Publications by authors named "Hervé Le Marec"

70 Publications

Gap-134, a Connexin43 activator, prevents age-related development of ventricular fibrosis in Scn5a mice.

Pharmacol Res 2020 09 25;159:104922. Epub 2020 May 25.

Université De Nantes, CNRS, INSERM, l'institut du thorax, F-44000, Nantes, France. Electronic address:

Down-regulation of Connexin43 (Cx43) has often been associated with the development of cardiac fibrosis. We showed previously that Scn5a heterozygous knockout mice (Scn5a), which mimic familial progressive cardiac conduction defect, exhibit an age-dependent decrease of Cx43 expression and phosphorylation concomitantly with activation of TGF-β pathway and fibrosis development in the myocardium between 45 and 60 weeks of age. The aim of this study was to investigate whether Gap-134 prevents Cx43 down-regulation with age and fibrosis development in Scn5a mice. We observed in 60-week-old Scn5a mouse heart a Cx43 expression and localization remodeling correlated with fibrosis. Chronic administration of a potent and selective gap junction modifier, Gap-134 (danegaptide), between 45 and 60 weeks, increased Cx43 expression and phosphorylation on serine 368 and prevented Cx43 delocalization. Furthermore, we found that Gap-134 prevented fibrosis despite the persistence of the conduction defects and the TGF-β canonical pathway activation. In conclusion, the present study demonstrates that the age-dependent decrease of Cx43 expression is involved in the ventricular fibrotic process occurring in Scn5a mice. Finally, our study suggests that gap junction modifier, such as Gap-134, could be an effective anti-fibrotic agent in the context of age-dependent fibrosis in progressive cardiac conduction disease.
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http://dx.doi.org/10.1016/j.phrs.2020.104922DOI Listing
September 2020

SCN5A mutations in 442 neonates and children: genotype-phenotype correlation and identification of higher-risk subgroups.

Eur Heart J 2018 08;39(31):2879-2887

L'institut du thorax, INSERM, CNRS, UNIV Nantes, CHU Nantes, Nantes, France.

Aims: To clarify the clinical characteristics and outcomes of children with SCN5A-mediated disease and to improve their risk stratification.

Methods And Results: A multicentre, international, retrospective cohort study was conducted in 25 tertiary hospitals in 13 countries between 1990 and 2015. All patients ≤16 years of age diagnosed with a genetically confirmed SCN5A mutation were included in the analysis. There was no restriction made based on their clinical diagnosis. A total of 442 children {55.7% boys, 40.3% probands, median age: 8.0 [interquartile range (IQR) 9.5] years} from 350 families were included; 67.9% were asymptomatic at diagnosis. Four main phenotypes were identified: isolated progressive cardiac conduction disorders (25.6%), overlap phenotype (15.6%), isolated long QT syndrome type 3 (10.6%), and isolated Brugada syndrome type 1 (1.8%); 44.3% had a negative electrocardiogram phenotype. During a median follow-up of 5.9 (IQR 5.9) years, 272 cardiac events (CEs) occurred in 139 (31.5%) patients. Patients whose mutation localized in the C-terminus had a lower risk. Compound genotype, both gain- and loss-of-function SCN5A mutation, age ≤1 year at diagnosis in probands and age ≤1 year at diagnosis in non-probands were independent predictors of CE.

Conclusion: In this large paediatric cohort of SCN5A mutation-positive subjects, cardiac conduction disorders were the most prevalent phenotype; CEs occurred in about one-third of genotype-positive children, and several independent risk factors were identified, including age ≤1 year at diagnosis, compound mutation, and mutation with both gain- and loss-of-function.
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http://dx.doi.org/10.1093/eurheartj/ehy412DOI Listing
August 2018

Mental stress test: a rapid, simple, and efficient test to unmask long QT syndrome.

Europace 2018 12;20(12):2014-2020

l'institut du thorax, INSERM, CNRS, UNIV Nantes, CHU de Nantes, Boulevard Jacques Monod, Nantes, France.

Aims: QT prolongation during mental stress test (MST) has been associated with familial idiopathic ventricular fibrillation. In long QT syndrome (LQTS), up to 30% of mutation carriers have normal QT duration. Our aim was to assess the QT response during MST, and its accuracy in the diagnosis of concealed LQTS.

Methods And Results: All patients who are carrier of a KCNQ1 or KCNH2 mutations without QT prolongation were enrolled. A control group was constituted of patients with negative exercise and epinephrine tests. Electrocardiogram were recorded at rest and at the maximum heart rate during MST and reviewed by two physicians. Among the 70 patients enrolled (median age 41±2.1 years, 46% male), 36 were mutation carrier for LQTS (20 KCNQ1 and 16 KCNH2), and 34 were controls. KCNQ1 and KCNH2 mutation carriers presented a longer QT interval at baseline [405(389; 416) and 421 (394; 434) ms, respectively] compared with the controls [361(338; 375)ms; P < 0.0001]. QT duration during MST varied by 9 (4; 18) ms in KCNQ1, 3 (-6; 16) ms in KCNH2, and by -22 (-29; -17) ms in controls (P < 0.0001). These QT variations were independent of heart rate (P < 0.3751). Receiver operating characteristic curve analysis identified a cut-off value of QT variation superior to -11 ms as best predictor of LQTS. It provided 97% sensitivity and 97% specificity of QT prolongation in the diagnosis of LQTS.

Conclusion: We identified a paradoxical response of the QT interval during MST in LQTS. Easy to assess, MST may be efficient to unmask concealed LQTS in patients at risk of this pathology.
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http://dx.doi.org/10.1093/europace/euy078DOI Listing
December 2018

Genetics of syndromic and non-syndromic mitral valve prolapse.

Heart 2018 06 19;104(12):978-984. Epub 2018 Jan 19.

l'institut du thorax, INSERM, CNRS, Université de Nantes, Nantes, France.

Mitral valve prolapse (MVP) is a common condition that affects 2%-3% of the general population. MVP is thought to include syndromic forms such as Marfan syndrome and non-syndromic MVP, which is the most frequent form. Myxomatous degeneration and fibroelastic deficiency (FED) are regarded as two different forms of non-syndromic MVP. While FED is still considered a degenerative disease associated with ageing, frequent familial clustering has been demonstrated for myxomatous MVP. Familial and genetic studies led to the recognition of reduced penetrance and large phenotypic variability, and to the identification of prodromal or atypical forms as a part of the complex spectrum of the disease. Whereas autosomal dominant mode is the common inheritance pattern, an X linked form of non-syndromic MVP was recognised initially, related to Filamin-A gene, encoding for a cytoskeleton protein involved in mechanotransduction. This identification allowed a comprehensive description of a new subtype of MVP with a unique association of leaflet prolapse and paradoxical restricted motion in diastole. In autosomal dominant forms, three loci have been mapped to chromosomes 16p11-p12, 11p15.4 and 13q31-32. Although deciphering the underlying genetic defects is still a work in progress, mutations have been identified (11p15.4) in typical myxomatous disease, highlighting new molecular pathways and pathophysiological mechanisms leading to the development of MVP. Finally, a large international genome-wide association study demonstrated the implication of frequent variants in MVP development and opened new directions for future research. Hence, this review focuses on phenotypic, genetic and pathophysiological aspects of MVP.
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http://dx.doi.org/10.1136/heartjnl-2017-312420DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6168077PMC
June 2018

Rare Coding Variants in ANGPTL6 Are Associated with Familial Forms of Intracranial Aneurysm.

