Aldosterone synthase gene polymorphism as a determinant of atrial fibrillation in patients with heart failure

Recent progress in unraveling cardiovascular complications associated with primary aldosteronism: a succinct review

This comprehensive review offers a thorough exploration of recent advancements in our understanding of the intricate cardiovascular complications associated with Primary Aldosteronism (PA). PA encompasses a spectrum of conditions characterized by hypertension and excessive production of aldosterone operating independently of the renin-angiotensin system. Given its association with an elevated risk of cardiovascular and cerebrovascular complications, as well as a higher incidence of metabolic syndrome in comparison to individuals with essential hypertension (EH), an accurate diagnosis of PA is of paramount importance. This review delves into the intricate interplay between PA and cardiovascular health and focuses on the key pathophysiological mechanisms contributing to adverse cardiac outcomes. The impact of different treatment modalities on cardiovascular health is also examined, offering insights into potential therapeutic approaches. By highlighting the significance of recognizing PA as a significant contributor to cardiovascular morbidity, this review emphasizes the need for improved screening, early diagnosis, and tailored management strategies to both enhance patient care and mitigate the burden of cardiovascular diseases. The findings presented herein underscore the growing importance of PA in the context of cardiovascular medicine and emphasize the potential for translating these insights into targeted interventions to improve patient outcomes.

Contribution of the ACE (rs1799752) and CYP11B2 (rs1799998) Gene Polymorphisms to Atrial Fibrillation in the Tunisian Population

BACKGROUND

This study investigated the association of angiotensin-converting enzyme (ACE I/D) and aldosterone synthase (CYP11B2-344C/T) gene polymorphisms in the renin-angiotensin-aldosterone system (RAAS) with atrial fibrillation (AF) in the Tunisian population.

MATERIALS AND METHODS

The study population included 120 patients with AF and 123 age-matched controls. Genotyping of the I/D polymorphism in the ACE gene and the -344C/T polymorphism in the CYP11B2 gene was performed by polymerase chain reaction (PCR) and PCR-RFLP methods, respectively.

RESULTS

The genotype distribution of the ACE I/D and CYP11B2-344C/T polymorphisms was significantly different between AF patients and control participants (p < 0.01 and p < 0.006 respectively). In addition, ACE I/D increased the risk of AF significantly by 3.41-fold for the DD genotype (OR = 3.41; 95% CI [1.39-8.34]; p < 0.007), and after adjusting for confounding factors (age, diabetes, hypertension, and dyslipidemia), the risk was higher (OR = 5.71; 95% CI [1.48-21.98]; p < 0.01). Likewise, the CYP11B2-344C/T polymorphism increased the incidence of AF for the TT genotype (OR = 3.66; 95% CI [1.62-8.27]; p < 0.002) and the CT genotype (OR = 2.68; 95% CI [1.22-5.86]; p < 0.01). After adjusting for confounding factors (age, diabetes, hypertension and dyslipidemia), the risk remained higher for the TT genotype (OR = 3.58; 95% CI [1.08-11.77]; p < 0.03). Furthermore, the haplotype-based association of the ACE I/D and CYP11B2-344C/T polymorphisms showed that the D-T haplotype increased the risk for AF.

CONCLUSION

Our study suggests a significant association of the ACE (I/D) and CYP11B2-344C/T polymorphisms with AF in the Tunisian population.

Prognostic impact of new-onset atrial fibrillation associated with worsening heart failure in aging patients with severely decompensated acute heart failure

BACKGROUNDS

The prevalence of atrial fibrillation (AF) has been increasing in aging societies. The prognostic impact of AF associated with worsening heart failure (HF) remains obscure.

METHODS AND RESULTS

We analyzed 1170 acute heart failure (AHF) patients who required intensive care. Patients were assigned to two groups according to the prevalence of AF: no episode of AF (n = 940) and pre-existing AF (Group-1, n = 230). Patients with no episode of AF (n = 940) were further divided into two groups according to presence of new-onset of AF after admission (Group-2a, n = 258) or not (Group-2b, n = 682). Kaplan-Meier curve analysis showed that prognosis, including all-cause mortality and HF-events within 1000 days, was significantly poorer in the Group-1 compared to the Group-2b. However, a multivariate Cox regression model showed that the Group-1 was not an independent predictor of 1000-day mortality and HF-events. Furthermore, Kaplan-Meier curve analysis showed that prognosis, including all-cause mortality and HF-events within 1000 days, was significantly poorer in the Group-2a than in the Group-2b. A multivariate Cox regression model revealed that the Group-2a was an independent predictor of 1000-day mortality (HR: 1.403, 95% CI: 1.018-1.934) and HF-events (HR: 1.352, 95% CI: 1.071-1.708). A multivariate logistic regression model showed that only age (≥75 years old) was independently associated with new-onset of AF after admission (odds ratio: 1.556, 95% CI: 1.130-2.143).

CONCLUSIONS

New-onset AF associated with worsening HF increases with age and is independently-associated with adverse outcome in patients with AHF.

