Risk Factors and Genetics of Atrial Fibrillation

The role of galectin-3 in patients with permanent and paroxysmal Atrial Fibrillation and echocardiographic parameters of left atrial fibrosis

BACKGROUND

Biochemical markers and imaging tests have been used with the aim of stratifying the risk and detecting atrial fibrosis. Speckle-tracking echocardiography (STE) is used for the detection of atrial fibrosis and Gal-3 provides an important prognostic value. The objective of the study was to assess the association between atrial fibrosis markers and serum levels, genetic polymorphisms and genic expression of galectin-3.

METHODS

206 patients with permanent AF and 70 patients with paroxysmal AF were included in the study. Real time PCR (TaqMan) system was used to study SNPs rs4652 and 4644 of the gene LGALS3. Serum levels of Gal-3 were determined by ELISA and STE was performed to assess fibrosis.

RESULTS

Mean age of individuals with permanent AF was 66.56 ± 12 years. As for the echocardiography results, those patients showed an decrease in the following parameters peak atrial longitudinal strain (PALS) (p = 0.002) when compared to the same parameters from the paroxysmal AF group of patients. There was a correlation between serum levels of Gal-3 and PALS in the group of patients with permanent AF; the lower the levels of gal-3, the lower the LA strain (r = 0.24; p = 0.01).

CONCLUSIONS

Echocardiographic findings showed association with the groups, and with serum levels of Gal-3 in patients with permanent AF. The distribution of allelic and genotypic frequencies, and of the haplotypes of polymorphism LGALS3 rs4652 and rs4644 did not present statistical variation, which suggests that those SNPs are not associated with the AF clinical forms (permanent and paroxysmal).

Atrial Fibrillation and the Risk of Early‐Onset Dementia: A Systematic Review and Meta‐Analysis

Background

Recent studies have identified an increased risk of dementia in patients with atrial fibrillation (AF). However, both AF and dementia usually manifest late in life. Few studies have investigated this association in adults with early‐onset dementia. The aim of this study was to investigate the relationship between AF and early‐onset dementia.

Methods and Results

We searched the PubMed/MEDLINE, Embase, and Scopus databases through April 15, 2022, for studies reporting on the association between AF and dementia in adults aged <70 years, without language restrictions. Two reviewers independently performed the study selection, assessed the risk of bias, and extracted the study data. We performed a meta‐analysis of early‐onset dementia risk according to occurrence of AF using a random‐effects model. We retrieved and screened 1006 potentially eligible studies. We examined the full text of 33 studies and selected the 6 studies that met our inclusion criteria. The pooled analysis of their results showed an increased risk of developing dementia in individuals with AF, with a summary relative risk of 1.50 (95% CI, 1.00–2.26) in patients aged <70 years, and 1.06 (95% CI, 0.55–2.06) in those aged <65 years.

Conclusions

In this systematic review and meta‐analysis, AF was a risk factor for dementia in adults aged <70 years, with an indication of a slight and statistically imprecise excess risk already at ages <65 years. Further research is needed to assess which characteristics of the arrhythmia and which mechanisms play a role in this relationship.

Differential Presentations of Arterial Thromboembolic Events Between Venous Thromboembolism and Atrial Fibrillation Patients