Am J Hum Genet 2018 01;102(1):133-141

INSERM, CNRS, UNIV Nantes, l'institut du thorax, 44007 Nantes, France; CHU Nantes, l'institut du thorax, 44093 Nantes, France. Electronic address:

Intracranial aneurysms (IAs) are acquired cerebrovascular abnormalities characterized by localized dilation and wall thinning in intracranial arteries, possibly leading to subarachnoid hemorrhage and severe outcome in case of rupture. Here, we identified one rare nonsense variant (c.1378A>T) in the last exon of ANGPTL6 (Angiopoietin-Like 6)-which encodes a circulating pro-angiogenic factor mainly secreted from the liver-shared by the four tested affected members of a large pedigree with multiple IA-affected case subjects. We showed a 50% reduction of ANGPTL6 serum concentration in individuals heterozygous for the c.1378A>T allele (p.Lys460Ter) compared to relatives homozygous for the normal allele, probably due to the non-secretion of the truncated protein produced by the c.1378A>T transcripts. Sequencing ANGPTL6 in a series of 94 additional index case subjects with familial IA identified three other rare coding variants in five case subjects. Overall, we detected a significant enrichment (p = 0.023) in rare coding variants within this gene among the 95 index case subjects with familial IA, compared to a reference population of 404 individuals with French ancestry. Among the 6 recruited families, 12 out of 13 (92%) individuals carrying IA also carry such variants in ANGPTL6, versus 15 out of 41 (37%) unaffected ones. We observed a higher rate of individuals with a history of high blood pressure among affected versus healthy individuals carrying ANGPTL6 variants, suggesting that ANGPTL6 could trigger cerebrovascular lesions when combined with other risk factors such as hypertension. Altogether, our results indicate that rare coding variants in ANGPTL6 are causally related to familial forms of IA.
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http://dx.doi.org/10.1016/j.ajhg.2017.12.006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5778084PMC
January 2018

New insights into mitral valve dystrophy: a Filamin-A genotype-phenotype and outcome study.

Eur Heart J 2018 04;39(15):1269-1277

l'institut du thorax, INSERM, CNRS, UNIV Nantes, Nantes, France.

Aims: Filamin-A (FLNA) was identified as the first gene of non-syndromic mitral valve dystrophy (FLNA-MVD). We aimed to assess the phenotype of FLNA-MVD and its impact on prognosis.

Methods And Results: We investigated the disease in 246 subjects (72 mutated) from four FLNA-MVD families harbouring three different FLNA mutations. Phenotype was characterized by a comprehensive echocardiography focusing on mitral valve apparatus in comparison with control relatives. In this X-linked disease valves lesions were severe in men and moderate in women. Most men had classical features of mitral valve prolapse (MVP), but without chordal rupture. By contrast to regular MVP, mitral leaflet motion was clearly restricted in diastole and papillary muscles position was closer to mitral annulus. Valvular abnormalities were similar in the four families, in adults and young patients from early childhood suggestive of a developmental disease. In addition, mitral valve lesions worsened over time as encountered in degenerative conditions. Polyvalvular involvement was frequent in males and non-diagnostic forms frequent in females. Overall survival was moderately impaired in men (P = 0.011). Cardiac surgery rate (mainly valvular) was increased (33.3 ± 9.8 vs. 5.0 ± 4.9%, P < 0.0001; hazard ratio 10.5 [95% confidence interval: 2.9-37.9]) owing mainly to a lifetime increased risk in men (76.8 ± 14.1 vs. 9.1 ± 8.7%, P < 0.0001).

Conclusion: FLNA-MVD is a developmental and degenerative disease with complex phenotypic expression which can influence patient management. FLNA-MVD has unique features with both MVP and paradoxical restricted motion in diastole, sub-valvular mitral apparatus impairment and polyvalvular lesions in males. FLNA-MVD conveys a substantial lifetime risk of valve surgery in men.
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http://dx.doi.org/10.1093/eurheartj/ehx505DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5905589PMC
April 2018

Progressive Atrial Conduction Defects Associated With Bone Malformation Caused by a Connexin-45 Mutation.

J Am Coll Cardiol 2017 Jul;70(3):358-370

Department of Molecular Physiology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan. Electronic address:

Background: Inherited cardiac conduction disease is a rare bradyarrhythmia associated with mutations in various genes that affect action potential propagation. It is often characterized by isolated conduction disturbance of the His-Purkinje system, but it is rarely described as a syndromic form.

Objectives: The authors sought to identify the genetic defect in families with a novel bradyarrhythmia syndrome associated with bone malformation.

Methods: The authors genetically screened 15 European cases with genotype-negative de novo atrioventricular (AV) block and their parents by trio whole-exome sequencing, plus 31 Japanese cases with genotype-negative familial AV block or sick sinus syndrome by targeted exon sequencing of 457 susceptibility genes. Functional consequences of the mutation were evaluated using an in vitro cell expression system and in vivo knockout mice.

Results: The authors identified a connexin-45 (Cx45) mutation (p.R75H) in 2 unrelated families (a de novo French case and a 3-generation Japanese family) who presented with progressive AV block, which resulted in atrial standstill without ventricular conduction abnormalities. Affected individuals shared a common extracardiac phenotype: a brachyfacial pattern, finger deformity, and dental dysplasia. Mutant Cx45 expressed in Neuro-2a cells showed normal hemichannel assembly and plaque formation. However, Lucifer yellow dye transfer and gap junction conductance between cell pairs were severely impaired, which suggested that mutant Cx45 impedes gap junction communication in a dominant-negative manner. Tamoxifen-induced, cardiac-specific Cx45 knockout mice showed sinus node dysfunction and atrial arrhythmia, recapitulating the intra-atrial disturbance.

Conclusions: Altogether, the authors showed that Cx45 mutant p.R75H is responsible for a novel disease entity of progressive atrial conduction system defects associated with craniofacial and dentodigital malformation.
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http://dx.doi.org/10.1016/j.jacc.2017.05.039DOI Listing
July 2017

Sodium-channel blocker challenge in the familial screening of Brugada syndrome: Safety and predictors of positivity.