Mineralocorticoid Receptor Antagonism in Patients With Atrial Fibrillation: Findings From the ORBIT-AF (Outcomes Registry for Better Informed Treatment of Atrial Fibrillation) Registry

Background

Mineralocorticoid receptor antagonist (MRA) therapy may be beneficial to patients with atrial fibrillation (AF), but little is known about their use in patients with AF and subsequent outcomes.

Methods and Results

In order to better understand MRA use and subsequent outcomes, we performed a retrospective cohort study of the contemporary ORBIT‐AF (Outcomes Registry for Better Informed Treatment of Atrial Fibrillation) registry. AF progression and cardiovascular outcomes were compared using propensity‐matched Cox proportional hazards modeling according to MRA use at baseline and new MRA use at follow‐up versus patients with no MRA use. Among 7012 patients with nonpermanent AF, 320 patients were taking MRA at enrollment, and 416 patients initiated MRA use during follow‐up. The mean patient age was 72.5 years, 56.3% were men, and 70.4% had paroxysmal AF. Among all patients taking MRAs, 434 (59.0%) had heart failure, 655 (89.0%) had hypertension, and 380 (51.6%) had both. After adjustment, new MRA use was not associated with reduced AF progression (hazard ratio, 1.18; 95% confidence interval, 0.88–1.58; P=0.27) but showed a trend towards lower risk of stroke, transient ischemic attack, or systemic embolism (hazard ratio, 0.17; 95% confidence interval, 0.02–1.23; P=0.08). Results were similar for a comparison of new MRA users and baseline MRA users compared with nonusers.

Conclusions

In community‐based outpatients with AF, the majority of MRA use was for heart failure and hypertension. MRA use also trended towards lower adjusted stroke risk. Future studies should test the hypothesis that MRA use may decrease the risk of stroke in patients with AF.

Association of the -344T/C polymorphism in aldosterone synthase gene promoter with left ventricular structure in Chinese Han: A meta-analysis

No consensus view has been published on the relationship between the aldosterone synthase gene (CYP11B2) -344C/T polymorphism and left ventricular hypertrophy (LVH) in Chinese Han. We undertook a meta-analysis to investigate the potential association of this polymorphism and left ventricular structure-related phenotypes, including left ventricular mass (LVM), left ventricular mass index (LVMI), left ventricular end systolic diameter (LVESD), left ventricular end diastolic dimension (LVEDD), left ventricular posterior wall thickness (LVPWT), and interventricular septal wall thickness (IVS). Studies in English and Chinese were found based on a systematic search of Medline, Embase, CNKI, and Wanfang databases. The dominant model (TT vs. TC+CC) and homozygote model (TT vs. CC) were selected to examine the association between the -344C/T polymorphism and LVH. The random-effects model was used to pool data. From a total of 3104 participants, despite the investigation of six echocardiographic indicators, we found no significant association between the -344C/T variant and LVH in the whole group and the subgroup analyses by blood pressure. However, in the subgroup of northern Han Chinese, TT genotype had higher LVPWT than CC genotype and TC genotype (p_{heterogeneity} = 0.4, p_value = 0.04, 95% CI 0.09 (0.00, 0.18)). In addition, no evidence of publication bias was observed. In conclusion, our meta-analysis indicated that subjects with TT genotype might have higher risk of developing LVH in northern Han Chinese.

Mineralocorticoid receptor antagonists and atrial fibrillation: a meta-analysis

AIMS

Aldosterone has been implicated in atrial remodelling representing a potential target for upstream therapies. Accumulating evidence suggests that mineralocorticoid receptor blockade may have favourable effects on atrial fibrillation (AF) development, although some controversial results have been published. We, therefore, conducted a meta-analysis of randomized clinical trials (RCTs) and observational studies in order to examine the protective role of mineralocorticoid receptor antagonists (MRAs) on AF.

METHODS AND RESULTS

Of the 1337 initially identified records, 3 RCTs and 2 observational studies with 3640 patients were finally analysed. The pooled analysis of the included studies demonstrated that patients treated with MRAs have 31% lower risk of AF compared with controls [relative ratio (RR): 0.69; 95% confidence interval (CI): 0.58-0.83] without any heterogeneity across the studies (I(2) = 0%). This effect was consistent across RCTs (RR: 0.72; 95% CI: 0.55-0.94) and observational studies (RR: 0.67; 95% CI: 0.53-0.84) without heterogeneity. Also, MRAs reduce the risk of AF in both heart failure (HF) (RR: 0.63; 95% CI: 0.50-0.80) and after cardiac surgery (RR: 0.77; 95% CI: 0.61-0.98). Analysing the relative impact of eplerenone and spironolactone, we showed that only eplerenone significantly reduces AF burden (RR: 0.64; 95% CI: 0.44-0.90).

CONCLUSION

Our meta-analysis suggests that MRAs may be effective in AF prevention especially in the HF setting. However, there are insufficient data for the widespread use of aldosterone antagonists solely for AF prevention. Larger RCTs with long-term follow-up in different clinical settings are needed to clarify the impact of MRAs on AF.

