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

Biatrial arrhythmogenic substrate in patients with hypertrophic obstructive cardiomyopathy

BACKGROUND

Atrial fibrillation (AF) in patients with hypertrophic obstructive cardiomyopathy (HOCM) may be caused by a primary atrial myopathy. Whether HOCM-related atrial myopathy affects mainly electrophysiological properties of the left atrium (LA) or also the right atrium (RA) has never been investigated.

OBJECTIVE

The purpose of this study was to characterize atrial conduction and explore differences in the prevalence of conduction disorders, potential fractionation, and low-voltage areas (LVAs) between the RA and LA during sinus rhythm (SR) as indicators of potential arrhythmogenic areas.

METHODS

Intraoperative epicardial mapping of both atria during SR was performed in 15 HOCM patients (age 50 ± 12 years). Conduction delay (CD) and conductin block (CB), unipolar potential characteristics (voltages, fractionation), and LVA were quantified.

RESULTS

Conduction disorders and LVA were found scattered throughout both atria in all patients and did not differ between the RA and LA (CD: 2.9% [1.9%-3.6%] vs 2.6% [2.1%-6.4%], P = .541; CB: 1.7% [0.9%-3.1%] vs 1.5% [0.5%-2.8%], P = .600; LVA: 4.7% [1.6%-7.7%] vs 2.9% [2.1%-7.1%], P = .793). Compared to the RA, unipolar voltages of single potentials (SPs) and fractionated potentials (FPs) were higher in the LA (SP: P75 7.3 mV vs 10.9 mV; FP: P75 2.0 mV vs 3.7 mV). FP contained low-voltage components in only 18% of all LA sites compared to 36% of all RA sites.

CONCLUSION

In patients with HOCM, conduction disorders, LVA, and FP are equally present in both atria, supporting the hypothesis of a primary atrial myopathy. Conceptually, the presence of a biatrial substrate and high-voltage FP may contribute to failure of ablative therapy of atrial tachyarrhythmias in this population.

From Atrial Fibrillation Management to Atrial Myopathy Assessment: The Evolving Concept of Left Atrium Disease in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most prevalent genetically inherited cardiovascular disorder in adults and a significant cause of heart failure and sudden cardiac death. Historically, atrial fibrillation (AF) has been considered as a critical aspect in HCM patients as it is considered to be a marker of disease progression, escalates the frequency of heart failure hospitalisations, increases the risk of thromboembolic events, and worsens quality of life and outcome. Increasing evidence suggests that AF is the result of a subtle long-standing process that starts early in the history of HCM. The process of left atrial dilation accompanied by morphologic and functional remodelling is the quintessential prerequisite for the onset of AF. This review aims to describe the current understanding of AF pathophysiology in HCM, emphasising the role of left atrial myopathy in its development. In addition, we discuss risk factors and management strategies specific to AF in the context of HCM, providing insights into the complexities and challenges of treating this specific patient population.

Could echocardiographic left atrial characterization have additive value for detecting risks of atrial arrhythmias and stroke in patients with hypertrophic cardiomyopathy?

AIMS

Atrial arrhythmia (AA) is considered a turning point for prognosis in patients with hypertrophic cardiomyopathy (HCM). We sought to assess whether the occurrence of AA and stroke could be estimated by an echocardiographic evaluation.

METHODS AND RESULTS

A total of 216 patients with HCM (52 ± 16 years old) were analysed. All patients underwent transthoracic echocardiography for the evaluation of left atrial volume (LAV), peak left atrial strain (PLAS), and peak atrial contraction strain. The patients were followed for 2.9 years for the occurrence of a composite endpoint including AA and/or stroke and peripheral embolism. Among the 216 patients, 78 (36%) met the composite endpoint. These patients were older (57.1 ± 14.4 vs. 50.3 ± 16.7 years; P = 0.0035), had a higher prevalence of arterial hypertension (62.3 vs. 42.3%; P = 0.005), and had higher NT-proBNP. The LAV (47 ± 20 vs. 37.2 ± 15.7 mL/m²; P = 0.0001) was significantly higher in patients who met the composite endpoint, whereas PLAS was significantly impaired (19.3 ± 9.54 vs. 26.6 ± 9.12%; P < 0.0001). After adjustment, PLAS was independently associated with events with an odds ratio of 0.42 (95% confidence interval 0.29-0.61; P < 0.0001). Stroke occurred in 67% of the patients without any clinical AA. The PLAS with a cut-off of under 15.5% provided event prediction with 91% specificity. Using a 15% cut-off, PLAS also demonstrated a predictive value for new-onset of AA.

CONCLUSION

The decrease in PLAS was strongly associated with the risk of stroke, even in patients without any documented AA. Its value for guiding the management of patients with HCM requires further investigation.