Heart Rhythm 2017 10 27;14(10):1442-1448. Epub 2017 Jun 27.

l'institut du thorax, INSERM, CNRS, UNIV Nantes, CHU Nantes, Nantes, France. Electronic address:

Background: Sodium-channel blocker challenge (SCBC) is frequently performed to unmask Brugada syndrome.

Objective: We aim to identify predictors of positivity and complications of SCBC in the setting of familial screening of Brugada syndrome.

Methods: All consecutive patients from 2000 to 2014 who benefit from a sodium-channel blocker and belong to a family with at least 2 subjects affected by the syndrome were enrolled and followed prospectively. Data were reviewed by 2 physicians blinded to the clinical and genetic status.

Results: Of the 672 SCBCs performed in 137 families, 337 (50%) were positive. Multivariate analysis identified ajmaline (odds ratio [OR] 2.98; 95% CI 1.65-4.91) and a significant S wave in lead DII (OR 3.11; 95% CI 2.12-4.58), DIII (OR 2.75; 95% CI 1.78-4.25), or V (OR 3.71; 95% CI 2.54-5.44) as predictors of a positive SCBC (P < .0001). Eleven patients (1.6%) presented complications (10 ventricular arrhythmias and 1 atrial flutter), but no deaths occurred. Familial history of complications (OR 41; lower quartile, upper quartile 10, 203; P < .0001), young age (P = .04), and decreased electrocardiographic conduction parameters at baseline (P = .04) were predictors of complications. QRS enlargement during SCBC was not associated with complications. During a median follow-up of 106 months (lower quartile, upper quartile 54, 143 months), 11 life-threatening arrhythmias occurred.

Conclusion: SCBC in the screening of familial Brugada syndrome is safe. The risk of complication is considerably increased in the case of familial history of complicated SCBC, in young patients, and in the presence of decreased electrocardiographic conduction parameters. However, QRS enlargement during the test is not directly related to complications and should not be used to prematurely stop the test unless leading to false-negative results.
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http://dx.doi.org/10.1016/j.hrthm.2017.06.031DOI Listing
October 2017

The QUIDAM study: Hydroquinidine therapy for the management of Brugada syndrome patients at high arrhythmic risk.

Heart Rhythm 2017 08 12;14(8):1147-1154. Epub 2017 Apr 12.

L'institut du thorax, INSERM, CNRS, UNIV Nantes, CHU Nantes, Nantes, France.

Background: Although the implantable cardioverter-defibrillator (ICD) remains the main therapy for Brugada syndrome (BrS), it does not reduce life-threatening ventricular arrhythmia. Based on pathophysiologic mechanisms, hydroquinidine (HQ) has been suggested for effective prevention of arrhythmia.

Objective: The purpose of this study was to provide evidence-based data supporting HQ use to prevent life-threatening ventricular arrhythmia in high-risk patients with BrS.

Methods: We performed a prospective multicenter randomized (HQ vs placebo) double-blind study with two 18-month crossover phases in patients with BrS and implanted with an ICD.

Results: Among the 50 patients enrolled (mean age 47.0 ± 11.4 years, 42 [84%] male), 26 (52%) fully completed both phases. Thirty-four (68%) presented HQ-related side effects, mainly gastrointestinal, which led to discontinuation of the therapy in 13 (26%). HQ lengthened the QTc interval (409 ± 32 ms vs 433 ± 37 ms; P = .027) and increased repolarization dispersion as evaluated by Tpe max in precordial leads (89 ± 15 ms vs 108 ± 27 ms; P <.0001) with no significant changes in J-point elevation. During the 36-month follow-up, 1 appropriate ICD shock (0.97% event per year), 1 self-terminating ventricular fibrillation, and 1 inappropriate ICD shock occurred under placebo therapy. No arrhythmic events were reported under HQ therapy.

Conclusion: Although HQ seems to be effective in preventing life-threatening ventricular arrhythmia, it could not be an alternative for ICD implantation. Its frequent side effects greatly reduce its probable compliance and therefore do not reveal a significant effect. HQ increases repolarization dispersal with no changes in BrS pattern, which could indicate a more complex action of HQ than its I blocking effect alone.
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http://dx.doi.org/10.1016/j.hrthm.2017.04.019DOI Listing
August 2017

Understanding the Pathophysiology of Intracranial Aneurysm: The ICAN Project.

Neurosurgery 2017 04;80(4):621-626

Neuroradiological Department, Centre Hospitalier Universitaire of Nantes, Nan-tes, France.

Background: Understanding the pathophysiologic mechanism of intracranial aneurysm (IA) formation is a prerequisite to assess the potential risk of rupture. Nowadays, there are neither reliable biomarkers nor diagnostic tools to predict the formation or the evolution of IA. Increasing evidence suggests a genetic component of IA but genetics studies have failed to identify genetic variation causally related to IA.

Objective: To develop diagnostic and predictive tools for the risk of IA formation and rupture.

Methods: The French ICAN project is a noninterventional nationwide and multicentric research program. Each typical IA of bifurcation will be included. For familial forms, further IA screening will be applied among first-degree relatives. By accurate phenotype description with high-throughput genetic screening, we aim to identify new genes involved in IA. These potential genetic markers will be tested in large groups of patients. Any relevant pathway identified will be further explored in a large cohort of sporadic carriers of IA, which will be well documented with clinical, biological, and imaging data.

Expected Outcomes: Discovering genetic risk factors, better understanding the pathophysiology, and identifying molecular mechanisms responsible for IA formation will be essential bases for the development of biomarkers and identification of therapeutic targets.

Discussion: Our protocol has many assets. A nationwide recruitment allows for the inclusion of large pedigrees with familial forms of IA. It will combine accurate phenotyping and comprehensive imaging with high-throughput genetic screening. Last, it will enable exploiting metadata to explore new pathophysiological pathways of interest by crossing clinical, genetic, biological, and imaging information.
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http://dx.doi.org/10.1093/neuros/nyw135DOI Listing
April 2017

Brugada syndrome: Diagnosis, risk stratification and management.

Arch Cardiovasc Dis 2017 Mar 27;110(3):188-195. Epub 2017 Jan 27.

l'Institut du Thorax, INSERM, CNRS, UNIV Nantes, CHU Nantes, Nantes, France.

