Chromosome 4q25 variants and atrial fibrillation recurrence after catheter ablation

Genome-wide association studies reveal differences in genetic susceptibility between single events vs. recurrent events of atrial fibrillation and myocardial infarction: the HUNT study

Genetic research into atrial fibrillation (AF) and myocardial infarction (MI) has predominantly focused on comparing afflicted individuals with their healthy counterparts. However, this approach lacks granularity, thus overlooking subtleties within patient populations. In this study, we explore the distinction between AF and MI patients who experience only a single disease event and those experiencing recurrent events. Integrating hospital records, questionnaire data, clinical measurements, and genetic data from more than 500,000 HUNT and United Kingdom Biobank participants, we compare both clinical and genetic characteristics between the two groups using genome-wide association studies (GWAS) meta-analyses, phenome-wide association studies (PheWAS) analyses, and gene co-expression networks. We found that the two groups of patients differ in both clinical characteristics and genetic risks. More specifically, recurrent AF patients are significantly younger and have better baseline health, in terms of reduced cholesterol and blood pressure, than single AF patients. Also, the results of the GWAS meta-analysis indicate that recurrent AF patients seem to be at greater genetic risk for recurrent events. The PheWAS and gene co-expression network analyses highlight differences in the functions associated with the sets of single nucleotide polymorphisms (SNPs) and genes for the two groups. However, for MI patients, we found that those experiencing single events are significantly younger and have better baseline health than those with recurrent MI, yet they exhibit higher genetic risk. The GWAS meta-analysis mostly identifies genetic regions uniquely associated with single MI, and the PheWAS analysis and gene co-expression networks support the genetic differences between the single MI and recurrent MI groups. In conclusion, this work has identified novel genetic regions uniquely associated with single MI and related PheWAS analyses, as well as gene co-expression networks that support the genetic differences between the patient subgroups of single and recurrent occurrence for both MI and AF.

Clinical Genetic Testing for Atrial Fibrillation: Are We There Yet?

Important progress has been made toward unravelling the complex genetics underlying atrial fibrillation (AF). Initial studies were aimed to identify monogenic causes; however, it has become increasingly clear that the most common predisposing genetic substrate for AF is polygenic. Despite intensive investigations, there is robust evidence for rare variants for only a limited number of genes and cases. Although the current yield for genetic testing in early onset AF might be modest, there is an increasing appreciation that genetic culprits for potentially life-threatening ventricular cardiomyopathies and channelopathies might initially present with AF. The potential clinical significance of this recognition is highlighted by evidence that suggests that identification of a pathogenic or likely pathogenic rare variant in a patient with early onset AF is associated with an increased risk of death. These findings suggest that it might be warranted to screen patients with early onset AF for these potentially more sinister cardiac conditions. Beyond facilitating the early identification of genetic culprits associated with potentially malignant phenotypes, insight into underlying AF genetic substrates might improve the selection of patients for existing therapies and guide the development of novel ones. Herein, we review the evidence that links genetic factors to AF, then discuss an approach to using genetic testing for early onset AF patients in the present context, and finally consider the potential value of genetic testing in the foreseeable future. Although further work might be necessary before recommending uniform integration of genetic testing in cases of early onset AF, ongoing research increasingly highlights its potential contributions to clinical care.

Association of genetic risk and outcomes in patients with atrial fibrillation: interactions with early rhythm control in the EAST-AFNET4 trial

AIMS

The randomized Early Treatment of Atrial Fibrillation for Stroke Prevention Trial found that early rhythm control reduces cardiovascular events in patients with recently diagnosed atrial fibrillation (AF) compared with usual care. How genetic predisposition to AF and stroke interacts with early rhythm-control therapy is not known.

METHODS AND RESULTS

Array genotyping and imputation for common genetic variants were performed. Polygenic risk scores (PRS) were calculated for AF (PRS-AF) and ischaemic stroke risk (PRS-stroke). The effects of PRS-AF and PRS-stroke on the primary outcome (composite of cardiovascular death, stroke, and hospitalization for acute coronary syndrome or worsening heart failure), its components, and recurrent AF were determined.A total of 1567 of the 2789 trial patients were analysed [793 randomized to early rhythm control; 774 to usual care, median age 71 years (65-75), 704 (44%) women]. Baseline characteristics were similar between randomized groups. Early rhythm control reduced the primary outcome compared with usual care [HR 0.67, 95% CI: (0.53, 0.84), P < 0.001]. The randomized intervention, early rhythm control, did not interact with PRS-AF (interaction P = 0.806) or PRS-stroke (interaction P = 0.765). PRS-AF was associated with recurrent AF [HR 1.08 (01.0, 1.16), P = 0.047]. PRS-stroke showed an association with the primary outcome [HR 1.13 (1.0, 1.27), P = 0.048], driven by more heart failure events [HR 1.23 (1.05-1.43), P = 0.010] without differences in stroke [HR 1.0 (0.75, 1.34), P = 0.973] in this well-anticoagulated cohort. In a replication analysis, PRS-stroke was associated with incident AF [HR 1.16 (1.14, 1.67), P < 0.001] and with incident heart failure in the UK Biobank [HR 1.08 (1.06, 1.10), P < 0.001]. The association with heart failure was weakened when excluding AF patients [HR 1.03 (1.01, 1.05), P = 0.001].

CONCLUSIONS

Early rhythm control is effective across the spectrum of genetic AF and stroke risk. The association between genetic stroke risk and heart failure calls for research to understand the interactions between polygenic risk and treatment.

REGISTRATION

ISRCTN04708680, NCT01288352, EudraCT2010-021258-20, www.easttrial.org.

Pulmonary Vein Myocardial Sleeve Length and its Association With Sex and 4q25/PITX2 Genotype

BACKGROUND

Experimental evidence suggests genetic variation in 4q25/PITX2 modulates pulmonary vein (PV) myocardial sleeve length. Although PV sleeves are the main target of atrial fibrillation (AF) ablation, little is known about the association between different PV sleeve characteristics with ablation outcomes.

OBJECTIVES

This study sought to evaluate the association between clinical and genetic (4q25) risk factors with PV sleeve length in humans, and to evaluate the association between PV sleeve length and recurrence after AF ablation.

METHODS

In a prospective, observational study of patients undergoing de novo AF ablation, PV sleeve length was measured using electroanatomic voltage mapping before ablation. The sentinel 4q25 AF susceptibility single nucleotide polymorphism, rs2200733, was genotyped. The primary analysis tested the association between clinical and genetic (4q25) risk factors with PV sleeve length using a multivariable linear regression model. Covariates included age, sex, body mass index, height, and persistent AF. The association between PV sleeve length and atrial arrhythmia recurrence (>30 seconds) was tested using a multivariable Cox proportional hazards model.

RESULTS

Between 2014 and 2019, 197 participants were enrolled (median age 63 years [IQR: 55 to 70 years], 133 male [67.5%]). In multivariable modeling, men were found to have PV sleeves 2.94 mm longer than women (95% CI: 0.99-4.90 mm; P < 0.001). Sixty participants (30.5%) had one 4q25 risk allele and 6 (3.1%) had 2 alleles. There was no association between 4q25 genotype and PV sleeve length. Forty-six participants (23.4%) experienced arrhythmia recurrence within 3 to 12 months, but there was no association between recurrence and PV sleeve length.

CONCLUSIONS

Common genetic variation at 4q25 was not associated with PV sleeve length and PV sleeve length was not associated with ablation outcomes. Men did have longer PV sleeves than women, but more research is needed to define the potential clinical significance of this observation.

Genome and atrial fibrillation

Atrial fibrillation (AF), the most common type of arrhythmia, can cause several adverse effects, such as stroke, heart failure, and cognitive dysfunction, also in addition to reducing quality of life and increasing mortality. Evidence suggests that AF is caused by a combination of genetic and clinical predispositions. In line with this, genetic studies on AF have progressed significantly through linkage studies, genome-wide association studies, use of polygenic risk scores, and studies on rare coding variations, gradually elucidating the relationship between genes and the pathogenesis and prognosis of AF. This article will review current trends in genetic analysis concerning AF.

Pitx2c deficiency confers cellular electrophysiological hallmarks of atrial fibrillation to isolated atrial myocytes

AIMS

Atrial fibrillation (AF) has been associated with altered expression of the transcription factor Pitx2c and a high incidence of calcium release-induced afterdepolarizations. However, the relationship between Pitx2c expression and defective calcium homeostasis remains unclear and we here aimed to determine how Pitx2c expression affects calcium release from the sarcoplasmic reticulum (SR) and its impact on electrical activity in isolated atrial myocytes.

METHODS

To address this issue, we applied confocal calcium imaging and patch-clamp techniques to atrial myocytes isolated from a mouse model with conditional atrial-specific deletion of Pitx2c.