Objective: Atrial fibrillation (AF) and venous thromboembolism (VTE) share several risk factors related to arterial thromboembolism. No study has reported the differential contribution to arterial thromboembolic events and mortality between these two conditions in the same population. We therefore assessed the differential arterial thromboembolic events between AF and VTE. Methods: We included AF and VTE national cohorts derived from Taiwan National Health Insurance Research Database between 2001 and 2013. The eligible population was 314,861 patients in the AF cohort and 41,102 patients in the VTE cohort. The primary outcome was arterial thromboembolic events, including ischemic stroke, extracranial arterial thromboembolism (ECATE) and myocardial infarction (MI). Secondary outcomes were all-cause mortality and cardiovascular death. Results: After a 1:1 propensity matching, 32,688 patients in either group were analyzed. The risk of arterial thromboembolic events was lower in the VTE cohort than that in the AF cohort (subdistribution hazard ratio [SHR], 0.60; 95% confidence interval [CI], 0.57-0.62). The risk of ischemic stroke (SHR, 0.44; 95% CI, 0.42-0.46) and MI (SHR, 0.80; 95% CI, 0.72-0.89) were lower in the VTE cohort, while the risk of ECATE (SHR, 1.23; 95% CI, 1.14-1.33; particularly lower extremities) was higher in the VTE cohort. All-cause mortality rate was higher in the VTE cohort (HR, 1.18; 95% CI, 1.15-1.21) while the risk of cardiovascular death was lower in the VTE cohort (HR, 0.96; 95% CI, 0.93-0.995). Conclusions: Patients with AF had higher risks of arterial thromboembolic events compared to patients with VTE, despite having risk factors in common. The VTE cohort had higher risks of all-cause mortality and ECATE, particularly lower extremity events, compared to AF patients. The differential manifestations of thromboembolism sequelae and mortality between AF and VTE patients merit further investigation.

Generation of IBMS-iPSC-015, -016, -017 human induced pluripotent stem cells (IBMSi013-A, IBMSi014-A, and IBMSi015-A) derived from patients with atrial fibrillation

Atrial fibrillation is the most common heart disease in the world, with around 35 million patients in 2020. Here we reported the generation of IBMS-iPSC-015-06, IBMS-iPSC-016-06, and IBMS-iPSC-017-02 as human induced pluripotent stem cell (iPSC) lines from patients' peripheral blood mononuclear cells (PBMCs) with atrial fibrillation. The cell lines expressed properties of pluripotent stem cells, including pluripotent markers and the ability to differentiate into three germ layers. These cell lines served as suitable models for studying alternative therapies of atrial fibrillation.

Galectin-3 and risk of atrial fibrillation: A systematic review and meta-analysis

BACKGROUND

Galectin-3 is an inflammatory marker that is raised in myocardial fibrosis and inflammation. Recent studies have explored its role in predicting atrial fibrillation (AF) outcomes. The aim of this systematic review and meta-analysis is to examine the association between serum concentration of galectin-3 and AF.

METHODS

PubMed, EMBASE, and the Cochrane Database were searched. A total of 280 studies were identified, of which 28 studies involving 10 830 patients were included in our meta-analysis.

RESULTS

Galectin-3 is present at higher concentrations in patients with AF than those in sinus rhythm (mean difference [MD] = -0.68 ng/mL, 95% CI: -0.92, -0.44, Z = 5.61, P < .00001). Galectin-3 levels were significantly higher in the persistent AF than in the paroxysmal AF group (MD = -0.94 ng/mL, 95% CI: -1.85, -0.03, Z = 2.04, P = .04). Higher galectin-3 levels were associated with a 45% increase in the odds of developing AF (odds ratio [OR] = 1.45, 95% CI: 1.15, 1.83, Z = 3.11, P = .002) and risk of AF recurrence (hazard ratio [HR] =1.17, 95% CI: 1.06, 1.29, Z = 3.12, P = .002).

CONCLUSIONS

Our meta-analysis found that galectin-3 is significantly higher in patients with persistent AF than in those with paroxysmal AF, and can predict both AF development and recurrence after treatment.