Brugada syndrome is a rare inherited arrhythmia syndrome leading to an increased risk of sudden cardiac death, despite a structurally normal heart. Diagnosis is based on a specific electrocardiogram pattern, observed either spontaneously or during a sodium channel blocker test. Among affected patients, risk stratification remains a challenge, despite recent insights from large population cohorts. As implantable cardiac defibrillators - the main therapy in Brugada syndrome - are associated with a high rate of complications in this population, the main challenge is risk stratification of patients with Brugada syndrome. Aside from the two main predictors of arrhythmia (symptoms and spontaneous electrocardiogram pattern), many risk factors have been recently suggested for stratifying risk of sudden cardiac death in Brugada syndrome. We have reviewed these data and discuss current guidelines in light of recent progress in this complex field.
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http://dx.doi.org/10.1016/j.acvd.2016.09.009DOI Listing
March 2017

Polymorphisms in the GNAS Gene as Predictors of Ventricular Tachyarrhythmias and Sudden Cardiac Death: Results From the DISCOVERY Trial and Oregon Sudden Unexpected Death Study.

J Am Heart Assoc 2016 11 28;5(12). Epub 2016 Nov 28.

Institute of Pharmacogenetics, University Hospital Essen, Essen, Germany.

Background: Population-based studies suggest that genetic factors contribute to sudden cardiac death (SCD).

Methods And Results: In the first part of the present study (Diagnostic Data Influence on Disease Management and Relation of Genetic Polymorphisms to Ventricular Tachy-arrhythmia in ICD Patients [DISCOVERY] trial) Cox regression was done to determine if 7 single-nucleotide polymorphisms (SNPs) in 3 genes coding G-protein subunits (GNB3, GNAQ, GNAS) were associated with ventricular tachyarrhythmia (VT) in 1145 patients receiving an implantable cardioverter-defibrillator (ICD). In the second part of the study, SNPs significantly associated with VT were further investigated in 1335 subjects from the Oregon SUDS, a community-based study analyzing causes of SCD. In the DISCOVERY trial, genotypes of 2 SNPs in the GNAS gene were nominally significant in the prospective screening and significantly associated with VT when viewed as recessive traits in post hoc analyses (TT vs CC/CT in c.393C>T: HR 1.42 [CI 1.11-1.80], P=0.005; TT vs CC/CT in c.2273C>T: HR 1.57 [CI 1.18-2.09], P=0.002). TT genotype in either SNP was associated with a HR of 1.58 (CI 1.26-1.99) (P=0.0001). In the Oregon SUDS cohort significant evidence for association with SCD was observed for GNAS c.393C>T under the additive (P=0.039, OR=1.21 [CI 1.05-1.45]) and recessive (P=0.01, OR=1.52 [CI 1.10-2.13]) genetic models.

Conclusions: GNAS harbors 2 SNPs that were associated with an increased risk for VT in ICD patients, of which 1 was successfully replicated in a community-based population of SCD cases. To the best of our knowledge, this is the first example of a gene variant identified by ICD VT monitoring as a surrogate parameter for SCD and also confirmed in the general population.

Clinical Trial Registration: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00478933.
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http://dx.doi.org/10.1161/JAHA.116.003905DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5210425PMC
November 2016

Dysfunction of the Voltage-Gated K+ Channel β2 Subunit in a Familial Case of Brugada Syndrome.

J Am Heart Assoc 2016 06 10;5(6). Epub 2016 Jun 10.

INSERM, UMR 1087, l'Institut du Thorax, Nantes, France CNRS, UMR 6291, Nantes, France Université de Nantes, Nantes, France CHU Nantes, l'Institut du Thorax, Service de Cardiologie, Nantes, France

Background: The Brugada syndrome is an inherited cardiac arrhythmia associated with high risk of sudden death. Although 20% of patients with Brugada syndrome carry mutations in SCN5A, the molecular mechanisms underlying this condition are still largely unknown.

Methods And Results: We combined whole-exome sequencing and linkage analysis to identify the genetic variant likely causing Brugada syndrome in a pedigree for which SCN5A mutations had been excluded. This approach identified 6 genetic variants cosegregating with the Brugada electrocardiographic pattern within the pedigree. In silico gene prioritization pointed to 1 variant residing in KCNAB2, which encodes the voltage-gated K(+) channel β2-subunit (Kvβ2-R12Q). Kvβ2 is widely expressed in the human heart and has been shown to interact with the fast transient outward K(+) channel subunit Kv4.3, increasing its current density. By targeted sequencing of the KCNAB2 gene in 167 unrelated patients with Brugada syndrome, we found 2 additional rare missense variants (L13F and V114I). We then investigated the physiological effects of the 3 KCNAB2 variants by using cellular electrophysiology and biochemistry. Patch-clamp experiments performed in COS-7 cells expressing both Kv4.3 and Kvβ2 revealed a significant increase in the current density in presence of the R12Q and L13F Kvβ2 mutants. Although biotinylation assays showed no differences in the expression of Kv4.3, the total and submembrane expression of Kvβ2-R12Q were significantly increased in comparison with wild-type Kvβ2.

Conclusions: Altogether, our results indicate that Kvβ2 dysfunction can contribute to the Brugada electrocardiographic pattern.
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http://dx.doi.org/10.1161/JAHA.115.003122DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4937261PMC
June 2016

The Brugada Syndrome: A Rare Arrhythmia Disorder with Complex Inheritance.

Front Cardiovasc Med 2016 25;3. Epub 2016 Apr 25.

Service de Cardiologie, Centre Hospitalier Universitaire (CHU) de Nantes, l'institut du thorax, Nantes, France; Institut National de la Santé et de la Recherche Médicale (INSERM) Unité Mixte de Recherche (UMR) 1087, l'institut du thorax, Nantes, France; Centre National de la Recherche Scientifique (CNRS) UMR 6291, l'institut du thorax, Nantes, France; l'institut du thorax, Université de Nantes, Nantes, France.

For the last 10 years, applying new sequencing technologies to thousands of whole exomes has revealed the high variability of the human genome. Extreme caution should thus be taken to avoid misinterpretation when associating rare genetic variants to disease susceptibility. The Brugada syndrome (BrS) is a rare inherited arrhythmia disease associated with high risk of sudden cardiac death in the young adult. Familial inheritance has long been described as Mendelian, with autosomal dominant mode of transmission and incomplete penetrance. However, all except 1 of the 23 genes previously associated with the disease have been identified through a candidate gene approach. To date, only rare coding variants in the SCN5A gene have been significantly associated with the syndrome. However, the genotype/phenotype studies conducted in families with SCN5A mutations illustrate the complex mode of inheritance of BrS. This genetic complexity has recently been confirmed by the identification of common polymorphic alleles strongly associated with disease risk. The implication of both rare and common variants in BrS susceptibility implies that one should first define a proper genetic model for BrS predisposition prior to applying molecular diagnosis. Although long remains the way to personalized medicine against BrS, the high phenotype variability encountered in familial forms of the disease may partly find an explanation into this specific genetic architecture.
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http://dx.doi.org/10.3389/fcvm.2016.00009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4842929PMC
May 2016

Identification of novel APOB mutations by targeted next-generation sequencing for the molecular diagnosis of familial hypobetalipoproteinemia.