RESULTS

Our findings demonstrate that heterozygous deletion of Pitx2c doubles the calcium spark frequency, increases the frequency of sparks/site 1.5-fold, the calcium spark decay constant from 36 to 42 ms and the wave frequency from none to 3.2 min^-1. Additionally, the cell capacitance increased by 30% and both the SR calcium load and the transient inward current (I_TI) frequency were doubled. Furthermore, the fraction of cells with spontaneous action potentials increased from none to 44%. These effects of Pitx2c deficiency were comparable in right and left atrial myocytes, and homozygous deletion of Pitx2c did not induce any further effects on sparks, SR calcium load, I_TI frequency or spontaneous action potentials.

CONCLUSION

Our findings demonstrate that heterozygous Pitx2c deletion induces defects in calcium homeostasis and electrical activity that mimic derangements observed in right atrial myocytes from patients with AF and suggest that Pitx2c deficiency confers cellular electrophysiological hallmarks of AF to isolated atrial myocytes.

Bone Morphogenetic Protein 10-A Novel Biomarker to Predict Adverse Outcomes in Patients With Atrial Fibrillation

Background Patients with atrial fibrillation (AF) face an increased risk of death and major adverse cardiovascular events (MACE). We aimed to assess the predictive value of the novel atrial-specific biomarker BMP10 (bone morphogenetic protein 10) for death and MACE in patients with AF in comparison with NT-proBNP (N-terminal prohormone of B-type natriuretic peptide). Methods and Results BMP10 and NT-proBNP were measured in patients with AF enrolled in Swiss-AF (Swiss Atrial Fibrillation Study), a prospective multicenter cohort study. A total of 2219 patients were included (median follow-up 4.3 years [interquartile range 3.9, 5.1], mean age 73±9 years, 73% male). In multivariable Cox proportional hazard models, the adjusted hazard ratio (aHR) associated with 1 ng/mL increase of BMP10 was 1.60 (95% CI, 1.37-1.87) for all-cause death, and 1.54 (95% CI, 1.35-1.76) for MACE. For all-cause death, the concordance index was 0.783 (95% CI, 0.763-0.809) for BMP10, 0.784 (95% CI, 0.765-0.810) for NT-proBNP, and 0.789 (95% CI, 0.771-0.815) for both biomarkers combined. For MACE, the concordance index was 0.732 (95% CI, 0.715-0.754) for BMP10, 0.747 (95% CI, 0.731-0.768) for NT-proBNP, and 0.750 (95% CI, 0.734-0.771) for both biomarkers combined. When grouping patients according to NT-proBNP categories (<300, 300-900, >900 ng/L), higher aHRs were observed in patients with high BMP10 in the categories of low NT-proBNP (all-cause death aHR, 2.28 [95% CI, 1.15-4.52], MACE aHR, 1.88 [95% CI, 1.07-3.28]) and high NT-proBNP (all-cause death aHR, 1.61 [95% CI, 1.14-2.26], MACE aHR, 1.38 [95% CI, 1.07-1.80]). Conclusions BMP10 strongly predicted all-cause death and MACE in patients with AF. BMP10 provided additional prognostic information in low- and high-risk patients according to NT-proBNP stratification. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT02105844.

Bone morphogenetic protein 10: a novel risk marker of ischaemic stroke in patients with atrial fibrillation

AIMS

Biomarkers specifically related to atrial tissue may increase the understanding of the pathophysiology of atrial fibrillation (AF) and further improve risk prediction in this setting. Bone morphogenetic protein 10 (BMP10) is a protein expressed in the atrial myocardium. We evaluated the association between BMP10 and the risk of ischaemic stroke and other cardiovascular events in large cohorts of patients with AF, treated with and without oral anticoagulation (OAC).

METHODS AND RESULTS

BMP10 was measured in plasma samples collected at randomisation in patients with AF without OAC in the ACTIVE A and AVERROES trials (n = 2974), and with OAC in the ARISTOTLE trial (n = 13 079). BMP10 was analysed with a prototype Elecsys immunoassay. Associations with outcomes were evaluated by Cox-regression models adjusted for clinical characteristics, kidney function, and N-terminal pro-B-type natriuretic peptide (NT-proBNP). Median concentrations of BMP10 were 2.47 and 2.44 ng/mL, in the non-OAC and OAC cohort, respectively. Increasing BMP10 was associated with lower body mass index, older age, female sex, kidney dysfunction, and AF rhythm. BMP10 was consistently associated with ischaemic stroke. In the non-OAC cohort, BMP10 increased the concordance index of the multivariable model from 0.713 to 0.733 (P = 0.004) and in the OAC cohort from 0.673 to 0.694 (P < 0.001). Additionally, BMP10 maintained a significant prognostic value after additionally adjusting for NT-proBNP. BMP10 was not independently associated with bleeding or with death.

CONCLUSION

The novel atrial biomarker BMP10 was independently associated with ischaemic stroke in patients with AF irrespective of OAC treatment. BMP10 seems to be more specifically related to the risk of ischaemic stroke in AF.

ONE-SENTENCE SUMMARY

In this study, BMP10 may be a novel specific biomarker of ischaemic stroke in patients with atrial fibrillation, irrespective of oral anticoagulation.

Advances of Liquid Biopsy for Diagnosis of Atrial Fibrillation and Its Recurrence After Ablation in Clinical Application

Atrial fibrillation (AF) is a common arrhythmia disease with high morbidity in clinical practice and leads to stroke, heart failure, peripheral embolism, and other severe complications. With aging of the society, AF has become one of the biggest public health challenges. Effective treatments including antiarrhythmic drugs, electrical cardioversion, and ablation (with or without catheters) can alleviate the symptoms of AF. Ablation is the most effective method for the treatment of persistent AF, but cannot cure all patients. Recurrence of AF is a realistic and unavoidable problem. For early predicting and warning of AF and its recurrence, liquid biopsy for accurate molecular analysis of biofluids is a new strategy with potential value and easy sampling and can detect genetic and epigenetic polymorphisms, especially microRNAs. In this review, liquid biopsy is constructed as a new powerful way for diagnosing AF and predicting its recurrence, contributing to the treatment of AF.

Ablation and antiarrhythmic drug effects on PITX2+/− deficient atrial fibrillation: A computational modeling study

Introduction

Atrial fibrillation (AF) is a heritable disease, and the paired-like homeodomain transcription factor 2 (PITX2) gene is highly associated with AF. We explored the differences in the circumferential pulmonary vein isolation (CPVI), which is the cornerstone procedure for AF catheter ablation, additional high dominant frequency (DF) site ablation, and antiarrhythmic drug (AAD) effects according to the patient genotype (wild-type and PITX2+/− deficient) using computational modeling.

Methods

We included 25 patients with AF (68% men, 59.8 ± 9.8 years of age, 32% paroxysmal AF) who underwent AF catheter ablation to develop a realistic computational AF model. The ion currents for baseline AF and the amiodarone, dronedarone, and flecainide AADs according to the patient genotype (wild type and PITX2+/− deficient) were defined by relevant publications. We tested the virtual CPVI (V-CPVI) with and without DF ablation (±DFA) and three virtual AADs (V-AADs, amiodarone, dronedarone, and flecainide) and evaluated the AF defragmentation rates (AF termination or changes to regular atrial tachycardia (AT), DF, and maximal slope of the action potential duration restitution curves (Smax), which indicates the vulnerability of wave-breaks.

Results

At the baseline AF, mean DF (p = 0.003), and Smax (p &lt; 0.001) were significantly lower in PITX2+/− deficient patients than wild-type patients. In the overall AF episodes, V-CPVI (±DFA) resulted in a higher AF defragmentation relative to V-AADs (65 vs. 42%, p &lt; 0.001) without changing the DF or Smax. Although a PITX2+/− deficiency did not affect the AF defragmentation rate after the V-CPVI (±DFA), V-AADs had a higher AF defragmentation rate (p = 0.014), lower DF (p &lt; 0.001), and lower Smax (p = 0.001) in PITX2+/− deficient AF than in wild-type patients. In the clinical setting, the PITX2+/− genetic risk score did not affect the AF ablation rhythm outcome (Log-rank p = 0.273).

Conclusion

Consistent with previous clinical studies, the V-CPVI had effective anti-AF effects regardless of the PITX2 genotype, whereas V-AADs exhibited more significant defragmentation or wave-dynamic change in the PITX2+/− deficient patients.

RA signaling pathway combined with Wnt signaling pathway regulates human-induced pluripotent stem cells (hiPSCs) differentiation to sinus node-like cells

BACKGROUND

The source of SAN is debated among researchers. Many studies have shown that RA and Wnt signaling are involved in heart development. In this study, we investigated the role of retinoic acid (RA) and Wnt signaling in the induction of sinus node-like cells.

METHODS

The experimental samples were divided into four groups: control group (CHIR = 0), CHIR = 3, RA + CHIR = 0 andRA + CHIR = 3. After 20 days of differentiation, Western blot, RT-qPCR, immunofluorescence and flow cytometry were performed to identify sinus node-like cells. Finally, whole-cell patch clamp technique was used to record pacing funny current and action potential (AP) in four groups.