Polymorphisms of renin-angiotensin-aldosterone system gene in chinese han patients with nonfamilial atrial fibrillation

Background

Atrial fibrillation(AF) is the most common arrhythmia in the adult population. The activated renin-angiotensin-aldosterone system (RAS) has been reported to play an important role in the pathogenesis of atrial fibrillation. The aim of this study was to investigate the association between nonfamilial AF and polymorphisms in RAS gene.

Methods

A total of 931 patients with nonfamilial AF, 663 non-AF heart disease patients and 727 healthy subjects were selected. 10 tagSNPs (tSNPs) (ACE gene rs8066114, AGT gene rs7539020, rs3789678, rs2478544, rs11568023, rs2478523, rs4762, rs699 and CYP11B2 rs3802230, rs3097) were chosen and genotyped in our study. Single-locus analysis and haplotype analysis were used in this study.

Results

In single-locus analysis, we found rs11568023 and rs3789678 in AGT gene were associated with nonfamilial AF in Chinese Han population. AF risk was associated with rs3789678 between the AF group and control groups. Under dominant model, the significant AF risk was observed in rs3789678 between the AF group and non AF heart control group; And the protective effect was found in rs11568023, compared with the non-AF heart disease control group. In multilocus haplotype analysis, the association between frequencies of the haplotypes and AF risk was showed in AGT gene (rs7539020-rs3789678), compared ‘TT’ haplotype with the common ‘TC’ haplotype, adjusted for age, gender, LVEF, LVEDD, LAD and frequency of hypertension and diabetes. The diplotype with ‘TC’, carrying rs3789678-C-allele, was associated with reduced risk of AF between the AF group and the healthy control group. The diplotype with ‘TT’ haplotype in the same block, carrying rs3789678-T-allele, was associated with increased risk of AF.

Conclusions

Via a large-scale case-control study, we found that rs3789678 site was potential susceptible locus of AF whereas rs11568023 was protective factor.

Relationship between CYP11B2-344T>C polymorphsim and atrial fibrillation: A meta-analysis

INTRODUCTION

The aldosterone synthase (CYP11B2)-344T>C gene polymorphism has been reported to influence the risk of atrial fibrillation (AF) in many studies; however, the results remain controversial and ambiguous.

MATERIALS AND METHODS

We therefore carried out a meta-analysis of published case-control studies to investigate the association between CYP11B2-344T>C polymorphism and AF susceptibility. Electronic searches were conducted on links between this variant and AF in several databases. Odds ratios (ORs) and 95% confidence intervals (CIs) for homozygous, dominant model, recessive model and allele were calculated to estimate the strength of associations in fixed and random effect models. Heterogeneity and publication bias were also assessed.

RESULTS

A total of nine case-control studies were identified. The C allele was associated with an increased susceptibility risk of AF compared with the T allele among hypertension populations (OR=1.26; 95% CI=1.09-1.45). The contrast of homozygotes and the recessive model produced the same pattern of results as the allele contrast. In the hypertension population, a significant association was found for the genetic models that were examined.

CONCLUSIONS

Our pooled data suggest a significant association exists between CYP11B2-344T>C polymorphism and AF among hypertension populations.

Prognostic value of two polymorphisms in non-sarcomeric genes for the development of atrial fibrillation in patients with hypertrophic cardiomyopathy

BACKGROUND

Several non-sarcomeric genes have been postulated to act as modifiers in the phenotypic manifestations of hypertrophic cardiomyopathy (HCM). The development of atrial fibrillation (AF) in HCM has adverse prognostic implications with increased thromboembolism and functional class impairment.

AIM

We tested the hypothesis that 2 non-sarcomeric genes [CYP11B2 (-344T>C) and COL1A1 (2046G>T)] are associated with the development of AF.

DESIGN

Prospective study.

METHODS

Two polymorphisms in non-sarcomeric genes [CYP11B2 (-344T>C) and COL1A1 (2046G>T)] were analysed in 159 HCM patients (49.3 ± 14.9 years, 70.6% male) and 136 controls. All subjects were clinically stable and in sinus rhythm at entry in the study, without ischemic heart disease or other significant co-morbidities that could mask the effect of the analysed polymorphisms (i.e. previous AF). Thirty-nine patients (24.4%) developed AF during a median follow-up of 49.5 months.

RESULTS

Patients with the -344T>C polymorphism in CYP11B2 gene had a higher risk for AF development [HR: 3.31 (95% CI 1.29-8.50); P = 0.008]. In a multivariate analysis, the presence of the C allele in CYP11B2 gene [HR: 3.02 (1.01-8.99); P = 0.047], previous AF [HR: 2.81 (1.09-7.23); P = 0.033] and a left atrial diameter of ≥42 mm [HR: 2.69 (1.01-7.18); P = 0.048] were independent predictors of AF development. The presence of the polymorphic allele was associated with higher aldosterone serum levels.