Correlation between HCN4 gene polymorphisms and lone atrial fibrillation risk

Background and objective: Atrial electrical remodelling (AER) was significantly associated with atrial fibrillation (AF) development. Polymorphisms in hyperpolarization activated cyclic nucleotide gated potassium channel 4 (HCN4) gene might be correlated with AER. In the present study, we explored the association of HCN4 polymorphisms (rs498005 and rs7164883) with lone AF risk in a Chinese Han population. Methods: In this case-control study, the Sanger sequencing method was utilized to genotype the HCN4 polymorphisms. Relative risk of AF was assessed by the χ² test, and presented by odds ratios (ORs) and corresponding 95% confidence intervals (CIs). Logistic regression analysis was performed for multivariate analysis. The effects of HCN4 polymorphisms on AF clinical features were analyzed by the Mann-Whitney U test and adjusted by the Bonferroni method. Results: C allele of rs498005 was significantly correlated with increased risk of AF (OR = 1.412, 95%CI = 1.012-1.970), and the association still exited after adjustment by age, gender, the status of smoking and drinking, histories of diabetes, hyperlipidaemia and myocardial infarction (adjusted OR = 1.473, 95%CI = 1.043-2.081). G allele of rs7164883 SNP was marginally associated with enhanced AF risk after adjustment by the above clinical parameters (adjusted OR = 1.742, 95%CI = 1.019-2.980). Atrial late potential (ALP), including TP (P wave duration after filtering) and LP₂₀ (the amplitude of superimposed potential in the final 20 ms of P wave) were significantly associated with rs498005 genotype (p < .001). Conclusion: HCN4 rs498005 and rs7164883 polymorphisms are significantly associated with AF risk.

Socioeconomic factors and mortality in patients with atrial fibrillation-a cohort study in Swedish primary care

Background

Preventing ischaemic stroke attracts significant focus in atrial fibrillation (AF) cases. Less is known on the association between socioeconomic factors and mortality and cardiovascular outcomes in patients with AF.

Methods

Our study population included adults (n=12 283) ≥45 years diagnosed with AF at 75 primary care centres in Sweden 2001-07. Cox regression was used to calculate hazard ratios (HRs) with 95% confidence intervals (CIs) for the association between the exposures educational level, marital status, neighbourhood socioeconomic status and the outcomes all-cause mortality, after adjustment for age, and comorbid cardiovascular conditions.

Results

During a mean of 5.8 years (SD 2.4) of follow-up, 3954 (32.3%) patients had died; 1971 were women (35.0%) and 1983 were men (29.8%). Higher educational level was associated with a reduced mortality in fully adjusted models: HR 0.85 (95% CI 0.77-0.96) for secondary school in men, HR 0.73 (95% CI 0.60-0.88) for college/university in women, and HR 0.82 (95% CI 0.71-0.94) for college/university in men, compared to primary school. Unmarried men and divorced men had an increased risk of death, compared with married men: HR 1.25 (95% CI 1.05-1.50), and HR 1.23 (95% CI 1.07-1.42), respectively. College/university education level was also associated with lower risk of myocardial infarction in men and women, and lower risk of congestive heart failure in women.

Conclusion

More attention could be paid to individuals of lower levels of formal education, and unmarried men, in order to provide timely management for AF and prevent its debilitating complications.

Atrial fibrillation in immigrants under the age of 45 y in Sweden

AIM

To study association between country of birth and risk of first-onset atrial fibrillation (AF) in first- and second-generation immigrants to Sweden under 45 y of age.

METHODS

The study population included all individuals (n = 3 248 457) under the age of 45 y in Sweden, including immigrants (n = 722 249). AF was defined as first registered diagnosis in the National Patient Register. Association between country of birth and risk of AF was assessed by Cox regression, calculating HRs and 95% CIs, using Swedish-born individuals as referents. All models were stratified by sex, and in different models were adjusted for age, area of residence in Sweden, educational level, marital status, neighbourhood socioeconomic status and co-morbidity(ies).

RESULTS

A higher fully adjusted HR of incident AF was found in the total sample of first-generation immigrants, 1.44 (95% CI 1.35 to 1.54), in males born in Denmark, Lebanon and Iraq, and in females born in Turkey and Iraq. Lower HRs were found in male and female immigrants from Latin America and Iran, and female immigrants from Finland. Among second-generation immigrants, the fully adjusted HR was significantly lower, 0.70 (95% CI 0.58 to 0.83).

CONCLUSIONS

Clinicians may show a greater awareness of AF in some groups of younger immigrants to enable early diagnosis.