RESULTS

The best intervention method used in our experiment was RA = 0.25 µmol/L D5-D9 + CHIR = 3 µmol/L D5-D7. Results showed that CHIR can increase the expression of ISL-1 and TBX3, while RA mainly elevated Shox2. Immunofluorescence assay and flow cytometry further illustrated that combining RA with CHIR can induce sinus node-like cells (CTNT+Shox2+Nkx2.5-). Moreover, CHIR might reduce the frequency of cell beats, but in conjunction with RA could partly compensate for this side effect. Whole cell patch clamps were able to record funny current and the typical sinus node AP in the experimental group, which did not appear in the control group.

CONCLUSIONS

Combining RA with Wnt signaling within a specific period can induce sinus node-like cells.

Lower pulmonary vein-to-left atrium volume ratio predicts poor rhythm outcome after atrial fibrillation catheter ablation

Although left atrial (LA) dimension (LAD) is one of the predictors of atrial fibrillation (AF) recurrence after catheter ablation, repetitive recurrences occur in patients without enlarged LAD. We explored the predictive value of pulmonary vein (PV) to LA volume percent ratio (PV/LA%vol) for rhythm outcomes after AF catheter ablation (AFCA). We included 2913 patients (73.5% male, 60.0 [52.0–67.0] years old, 60.6% paroxysmal AF) who underwent AFCA. We evaluated the association between PV/LA%vol and AF recurrence after AFCA and compared the predictive value for AF recurrences according to the LA size with LAD. We additionally investigated the association between PV/LA%vol and PITX2 gene using a genome-wide association study. LAD affected 1-year recurrence only in the highest tertile group (T3, p = 0.046), but PV/LA%vol determined 1-year recurrence in all LAD groups (T1, p = 0.044; T2, p = 0.021; and T3, p = 0.045). During 20.0 (8.0–45.0) months of follow-up, AF recurrence rate was significantly higher in patients with lower PV/LA%vol (Log-rank p = 0.004, HR 0.91 [0.84–1.00], p = 0.044). In the T1 and T2 LAD groups, predicting AF recurrences was better with PV/LA%vol than with LAD (AUC 0.63 vs. 0.51, p < 0.001 at T1; AUC 0.61 vs. 0.50, p = 0.007 at T2). We replicated PITX2-related rs12646447, which was independently associated with PV/LA%vol (β = 0.15 [0–0.30], p = 0.047). In conclusion, smaller PV volumes after LA volume adjustments have genetic background of PITX2 gene and predictive value for poorer rhythm outcomes after AFCA, especially in patients without LA enlargement.

Genetically Based Atrial Fibrillation: Current Considerations for Diagnosis and Management

Atrial fibrillation (AF) is the most common atrial arrhythmia and is subcategorized into numerous clinical phenotypes. Given its heterogeneity, investigations into the genetic mechanisms underlying AF have been pursued in recent decades, with predominant analyses focusing on early onset or lone AF. Linkage analyses, genome wide association studies (GWAS), and single gene analyses have led to the identification of rare and common genetic variants associated with AF risk. Significant overlap with genetic variants implicated in dilated cardiomyopathy syndromes, including truncating variants of the sarcomere protein titin, have been identified through these analyses, in addition to other genes associated with cardiac structure and function. Despite this, widespread utilization of genetic testing in AF remains hindered by the unclear impact of genetic risk identification on clinical outcomes and the high prevalence of variants of unknown significance (VUS). However, genetic testing is a reasonable option for patients with early onset AF and in those with significant family history of arrhythmia. While many knowledge gaps remain, emerging data support genotyping to inform selection of AF therapeutics. In this review we highlight the current understanding of the complex genetic basis of AF and explore the overlap of AF with inherited cardiomyopathy syndromes. We propose a set of criteria for clinical genetic testing in AF patients and outline future steps for the integration of genetics into AF care. This article is protected by copyright. All rights reserved.

Late arrhythmia recurrence after atrial fibrillation ablation: incidence, mechanisms and clinical implications

Background and objectives

Catheter ablation of atrial fibrillation (AF) has become a well-established and widely used therapy, with pulmonary vein isolation (PVI) being the key modality of ablation. However, arrhythmia recurrences after PVI are common, with a relevant number of patients undergoing repeat ablation. Arrhythmia recurrence after PVI may vary regarding time point and mode of recurrence. While early arrhythmia recurrences of AF after PVI are mostly found to be the product of electrical reconnection of the pulmonary veins, the exact mechanisms of very late arrhythmia recurrence, occurring later than 12 months after successful PVI, remain unclear. This review provides an overview on the current evidence on time point and mechanisms of arrhythmia recurrence after PVI focussing on late arrhythmia recurrence.

Recent findings

The incidence of late arrhythmia recurrence after PVI can lie at a rate of up to 30% according to long-term follow-up studies. Mechanisms of recurrence include electrical reconnection of previously isolated pulmonary veins and development of atrial fibrosis. The use of cryoballoon ablation is likely to be more effective in reducing late arrhythmia recurrences compared to radiofrequency ablation. Novel scores such as the MB-LATER score or the APPLE score may become useful tools in predicting arrhythmia recurrence after PVI.

Results and conclusion

Late arrhythmia recurrence after PVI is common and leads to a relevant impairment of long-term success. Relevant data are currently limited and exact mechanisms of arrhythmia recurrence remain unclear. Further studies are needed to elucidate pathogenetic mechanisms of late arrhythmia recurrence after PVI in order to improve treatment strategies.

Association of ZFHX3 Genetic Polymorphisms and Extra-Pulmonary Vein Triggers in Patients With Atrial Fibrillation Who Underwent Catheter Ablation

Background: The ZFHX3 gene (16q22) is the second most highly associated gene with atrial fibrillation (AF) and is related to inflammation and fibrosis. We hypothesized that ZFHX3 is associated with extra-pulmonary vein (PV) triggers, left atrial (LA) structural remodeling, and poor rhythm outcomes of AF catheter ablation (AFCA). Methods: We included 1,782 patients who underwent a de novo AFCA (73.5% male, 59.4 ± 10.8 years old, 65.9% paroxysmal AF) and genome-wide association study and divided them into discovery (n = 891) and replication cohorts (n = 891). All included patients underwent isoproterenol provocation tests and LA voltage mapping. We analyzed the ZFHX3, extra-PV trigger-related factors, and rhythm outcomes. Result: Among 14 single-nucleotide polymorphisms (SNPs) of ZFHX3, rs13336412, rs61208973, rs2106259, rs12927436, and rs1858801 were associated with extra-PV triggers. In the overall patient group, extra-PV triggers were independently associated with the ZFHX3 polygenic risk score (PRS) (OR 1.65 [1.22-2.22], p = 0.001, model 1) and a low LA voltage (OR 0.74 [0.56-0.97], p = 0.029, model 2). During 49.9 ± 40.3 months of follow-up, clinical recurrence of AF was significantly higher in patients with extra-PV triggers (Log-rank p < 0.001, HR 1.89 [1.49-2.39], p < 0.001, model 1), large LA dimensions (Log-rank p < 0.001, HR 1.03 [1.01-1.05], p = 0.002, model 2), and low LA voltages (Log-rank p < 0.001, HR 0.73 [0.61-0.86], p < 0.001, model 2) but not the ZFHX3 PRS (Log-rank p = 0.819). Conclusion: The extra-PV triggers had significant associations with both ZFHX3 genetic polymorphisms and acquired LA remodeling. Although extra-PV triggers were an independent predictor of AF recurrence after AFCA, the studied AF risk SNPs intronic in ZFHX3 were not associated with AF recurrence.

Genomic enhancers in cardiac development and disease

The Human Genome Project marked a major milestone in the scientific community as it unravelled the ~3 billion bases that are central to crucial aspects of human life. Despite this achievement, it only scratched the surface of understanding how each nucleotide matters, both individually and as part of a larger unit. Beyond the coding genome, which comprises only ~2% of the whole genome, scientists have realized that large portions of the genome, not known to code for any protein, were crucial for regulating the coding genes. These large portions of the genome comprise the 'non-coding genome'. The history of gene regulation mediated by proteins that bind to the regulatory non-coding genome dates back many decades to the 1960s. However, the original definition of 'enhancers' was first used in the early 1980s. In this Review, we summarize benchmark studies that have mapped the role of cardiac enhancers in disease and development. We highlight instances in which enhancer-localized genetic variants explain the missing link to cardiac pathogenesis. Finally, we inspire readers to consider the next phase of exploring enhancer-based gene therapy for cardiovascular disease.