CONCLUSION

We have shown for the first time that the CYP11B2 polymorphism is an independent predictor for AF development in HCM patients. This highlights the importance of non-sarcomeric genes in the phenotypic heterogeneity of HCM. The association with higher aldosterone serum levels could relate to greater fibrosis and cardiac remodelling.

The Role Of Renin Angiotensin System In Atrial Fibrillation

Atrial fibrillation (AF) is the most prevalent arrhythmia and its incidence is on the rise. AF causes significant morbidity and mortality leading to rising AF-related health care costs. There is experimental and clinical evidence from animal and human studies that suggests a role for the renin angiotensin system (RAS) in the etiopathogenesis of AF. This review appraises the current understanding of RAS antagonism, using angiotensin converting enzyme inhibitors (ACE-I), angiotensin receptor blockers (ARB) and aldosterone antagonists (AA), for prevention of AF. RAS antagonism has proven to be effective for primary and secondary prevention of AF in subjects with heart failure and left ventricular (LV) dysfunction.However, most of the evidence for the protective effect of RAS antagonism is from clinical trials that had AF as a secondary outcome or from unspecified post-hoc analyses. The evidence for prevention in subjects without heart failure and with normal LV function is not as clear. RAS antagonism, in the absence of concomitant antiarrhythmic therapy, was not shown to reduce post cardioversion AF recurrences. RAS antagonism in subjects undergoing catheter ablation has also been ineffective in preventing AF recurrences.

Cross-talk between mineralocorticoid receptor/angiotensin II type 1 receptor and mitogen-activated protein kinase pathways underlies aldosterone-induced atrial fibrotic responses in HL-1 cardiomyocytes

BACKGROUND

Aldosterone is increasingly recognized for its involvement in atrial structural remodeling. However, the precise molecular mechanisms and signal pathways underlying aldosterone-induced atrial fibrosis are unknown.

METHODS

Western blotting was used to investigate the effects of aldosterone on the expression of mineralocorticoid receptor (MR), angiotensin II type I receptor (AT1), mitogen-activated protein kinases (MAPKs), and fibrotic marker proteins in cultured HL-1 cardiomyocytes.

RESULTS

Aldosterone upregulated MR and AT1 expressions in a concentration-dependent and time-dependent manner. Aldosterone (10(-6)M) significantly and time-dependently increased activation of the extracellular signal-regulated protein kinase (ERK), c-Jun N-terminal kinase (JNK), p38MAPK pathways, and the protein expression of collagen 1A and 3A (COL1A and COL3A), transforming growth factor (TGF)-β1, and α-smooth muscle actin (SMA). Pre-treatment with eplerenone (10(-10)M) prevented the increased expression of MR, MAPK signals and the above profibrotic molecules, but amplified the increase in AT1 level stimulated by aldosterone (10(-6)M). Pre-treatment with losartan (10(-10)M) or MAPK pathway inhibitors (U0126 or SP600125) abolished aldosterone-induced MR upregulation and significantly inhibited the expression of the above fibrotic marker proteins, indicating the critical role of MR and the requirement for active AT1 in the development of aldosterone-induced atrial fibrosis.

CONCLUSIONS

Elevated MR activity plays a central role in aldosterone-mediated activation of the MAPK signaling pathway and subsequent profibrotic effects in HL-1 atrial cells. MR/AT1 and the MAPK signaling pathway interact to trigger the molecular mechanism underlying the aldosterone-induced atrial fibrotic response. Our results support the view that MR blockade in conjunction with AT1 blockade can prevent the occurrence of atrial fibrillation.

Impact of aldosterone antagonists on the substrate for atrial fibrillation: aldosterone promotes oxidative stress and atrial structural/electrical remodeling

Atrial fibrillation (AF), the most common cardiac arrhythmia, is an electrocardiographic description of a condition with multiple and complex underlying mechanisms. Oxidative stress is an important driver of structural remodeling that creates a substrate for AF. Oxidant radicals may promote increase of atrial oxidative damage, electrical and structural remodeling, and atrial inflammation. AF and other cardiovascular morbidities activate angiotensin (Ang-II)-dependent and independent cascades. A key component of the renin-angiotensin-aldosterone system (RAAS) is the mineralocorticoid aldosterone. Recent studies provide evidence of myocardial aldosterone synthesis. Aldosterone promotes cardiac oxidative stress, inflammation and structural/electrical remodeling via multiple mechanisms. In HF patients, aldosterone production is enhanced. In patients and in experimental HF and AF models, aldosterone receptor antagonists have favorable influences on cardiac remodeling and oxidative stress. Therapeutic approaches that seek to reduce AF burden by modulating the aldosterone system are likely beneficial but underutilized.