Atherosclerosis 2016 07 11;250:52-6. Epub 2016 Apr 11.

INSERM, UMR1087, l'institut du thorax, Nantes, F-44000, France; CNRS, UMR 6291, Nantes, F-44000, France; Université de Nantes, Nantes, F-44000, France; CHU Nantes, l'institut du Thorax, Nantes, F-44000, France; CIC Thorax, CHU Nantes, l'institut du Thorax, Nantes, F-44000, France. Electronic address:

Background And Aims: Familial hypobetalipoproteinemia (FHBL) is a co-dominant disorder characterized by decreased plasma levels of LDL-cholesterol and apolipoprotein B (ApoB). Currently, genetic diagnosis in FHBL relies largely on Sanger sequencing to identify APOB and PCSK9 gene mutations and on western blotting to detect truncated ApoB species.

Methods: Here, we applied targeted enrichment and next-generation sequencing (NGS) on a panel of three FHBL genes and two abetalipoproteinemia genes (APOB, PCSK9, ANGPTL3, MTTP and SAR1B).

Results: In this study, we identified five likely pathogenic heterozygous rare variants. These include four novel nonsense mutations in APOB (p.Gln845*, p.Gln2571*, p.Cys2933* and p.Ser3718*) and a rare variant in PCSK9 (Minor Allele Frequency <0.1%). The affected family members tested were shown to be carriers, suggesting co-segregation with low LDL-C.

Conclusions: Our study further demonstrates that NGS is a reliable and practical approach for the molecular screening of FHBL-causative genes that may provide a mean for deciphering the genetic basis in FHBL.
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http://dx.doi.org/10.1016/j.atherosclerosis.2016.04.010DOI Listing
July 2016

Targeted resequencing identifies TRPM4 as a major gene predisposing to progressive familial heart block type I.

Int J Cardiol 2016 Mar 11;207:349-58. Epub 2016 Jan 11.

Institut National de la Santé et de la Recherche Médicale (INSERM) Unité Mixte de Recherche (UMR) 1087, l'institut du thorax, Nantes, France; Centre National de la Recherche Scientifique (CNRS) UMR 6291, l'institut du thorax, Nantes, France; Université de Nantes, l'institut du thorax, Nantes, France; Centre Hospitalier Universitaire (CHU) de Nantes, l'institut du thorax, Service de Cardiologie, Nantes, France. Electronic address:

Background: Progressive cardiac conduction disease (PCCD) is one of the most common cardiac conduction disturbances. It has been causally related to rare mutations in several genes including SCN5A, SCN1B, TRPM4, LMNA and GJA5.

Methods And Results: In this study, by applying targeted next-generation sequencing (NGS) in 95 unrelated patients with PCCD, we have identified 13 rare variants in the TRPM4 gene, two of which are currently absent from public databases. This gene encodes a cardiac calcium-activated cationic channel which precise role and importance in cardiac conduction and disease is still debated. One novel variant, TRPM4-p.I376T, is carried by the proband of a large French 4-generation pedigree. Systematic familial screening showed that a total of 13 family members carry the mutation, including 10 out of the 11 tested affected individuals versus only 1 out of the 21 unaffected ones. Functional and biochemical analyses were performed using HEK293 cells, in whole-cell patch-clamp configuration and Western blotting. TRPM4-p.I376T results in an increased current density concomitant to an augmented TRPM4 channel expression at the cell surface.

Conclusions: This study is the first extensive NGS-based screening of TRPM4 coding variants in patients with PCCD. It reports the third largest pedigree diagnosed with isolated Progressive Familial Heart Block type I and confirms that this subtype of PCCD is caused by mutation-induced gain-of-expression and function of the TRPM4 ion channel.
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http://dx.doi.org/10.1016/j.ijcard.2016.01.052DOI Listing
March 2016

Mitral valve disease--morphology and mechanisms.

Nat Rev Cardiol 2015 Dec 20;12(12):689-710. Epub 2015 Oct 20.

Aix-Marseille University, INSERM UMR 910, Marseille, France.

Mitral valve disease is a frequent cause of heart failure and death. Emerging evidence indicates that the mitral valve is not a passive structure, but--even in adult life--remains dynamic and accessible for treatment. This concept motivates efforts to reduce the clinical progression of mitral valve disease through early detection and modification of underlying mechanisms. Discoveries of genetic mutations causing mitral valve elongation and prolapse have revealed that growth factor signalling and cell migration pathways are regulated by structural molecules in ways that can be modified to limit progression from developmental defects to valve degeneration with clinical complications. Mitral valve enlargement can determine left ventricular outflow tract obstruction in hypertrophic cardiomyopathy, and might be stimulated by potentially modifiable biological valvular-ventricular interactions. Mitral valve plasticity also allows adaptive growth in response to ventricular remodelling. However, adverse cellular and mechanobiological processes create relative leaflet deficiency in the ischaemic setting, leading to mitral regurgitation with increased heart failure and mortality. Our approach, which bridges clinicians and basic scientists, enables the correlation of observed disease with cellular and molecular mechanisms, leading to the discovery of new opportunities for improving the natural history of mitral valve disease.
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http://dx.doi.org/10.1038/nrcardio.2015.161DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4804623PMC
December 2015

Genetic association analyses highlight biological pathways underlying mitral valve prolapse.

Nat Genet 2015 Oct 24;47(10):1206-11. Epub 2015 Aug 24.

Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, Massachusetts, USA.

Nonsyndromic mitral valve prolapse (MVP) is a common degenerative cardiac valvulopathy of unknown etiology that predisposes to mitral regurgitation, heart failure and sudden death. Previous family and pathophysiological studies suggest a complex pattern of inheritance. We performed a meta-analysis of 2 genome-wide association studies in 1,412 MVP cases and 2,439 controls. We identified 6 loci, which we replicated in 1,422 cases and 6,779 controls, and provide functional evidence for candidate genes. We highlight LMCD1 (LIM and cysteine-rich domains 1), which encodes a transcription factor and for which morpholino knockdown of the ortholog in zebrafish resulted in atrioventricular valve regurgitation. A similar zebrafish phenotype was obtained with knockdown of the ortholog of TNS1, which encodes tensin 1, a focal adhesion protein involved in cytoskeleton organization. We also showed expression of tensin 1 during valve morphogenesis and describe enlarged posterior mitral leaflets in Tns1(-/-) mice. This study identifies the first risk loci for MVP and suggests new mechanisms involved in mitral valve regurgitation, the most common indication for mitral valve repair.
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http://dx.doi.org/10.1038/ng.3383DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4773907PMC
October 2015

Testing the burden of rare variation in arrhythmia-susceptibility genes provides new insights into molecular diagnosis for Brugada syndrome.