Association between the rs2106261 polymorphism in the zinc finger homeobox 3 gene and risk of atrial fibrillation: Evidence from a PRISMA-compliant meta-analysis

INTRODUCTION

Previous genome-wide studies have identified an association between the rs2106261 single-nucleotide polymorphism (SNP) in the zinc finger homeobox 3 (ZFHX3) gene and an increased risk of atrial fibrillation (AF). However, this association remains controversial, since conflicting results have been reported in previous studies. We aimed to investigate the association between the ZFHX3 rs2106261 polymorphism and susceptibility to AF.

METHODS

A comprehensive literature search, of articles written in either English or Chinese, was conducted on various databases, including PubMed, Embase, Web of Science, the Cochrane library, Wan Fang, and CNKI, for studies performed up to August 1, 2020. Data were abstracted and pooled using Stata 14.0 software. A meta-analysis was performed on all selected studies based on ZFHX3 rs2106261 polymorphism genotypes.

RESULTS

Nine studies, including 10,107 cases and 58,663 controls, were analyzed in the meta-analysis. In the overall population, a significant association was found between AF and the T-allelic ZFHX 3 rs2106261 SNP (odds ratio [OR] = 1.32, 95% confidence interval [CI] 1.19-1.46). In subgroup analysis, a significant association between the T-allele of rs7193343 and risk of AF in Caucasian (OR = 1.23, 95% CI 1.10-1.37) and Asian subgroups (OR = 1.58, 95% CI 1.32-1.89) was observed. However, no statistically significant association was found in African populations (OR = 1.06, 95% CI 0.95-1.19).

CONCLUSION

The genetic variant rs2106261 SNP is associated with susceptibility to AF in Caucasian and Asian individuals, with Asian samples showing a stronger association. However, based on the current evidence, no association was found in African samples. Future studies, with larger sample sizes and multiple ethnicities, are still necessary.

A Higher Polygenic Risk Score Is Associated with a Higher Recurrence Rate of Atrial Fibrillation in Direct Current Cardioversion-Treated Patients

Background and Objectives: Recurrence of atrial fibrillation (AF) within six months after sinus rhythm restoration with direct current cardioversion (DCC) is a significant treatment challenge. Currently, the factors influencing outcome are mostly unknown. Studies have found a link between genetics and the risk of AF and efficacy of rhythm control. The aim of this study was to examine the association between eight single-nucleotide variants (SNVs) and the risk of AF development and recurrence after DCC. Materials and Methods: Regarding the occurrence of AF, 259 AF cases and 108 controls were studied. Genotypes for the eight SNVs located in the genes CAV1, MYH7, SOX5, KCNN3, ZFHX3, KCNJ5 and PITX2 were determined using high-resolution melting analysis and confirmed with Sanger sequencing. Six months after DCC, a telephone interview was conducted to determine whether AF had recurred. A polygenic risk score (PRS) was calculated as the unweighted sum of risk alleles. Multivariate regression analyses were performed to assess SNV and PRS association with AF occurrence and recurrence after DCC. Results: The risk allele of rs2200733 (PITX2) was significantly associated with the development of AF (p = 0.012, OR = 2.31, 95% CI = 1.206–4.423). AF recurred in 60% of patients and the allele generally associated with a decreased risk of AF of rs11047543 (SOX5) was associated with a greater risk of AF recurrence (p = 0.014, OR = 0.223, 95% CI = 0.067–0.738). A PRS of greater than 7 was significantly associated (p = 0.008) with a higher likelihood of developing AF after DCC (OR = 4.174, 95% CI = 1.454–11.980). Conclusions: A higher PRS is associated with increased odds of AF recurrence after treatment with DCC. PITX2 (rs2200733) is significantly associated with an increased risk of AF. The protective allele of rs11047543 (SOX5) is associated with a greater risk of AF recurrence. Further studies are needed to predict the success of rhythm control and guide patient selection towards the most efficacious treatment.

Association of the MYH6 Gene Polymorphism with the Risk of Atrial Fibrillation and Warfarin Anticoagulation Therapy

Objective: To study the associations of single nucleotide polymorphisms (SNP) of the myosin heavy chain 6 (MYH6) gene with the risk of atrial fibrillation (AF) and warfarin anticoagulation therapy. Methods: Sanger sequencing was employed to analyze the genotypes of the MYH6 gene's rs28730771, rs365990, and rs2277473 loci in 243 AF patients and 243 non-AF patients (control group) selected according to the age and sex of AF patients at a 1:1 ratio. A multiple logistic regression analysis was used to analyze the risk factors in AF. SHEsis was adopted to analyze the association between rs28730771, rs365990, rs2277473 haplotypes and susceptibility to AF. The average weekly doses of warfarin administered to AF patients with different genotypes were compared. Results: The T allele at rs28730771 of the MYH6 gene (odds ratio [OR] = 2.82, 95% confidence interval [CI]: 1.73-4.59, p < 0.01), the G allele at rs365990 (OR = 1.65, 95% CI: 1.22-2.24, p < 0.01) and the T allele at rs2277473 (OR = 1.91, 95% CI: 1.25-2.91, p < 0.01) were significantly associated with an elevated risk of AF. The results of a logistic regression analysis demonstrated that hypertension, smoking, drinking, family history of stroke, as well as the genotypes at the rs28730771, rs365990, and rs2277473 loci were all risk factors in AF (p < 0.05). The CAG haplotype for the three SNPs was associated with a reduced risk of AF susceptibility (OR = 0.61, 95% CI: 0.46-0.81, p < 0.01), and the CGG haplotype was related to an increased risk of AF (OR = 1.49, 95% CI: 1.07-2.06, p = 0.02). The doses of warfarin used in AF patients with different genotypes at the MYH6 rs28730771, rs365990, and rs2277473 loci were significantly different (p < 0.05). Conclusion: The three SNPs (rs28730771, rs365990, and rs2277473) of the MYH6 gene loci were significantly associated with the risk of AF susceptibility and the dose of warfarin anticoagulant therapy.

Ethnic similarities in genetic polymorphisms associated with atrial fibrillation: Far East Asian vs European populations

BACKGROUND

In European ancestry, 111 genetic loci were identified as associated with atrial fibrillation (AF). We explored the reproducibility of those single nucleotide polymorphisms (SNPs) in a genome-wide association study (GWAS) meta-analysis of Far East Asian populations.

METHODS

We performed a meta-analysis of the Korean AF network and Japanese AF data sets (9118 cases and 33 467 controls) by an inverse-variance fixed-effects model. We compared the results with 111 previously reported SNPs proven in Europeans after excluding 36 missing loci and a locus with a minor allelic frequency (MAF) < 0.01 in the European population.

RESULTS

Among remaining 74 loci, 29 loci were replicated at a P < .05, and 17 of those loci were newly found in the Far East Asian population: 3 loci with a P < 5×10^-8 (METTL11B at 1q24, KCNN2 at 5q22 and LRMDA at 10q22), 4 loci at the threshold of the Bonferroni correction of P = 4.5 × 10^-4  ~ 5×10^-8 (KIF3C at 2p23, REEP3, NRBF2 at 10q21, SIRT1, MYPN at 10q21 and CFL2 at 14q13) and 10 SNPs with a P = .05 ~ 4.5 × 10^-4 . Among 18 AF loci with a MAF< 0.01 in the Far East Asian populations, 2 loci (GATA4 at 8q23 and SGCG at 13q12) were replicated after a fine mapping. Twenty-seven AF loci, including a locus, which had a sufficient sample size to get a power of over 80% (with a type 1 error α = 4.5 × 10^-4 ), were not replicated in the Far East Asian populations.

CONCLUSIONS

We newly replicated 19 AF-associated genetic loci in the European descent among the Far East Asian populations. It highlights the extensive sharing of AF genetic risks across Far East Asian populations.

Genetics of atrial fibrillation-practical applications for clinical management: if not now, when and how?

The prevalence and economic burden of atrial fibrillation (AF) are predicted to more than double over the next few decades. In addition to anticoagulation and treatment of concomitant cardiovascular conditions, early and standardized rhythm control therapy reduces cardiovascular outcomes as compared with a rate control approach, favouring the restoration, and maintenance of sinus rhythm safely. Current therapies for rhythm control of AF include antiarrhythmic drugs (AADs) and catheter ablation (CA). However, response in an individual patient is highly variable with some remaining free of AF for long periods on antiarrhythmic therapy, while others require repeat AF ablation within weeks. The limited success of rhythm control therapy for AF is in part related to incomplete understanding of the pathophysiological mechanisms and our inability to predict responses in individual patients. Thus, a major knowledge gap is predicting which patients with AF are likely to respond to rhythm control approach. Over the last decade, tremendous progress has been made in defining the genetic architecture of AF with the identification of rare mutations in cardiac ion channels, signalling molecules, and myocardial structural proteins associated with familial (early-onset) AF. Conversely, genome-wide association studies have identified common variants at over 100 genetic loci and the development of polygenic risk scores has identified high-risk individuals. Although retrospective studies suggest that response to AADs and CA is modulated in part by common genetic variation, the development of a comprehensive clinical and genetic risk score may enable the translation of genetic data to the bedside care of AF patients. Given the economic impact of the AF epidemic, even small changes in therapeutic efficacy may lead to substantial improvements for patients and health care systems.