Association of aldosterone synthase polymorphism (CYP11B2 -344T>C) and genetic ancestry with atrial fibrillation and serum aldosterone in African Americans with heart failure

The objective of this study was to examine the extent to which aldosterone synthase genotype (CYP11B2) and genetic ancestry correlate with atrial fibrillation (AF) and serum aldosterone in African Americans with heart failure. Clinical data, echocardiographic measurements, and a genetic sample for determination of CYP11B2 -344T>C (rs1799998) genotype and genetic ancestry were collected from 194 self-reported African Americans with chronic, ambulatory heart failure. Genetic ancestry was determined using 105 autosomal ancestry informative markers. In a sub-set of patients (n = 126), serum was also collected for determination of circulating aldosterone. The CYP11B2 -344C allele frequency was 18% among the study population, and 19% of patients had AF. Multiple logistic regression revealed that the CYP11B2 -344CC genotype was a significant independent predictor of AF (OR 12.7, 95% CI 1.60-98.4, p = 0.0150, empirical p = 0.011) while holding multiple clinical factors, left atrial size, and percent European ancestry constant. Serum aldosterone was significantly higher among patients with AF (p = 0.036), whereas increased West African ancestry was inversely correlated with serum aldosterone (r = -0.19, p = 0.037). The CYP11B2 -344CC genotype was also overrepresented among patients with extreme aldosterone elevation (≥90th percentile, p = 0.0145). In this cohort of African Americans with chronic ambulatory heart failure, the CYP11B2 -344T>C genotype was a significant independent predictor of AF while holding clinical, echocardiographic predictors, and genetic ancestry constant. In addition, increased West African ancestry was associated with decreased serum aldosterone levels, potentially providing an explanation for the lower risk for AF observed among African Americans.

Aldosterone synthase gene (CYP11B2) -344C/T polymorphism contributes to the risk of recurrent cerebral ischemia

BACKGROUND

Accumulating evidence suggests that CYP11B2 rs1799998 (-344C/T) polymorphism is independently associated with an increased risk of stroke. Our aim was to determine whether -344C/T also predisposes to recurrent cerebral ischemia following in patients with symptomatic intracranial atherosclerosis disease (ICAD).

METHODS

Genotypes of the CYP11B2 -344C/T polymorphism were determined by polymerase chain reaction-restriction fragment length polymorphism. A total of 208 ICAD patients were enrolled and underwent a long-term clinical follow-up to detect the recurrent cerebral ischemia.

RESULTS

During a median follow-up time of 35 months, 40 recurrent strokes (19.2%) were documented. Kaplan-Meier and multivariable Cox regression analyses adjusted for age, gender, and other cardiovascular risk factors identified that the presence of the TT genotype within the CYP11B2 -344C/T polymorphism was associated with an increased risk of 1.98-fold for recurrent cerebral ischemia (the hazard ratio 1.98, 95% confidence interval 1.16-3.41; p=0.01).

CONCLUSIONS

Our findings suggest that the -344C/T polymorphism of the CYP11B2 gene confers an increased risk of recurrent cerebral ischemia.

The 894G Allele of the Endothelial Nitric Oxide Synthase 3 (eNOS) is Associated with Atrial Fibrillation in Chronic Systolic Heart Failure

BACKGROUND

Atrial fibrillation (AF) in patients with heart failure signals poor prognosis. The endothelial nitric oxide synthase (eNOS) enzyme is a key player in the counterregulation of oxidative stress, which is related in part to AF pathogenesis. The purpose of this study was to investigate a possible clinical association in heart failure patients between the presence of exon 7 G894T eNOS polymorphism, known to result in the Glu298Asp protein variant, and the occurrence of AF.

METHODS

We analyzed the DNA of 344 patients with chronic systolic heart failure for exon 7 G894T eNOS polymorphism, using PCR. Odds ratios for AF were calculated for the homo- and heterozygous G-allele G894T variants relative to the TT variant.

RESULTS

Of the 344 patients, 204 (59%) were homozygous for the G allele, 122 (36%) were heterozygous (GT), and 18 (5%) were homozygous for the T allele. AF episodes were documented in 73 patients (36%) with the GG genotype, in 35 (29%) with GT, and in 2 (11%) with TT. The odds ratio for AF, based on the presence of at least one G allele in the eNOS 894 gene, was 3.96 (95% confidence interval, 1.17‒13.56, p=0.04). Having two G alleles increased the odds ratio to 4.5 (95% confidence interval, 1.0‒20.0, p=0.02).

CONCLUSION

Patients with systolic heart failure demonstrate strong correlation between AF and the presence of a G allele in the exon 7 G894T eNOS genotype. These findings support the importance of eNOS polymorphism in the pathogenesis of AF in heart failure patients.

CYP11B2 T-344C gene polymorphism and atrial fibrillation: a meta-analysis of 2,758 subjects

BACKGROUND

Aldosterone synthase (CYP11B2) T-344C gene polymorphism was found to be correlated with atrial fibrillation (AF) risk. However, the results of individual studies remain conflicting.

OBJECTIVE AND METHODS

A meta-analysis including 2,758 subjects from six individual studies was performed to explore the correlation between CYP11B2 T-344C gene polymorphisms and AF. The pooled odds ratios (ORs) and their corresponding 95% confidence intervals (95% CIs) were evaluated by the fixed- or random-effects model.