Clinical outcomes of solitary atrial flutter patients using anticoagulation therapy: a national cohort study

AIMS

Anticoagulation therapy is indicated to prevent stroke in atrial flutter (AFL) and atrial fibrillation (AF) patients. However, the outcomes of solitary AFL patients may differ from those with AFL who develop AF during follow-up. This study aimed to investigate the differences in clinical outcomes: (i) among patients with solitary AFL, AF, and AFL developing AF thereafter and (ii) between solitary AFL patients with vs. without anticoagulation therapy.

METHODS AND RESULTS

This nationwide cohort study enrolled patients with solitary AFL, solitary AF, and AFL developing AF from a 12 years National Health Insurance Research Database in Taiwan. There were 230 367 patients without anticoagulation therapy in the solitary AF cohort, 8064 in the solitary AFL cohort, and 4495 in the AFL with AF cohort. The AFL with AF and solitary AF cohorts had higher incidences of ischaemic stroke and major bleeding than the solitary AFL cohort. Solitary AFL patients with anticoagulation therapy had a lower ischaemic stroke rate than those without (P < 0.05) at the level of a CHA2DS2-VASc score ≥3. Solitary AFL patients with anticoagulation therapy had a higher intracranial haemorrhage rate than those without (P < 0.05) at the level of a CHA2DS2-VASc score ≤3. Net clinical outcomes including ischaemic stroke, systemic embolization, and major bleeding favoured anticoagulation use in solitary AFL patients with a CHA2DS2-VASc score ≥4.

CONCLUSION

Solitary AFL patients without anticoagulation therapy had better clinical outcomes than AFL patients developing AF in this study. Anticoagulation therapy may offer the best net clinical outcome for solitary AFL patients with a CHA2DS2-VASc score ≥4.

Comparison of Clinical Outcomes Among Patients With Atrial Fibrillation or Atrial Flutter Stratified by CHA2DS2-VASc Score

Importance

Current guidelines support treating atrial fibrillation (AF) and atrial flutter (AFL) as equivalent risk factors for ischemic stroke stratified by CHA2DS2-VASc scores, recommending anticoagulation therapy for patients with a CHA2DS2-VASc score of 2 or higher, but some studies found differences in clinical outcomes.

Objective

To investigate differences in clinical outcomes among AF, AFL, and matched control cohorts.

Design, Setting, and Participants

This nationwide cohort study analyzed data from the Taiwan National Health Insurance Research Database from January 1, 2001, through December 31, 2012. Follow-up and data analysis ended December 31, 2012. A total of 219 416 age- and sex-matched individuals participated in the study. Clinical outcomes were compared after stratification by CHA2DS2-VASc score (possible score range, 0-9; higher scores indicate greater risk of ischemic stroke).

Main Outcomes and Measures

Ischemic stroke, heart failure hospitalization, and all-cause mortality among the AF, AFL, and matched control cohorts were analyzed using Cox proportional hazards regression.

Results

This study comprised 188 811 patients in the AF cohort (mean [SD] age, 73.8 [13.4] years; 104 703 [55.5%] male), 6121 patients in the AFL cohort (mean [SD] age, 67.7 [15.8] years; 3735 [61.0%] male), and 24 484 patients in the matched control cohort (mean [SD] age, 67.3 [15.6] years; 14 940 [61.0%] male). The patients with AF were older, were more predominantly female, and had higher CHA2DS2-VASc scores than the patients with AFL and the control participants. After stratification by CHA2DS2-VASc score, the incidence densities (IDs; events per 100 person-years) of ischemic stroke (AF cohort: ID, 3.08; 95% CI, 3.03-3.13; AFL cohort: ID, 1.45; 95% CI, 1.28-1.62; controls: ID, 0.97; 95% CI, 0.92-1.03), heart failure hospitalization (AF cohort: ID, 3.39; 95% CI, 3.34-3.44; AFL cohort: ID, 1.57; 95% CI, 1.39-1.74; controls: ID, 0.32; 95% CI, 0.29-0.35), and all-cause mortality (AF cohort: ID, 17.8; 95% CI, 17.7-17.9; AFL cohort: ID, 13.9; 95% CI, 13.4-14.4; controls: ID, 4.2; 95% CI, 4.1-4.4) were significantly higher in the AF cohort than in the matched control cohort. For the AFL cohort vs the matched control cohort, the incidences of heart failure hospitalization and all-cause mortality were significantly higher across all levels, but the incidence of ischemic stroke was only significantly higher at CHA2DS2-VASc scores of 5 to 9. For the AF cohort vs the AFL cohort, the incidences of ischemic stroke and heart failure hospitalization were significantly higher at a CHA2DS2-VASc score of 1 or higher, but the incidence of all-cause mortality was significantly higher only at CHA2DS2-VASc scores of 1 to 3.