Hum Mol Genet 2015 May 3;24(10):2757-63. Epub 2015 Feb 3.

Inserm, UMR 1087, l'institut du thorax, Nantes, France, CNRS, UMR 6291, Nantes, France, Université de Nantes, Nantes, France, CHU Nantes, l'institut du thorax, Service de Cardiologie, Nantes, France,

The Brugada syndrome (BrS) is a rare heritable cardiac arrhythmia disorder associated with ventricular fibrillation and sudden cardiac death. Mutations in the SCN5A gene have been causally related to BrS in 20-30% of cases. Twenty other genes have been described as involved in BrS, but their overall contribution to disease prevalence is still unclear. This study aims to estimate the burden of rare coding variation in arrhythmia-susceptibility genes among a large group of patients with BrS. We have developed a custom kit to capture and sequence the coding regions of 45 previously reported arrhythmia-susceptibility genes and applied this kit to 167 index cases presenting with a Brugada pattern on the electrocardiogram as well as 167 individuals aged over 65-year old and showing no history of cardiac arrhythmia. By applying burden tests, a significant enrichment in rare coding variation (with a minor allele frequency below 0.1%) was observed only for SCN5A, with rare coding variants carried by 20.4% of cases with BrS versus 2.4% of control individuals (P = 1.4 × 10(-7)). No significant enrichment was observed for any other arrhythmia-susceptibility gene, including SCN10A and CACNA1C. These results indicate that, except for SCN5A, rare coding variation in previously reported arrhythmia-susceptibility genes do not contribute significantly to the occurrence of BrS in a population with European ancestry. Extreme caution should thus be taken when interpreting genetic variation in molecular diagnostic setting, since rare coding variants were observed in a similar extent among cases versus controls, for most previously reported BrS-susceptibility genes.
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http://dx.doi.org/10.1093/hmg/ddv036DOI Listing
May 2015

Complex Brugada syndrome inheritance in a family harbouring compound SCN5A and CACNA1C mutations.

Basic Res Cardiol 2014 24;109(6):446. Epub 2014 Oct 24.

INSERM, UMR 1087, l'institut du thorax, 8 Quai Moncousu, BP 70721, 44007, Nantes cedex 1, France.

Brugada syndrome (BrS) is characterized by ST-segment elevation in the right precordial leads and is associated with increased risk of sudden cardiac death. We have recently reported families with BrS and SCN5A mutations where some affected members do not carry the familial mutation. We evaluated the involvement of additional genetic determinants for BrS in an affected family. We identified three distinct gene variants within a family presenting BrS (5 individuals), cardiac conduction defects (CCD, 3 individuals) and shortened QT interval (4 individuals). The first mutation is nonsense, p.Q1695*, lying within the SCN5A gene, which encodes for NaV1.5, the α-subunit of the cardiac Na(+) channel. The second mutation is missense, p.N300D, and alters the CACNA1C gene, which encodes the α-subunit CaV1.2 of the L-type cardiac Ca(2+) channel. The SCN5A mutation strictly segregates with CCD. Four out of the 5 BrS patients carry the CACNA1C variant, and three of them present shortened QT interval. One of the BrS patients carries none of these mutations but a rare variant located in the ABCC9 gene as well as his asymptomatic mother. Patch-clamp studies identified a loss-of-function of the mutated CaV1.2 channel. Western-blot experiments showed a global expression defect while increased mobility of CaV1.2 channels on cell surface was revealed by FRAP experiments. Finally, computer simulations of the two mutations recapitulated patient phenotypes. We report a rare CACNA1C mutation as causing BrS and/or shortened QT interval in a family also carrying a SCN5A stop mutation, but which does not segregate with BrS. This study underlies the complexity of BrS inheritance and its pre-symptomatic genetic screening interpretation.
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http://dx.doi.org/10.1007/s00395-014-0446-5DOI Listing
May 2015

Fine-scale human genetic structure in Western France.

Eur J Hum Genet 2015 Jun 3;23(6):831-6. Epub 2014 Sep 3.

1] INSERM UMR 1087, Nantes, France [2] CNRS, UMR 6291 institut du thorax, Nantes, France [3] Université de Nantes, Nantes, France [4] CHU Nantes, l'institut du thorax, Service de Cardiologie, Nantes, France.

The difficulties arising from association analysis with rare variants underline the importance of suitable reference population cohorts, which integrate detailed spatial information. We analyzed a sample of 1684 individuals from Western France, who were genotyped at genome-wide level, from two cohorts D.E.S.I.R and CavsGen. We found that fine-scale population structure occurs at the scale of Western France, with distinct admixture proportions for individuals originating from the Brittany Region and the Vendée Department. Genetic differentiation increases with distance at a high rate in these two parts of Northwestern France and linkage disequilibrium is higher in Brittany suggesting a lower effective population size. When looking for genomic regions informative about Breton origin, we found two prominent associated regions that include the lactase region and the HLA complex. For both the lactase and the HLA regions, there is a low differentiation between Bretons and Irish, and this is also found at the genome-wide level. At a more refined scale, and within the Pays de la Loire Region, we also found evidence of fine-scale population structure, although principal component analysis showed that individuals from different departments cannot be confidently discriminated. Because of the evidence for fine-scale genetic structure in Western France, we anticipate that rare and geographically localized variants will be identified in future full-sequence analyses.
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http://dx.doi.org/10.1038/ejhg.2014.175DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4795055PMC
June 2015

Correlation of intracardiac electrogram with surface electrocardiogram in Brugada syndrome patients.

Europace 2014 Jun 25;16(6):908-13. Epub 2013 Sep 25.

Saint Jude Medical, 15900 Valley View Court Sylmar, CA 91342, USA.

Aims: The objective of this study was to correlate the electrocardiogram (ECG) modification during an Ajmaline challenge in patients affected by the Brugada syndrome and implanted with an implantable cardioverter-defibrillator (ICD) with the morphological changes of their ICD's intracardiac electrogram (IEGM).