RESULTS

A significant relationship between CYP11B2 T-344C gene polymorphism and AF was found under allelic (OR: 1.26, 95% CI: 1.11-1.42, P = 0.0002), recessive (OR: 1.99, 95% CI: 1.26-3.14, P = 0.003), dominant (OR: 0.903, 95% CI: 0.820-0.994, P = 0.036), homozygous (OR: 1.356, 95% CI: 1.130-1.628, P = 0.001), and additive (OR: 1.153, 95% CI: 1.070-1.243, P = 1.0×10(-10)) genetic models. No significant association between CYP11B2 T-344C gene polymorphism and AF was found under the heterozygous genetic model (OR: 1.040, 95% CI: 0.956-1.131, P = 0.361).

CONCLUSIONS

A significant association was found between CYP11B2 T-344C gene polymorphism and AF risk. Individuals with the C allele of CYP11B2 T-344C gene polymorphism have higher risk for AF.

Association of angiotensin-converting enzyme gene I/D and CYP11B2 gene -344T/C polymorphisms with lone atrial fibrillation and its recurrence after catheter ablation

The renin-angiotensin-aldosterone system (RAAS) plays a key role in atrial structural and electrical remodeling. The aim of this study was to investigate the potential associations of angiotensin-converting enzyme (ACE) gene insertion/ deletion (I/D) and aldosterone synthase (CYP11B2) gene −344T/C polymorphisms with the risk and recurrence of lone atrial fibrillation (AF). One hundred and ninety-three patients who underwent successful catheter ablation for lone AF were recruited. Two hundred and ninety-seven sinus rhythm subjects without a history of arrhythmia served as controls. The subjects were genotyped for ACE gene I/D and CYP11B2 gene −344T/C polymorphisms. Results showed that the ACE gene DD genotype and D allele were associated with a greater prevalence of lone AF (both P<0.01). In addition, the ACE gene DD genotype had a significantly larger left atrial dimension (LAD; 41.6±5.7 mm vs. 39.6±5.2 mm; P=0.043) and higher risk of AF recurrence [44.7% vs. 23.2%; odds ratio (OR), 2.68; 95% confidence interval (CI), 1.28–5.61; P=0.008] compared with the II+ID genotype in lone AF patients. After adjustment for a variety of risk factors, the ACE gene DD genotype had a 1.97-fold increased risk for lone AF (OR, 1.97; 95% CI, 1.15–3.37; P= 0.013) and 2.35-fold increased risk for AF recurrence (RR, 2.35; 95% CI, 1.10–5.04; P=0.028) compared with the ACE gene II+ID genotype. However, no correlation between the CYP11B2 gene −344T/C polymorphism and lone AF or its recurrence was observed in this cohort. In conclusion, the ACE gene DD genotype was associated with an increased incidence of lone AF and its recurrence following ablation, which was partly mediated by LAD.

Abnormal vascular function in PR-interval prolongation

BACKGROUND

Underlying mechanisms of PR-interval prolongation leading to increased risk of adverse cardiovascular outcomes, including atrial fibrillation, are unclear. This study aims to investigate the relation between PR interval and changes in vascular function.

HYPOTHESIS

We hypothesize that there exists an intermediate pathological stage between electrocardiographic PR prolongation and adverse cardiovascular outcomes, which could be reflected by changes in surrogate measurements of vascular function.

METHODS

We recruited 88 healthy subjects (mean age 57.5 ± 9.8 y, 46% male) from a community-based health screening program who had no history of cardiovascular disease or diabetes mellitus. PR interval was determined from a resting 12-lead electrocardiogram. Vascular function was noninvasively assessed by flow-mediated dilation (FMD) using high-resolution ultrasound and brachial-ankle pulse wave velocity (PWV) using a vascular profiling system.

RESULTS

Only 3 subjects had a PR-interval length longer than the conventional cutoff of 200 ms. The PR-interval length was associated inversely with FMD (Pearson r = -0.30, P = 0.004) and positively with PWV (r = 0.40, P < 0.001). Adjusting for potential confounders, increased PR-interval length by each 25 ms was independently associated with reduced FMD by -1 unit (absolute %, B = -0.04 [95% confidence interval: -0.080 to -0.002, P = 0.040)] and increased PWV by +103 cm/second (B = +4.1 [95% confidence interval: 0.6-7.6, P = 0.023]).

CONCLUSIONS

This study shows that PR-interval length, even in the conventionally normal range, is independently associated with endothelial dysfunction and increased arterial stiffness in healthy subjects free of atherosclerotic disease. This suggests the presence of a systemic, intermediate pathologic stage of the vasculature in PR prolongation before clinically manifest cardiovascular events, and could represent a mediating mechanism.

Relationship between -344T/C polymorphism in the aldosterone synthase gene and atrial fibrillation in patients with essential hypertension

INTRODUCTION

Aldosterone plays an important role in the pathogenesis of non-familial atrial fibrillation (AF). We tested the hypothesis that the -344T/C polymorphism in the aldosterone synthase gene may be associated with non-familial AF in Chinese patients with hypertension.

