areas for further investigation.

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

Atrial fibrillation (AF) is associated with structural, electrical, and contractile remodeling of the atria. Development and progression of atrial fibrosis is the hallmark of structural remodeling in AF and is considered the substrate for AF perpetuation. In contrast, experimental and clinical data on the effect of ventricular fibrotic processes in the pathogenesis of AF and its complications are controversial. Ventricular fibrosis seems to contribute to abnormalities in cardiac relaxation and contractility and to the development of heart failure, a common finding in AF. Given that AF and heart failure frequently coexist and that both conditions affect patient prognosis, a better understanding of the mutual effect of fibrosis in AF and heart failure is of particular interest. In this review paper, we provide an overview of the general mechanisms of cardiac fibrosis in AF, differences between fibrotic processes in atria and ventricles, and the clinical and prognostic significance of cardiac fibrosis in AF.

Inflammation and the pathogenesis of atrial fibrillation

Atrial fibrillation (AF) is the most common cardiac arrhythmia. However, the development of preventative therapies for AF has been disappointing. The infiltration of immune cells and proteins that mediate the inflammatory response in cardiac tissue and circulatory processes is associated with AF. Furthermore, the presence of inflammation in the heart or systemic circulation can predict the onset of AF and recurrence in the general population, as well as in patients after cardiac surgery, cardioversion, and catheter ablation. Mediators of the inflammatory response can alter atrial electrophysiology and structural substrates, thereby leading to increased vulnerability to AF. Inflammation also modulates calcium homeostasis and connexins, which are associated with triggers of AF and heterogeneous atrial conduction. Myolysis, cardiomyocyte apoptosis, and the activation of fibrotic pathways via fibroblasts, transforming growth factor-β and matrix metalloproteases are also mediated by inflammatory pathways, which can all contribute to structural remodelling of the atria. The development of thromboembolism, a detrimental complication of AF, is also associated with inflammatory activity. Understanding the complex pathophysiological processes and dynamic changes of AF-associated inflammation might help to identify specific anti-inflammatory strategies for the prevention of AF.

TGF-β1 signal pathway in the regulation of inflammation in patients with atrial fibrillation

OBJECTIVE

To observe the expression changes of inflammatory markers TGF-β1, Smad3 and IL-6 in patients with atrial fibrillation (AF), and to explore the significance of TGF-β1 signaling pathway in the structural remodeling of AF.

METHODS

The expression of TGF-β1, Smad3 and IL-6 in 50 cases with AF and 30 normal cases were detected by RT-PCR and ELISA.

RESULTS

The TGF-β1, Smad3 and IL-6 mRNA and protein expression levels in patients with AF were significantly higher than that in the control group (P<0.05), but there was no significantly different between the paroxysmal AF group and the persistent AF group (P>0.05). The TGF-β1mRNA expression in the ⩾ 50 years subgroup was significantly higher than that in the <50 years subgroups, and it was higher in the NYHA III subgroup than in the I/II grade subgroup. It was also higher in the left ventricular ejection fraction (LVEF) <50% subgroup than in LVEF ⩾ 50% group, and it was significantly higher in the AF time ⩾ 36 months subgroup than that in <36 months subgroup (P<0.05). The Smad3 and IL-6 expressions in the in the LVEF <50% subgroup were both high that than that in LVEF ⩾ 50% group, and higher in the AF time ⩾ 36 months subgroup than that in <36 months subgroup (P<0.05). There were a positive correlation between TGF-β1, Smad3 and IL-6 (r=0.687, r=0.547). There were also a positive correlation between Smad3 and IL-6 mRNA (r=0.823).

CONCLUSIONS

AF is associated with inflammation, and the inflammation is also involved in the fibrillation and sustain of AF. The TGF-β1 signal pathway may be involved in the process of atrial structural remodeling in patients with AF, and iss related with the occurrence and maintenance of AF.

TheTGFB1 functional polymorphism rs1800469 and susceptibility to atrial fibrillation in two Chinese Han populations

Transforming growth factor-β1 (TGF-β1) is related to the degree of atrial fibrosis and plays critical roles in the induction and perpetuation of atrial fibrillation (AF). To investigate the association of the common promoter polymorphism rs1800469 in the TGF-β1 gene (TGFB1) with the risk of AF in Chinese Han population, we carried out a case-control study of two hospital-based independent populations: Southeast Chinese population (581 patients with AF and 723 controls), and Northeast Chinese population (308 AF patients and 292 controls). Two hundred and seventy-eight cases of AF were lone AF and 334 cases of AF were diagnosed as paroxysmal AF. In both populations, AF patients had larger left atrial diameters than the controls did. The rs1800469 genotypes in the TGFB1 gene were determined by polymerase chain reaction-restriction fragment length polymorphism. The genotype and allele frequencies of rs1800469 were not different between AF patients and controls of the Southeast Chinese population, Northeast Chinese population, and total Study Population. After adjustment for age, sex, hypertension and LAD, there was no association between the rs1800469 polymorphism and the risk of AF under the dominant, recessive and additive genetic models. Similar results were obtained from subanalysis of the lone and paroxymal AF subgroups. Our results do not support the role of the TGFB1 rs1800469 functional gene variant in the development of AF in the Chinese Han population.