Early and late post-operative arrhythmias after surgical myectomy: 45 years of follow-up

AIMS

The aims of this study are to investigate the incidence and determinants of post-operative atrial arrhythmias, conduction disorders and mortality in hypertrophic obstructive cardiomyopathy (HOCM) patients undergoing transaortic myectomy.

METHODS AND RESULTS

This retrospective single-center study was conducted in 249 patients (median age 54 years [40-64], 42% female) undergoing transaortic myectomy. Post-operative atrial fibrillation (AF) was reported in 84 patients (33.7%), including 56 patients (22.5%) with de novo AF. Older age (HR = 1.027 (1.003-1.052), p = 0.029) and hypercholesterolemia (HR = 2.296 (1.091-4.832) p = 0.029) were independent predictors for de novo post-operative AF. Late post-operative AF and atrial flutter (AFL) occurred in 18.9% and 6.8% of the patients, respectively. De novo early post-operative AF increased the risk of late post-operative AF (HR = 3.138 (1.450-6.789), p = 0.004). Patients with a right bundle branch block had a higher risk of early-postoperative pacemaker implantation (p = 0.003, HR = 9.771 (2.195-43.505)). Higher age at time of surgery (HR = 1.053 (1.026-1.081), p < 0.001) was a predictor for late mortality (n = 47, 18.9%).

CONCLUSION

Early and late post-operative AF, AFL and other SVTs are common sequelae after myectomy and are associated with older age at surgery, history of AF and early post-operative AF. Early post-operative arrhythmias are not transient and periodic rhythm monitoring is therefore essential to initiate therapy as soon as possible.

Left Atrial Size and Function in Hypertrophic Cardiomyopathy Patients and Risk of New-Onset Atrial Fibrillation

BACKGROUND

The value of left atrial (LA) diameter, volume, and strain to risk stratify hypertrophic cardiomyopathy patients for new-onset atrial fibrillation (AF) was explored.

METHODS AND RESULTS

A total of 242 hypertrophic cardiomyopathy patients without AF history were evaluated by (speckle-tracking) echocardiography. During mean follow-up of 4.8±3.7 years, 41 patients (17%) developed new-onset AF. Multivariable analysis showed LA volume (≥37 mL/m²; hazard ratio, 2.68; 95% confidence interval, 1.30-5.54; P=0.008) and LA strain (≤23.4%; hazard ratio, 3.22; 95% confidence interval, 1.50-6.88; P=0.003), but not LA diameter (≥45 mm; hazard ratio, 1.67; 95% confidence interval, 0.84-3.32; P=0.145), as independent AF correlates. Importantly, 59% (n=24) of AF events occurred despite a baseline LA diameter <45 mm, observed in 185 patients. In this patient subset, LA strain (area under the curve 0.73) and LA volume (area under the curve 0.83) showed good predictive value for new-onset AF. Furthermore, patients with LA volume <37 versus ≥37 mL/m² and LA strain >23.4% versus ≤23.4% had superior 5-year AF-free survival of 93% versus 80% (P=0.003) and 98% versus 74% (P=0.002), respectively. Importantly, LA volume <37 mL/m² and strain >23.4% yielded high negative predictive value (93% and 98%, respectively) for new-onset AF. Likelihood ratio test indicated incremental value of LA volume assessment (P=0.011) on top of LA diameter to predict new-onset AF in hypertrophic cardiomyopathy patients with LA diameter <45 mm, which tended to increase further by addition of LA strain (P=0.126).

CONCLUSIONS

LA diameter, volume, and strain all relate to new-onset AF in hypertrophic cardiomyopathy patients. In patients with normal LA size, however, both LA volume and strain further refine risk stratification for new-onset AF.

Clinical implications of nonsarcomeric gene polymorphisms in hypertrophic cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is characterized by cardiomyocyte hypertrophy and fibrosis. Although is an autosomal dominant trait, a group of nonsarcomeric genes have been postulated as modifiers of the phenotypic heterogeneity.

MATERIAL AND METHODS

We prospectively recruited 168 HCM patients and 136 healthy controls from three referral centres. Patients and controls were clinically stable at entry in the study. Nine polymorphisms previously associated with ventricular remodelling were determined: I/D ACE, AGTR1(A1666C), CYP11B2(C344T), PGC1-α(G482S), COLIA1(G2046T), ADRB1(R389G), NOS3(G894T), RETN(-420C>G) and CALM3(-34T>A). Their potential influence on prognosis, assessed by hospital admissions, and their cause were recorded.