Genetics of atrial fibrillation

PURPOSE OF REVIEW

Atrial fibrillation is the most common sustained cardiac arrhythmia. In addition to traditional risk factors, it is increasingly recognized that a genetic component underlies atrial fibrillation development. This review aims to provide an overview of the genetic cause of atrial fibrillation and clinical applications, with a focus on recent developments.

RECENT FINDINGS

Genome-wide association studies have now identified around 140 genetic loci associated with atrial fibrillation. Studies into the effects of several loci and their tentative gene targets have identified novel pathways associated with atrial fibrillation development. However, further validations of causality are still needed for many implicated genes. Genetic variants at identified loci also help predict individual atrial fibrillation risk and response to different therapies.

SUMMARY

Continued advances in the field of genetics and molecular biology have led to significant insight into the genetic underpinnings of atrial fibrillation. Potential clinical applications of these studies include the identification of new therapeutic targets and development of genetic risk scores to optimize management of this common cardiac arrhythmia.

A new machine learning approach for predicting likelihood of recurrence following ablation for atrial fibrillation from CT

OBJECTIVE

To investigate left atrial shape differences on CT scans of atrial fibrillation (AF) patients with (AF+) versus without (AF-) post-ablation recurrence and whether these shape differences predict AF recurrence.

METHODS

This retrospective study included 68 AF patients who had pre-catheter ablation cardiac CT scans with contrast. AF recurrence was defined at 1 year, excluding a 3-month post-ablation blanking period. After creating atlases of atrial models from segmented AF+ and AF- CT images, an atlas-based implicit shape differentiation method was used to identify surface of interest (SOI). After registering the SOI to each patient model, statistics of the deformation on the SOI were used to create shape descriptors. The performance in predicting AF recurrence using shape features at and outside the SOI and eight clinical factors (age, sex, left atrial volume, left ventricular ejection fraction, body mass index, sinus rhythm, and AF type [persistent vs paroxysmal], catheter-ablation type [Cryoablation vs Irrigated RF]) were compared using 100 runs of fivefold cross validation.

RESULTS

Differences in atrial shape were found surrounding the pulmonary vein ostia and the base of the left atrial appendage. In the prediction of AF recurrence, the area under the receiver-operating characteristics curve (AUC) was 0.67 for shape features from the SOI, 0.58 for shape features outside the SOI, 0.71 for the clinical parameters, and 0.78 combining shape and clinical features.

CONCLUSION

Differences in left atrial shape were identified between AF recurrent and non-recurrent patients using pre-procedure CT scans. New radiomic features corresponding to the differences in shape were found to predict post-ablation AF recurrence.

Effect of family history of atrial fibrillation on recurrence after atrial fibrillation ablation: A report from the Chinese Atrial Fibrillation Registry Study

BACKGROUND

To evaluate the impact of family history of atrial fibrillation (FAF) on postablation atrial tachyarrhythmia (AT) recurrence.

METHODS

All the 8198 patients undergoing initial AF ablation registered in the Chinese Atrial Fibrillation Registry study were analyzed. FAF was defined as having first-degree relatives diagnosed as AF at age 65 years or younger, and before the time the case in this study was diagnosed. Cox proportional hazards models were used to evaluate the impact of FAF on postablation AT recurrence. Age, sex, body mass index, AF type, history of congestive heart failure, hypertension, diabetes mellitus, prior stroke/transient ischemic attack/systemic embolism, vascular diseases, use of contact force-sensing catheter, and completion of high school were adjusted. The definition of AT recurrence was any documented AF, atrial flutter, or AT lasting more than or equal to 30 s after 3 months blanking period.

RESULTS

After a mean follow-up of 26.2 ± 19.6 months, 318 out of the 645 patients (49.3%) with FAF and 3339 out of the 7553 patients (44.2%) without FAF experienced AT recurrence, corresponding to annual recurrence rates of 22.8% and 20.2%, respectively. Patients with FAF had a significant higher risk of AT recurrence (adjusted hazard ratio 1.129, 95% confidence interval 1.005-1.267) in multivariable analysis. Moreover, FAF had a significant higher impact on AT recurrence in the subgroup of patients diagnosed with AF at age 50 years or younger (p for interaction = .036).

CONCLUSION

FAF is a risk factor for postablation AT recurrence. This is especially true in those with AF diagnosed at 50 years or younger.

Genetic variants associated with atrial fibrillationand long-term recurrence after catheter ablation for atrialfibrillation in Turkish patients

OBJECTIVE

Genome-wide association studies have revealed that single nucleotide polymorphisms (SNPs) are associated with atrial fibrillation (AF) and can predict AF recurrence after catheter ablation in different populations. However, there exists no such data for the Turkish population. We aimed to investigate whether 11 SNPs in the PITX2, ZFHX3, EPHX2, CAV1, TBX5, TGF-1, and SCN10A were related to AF and whether these SNPs can predict long-term atrial tachyarrhythmia (ATa) recurrence after pulmonary vein isolation (PVI) for AF in Turkish patients.

METHODS

A total of 245 consecutive patients with non-valvular AF (44.9% men, mean age: 60.2±13.2 years, 65.3% paroxysmal AF) and 50 age- and sex-matched controls were included in this analysis. The clinical features and genetic variants were compared between the 2 groups. Of the 245 patients, 128 who underwent PVI with second-generation cryoballoon were further examined for long-term recurrence after the procedure.

RESULTS

Four SNPs in PITX2 were significantly associated with AF (rs10033464_T: OR 3.29, 95%CI: 1.38-7.82, p=0.007; rs6838973_T: OR 3.06, 95% CI 1.36-6.87, p=0.007; rs3853445_C: OR 2.84, 95%CI: 1.27-6.36, p=0.011; rs17570669_T: OR 4.03, 95% CI: 1.71-9.51, p=0.001). Among these patients who underwent PVI, one locus in CAV1 (rs3807989_G: OR 4.50, 95% CI 1.04-19.31, p=0.043) and early recurrence (OR: 8.06, 95% CI: 2.12-30.55, p=0.002) predicted long-term AF recurrence after catheter ablation.

CONCLUSION

Significant associations exists between 4 SNPs in PITX2 and AF (rs10033464, rs6838973, rs3853445, and rs17570669) in Turkish patients. In addition, 1 genetic variant in CAV1 (rs3807989) and early recurrence can predict long-term ATa recurrence after catheter ablation.

The Effects of Single Nucleotide Polymorphisms in Korean Patients with Early-onset Atrial Fibrillation after Catheter Ablation

BACKGROUND

This study evaluated the status of single nucleotide polymorphisms (SNPs) in Korean patients with early-onset (< 40 years old) atrial fibrillation (AF) and their effects on the outcome after catheter ablation.

METHODS

A total of 89 patients (35.7 ± 3.7 years, 81 males) with drug-refractory AF (paroxysmal 64.0%) who underwent catheter ablation were included in this study. Sixteen SNPs, including rs13376333, rs10465885, rs10033464, rs2200733, rs17042171, rs6843082, rs7193343, rs2106261, rs17570669, rs853445, rs11708996, rs6800541, rs251253, rs3807989, rs11047543, and rs3825214, were genotyped. Serial 48-hour Holter monitoring was conducted to detect AF recurrences during long-term follow up.

RESULTS

Wild-type genotypes of rs11047543 (GG; 26/69 [37.7%] vs. GA; 13/18 [72.2%] vs. AA; 0/0 [0%], P = 0.009) and rs7193343 (CC; 0/7 [0%] vs. CT; 22/40 [55.0%] vs. TT; 18/41 [43.9%], P = 0.025) and the homozygous variant of rs3825214 (AA; 16/31 [51.6%] vs. AG; 22/43 [51.2%] vs. GG; 2/13 [15.4%], P = 0.056) were significantly associated with a lower rate of late recurrence. When the patients were assigned to four groups according to the number of risk alleles (n = 0-3), there were significant differences in recurrence rate (n = 0; 0/3 vs. n = 1; 2/13 [15.4%] vs. n = 2; 24/52 [46.2%] vs. n = 3; 13/17 [76.5%], P = 0.003). When correcting for multiple variables, rs11047543 (hazard ratio [HR], 2.723; 95% confidence interval [CI], 1.358-5.461; P = 0.005) and the number of risk alleles (HR, 2.901; 95% CI, 1.612-5.219; P < 0.001) were significantly associated with recurrence of AF after catheter ablation.

CONCLUSION

Polymorphisms on rs7193343 closest to ZFHX3 (16q22), rs3825214 near to TBX5 (12q24), and rs11047543 near to SOX5 (12p12) modulate the risk for AF recurrence after catheter ablation. The number of risk alleles of these 3 SNPs was an independent predictor of recurrence during long-term follow up in Korean patients with early-onset AF.