Methods And Results: Sixteen type 1 Brugada syndrome patients implanted with a St Jude Medical AnalyST(®) ICD were enrolled and underwent ajmaline challenge. Intracardiac electrograms and 12 lead ECG signals were collected over the duration of the study and analysed off-line. The right precordial ECG leads were in both the third and fourth intercostal space by putting V5 and V6 in V1 and V2 at the third intercostal space. Two patients were excluded from the analysis due to signal noise issues. Of the remaining 14 patients, 12 and 2 patients were adjudicated to have positive and negative ajmaline challenges, respectively, based on standard ECG criteria. In the ajmaline positive patients, the IEGM T wave amplitude changes were more prominent than those of the IEGM ST segment (-898 ± 463 vs. -55 ± 381 µV, P < 0.05). Furthermore, all of these T wave amplitude changes were in the negative polarity, whereas the change in polarity of the ST segment was mixed. The changes in the IEGM T wave amplitude and ST segment were significantly smaller in the ajmaline negative patients compared with those in the ajmaline positive patients [211 ± 158 (P < 0.05) and 107 ± 54 (P < 0.05) µV, respectively). Over all 14 analysable patients, the change in the ECG ST segment over the timecourse of the ajmaline challenge correlated better with the IEGM T wave amplitude change (R = 0.72 ± 0.33) than the IEGM ST segment change (R = 0.63 ± 0.33). Applying an IEGM T wave amplitude change cut-off of 400 µV for predicting the outcome of the ajmaline challenge yielded 92% sensitivity (11/12) and 100% specificity (2/2).

Conclusion: In Brugada patients, ajmaline challenge elicits significant T wave amplitude changes within the ICD IEGM, greater than those of the IEGM ST segment. This study is the first step to provide new tools able to continuously monitor the type I Brugada aspect in patients affected by the Brugada syndrome.
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http://dx.doi.org/10.1093/europace/eut294DOI Listing
June 2014

Common variants at SCN5A-SCN10A and HEY2 are associated with Brugada syndrome, a rare disease with high risk of sudden cardiac death.

Nat Genet 2013 Sep 21;45(9):1044-9. Epub 2013 Jul 21.

Department of Clinical and Experimental Cardiology, Heart Failure Research Center, Academic Medical Center, Amsterdam, The Netherlands.

Brugada syndrome is a rare cardiac arrhythmia disorder, causally related to SCN5A mutations in around 20% of cases. Through a genome-wide association study of 312 individuals with Brugada syndrome and 1,115 controls, we detected 2 significant association signals at the SCN10A locus (rs10428132) and near the HEY2 gene (rs9388451). Independent replication confirmed both signals (meta-analyses: rs10428132, P = 1.0 × 10(-68); rs9388451, P = 5.1 × 10(-17)) and identified one additional signal in SCN5A (at 3p21; rs11708996, P = 1.0 × 10(-14)). The cumulative effect of the three loci on disease susceptibility was unexpectedly large (Ptrend = 6.1 × 10(-81)). The association signals at SCN5A-SCN10A demonstrate that genetic polymorphisms modulating cardiac conduction can also influence susceptibility to cardiac arrhythmia. The implication of association with HEY2, supported by new evidence that Hey2 regulates cardiac electrical activity, shows that Brugada syndrome may originate from altered transcriptional programming during cardiac development. Altogether, our findings indicate that common genetic variation can have a strong impact on the predisposition to rare diseases.
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http://dx.doi.org/10.1038/ng.2712DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3869788PMC
September 2013

Cardiac characteristics and long-term outcome in Andersen-Tawil syndrome patients related to KCNJ2 mutation.

Europace 2013 Dec 17;15(12):1805-11. Epub 2013 Jul 17.

L'Institut du Thorax, Department of Cardiology, Bd Monod, Nantes University Hospital, 44093, Nantes, France.

Aims: Andersen-Tawil syndrome (ATS) is an uncommon form of channelopathy linked to mutations in the KCNJ2 gene. Currently, little is known about the long-term arrhythmic prognosis of this disease.

Methods And Results: We conducted a retrospective multicentre study in nine French hospitals. Patients were recruited only if they were KCNJ2 mutation carriers. Thirty-six patients (female n = 22, 61%) from 20 unrelated kindred were included with a mean follow-up of 9.5 ± 8.2 years. We found 12 distinct KCNJ2 mutations in the 20 probands. Three of them were novel. Thirteen patients (36%) experienced syncope and one patient was resuscitated from cardiac arrest before diagnosis. The mean QTc interval was 439 ± 57 ms and QUc was 642 ± 64 ms. All patients had normal ejection fraction. Holter recordings in 33 patients found 11 272 premature ventricular complexes (PVCs) per day on average, 25 patients had episodes of bigeminy, and 25 patients had polymorphic PVCs. Twenty-three patients (70%) had non-sustained polymorphic ventricular tachycardia (VT), and six sustained polymorphic VT. Only one patient presented with torsades de pointes. Patients were treated with beta-blocker (n = 20), beta-blocker and amiodarone (n = 2), beta-blocker and flecainide (n = 6), or acetazolamide (n = 6). Radiofrequency ablation was attempted in five patients without clinical success. An implantable cardiac defibrillator was implanted in three patients. During follow-up, none of the patients died, four patients experienced syncope under treatment, and one patient had non-fatal cardiac arrest.

Conclusion: Despite a severe clinical presentation with a very high rate of ventricular arrhythmias, the arrhythmic prognosis of the ATS patients is relatively good under treatment.
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http://dx.doi.org/10.1093/europace/eut160DOI Listing
December 2013

Identification of large families in early repolarization syndrome.

J Am Coll Cardiol 2013 Jan;61(2):164-72

INSERM, UMR1087, L'Institut du Thorax, Nantes, France.

Objectives: The aim of this study was to identify families affected by early repolarization syndrome (ERS) and to determine the mode of transmission of the disease.

Background: Early repolarization (ER) has recently been linked to idiopathic ventricular fibrillation. Familial inheritance of the disease has been suggested but not demonstrated.

Methods: We screened relatives of 4 families affected by ERS. ER was defined as a distinct J-wave in at least 2 consecutive leads and a 1-mm amplitude above baseline. The Valsalva maneuver was performed in affected and unaffected family members to decrease heart rate and thus increase or reveal an ER pattern.

Results: Twenty-two sudden cardiac deaths occurred in the 4 families including 10 before 35 years of age. In the 4 families, the prevalence of ER was 56%, 34%, 61%, and 33% of, respectively, 30, 82, 29, and 30 screened relatives. In these families, transmission of an ER pattern is compatible with an autosomal dominant mode of inheritance. All probands were screened for genes identified in ERS, and no mutation was found. The Valsalva maneuver was performed in 80 relatives, resulting in increased J-wave amplitude for 17 of 20 affected patients and revealing an ER pattern in 17 relatives in whom 5 are obligate transmitters of an ER pattern.

Conclusions: ERS can be inherited through autosomal dominant transmission and should be considered a real inherited arrhythmia syndrome. Familial investigation can be facilitated by using the Valsalva maneuver to reveal the electrocardiographic pattern in family members. The prognosis value of this test remains to be assessed.
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http://dx.doi.org/10.1016/j.jacc.2012.09.040DOI Listing
January 2013

Risk Stratification and Therapeutic Approach in Brugada Syndrome.