Conclusions and Relevance

This study found different clinical outcomes between patients with AFL and AF and those without AF and AFL. The current recommended level of the CHA2DS2-VASc score in preventing ischemic stroke in patients with AFL should be reevaluated.

Mortality in patients with atrial fibrillation and common co-morbidities - a cohort study in primary care

OBJECTIVE

To study the association between cardiovascular co-morbidities and mortality risk in primary care patients with atrial fibrillation.

METHODS

The study population included all adults (n = 12,283) ≥ 45 years diagnosed with AF at 75 primary care centres in Sweden between 2001 and 2007. The outcome was mortality (until 2010) and data were explored for co-morbidities using Cox regression with hazard ratios (HRs). Analyses were performed stratified by sex and by age-group (45-64, 65-74 and ≥75 years of age) with adjustment for age, socio-economic factors and relevant co-morbidities.

RESULTS

During a mean of 5.8 years (standard deviation 2.4) of follow-up, 3954 (32%) patients died (1971 (35%) women, and 1983 (30%) men). High HRs were found for congestive heart disease (CHF) and cerebrovascular diseases for all age-groups among men and women (except for the 45-64 year old women); for coronary heart disease among the oldest men; for diabetes among the 65-74 year old men and the 45-64 year old women. Low HRs were found for hypertension among women ≥75 years of age.

CONCLUSIONS

In this clinical setting, CHF and cerebrovascular diseases were consistently associated with mortality in all age-groups. The possible protective effect by hypertension among elderly women should be interpreted with caution. KEY MESSAGES We found congestive heart failure and cerebrovascular diseases to be consistently associated with mortality in both women and men. We found hypertension to be associated with lower mortality risk among women ≥75 years of age, although this finding must be interpreted with caution. Depression was found to be associated with increased mortality risk among men and women aged 65-74 years of age.

Genomic Variants in NEURL, GJA1 and CUX2 Significantly Increase Genetic Susceptibility to Atrial Fibrillation

Atrial fibrillation (AF) is the most common arrhythmia. In 2014, two new meta-GWAS identified 5 AF loci, including the NEURL locus, GJA1 locus, CAND2 locus, and TBX5 locus in the European ancestry populations and the NEURL locus and CUX2 locus in a Japanese population. The TBX5 locus for AF was reported by us in 2013 in the Chinese population. Here we assessed the association between AF and SNPs in the NEURL, GJA1, CAND2 and CUX2 loci in the Chinese Han population. We carried out a large case-control association study with 1,164 AF patients and 1,460 controls. Significant allelic and genotypic associations were identified between NEURL variant rs6584555 and GJA1 variant rs13216675 and AF. Significant genotypic association was found between CUX2 SNP rs6490029 and AF. No association was found between CAND2 variant rs4642101 and AF, which may be due to an insufficient power of the sample size for rs4642101. Together with our previous findings, seven of fifteen AF loci (<50%) identified by GWAS in the European ancestry populations conferred susceptibility to AF in the Chinese population, and explained approximately 14.5% of AF heritability. On the other hand, two AF loci identified in the Japanese population were both replicated in the Chinese population.