Rhythm outcomes after catheter ablation of atrial fibrillation. Clinical implication of biomarkers

Atrial fibrillation (AF) occurs as the result of numerous complex physiological processes in the atria leading to AF promotion and maintenance. Improved diagnostic techniques have identified various biomarkers which may play an important role in the prediction of AF related outcomes (cardio- and cerebrovascular events, as well as mortality and rhythm outcomes). Biomarkers refer to 'biological markers' and biomarkers in blood, urine as well as imaging marker (eg, dimensions (left atrial diameter and volume), anatomical features (left appendage and pulmonary vein anatomy), and physiological pattern (LAA flow velocity)) may play important role(s) as clinically important indices in relation to outcomes after different therapeutic strategies. However, the main domain in the biomarker field has focused on blood-based biomarkers, which are widely used to predict therapeutic success regarding underlying pathophysiological mechanism, such as inflammation, fibrosis, endothelial damage. This review provides an update of the role of clinically relevant biomarkers in AF, with particular focus on AF rhythm outcomes.

Genetic ACE I/D polymorphism and recurrence of atrial fibrillation after catheter ablation

BACKGROUND

The angiotensin-converting enzyme (ACE) deletion allele, ACE D, is associated with increased cardiac ACE activity, cardiac fibrosis, and adverse outcomes in cardiovascular disease and has been linked with failure of antiatrial fibrillation (anti-AF) drug treatment. This study tested the hypothesis that the ACE gene insertion/deletion polymorphism associates with AF recurrence after catheter ablation.

METHODS AND RESULTS

In 238 consecutive patients (69% male; mean age, 58±11 years) undergoing catheter ablation of paroxysmal (59%) or persistent (41%) AF, the ACE insertion/deletion polymorphism was genotyped using polymerase chain reaction. After a blanking period of 3 months, AF recurrence (defined as any atrial arrhythmia lasting ≥30 s) was detected using serial 7-day Holter ECG recordings after 3, 6, and 12 months. AF recurrence was observed in 39% and was associated with persistent AF, longer history of AF, previous antiarrhythmic drug use, previous use of diuretics, increased left atrial diameter, increased left ventricular end-diastolic diameter, additional linear ablation lesions, and ACE DD polymorphism. In multivariable analysis, left atrial diameter (odds ratio, 1.111; 95% confidence interval, 1.040-1.187; P=0.002) and ACE DD genotype (odds ratio, 2.251; 95% confidence interval, 1.056-4.798; P=0.036) remained predictors for AF recurrence.

CONCLUSIONS

Left atrial enlargement and the ACE DD polymorphism are predictors for AF recurrence after catheter ablation. The association between the ACE DD polymorphism and AF recidivism supports the use of genetic data for predicting response to AF therapies and highlights the role of fibrosis in AF development.

Predictive value of transforming growth factor-β1in Chagas disease: towards a biomarker surrogate of clinical outcome

BACKGROUND

Transforming growth factor-β1 (TGF-β1) may be implicated in the development of Chagas heart disease. However, the clinical value of TGF-β1 measurement is yet to be determined.

METHODS

We retrospectively analyzed the outcome of 54 Chagas disease patients without heart failure and with left ventricular (LV) ejection fraction >45% whose TGF-β1 serum values were determined between January 1998 and December 1999. Primary end point was all-cause mortality and secondary end point was the combination of all-cause mortality or hospitalization due to worsening heart failure or cardiac arrhythmias.

RESULTS

TGF-β1 was independently associated with the occurrence of the primary and secondary end points. The optimal cutoff for TGF-β1 to identify the primary end point was 12.9 ng/ml (area under the curve = 0.82, p = 0.004, sensitivity 100%, and specificity 57%) and to identify the secondary end point was 30.8 ng/ml (area under the curve = 0.72, p = 0.03, sensitivity 60%, and specificity 86%). LV ejection fraction and LV end-diastolic diameter were also independent predictors of the primary and secondary endpoints, respectively.

CONCLUSION

The described association between TGF-β1 and clinical outcome provides evidence towards the clinical value of TGF-β1 in Chagas disease.