Arrhythm Electrophysiol Rev 2012 Sep;1(1):17-21

Professor of Cardiology and Head, Thorax Institute, Nantes, France.

Brugada syndrome (BrS) is a clinical entity characterised by an incomplete right bundle branch block associated with an ST segment elevation in the right precordial leads and a risk of ventricular arrhythmia and sudden death in the absence of structural abnormalities. Patients with a personal history of sudden death have an annual arrhythmia risk of recurrence as high as 10 %. Similarly, the presence of syncope is consistently associated with an increased arrhythmic risk. This risk can be estimated at about 1.5 % per year. The risk is lower in asymptomatic patients. Regarding the relatively high rate of complication of Implantable cardioverter defibrillator (ICD) implantation, in most of the cases, asymptomatic patients with a Brugada syndrome revealed during ajmaline challenge do not need to be implanted. The situation is more complex in patients with a spontaneous type 1 aspect since the risk could be estimated to be around 0.8 % per year. For these patients, a careful evaluation of the arrhythmic risk using all the different tools available is mandatory.
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http://dx.doi.org/10.15420/aer.2012.1.17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4711526PMC
September 2012

Parental electrocardiographic screening identifies a high degree of inheritance for congenital and childhood nonimmune isolated atrioventricular block.

Circulation 2012 Sep 16;126(12):1469-77. Epub 2012 Aug 16.

Department de Chirurgie Cardiaque des Cardiopathies Congénitales, Centre Chirurgical Marie Lannelongue, Le Plessis-Robinson, France.

Background: The origin of congenital or childhood nonimmune isolated atrioventricular (AV) block remains unknown. We hypothesized that this conduction abnormality in the young may be a heritable disease.

Methods And Results: A multicenter retrospective study (13 French referral centers, from 1980-2009) included 141 children with AV block diagnosed in utero, at birth, or before 15 years of age without structural heart abnormalities and without maternal antibodies. Parents and matched control subjects were investigated for family history and for ECG screening. In parents, a family history of sudden death or progressive cardiac conduction defect was found in 1.4% and 11.1%, respectively. Screening ECGs from 130 parents (mean age 42.0 ± 6.8 years, 57 couples) were compared with those of 130 matched healthy control subjects. All parents were asymptomatic and in sinus rhythm, except for 1 with undetected complete AV block. Conduction abnormalities were more frequent in parents than in control subjects, found in 50.8% versus 4.6%, respectively (P<0.001). A long PR interval was found in 18.5% of the parents but never in control subjects (P<0.0001). Complete or incomplete right bundle-branch block was observed in 39.2% of the parents and 1.5% of the control subjects (P<0.0001). Complete or incomplete left bundle-branch block was found in 15.4% of the parents and 3.1% of the control subjects (P<0.0006). Estimated heritability for isolated conduction disturbances was 91% (95% confidence interval, 80%-100%). SCN5A mutation screening identified 2 mutations in 2 patients among 97 children.

Conclusions: ECG screening in parents of children affected by idiopathic AV block revealed a high prevalence of conduction abnormalities. These results support the hypothesis of an inheritable trait in congenital and childhood nonimmune isolated AV block.
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http://dx.doi.org/10.1161/CIRCULATIONAHA.111.069161DOI Listing
September 2012

Identification of a strong genetic background for progressive cardiac conduction defect by epidemiological approach.

Heart 2012 Sep 19;98(17):1305-10. Epub 2012 Jun 19.

INSERM, UMR1087, CNRS UMR 6291, l’institut du thorax, Nantes, France.

Introduction: Progressive cardiac conduction defect (PCCD) is a frequent disease attributed to degeneration and fibrosis of the His bundle. Over the past years, gene defects have been identified demonstrating that PCCD could be a genetic disease. The aim of this study was to show a familial aggregation for PCCD using a genetic epidemiological approach to improve in fine genetic knowledge of the transmission of the disease.

Methods And Results: Using the French social security number, the authors have been able to determine the city of birth of the 6667 patients implanted with a pacemaker (PM) for PCCD between 1995 and 2005 in the western part of France. The authors then mapped the frequency of PM implantations for PCCD. A large heterogeneity of the frequency of the disease has been observed, with a frequency of 0.21% in the major city (Nantes) ranging up to 2.28% in specific parishes. Familial studies performed in the parishes with the highest frequency of the disease allowed the authors to identify five large families with PCCD. Clinical investigations demonstrated phenotype heterogeneity between families. Three patterns have been differentiated.

Conclusions: This study demonstrates a disparate geographical repartition of the frequency of PM implantation in the area of the authors at least in part related to a hereditary factor. The identification of five large families affected by PCCD using epidemiological approach underlines the existence of a major genetic background in PCCD.
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http://dx.doi.org/10.1136/heartjnl-2012-301872DOI Listing
September 2012

Absence of triadin, a protein of the calcium release complex, is responsible for cardiac arrhythmia with sudden death in human.

Hum Mol Genet 2012 Jun 14;21(12):2759-67. Epub 2012 Mar 14.

INSERM U836, Grenoble Institut des Neurosciences, Equipe Muscle et Pathologies, Grenoble, France.

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited arrhythmogenic disease so far related to mutations in the cardiac ryanodine receptor (RYR2) or the cardiac calsequestrin (CASQ2) genes. Because mutations in RYR2 or in CASQ2 are not retrieved in all CPVT cases, we searched for mutations in the physiological protein partners of RyR2 and CSQ2 in a large cohort of CPVT patients with no detected mutation in these two genes. Based on a candidate gene approach, we focused our investigations on triadin and junctin, two proteins that link RyR2 and CSQ2. Mutations in the triadin (TRDN) and in the junctin (ASPH) genes were searched in a cohort of 97 CPVT patients. We identified three mutations in triadin which cosegregated with the disease on a recessive mode of transmission in two families, but no mutation was found in junctin. Two TRDN mutations, a 4 bp deletion and a nonsense mutation, resulted in premature stop codons; the third mutation, a p.T59R missense mutation, was further studied. Expression of the p.T59R mutant in COS-7 cells resulted in intracellular retention and degradation of the mutant protein. This was confirmed after in vivo expression of the mutant triadin in triadin knock-out mice by viral transduction. In this work, we identified TRDN as a new gene responsible for an autosomal recessive form of CPVT. The mutations identified in the two families lead to the absence of the protein, thereby demonstrating the importance of triadin for the normal function of the cardiac calcium release complex in humans.
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http://dx.doi.org/10.1093/hmg/dds104DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3363337PMC
June 2012
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