MATERIALS AND METHODS

We performed a 1:1 paired case-control study in 310 cases of hypertension with AF and same number matched controls. The -344T/C polymorphism was determined with polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

The distribution of the CYP11B2 genotypes (TT, TC and CC) was 41.9%, 50.6%, and 7.4% in AF patients, which was not different from controls (48.4%, 44.5%, and 7.1%, χ(2) = 2.675, p = 0.263). The difference between the C allele (32.3% vs. 29.4%) was also not significant between two groups (χ(2) = 1.661, p = 0.197). Logistic regression analysis showed that LAD and LVEDD (both p < 0.001), rather than the C allele of the CYP11B2 gene (p= 0.107) were significant predictors for AF. The LAD of C allele carriers is significantly larger than that of non-C allele carriers (p = 0.009).

CONCLUSIONS

Our results indicate that the -344T/C polymorphism in the aldostrone synthase gene is not associated with AF but it might be associated with atrial remodelling in hypertensives.

Genetics of atrial fibrillation

Recent studies of atrial fibrillation (AF) have identified mutations in a series of ion channels; however, these mutations appear to be relatively rare causes of AF. A genome-wide association study has identified novel variants on chromosome 4 associated with AF, although the mechanism of action for these variants remains unknown. Ultimately, a greater understanding of the genetics of AF should yield insights into novel pathways, therapeutic targets, and diagnostic testing for this common arrhythmia.

A comprehensive genetic study on left atrium size in Caribbean Hispanics identifies potential candidate genes in 17p10

BACKGROUND

Left atrial (LA) enlargement is associated with cardiovascular disease and stroke. Genetic factors contributing to the LA dimension are poorly understood. We sought to map susceptibility genes for LA size in a large Dominican family data set and an independent population-based sample from the Northern Manhattan Study.

METHODS AND RESULTS

One hundred Dominican families comprising 1350 individuals were studied to estimate heritability and map quantitative trait loci for LA size using variance components analysis. LA dimension was measured by transthoracic echocardiography. A polygenic covariate screening was used to identify significant covariates. LA size had a moderate estimate of heritability (h(2)=0.42) after adjusting for significant covariates. Linkage analysis revealed suggestive evidence on chromosome 10p19 (D10S1423, MLOD=2.00) and 17p10 (D17S974, MLOD=2.05). Ordered subset analysis found significantly enhanced (P<0.05 for increase of LOD score) evidence for linkage at 17p10 (MLOD=2.9) in families with lower LDL level. Single nucleotide polymophisms (n=2233)were used to perform a peak-wide association mapping across 17p10 in 825 NOMAS individuals. Evidence for association were found in NTN1, MYH10, COX10, and MYOCD genes (P=0.00005 to 0.005).

CONCLUSIONS

Using nonbiased genome-wide linkage followed by peak-wide association analysis, we identified several possible susceptibility genes affecting LA size. Among them, MYOCD has been shown to serve as a key transducer of hypertrophic signals in cardiomyocytes. Our data support that polymorphisms in MYOCD modify LA size.

Increased expression of mineralocorticoid receptor in human atrial fibrillation and a cellular model of atrial fibrillation

OBJECTIVES

This study was designed to evaluate the status of steroidogenesis proteins and de novo synthesis of aldosterone in the atrium, and relationships of these factors to atrial fibrillation (AF).

BACKGROUND

The role of mineralocorticoid in the pathogenesis of AF is unknown.

METHODS

We studied atrial expression of steroidogenesis proteins and aldosterone level in patients with and without AF, and in HL-1 atrial myocytes. We also investigated the electrophysiologic effects and signal transduction of aldosterone on atrial myocytes.

RESULTS

We found basal expressions of mineralocorticoid receptors (MRs), glucocorticoid receptors, and 11-beta-hydroxysteroid dehydrogenase type 2 (11bHSD2) but not 11-beta-hydroxylase (CYP11B1) or aldosterone synthase (CYP11B2) in human atria and HL-1 myocytes. There was no significant difference of mean atrial aldosterone level between patients with AF and those with normal sinus rhythm. However, patients with AF had a significantly higher atrial MR expression compared with those with normal sinus rhythm (1.73 +/- 0.24-fold, p < 0.001). Using mouse HL-1 atrial myocytes as a cellular AF model, we found that rapid depolarization increased MR expression (1.97 +/- 0.72-fold, p = 0.008) through a calcium-dependent mechanism, thus augmenting the genomic effect of aldosterone signaling as evaluated by MR reporter. Aldosterone increased intracellular oxidative stress through a nongenomic pathway, which was attenuated by nicotinamide adenine dinucleotide phosphate oxidase inhibitor diphenyleneiodonium, but not by MR-blockade spironolactone. Aldosterone increased expression of the alpha-1G and -1H subunits of the T-type calcium channel and thus increased the T-type calcium current (-13.6 +/- 2.9 pA/pF vs. -4.5 +/- 1.6 pA/pF, p < 0.01) and the intracellular calcium load through a genomic pathway, which were attenuated by spironolactone, but not by diphenyleneiodonium.