Genetic Susceptibility to Atrial Fibrillation Is Associated With Atrial Electrical Remodeling and Adverse Post-Ablation Outcome

OBJECTIVES

This study sought to assess the atrial electrophysiological properties and post-ablation outcomes in patients with atrial fibrillation (AF) with and without the rs2200733 single nucleotide variant.

BACKGROUND

The phenotype associated with chromosome 4q25 of the AF-susceptibility locus remains unknown.

METHODS

In this study, 102 consecutive patients (ages 61 ± 9 years, 64% male) with paroxysmal or persistent AF were prospectively recruited prior to ablation. Patients were genotyped for rs2200733 and high-density left atrial (LA) electroanatomic maps were created using a multipolar catheter during distal coronary sinus (CS) pacing at 600 ms. Voltage, conduction velocity (CV), CV heterogeneity, and fractionated signals of 6 LA segments were determined. Arrhythmia recurrence was assessed by continuous device (51%) and Holter monitoring.

RESULTS

Overall, 41 patients (40%) were single nucleotide variant carriers (38 heterozygous, 3 homozygous). A mean of 2,239 ± 852 points per patient were collected. Carriers had relatively increased CV heterogeneity (45.7 ± 7.5% vs. 35.9 ± 2.3%; p < 0.001), complex signals (9.4 ± 2.9% vs 6.0 ± 1.2%; p = 0.008), regional LA slowing, or conduction block (31.7 ± 8.2% vs. 17.9 ± 1.9%; p = 0.013) particularly in the posterior and lateral walls. There were no differences in CV, voltage, atrial refractoriness, or sinus node function. At follow-up (median: 27 months; range 19 to 31 months), carriers had lower arrhythmia-free survival (51% vs. 80%; p = 0.003). On multivariable analysis, carrier status was independently associated with CV heterogeneity (p = 0.001), complex signals (p = 0.002), and arrhythmia recurrence (p = 0.019).

CONCLUSIONS

These data provide the first evidence that the rs2200733-tagged haplotype alters LA electrical remodeling and is a determinant of long-term outcome following AF ablation. The molecular mechanisms underpinning these changes warrant further investigation.

Reduced left atrial cardiomyocyte PITX2 and elevated circulating BMP10 predict atrial fibrillation after ablation

BACKGROUNDGenomic and experimental studies suggest a role for PITX2 in atrial fibrillation (AF). To assess if this association is relevant for recurrent AF in patients, we tested whether left atrial PITX2 affects recurrent AF after AF ablation.METHODSmRNA concentrations of PITX2 and its cardiac isoform, PITX2c, were quantified in left atrial appendages (LAAs) from patients undergoing thoracoscopic AF ablation, either in whole LAA tissue (n = 83) or in LAA cardiomyocytes (n = 52), and combined with clinical parameters to predict AF recurrence. Literature suggests that BMP10 is a PITX2-repressed, atrial-specific, secreted protein. BMP10 plasma concentrations were combined with 11 cardiovascular biomarkers and clinical parameters to predict recurrent AF after catheter ablation in 359 patients.RESULTSReduced concentrations of cardiomyocyte PITX2, but not whole LAA tissue PITX2, were associated with AF recurrence after thoracoscopic AF ablation (16% decreased recurrence per 2-(ΔΔCt) increase in PITX2). RNA sequencing, quantitative PCR, and Western blotting confirmed that BMP10 is one of the most PITX2-repressed atrial genes. Left atrial size (HR per mm increase [95% CI], 1.055 [1.028, 1.082]); nonparoxysmal AF (HR 1.672 [1.206, 2.318]), and elevated BMP10 (HR 1.339 [CI 1.159, 1.546] per quartile increase) were predictive of recurrent AF. BMP10 outperformed 11 other cardiovascular biomarkers in predicting recurrent AF.CONCLUSIONSReduced left atrial cardiomyocyte PITX2 and elevated plasma concentrations of the PITX2-repressed, secreted atrial protein BMP10 identify patients at risk of recurrent AF after ablation.TRIAL REGISTRATIONClinicalTrials.gov NCT01091389, NL50069.018.14, Dutch National Registry of Clinical Research Projects EK494-16.FUNDINGBritish Heart Foundation, European Union (H2020), Leducq Foundation.

How Will Genetics Inform the Clinical Care of Atrial Fibrillation?

Susceptibility to atrial fibrillation (AF) is determined by well-recognized risk factors such as diabetes mellitus or hypertension, emerging risk factors such as sleep apnea or inflammation, and increasingly well-defined genetic variants. As discussed in detail in a companion article in this series, studies in families and in large populations have identified multiple genetic loci, specific genes, and specific variants increasing susceptibility to AF. Since it is becoming increasingly inexpensive to obtain genotype data and indeed whole genome sequence data, the question then becomes to define whether using emerging new genetics knowledge can improve care for patients both before and after development of AF. Examples of improvements in care could include identifying patients at increased risk for AF (and thus deploying increased surveillance or even low-risk preventive therapies should these be available), identifying patient subsets in whom specific therapies are likely to be effective or ineffective or in whom the driving biology could motivate the development of new mechanism-based therapies or identifying an underlying susceptibility to comorbid cardiovascular disease. While current guidelines for the care of patients with AF do not recommend routine genetic testing, this rapidly increasing knowledge base suggests that testing may now or soon have a place in the management of select patients. The opportunity is to generate, validate, and deploy clinical predictors (including family history) of AF risk, to assess the utility of incorporating genomic variants into those predictors, and to identify and validate interventions such as wearable or implantable device-based monitoring ultimately to intervene in patients with AF before they present with catastrophic complications like heart failure or stroke.

Effectiveness and safety of atrial fibrillation ablation in females

BACKGROUND

Existing data on the effectiveness and safety of atrial fibrillation (AF) ablation in females are limited to studies of small sample size, lacking longer term follow-up or adjustment for potential confounders.

METHODS

A total of 6421 patients (2072 females) undergoing a first AF ablation procedure after enrollment in the Chinese Atrial Fibrillation Registry (China-AF) study between August 2011 and December 2017 were analyzed. We evaluated the effectiveness (recurrence of documented [symptomatic or not] atrial tachyarrhythmia (AT)) and the safety (incidence of procedure-related complications) of AF ablation in female patients compared to male patients. Sensitivity analyses based on routine data were also utilized to avoid potential sex differences in reporting of AF symptoms.

RESULTS

Females were about 5 years older than males at the time of ablation (mean age 63.4 ± 9.5 vs 58.3 ± 10.8, P < .0001). A higher proportion of female patients had paroxysmal AF (74.3% vs 56.7%, P < .0001), hypertension (69.7% vs 61.3%, P < .0001), and hyperlipidemia (57.2% vs 52.9%, P = .001). Female sex was found to be an independent risk factor of AT recurrence in multivariate analyses (HR = 1.26, 95% CI 1.15-1.38, P < .0001). These findings were confirmed in sensitivity analyses using only Holter data. Female sex was also associated with a higher risk of periprocedural complications after adjustment for baseline variables (OR = 1.41, 95% CI 1.03-1.94, P = .03).

CONCLUSIONS

Female sex is an independent risk factor of AT recurrence and periprocedural complications after AF ablation.

The 4q25 variant rs13143308T links risk of atrial fibrillation to defective calcium homoeostasis

AIMS

Single nucleotide polymorphisms on chromosome 4q25 have been associated with risk of atrial fibrillation (AF) but the exiguous knowledge of the mechanistic links between these risk variants and underlying electrophysiological alterations hampers their clinical utility. Here, we tested the hypothesis that 4q25 risk variants cause alterations in the intracellular calcium homoeostasis that predispose to spontaneous electrical activity.

METHODS AND RESULTS

Western blotting, confocal calcium imaging, and patch-clamp techniques were used to identify mechanisms linking the 4q25 risk variants rs2200733T and rs13143308T to defects in the calcium homoeostasis in human atrial myocytes. Our findings revealed that the rs13143308T variant was more frequent in patients with AF and that myocytes from carriers of this variant had a significantly higher density of calcium sparks (14.1 ± 4.5 vs. 3.1 ± 1.3 events/min, P = 0.02), frequency of transient inward currents (ITI) (1.33 ± 0.24 vs. 0.26 ± 0.09 events/min, P < 0.001) and incidence of spontaneous membrane depolarizations (1.22 ± 0.26 vs. 0.56 ± 0.17 events/min, P = 0.001) than myocytes from patients with the normal rs13143308G variant. These alterations were linked to higher sarcoplasmic reticulum calcium loading (10.2 ± 1.4 vs. 7.3 ± 0.5 amol/pF, P = 0.01), SERCA2 expression (1.37 ± 0.13 fold, P = 0.03), and RyR2 phosphorylation at ser2808 (0.67 ± 0.08 vs. 0.47 ± 0.03, P = 0.01) but not at ser2814 (0.28 ± 0.14 vs. 0.31 ± 0.14, P = 0.61) in patients carrying the rs13143308T risk variant. Furthermore, the presence of a risk variant or AF independently increased the ITI frequency and the increase in the ITI frequency observed in carriers of the risk variants was exacerbated in those with AF. By contrast, the presence of a risk variant did not affect the amplitude or properties of the L-type calcium current in patients with or without AF.