Sleep, sleep apnea and atrial fibrillation: Questions and answers

Sleep apnea (SA) is a common sleep disorder increasingly recognized as a risk for cardiovascular disease. Atrial fibrillation (AF) is the most common cardiac arrhythmia and is associated with significant morbidity and mortality. An increasing number of investigations in recent years have linked SA to AF. In this review, we aim to provide a critical overview of the existing evidence in a question and answer format by addressing the following: What is the prevalent association between the two conditions (separating nocturnally detected AF episodes from AF as a prevalent condition)? Is SA a risk factor for incident AF? Is SA a risk factor for recurrence of AF following cardioversion/catheter-based ablation? What is the association between SA and AF in patients with heart failure? Are there signature electrocardiographic markers of AF found in patients with SA? Are there electrophysiology-based studies supporting the link between SA and AF? What other sleep characteristics (beyond SA) are found in patients with AF? What is the impact of SA treatment on AF? What is the effect of AF treatment on sleep? Finally, we address unsolved questions and suggest future directions to enhance our understanding of the AF-SA relationship.

Impact of GGCX polymorphisms on warfarin dose requirements in atrial fibrillation patients

Background/aim: Warfarin is a common anticoagulant with large interindividual differences and a narrow therapeutic range. The polymorphisms of gamma-glutamyl carboxylase (GGCX) are important genetic factors for warfarin dose requirements. Materials and methods: Polymerase chain reaction and direct sequencing methods were used to detect the GGCX rs699664 genotype in 215 atrial fibrillation (AF) patients with warfarin administration. The effects on warfarin dose by different genotypes were analyzed. A warfarin dosing algorithm was developed based on age, height, CYP2C9, VKORC1, and GGCX genotype. Results: In 215 AF patients, there were 104 cases of wild-type GG genotype (48.4%), 92 cases of GA genotype (42.8%), and 19 cases of AA genotype (8.8%). Patients with the GGCX rs699664 A allele (GA or AA genotypes) needed higher warfarin doses than those with the GG genotype (P < 0.05). A warfarin dosing algorithm showed that age, height, CYP2C9, VKORC1, and GGCX genotype were the best variables for estimating warfarin dose (R2 = 41.2%). Another independent cohort of 60 AF patients showed a significant linear correlation between predicted warfarin maintenance dose and actual dose (R = 0.660, P < 0.01). Conclusion: AF patients with the GA and AA genotypes in GGCX rs699664 required significantly higher warfarin doses. GGCX rs699664 is a potential predictor for the warfarin dose of AF patients.

Different Implications of Heart Failure, Ischemic Stroke, and Mortality Between Nonvalvular Atrial Fibrillation and Atrial Flutter-a View From a National Cohort Study

BACKGROUND

Atrial flutter (AFL) has been identified to be equivalent to atrial fibrillation (AF) in terms of preventing ischemic stroke, although differences exist in atrial rate, substrate, and electrophysiological mechanisms. This study aimed to investigate differences in clinical outcomes between nonvalvular AF and AFL.

METHODS AND RESULTS

AF and AFL patients without any prescribed anticoagulation were enrolled from a 13-year national cohort database. Under series exclusion criteria, ischemic stroke, heart failure hospitalization, and all-cause mortality were compared between the groups in real-world conditions and after propensity score matching. We identified 175 420 patients in the AF cohort and 6239 patients in the AFL cohort, and the prevalence of most comorbidities and frequency of medications were significantly higher in the AF group than the AFL group. In the real-world setting the AF patients had higher incidence rates of ischemic stroke, heart failure hospitalization, and all-cause mortality than the AFL patients (all P<0.001). After propensity score matching, the incidence rate of ischemic stroke in the AF cohort was 1.63-fold higher than in the AFL cohort (P<0.001), the incidence rate of heart failure hospitalization in the AF cohort was 1.70-fold higher than in the AFL cohort (P<0.001), and the incidence rate of all-cause mortality in the AF cohort was 1.08-fold higher than in the AFL cohort (P=0.002).

CONCLUSIONS

There were differences between AF and AFL in comorbidities and prognosis with regard to ischemic stroke, heart failure hospitalization, and all-cause mortality.