CONCLUSIONS

Expression of MR increased in AF, thus augmenting the genomic effects of aldosterone. Aldosterone induced atrial ionic remodeling and calcium overload through a genomic pathway, which was attenuated by spironolactone. These results suggest that aldosterone may play a role in AF electrical remodeling and provide insight into the treatment of AF with MR blockade.

Atrial fibrillation and the risk of death in patients with heart failure: a literature-based meta-analysis

BACKGROUND

Heart failure (HF) and atrial fibrillation (AF) are common, associated with significant morbidity and mortality, and frequently coexist. It is uncertain from published data if the presence of AF in patients with HF is associated with an incremental adverse outcome. The aim of this study was to combine the results of all studies investigating prognosis for patients with HF and AF compared with those in sinus rhythm (SR) to asses the mortality risk associated with this arrhythmia.

METHODS

Electronic databases were searched (Biological Abstracts, Current Contents, EMBASE, Medline, Medline In-progress, PubMed and Scopus), to 31 December 2006, using the key words congestive heart failure, heart failure, ventricular dysfunction, atrial fibrillation, atrial flutter, sinus rhythm, prognosis, outcome, death and hospitalization. Bibliographies of retrieved publications were hand searched. Studies were eligible if they included a HF population and if outcomes were reported by cardiac rhythm (AF or SR). Studies were reviewed by predetermined protocol (including quality assessment). Data were pooled using a random effects model.

RESULTS

Twenty studies were included (from 3380 initially identified) representing 32946 patients (10819 deaths). Nine randomized controlled trials (RCT) were included. The prevalence of AF was 15%, crude mortality rates were 46% (AF) and 33% (SR). The odds ratio for death was 1.33 (95% confidence interval (CI) 1.12-1.59) for AF compared with SR. Eleven observational studies were included. The prevalence of AF was 23%, crude mortality rates were 38% (AF) and 25% (SR). The odds ratio for death was 1.57 (95% CI 1.20-2.05) for AF compared with SR.

CONCLUSION

This meta-analysis demonstrates that AF is associated with worse outcomes for patients with HF compared with those with SR. Further research is required to determine whether the adverse outcome associated with AF is related to the arrhythmia itself, or to variables, such as HF severity, patient age and comorbidity.

Genetics of atrial fibrillation

Recent studies of AF have identified mutations in a series of ion channels; however, these mutations appear to be relatively rare causes of AF. A genome-wide association study has identified novel variants on chromosome 4 associated with AF, although the mechanism of action for these variants remains unknown. Ultimately, a greater understanding of the genetics of AF should yield insights into novel pathways, therapeutic targets, and diagnostic testing for this common arrhythmia.

Functional polymorphisms in ACE and CYP11B2 genes and atrial fibrillation in patients with hypertensive heart disease

BACKGROUND

The activated renin-angiotensin-aldosterone system has been reported to play an important role in the pathogenesis of atrial fibrillation (AF). We hypothesized that functional genetic variations of angiotensin-converting enzyme (ACE) and CYP11B2 genes may influence the susceptibility to AF in patients with hypertensive heart disease.

METHODS

The I/D polymorphism of ACE was detected by polymerase chain reaction (PCR), and the -344C/T polymorphism of the CYP11B2 gene was detected using PCR and subsequent cleavage by HaeIII restriction endonuclease.

RESULTS

The overall distribution of ACE I/D genotypes in patients with and without AF was significantly different (p=0.001). The frequency of the DD genotype was significantly higher in patients with AF than in patients without AF (20.6% vs. 8.1%, OR 2.94, 95% CI 1.64-5.26, p<0.001). The frequency of the D allele was significantly higher in the AF group than in the non-AF group (p=0.001). After adjustment for age and left atrial dimension, multivariable analysis showed that the DD genotype of the ACE gene was an independent risk factor for AF in patients with hypertensive heart disease. No relationship between -344 C/T CYP11B2 polymorphism and AF was found in this cohort.

CONCLUSIONS

Our study suggests that ACE I/D polymorphism is associated with AF and the DD genotype may be an independent predictive factor for AF in patients with hypertensive heart disease.

Pathophysiology of concomitant atrial fibrillation and heart failure: implications for management

Atrial fibrillation (AF) and heart failure (HF) are two conditions regularly encountered in clinical practice. They share many common risk factors, and are often seen concurrently in an individual patient. Global aging of the population is likely to lead to an increase in the prevalence of both AF and HF alone, as well as in their combined state. The relationship between these two diseases is not simply coincidental; clinical and experimental data have defined multiple pathophysiological mechanisms to explain how either condition contributes to the de novo development of the other. The development of AF in the setting of HF, and vice versa, is associated with clinical deterioration and worsening prognosis, which indicates the need for an improved understanding of the clinical and pathological relationships between these conditions. Future research on pharmacologic therapies, such as antiarrhythmic medications, and nonpharmacologic strategies including atrioventricular nodal ablation and pulmonary vein isolation, will help to define the optimal therapeutic approach for concurrent AF and HF. This step is vital to improve both the outcomes of patients affected by these conditions and the cost-effectiveness of their care.