CONCLUSIONS

Here, we identify the 4q25 variant rs13143308T as a genetic risk marker for AF, specifically associated with excessive calcium release and spontaneous electrical activity linked to increased SERCA2 expression and RyR2 phosphorylation.

Ferrocene-labeled and purification-free electrochemical biosensor based on ligase chain reaction for ultrasensitive single nucleotide polymorphism detection

Single nucleotide polymorphisms (SNPs) are crucial during the early diagnosis of a given disease as well as in evaluating their response to certain drugs. Thus, this study sought the development of ferrocene (Fc)-labeled electrochemical biosensor for SNP detection. This proposed system involves the ligation of four short probes (e.g., A, B, A', and B', where B' is labeled with an Fc-tag) in the presence of target DNA via ligase chain reaction (LCR), resulting in the formation of Fc-tagged duplex AB-A'B' in 2ⁿ. Subsequently, immobilization of the Fc-tagged duplex AB-A'B' on a single-stranded DNA capture probe (SC-DNA)-carboxyl multi-wall carbon nanotube (MWCNT-COOH) modified glassy carbon electrode (GCE) was accomplished through hybridization. Owing to the specificity of hybridization, and the use of Fc as electrochemical probe for detection of duplex AB-A'B', such strategy realized directly analysis of LCR products without the need for purification. By taking advantage of the thermal stability and high-discrimination ability of HiFi Taq DNA ligase for single-base differences, the specificity of hybridization, the EGFR T790 M mutant DNA (MT-DNA) biosensor was developed to offer a low limit of detection (0.75 aM), a high discrimination of single-base mismatches [as low as 0.01% (molar fraction)], a wide linear range of more than 7 orders of magnitude (1 aM-10 pM), and the recovery rates (95.3%-107.8%) from human serum samples. Thus, the biosensor under development was found to be economical, highly-sensitive, and exceptionally selective for detection of SNPs, and as well as extending the versatile applications of LCR to offer great potential for diagnosis and individual clinical regimens.

Genetic Susceptibility for Atrial Fibrillation in Patients Undergoing Atrial Fibrillation Ablation

BACKGROUND

Ablation is a widely used therapy for atrial fibrillation (AF); however, arrhythmia recurrence and repeat procedures are common. Studies examining surrogate markers of genetic susceptibility to AF, such as family history and individual AF susceptibility alleles, suggest these may be associated with recurrence outcomes. Accordingly, the aim of this study was to test the association between AF genetic susceptibility and recurrence after ablation using a comprehensive polygenic risk score for AF.

METHODS

Ten centers from the AF Genetics Consortium identified patients who had undergone de novo AF ablation. AF genetic susceptibility was measured using a previously described polygenic risk score (N=929 single-nucleotide polymorphisms) and tested for an association with clinical characteristics and time-to-recurrence with a 3 month blanking period. Recurrence was defined as >30 seconds of AF, atrial flutter, or atrial tachycardia. Multivariable analysis adjusted for age, sex, height, body mass index, persistent AF, hypertension, coronary disease, left atrial size, left ventricular ejection fraction, and year of ablation.

RESULTS

Four thousand two hundred seventy-six patients were eligible for analysis of baseline characteristics and 3259 for recurrence outcomes. The overall arrhythmia recurrence rate between 3 and 12 months was 44% (1443/3259). Patients with higher AF genetic susceptibility were younger (P<0.001) and had fewer clinical risk factors for AF (P=0.001). Persistent AF (hazard ratio [HR], 1.39 [95% CI, 1.22-1.58]; P<0.001), left atrial size (per cm: HR, 1.32 [95% CI, 1.19-1.46]; P<0.001), and left ventricular ejection fraction (per 10%: HR, 0.88 [95% CI, 0.80-0.97]; P=0.008) were associated with increased risk of recurrence. In univariate analysis, higher AF genetic susceptibility trended towards a higher risk of recurrence (HR, 1.08 [95% CI, 0.99-1.18]; P=0.07), which became less significant in multivariable analysis (HR, 1.06 [95% CI, 0.98-1.15]; P=0.13).

CONCLUSIONS

Higher AF genetic susceptibility was associated with younger age and fewer clinical risk factors but not recurrence. Arrhythmia recurrence after AF ablation may represent a genetically different phenotype compared to AF susceptibility.

The Genetic Puzzle of Familial Atrial Fibrillation

Atrial fibrillation (AF) is the most common clinical tachyarrhythmia. In Europe, AF is expected to reach a prevalence of 18 million by 2060. This estimate will increase hospitalization for AF to 4 million and 120 million outpatient visits. Besides being an independent risk factor for mortality, AF is also associated with an increased risk of morbidities. Although there are many well-defined risk factors for developing AF, no identifiable risk factors or cardiac pathology is seen in up to 30% of the cases. The heritability of AF has been investigated in depth since the first report of familial atrial fibrillation (FAF) in 1936. Despite the limited value of animal models, the advances in molecular genetics enabled identification of many common and rare variants related to FAF. The importance of AF heritability originates from the high prevalence of lone AF and the lack of clear understanding of the underlying pathophysiology. A better understanding of FAF will facilitate early identification of people at high risk of developing FAF and subsequent development of more effective management options. In this review, we reviewed FAF epidemiological studies, identified common and rare variants, and discussed their clinical implications and contributions to developing new personalized therapeutic strategies.

Left atrial structure and function predictors of recurrent fibrillation after catheter ablation: a systematic review and meta-analysis

BACKGROUND

Catheter ablation (CA) has become a conventional treatment for atrial fibrillation (AF), but remains with high recurrence rate. The aim of this meta-analysis was to determine left atrial (LA) structure and function indices that predict recurrence of AF.

METHODS

We systematically searched PubMed-Medline, EMBASE, Scopus, Google Scholar and the Cochrane Central Registry, up to September 2017 in order to select clinical trials and observational studies which reported echocardiographic predictors of AF recurrence after CA. Eighty-five articles with a total of 16 126 patients were finally included.

RESULTS

The pooled analysis showed that after a follow-up period of 21 ± 12 months, patients with AF recurrence had larger LA diameter with weighted mean difference (WMD: 2·99 ([95% CI 2·50-3·47], P<0·001), larger LA volume index (LAVI) maximal and LAVI minimal (P<0·0001 for both), larger LA area (P<0·0001), lower LA strain (P<0·0001) and lower LA total emptying fraction (LA EF) (P<0·0001) compared with those without AF recurrence. The most powerful LA predictors (in accuracy order) of AF recurrence were as follows: LA strain <19% (OR: 3·1[95% CI, -1.3-10·4], P<0·0001), followed by LA diameter ≥50 mm (OR: 2·75, [95% CI 1·66-4·56,] P<0·0001), and LAVmax >150 ml (OR: 2·25, [95% CI, 1.1-5·6], P = 0·0002).

CONCLUSIONS

Based on this meta-analysis results, a dilated left atrium with diameter more than 50 mm and volume above 150 ml or myocardial strain below 19% reflect an unstable LA that is unlikely to hold sinus rhythm after catheter ablation for atrial fibrillation.

Genetics of Atrial Fibrillation

Background

Atrial fibrillation (AF) is a common arrhythmia seen in clinical practice. Occasionally, no common risk factors are present in patients with this arrhythmia. This suggests the potential underlying role of genetic factors associated with predisposition to developing AF.

Methods and Results

We conducted a comprehensive review of the literature through large online libraries, including PubMed. Many different potassium and sodium channel mutations have been discussed in their relation to AF. There have also been non–ion channel mutations that have been linked to AF. Genome‐wide association studies have helped in identifying potential links between single‐nucleotide polymorphisms and AF. Ancestry studies have also highlighted a role of genetics in AF. Blacks with a higher percentage of European ancestry are at higher risk of developing AF. The emerging field of ablatogenomics involves the use of genetic profiles in their relation to recurrence of AF after catheter ablation.

Conclusions

The evidence for the underlying role of genetics in AF continues to expand. Ultimately, the role of genetics in risk stratification of AF and its recurrence is of significant interest. No established risk scores that are useful in clinical practice are present to date.