RESULTS

The median follow-up time was 49·5 months. Allele and genotype frequencies did not differ between patients and controls. Thirty-six patients (21·5%) required urgent hospitalization (18·5% for heart failure, 22·2% for atrial arrhythmias, 11·1% for ventricular arrhythmias, 29·6% for ischaemic heart disease, 14·8% for stroke and 3·7% for other reasons) with a hospitalization rate of 8·75% per year. Multivariate analysis showed an independent predictive value for noncarriers of polymorphic COL1A1 allele [HR: 2·76(1·26-6·05), P = 0·011] and a trend in homozygous carriers of ADRB1 Arg389 variant [HR: 1·98(0·99-4·02); P = 0·057].

CONCLUSION

Our study suggests that COL1A1 polymorphism (2046G>T) is an independent predictor of prognosis in HCM patients supporting the importance of nonsarcomeric genes on clinical prognosis in HCM.

Involvement of the -420C>G RETN polymorphism in myocardial fibrosis in patients with hypertrophic cardiomyopathy

AIMS

Hypertrophic cardiomyopathy (HCM) is characterized by left ventricular hypertrophy and fibrosis. HCM is an autosomal-dominant disease caused by more than 400 mutations in sarcomeric genes. Changes in nonsarcomeric genes contribute to its phenotypic heterogeneity. Cardiac fibrosis can be studied using late gadolinium enhancement (LGE) cardiac magnetic resonance imaging. We evaluated the potential role of two polymorphisms in nonsarcomeric genes on interstitial fibrosis in HCM.

MATERIALS AND METHODS

Two polymorphisms in nonsarcomeric genes [ACE (deletion of 287 bp in the 16th intron) and RETN (-420C>G)] were analysed in 146 HCM patients. Cardiac fibrosis was assessed using LGE to determine the number of affected segments.

RESULTS

Allelic frequencies in ACE and RETN polymorphisms were consistent with the Hardy-Weinberg equilibrium (both P > 0.05). We found that the presence of the polymorphic allele in the -420C>G RETN polymorphism was independently associated with the number of affected segments of LGE (P = 0.038). Increased circulating resistin concentration, measured by enzyme-linked immunosorbent assay, was associated with a higher degree of cardiac fibrosis. Myocardial fibrosis, assessed by Masson's trichrome staining, was associated with the -420C>G RETN polymorphism in 46 tissue samples obtained by septal myectomy (P = 0.044).

CONCLUSIONS

The -420C>G RETN polymorphism was independently associated with the degree of cardiac fibrosis, assessed by LGE, in patients with HCM. In addition, there was an association between the polymorphism and the circulating resistin levels as well as with myocardial fibrosis in tissues obtained by myectomy. Investigating the physiological implication of the RETN polymorphism in HCM in combination with the use of imaging technologies might help to establish the severity of disease in patients with HCM.

Rs7193343 polymorphism in zinc finger homeobox 3 (ZFHX3) gene and atrial fibrillation: an updated meta-analysis of 10 case-control comparisons

Background

The previous genome-wide studies have shown that rs7193343 single-nucleotide polymorphism (SNP) in zinc finger homeobox 3 (ZFHX3) gene correlate with risk of atrial fibrillation (AF). However, the distribution of this SNP differs significantly among various populations. The present study was to investigate whether combined evidence shows the association between ZFHX3 rs7193343 SNP and the risk of AF in various populations.

Methods

A systematic search of all studies published through Dec 2014 was conducted using the Medline, Embase, WanFang, ScienceDirect, CNKI, and OVID databases. The case-control studies that evaluated an association between rs7193343 SNP and risk of AF were identified. The association between the ZFHX3 rs7193343 SNP and AF susceptibility was assessed using genetic models.

Results

We collected 10 comparisons from six studies for rs7193343 SNP, including 1037 cases and 4310 controls in Asian, 5583 cases and 38215 controls in Caucasian, and then performed an updated meta-analysis and subgroup analysis based on ethnicity. In overall population, the occurrence of AF was found to be associated with T-allelic of rs7193343 SNP in ZFHX3 (OR =1.17, 95% CI 1.10-1.26). In subgroup analysis, we observed there was significant association between T-allele of rs7193343 and risk of AF in Caucasian subgroups (OR =1.20, 95% CI 1.12-1.30), but no statistically significance (OR = 1.07, 95% CI 0.92-1.24) in Asian population.

Conclusion

In Caucasian population, genetic variant rs7193343 SNP is associated with risk of AF in Caucasian population. However, no association is found in Asian population based on the current evidence. Further studies with larger sample size involving case-control populations with multiple ethnics are still required in the future.

Predictors of Atrial Fibrillation Risk in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a genetic cardiovascular disease that predisposes individuals to the development of arrhythmias. The most common sustained arrhythmia is atrial fibrillation (AF). Compared with the general population, patients with HCM are more prone to the development of AF. To avoid embolic complications and the clinical deterioration caused by the development of AF in HCM, identifying patients with a tendency toward AF might affect the management of HCM. In this review, we evaluated the predictors of AF development in patients with HCM.

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.