Atrial fibrillation in immigrant groups: a cohort study of all adults 45 years of age and older in Sweden

To study the association between country of birth and incident atrial fibrillation (AF) in several immigrant groups in Sweden. The study population included all adults (n = 3,226,752) aged 45 years and older in Sweden. AF was defined as having at least one registered diagnosis of AF in the National Patient Register. The incidence of AF in different immigrant groups, using Swedish-born as referents, was assessed by Cox regression, expressed in hazard ratios (HRs) and 95% confidence intervals (CI). All models were stratified by sex and adjusted for age, geographical residence in Sweden, educational level, marital status, and neighbourhood socioeconomic status. Compared to their Swedish-born counterparts, higher incidence of AF [HR (95% CI)] was observed among men from Bosnia 1.74 (1.56–1.94) and Latvia 1.29 (1.09–1.54), and among women from Iraq 1.96 (1.67–2.31), Bosnia 1.88 (1.61–1.94), Finland 1.14 (1.11–1.17), Estonia 1.14 (1.05–1.24) and Germany 1.08 (1.03–1.14). Lower incidence of AF was noted among men (HRs ≤ 0.60) from Iceland, Southern Europe (especially Greece, Italy and Spain), Latin America (especially Chile), Africa, Asia (including Iraq, Turkey, Lebanon and Iran), and among women from Nordic countries (except Finland), Southern Europe, Western Europe (except Germany), Africa, North America, Latin America, Iran, Lebanon and other Asian countries (except Turkey and Iraq). In conclusion, we observed substantial differences in incidence of AF between immigrant groups and the Swedish-born population. A greater awareness of the increased risk of AF development in some immigrant groups may enable for a timely diagnosis, treatment and prevention of its debilitating complications, such as stroke.

Update about atrial fibrillation genetics

PURPOSE OF REVIEW

Atrial fibrillation is an important cause of morbidity in the aging population. The mechanisms responsible for the triggering and maintenance of the chaotic atrial rhythm are still poorly understood. In this review, we will focus on the genetic aspects of atrial fibrillation, to understand causality, with special emphasis on recent studies published in the field.

RECENT FINDINGS

Diseases such as hypertension, valvular heart disease, and heart failure may induce atrial fibrillation, which increases the risk of stroke and sudden cardiac death. Clinical studies published in these last two decades have provided evidence that genetics play a key role in atrial fibrillation. Thus, a family history of the disease has been identified in up to 30% of clinically diagnosed patients. In those genotyped families, most carry rare genetic variants in genes associated with ionic channels, calcium handling protein, or predisposing to fibrosis, conduction system disease, and inflammatory processes.

SUMMARY

Currently, atrial fibrillation is the most common sustained arrhythmia in clinical practice. The pathophysiological mechanisms of atrial fibrillation are complex. A better understanding of the molecular basis will help improve both current risk stratification and clinical management.

Interleukin-37 elevation in patients with atrial fibrillation

BACKGROUND

Inflammation is closely related to atrial fibrillation (AF) pathogenesis, and interleukin-37 (IL-37) represents a new member of the anti-inflammatory cytokines.

HYPOTHESIS

IL-37 might play an important role in AF development and act as a potential risk factor for AF diagnosis.

METHODS

The mRNA level of IL-37 in peripheral blood mononuclear cells (PBMCs) and serum IL-37 levels in AF patients and healthy controls were measured by real-time polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). PBMCs from AF patients were stimulated with recombinant IL-37. Levels of pro-inflammatory cytokines IL-6 and C-reactive protein were determined by RT-PCR and ELISA.

RESULTS

IL-37 mRNAs and serum protein levels were higher in patients with AF or lone AF compared with healthy controls. Patients with paroxysmal AF or persistent AF showed higher IL-37 mRNAs and serum protein levels compared with those with permanent AF as well as healthy controls. In vitro, IL-37 inhibited the production of IL-6 and C-reactive protein in PBMCs of patients with AF.

CONCLUSIONS

IL-37 is elevated in AF patients and its expression is closely associated with AF subgroups. Thus, IL-37 may provide a novel research target for the pathogenesis and therapy of AF. This study is the first to document elevated IL-37 in AF patients.