Atrial Fibrillation Genetics Update: Toward Clinical Implementation

Atrial fibrillation (AF) is the most common heart rhythm disorder worldwide and may have serious cardiovascular health consequences. AF is associated with increased risk of stroke, dementia, heart failure, and death. There are several known robust, clinical risk predictors for AF, such as male sex, increasing age, and hypertension; however, during the last couple of decades, a substantive genetic component has also been established. Over the last 10 years, the discovery of novel AF-related genetic variants has accelerated, increasing our understanding of mechanisms behind AF. Current studies are focusing on mapping the polygenic structure of AF, improving risk prediction, therapeutic development, and patient-specific management. Nevertheless, it is still difficult for clinicians to interpret the role of genetics in AF prediction and management. Here, we provide an overview of relevant topics within the genetics of AF and attempt to provide some guidance on how to interpret genetic advances and their implementation into clinical decision-making.

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.

Genetic, Epigenetic and Transcription Factors in Atrial Fibrillation

Atrial fibrillation (AF) is one of the most common arrhythmia that occurs in patients with cardiovascular diseases. Congenital forms of AF are quite rare. Many studies have shown that genetic, epigenetic and transcription factors may play an important role in the development and the progression of AF. In our review, studies have been conducted on the identification of mutations in ionic and non-ionic channels, possibly associated with AF. These mutations were found only in isolated groups of patients with AF, and in general, monogenic forms of AF are a rare subtype of the disease. Genomic association studies have helped to identify potential links between single nucleotide polymorphisms and AF. The risk of AF in the general population is likely to be determined by the interaction between environmental factors and many alleles. In recent years, the emergence of a genome-wide associative studies has significantly expanded the understanding of the genetic basis for the inheritance of AF and has led to the emergence of new evidence of the important role of genetic factors in the development of AF, in the risk stratification of AF and the recurrence of AF. Epigenetic factors are also important in AF. Epigenetic therapy aimed at treating a disease through exposure to epigenome is currently under development. A newly emerged area of ablatogenomics includes the use of genetic profiles that allow assessing the likelihood of recurrence of AF after catheter ablation. The results of genetic studies in AF show that, in addition to their role in the appearance of congenital heart pathologies, transcription factors play an important role in the pathogenesis of AF.

Association between gene variants and the recurrence of atrial fibrillation: An updated meta-analysis

BACKGROUND

Studies showed the controversial results about the effect of common genetic polymorphisms on the atrial fibrillation (AF) recurrence. We performed the systematic review and meta-analysis to qualify the association between common genetic polymorphisms and AF recurrence.

METHODS

Articles were systematically retrieved PubMed, Web of Science, EMBASE, Wanfang, and CNKI database and 9 studies including 3204 patients were enrolled in our meta-analysis.

RESULTS

Results showed that the associations were significant under rs2200733 3 genetic models (TT vs CC: odds ratio [OR] [confidence interval [CI]] = 1.336 [1.061-1.683], P = .014; CT vs CC: OR [CI] = 0.759 [0.614-0.937], P = .01; TT vs CT + CC: OR [CI] = 2.308 [1.440-3.700], P = .001). The association was significant under rs10033464 genetic model (TT vs GG: OR [CI] = 1.517 [1.165-1.976], P = .002).

CONCLUSIONS

Rs13376333 on chromosome 1q21 (in KCNN3), rs7193343 and rs2106261 on chromosome 16q22 (in ZFHX3) were not associated with AF recurrence in our meta-analysis. In total, our meta-analysis found that rs2200733 and rs10033464 on chromosome 4q25 (near PITX2) were associated with the risk of AF recurrence.

Study on the relationship between telomere length changes and recurrence of atrial fibrillation after radiofrequency catheter ablation

INTRODUCTION

Advanced age is the foremost risk factor for atrial fibrillation (AF). Telomere length is a surrogate for biological aging, but the association between shortened leukocyte telomere length (LTL) and recurrence of AF (RAF) after ablation remains inconclusive.

METHODS

In this prospective analysis, 282 patients underwent an initial catheter ablation for paroxysmal or persistent AF. The association between RAF and LTL was analyzed by univariate and multivariate Cox regression, as well as time-dependent receiver operating characteristic (ROC) analysis and Kaplan-Meier analysis.

RESULTS

After a mean follow-up of 14.20 ± 5.04 months, RAF was documented in 78 of the 277 patients who completed the study (28.16%). In Cox proportional hazards models, LTL, age, diagnosis to ablation time (DTAT), N-terminal pronatriuretic peptide, and CHA2DS2-VASc score were significantly associated with RAF. After multivariable adjustment, LTL and DTAT were predicted as independent risk factors for RAF with hazard ratio (HR) of 3.17 (95% confidence interval [CI]: 1.23-8.15, P = 0.017) and 1.43 (95% CI: 1.10-1.86, P = 0.007), respectively. In addition, ROC analysis indicated the potential diagnostic value of LTL with an area under the curve of 0.64 (P < 0.001; sensitivity = 60.3%, specificity = 57.8%), and an optimum cut-off value of 1.040. LTL less than or equal to 1.040 was defined as shortened LTL, while LTL greater than 1.040 nonshortened LTL. Kaplan-Meier analysis showed RAF rate curve was separated significantly between two groups (21.2% vs 35.9%, log-rank test result P = 0.007). Patients with shortened LTL might have a higher risk for RAF with HR = 1.84 (P = 0.008).

CONCLUSIONS

Shortened LTL is an independent risk factor for AF recurrence. Shortened LTL could be a potential biomarker in predicting RAF after ablation.

Catheter Ablation of Long-standing Persistent Atrial Fibrillation: a Reckless Challenge or a Way to Real Cure?

Long-standing persistent atrial fibrillation (L-PeAF) is a category in which rhythm control is attempted while atrial fibrillation (AF) is maintained for more than 1 year. Because AF is a progressive disease and L-PeAF accompanies significant electrical and structural remodeling of atria, it is difficult to restore and maintain sinus rhythm in patients with L-PeAF. Nonetheless, the rhythm outcome is being increasingly improved by the development of sophisticated mapping devices, highly efficient catheters, and evidence-based ablation strategies, and the rational choice of patient selection criteria. This review discusses the evolution of the rhythm control outcome of L-PeAF and its future direction of development.

Genetics of Atrial Fibrilation: In Search of Novel Therapeutic Targets

Atrial fibrillation (AF) is the most frequent arrhythmogenic disease in humans, ranging from 2% in the general population and rising up to 10-12% in 80+ years. Genetic analyses of AF familiar cases have identified a series of point mutations in distinct ion channels, supporting a causative link. However, these genetic defects only explain a minority of AF patients. Genomewide association studies identified single nucleotide polymorphisms (SNPs), close to PITX2 on 4q25 chromosome, that are highly associated to AF. Subsequent GWAS studies have identified several new loci, involving additional transcription and growth factors. Furthermore, these risk 4q25 SNPs serve as surrogate biomarkers to identify AF recurrence in distinct surgical and pharmacological interventions. Experimental studies have demonstrated an intricate signalling pathway supporting a key role of the homeobox transcription factor PITX2 as a transcriptional regulator. Furthermore, cardiovascular risk factors such as hyperthyroidism, hypertension and redox homeostasis have been identified to modulate PITX2 driven gene regulatory networks. We provide herein a state-of-the-art review of the genetic bases of atrial fibrillation, our current understanding of the genetic regulatory networks involved in AF and its plausible usage for searching novel therapeutic targets.

A Genetic Risk Score for Atrial Fibrillation Predicts the Response to Catheter Ablation

Background and Objectives

The association of susceptibility loci for atrial fibrillation (AF) with AF recurrence after ablation has been reported, although with controversial results. In this prospective cohort analysis, we aimed to investigate whether a genetic risk score (GRS) can predict the rhythm outcomes after catheter ablation of AF.

Methods

We determined the association between 20 AF-susceptible single nucleotide polymorphisms (SNPs) and AF recurrence after catheter ablation in 746 patients (74% males; age, 59±11 years; 56% paroxysmal AF). A GRS was calculated by summing the unweighted numbers of risk alleles of selected SNPs. A Cox proportional hazard model was used to identify the association between the GRS and risk of AF recurrence after catheter ablation.

Results

AF recurrences after catheter ablation occurred in 168 (22.5%) subjects with a median follow-up of 23 months. The GRS was calculated using 5 SNPs (rs1448818, rs2200733, rs6843082, rs6838973 at chromosome 4q25 [PITX2] and rs2106261 at chromosome 16q22 [ZFHX3]), which showed modest associations with AF recurrence. The GRS was significantly associated with AF recurrence (hazard ratio [HR] per each score, 1.13; 95% confidence interval [CI], 1.03–1.24). Patients with intermediate (GRS 4–6) and high risks (GRS 7–10) showed HRs of 2.00 (95% CI, 0.99–4.04) and 2.66 (95% CI, 1.32–5.37), respectively, compared to patients with low risk (GRS 0–3).

Conclusions

Our novel GRS using 5 AF-susceptible SNPs was strongly associated with AF recurrence after catheter ablation in Korean population, beyond clinical risk factors. Further efforts are warranted to construct a generalizable, robust genetic prediction model which can guide the optimal treatment strategies.