Circulating Acylcarnitines Associated with Hypertrophic Cardiomyopathy Severity: an Exploratory Cross-Sectional Study in MYBPC3 Founder Variant Carriers

Hypertrophic cardiomyopathy (HCM) is a relatively common genetic heart disease characterised by myocardial hypertrophy. HCM can cause outflow tract obstruction, sudden cardiac death and heart failure, but severity is highly variable. In this exploratory cross-sectional study, circulating acylcarnitines were assessed as potential biomarkers in 124 MYBPC3 founder variant carriers (59 with severe HCM, 26 with mild HCM and 39 phenotype-negative [G + P-]). Elastic net logistic regression identified eight acylcarnitines associated with HCM severity. C3, C4, C6-DC, C8:1, C16, C18 and C18:2 were significantly increased in severe HCM compared to G + P-, and C3, C6-DC, C8:1 and C18 in mild HCM compared to G + P-. In multivariable linear regression, C6-DC and C8:1 correlated to log-transformed maximum wall thickness (coefficient 5.01, p = 0.005 and coefficient 0.803, p = 0.007, respectively), and C6-DC to log-transformed ejection fraction (coefficient -2.50, p = 0.004). Acylcarnitines seem promising biomarkers for HCM severity, however prospective studies are required to determine their prognostic value.

Risk stratification and subclinical phenotyping of dilated and/or arrhythmogenic cardiomyopathy mutation-positive relatives: CVON eDETECT consortium

In relatives of index patients with dilated cardiomyopathy and arrhythmogenic cardiomyopathy, early detection of disease onset is essential to prevent sudden cardiac death and facilitate early treatment of heart failure. However, the optimal screening interval and combination of diagnostic techniques are unknown. The clinical course of disease in index patients and their relatives is variable due to incomplete and age-dependent penetrance. Several biomarkers, electrocardiographic and imaging (echocardiographic deformation imaging and cardiac magnetic resonance imaging) techniques are promising non-invasive methods for detection of subclinical cardiomyopathy. However, these techniques need optimisation and integration into clinical practice. Furthermore, determining the optimal interval and intensity of cascade screening may require a personalised approach. To address this, the CVON-eDETECT (early detection of disease in cardiomyopathy mutation carriers) consortium aims to integrate electronic health record data from long-term follow-up, diagnostic data sets, tissue and plasma samples in a multidisciplinary biobank environment to provide personalised risk stratification for heart failure and sudden cardiac death. Adequate risk stratification may lead to personalised screening, treatment and optimal timing of implantable cardioverter defibrillator implantation. In this article, we describe non-invasive diagnostic techniques used for detection of subclinical disease in relatives of index patients with dilated cardiomyopathy and arrhythmogenic cardiomyopathy.

BIO FOr CARE: biomarkers of hypertrophic cardiomyopathy development and progression in carriers of Dutch founder truncating MYBPC3 variants-design and status

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is the most prevalent monogenic heart disease, commonly caused by truncating variants in the MYBPC3 gene. HCM is an important cause of sudden cardiac death; however, overall prognosis is good and penetrance in genotype-positive individuals is incomplete. The underlying mechanisms are poorly understood and risk stratification remains limited.

AIM

To create a nationwide cohort of carriers of truncating MYBPC3 variants for identification of predictive biomarkers for HCM development and progression.

METHODS

In the multicentre, observational BIO FOr CARe (Identification of BIOmarkers of hypertrophic cardiomyopathy development and progression in Dutch MYBPC3 FOunder variant CARriers) cohort, carriers of the c.2373dupG, c.2827C > T, c.2864_2865delCT and c.3776delA MYBPC3 variants are included and prospectively undergo longitudinal blood collection. Clinical data are collected from first presentation onwards. The primary outcome constitutes a composite endpoint of HCM progression (maximum wall thickness ≥ 20 mm, septal reduction therapy, heart failure occurrence, sustained ventricular arrhythmia and sudden cardiac death).

RESULTS

So far, 250 subjects (median age 54.9 years (interquartile range 43.3, 66.6), 54.8% male) have been included. HCM was diagnosed in 169 subjects and dilated cardiomyopathy in 4. The primary outcome was met in 115 subjects. Blood samples were collected from 131 subjects.

CONCLUSION

BIO FOr CARe is a genetically homogeneous, phenotypically heterogeneous cohort incorporating a clinical data registry and longitudinal blood collection. This provides a unique opportunity to study biomarkers for HCM development and prognosis. The established infrastructure can be extended to study other genetic variants. Other centres are invited to join our consortium.

UNRAVEL: big data analytics research data platform to improve care of patients with cardiomyopathies using routine electronic health records and standardised biobanking

Introduction

Despite major advances in our understanding of genetic cardiomyopathies, they remain the leading cause of premature sudden cardiac death and end-stage heart failure in persons under the age of 60 years. Integrated research databases based on a large number of patients may provide a scaffold for future research. Using routine electronic health records and standardised biobanking, big data analysis on a larger number of patients and investigations are possible. In this article, we describe the UNRAVEL research data platform embedded in routine practice to facilitate research in genetic cardiomyopathies.

Design

Eligible participants with proven or suspected cardiac disease and their relatives are asked for permission to use their data and to draw blood for biobanking. Routinely collected clinical data are included in a research database by weekly extraction. A text-mining tool has been developed to enrich UNRAVEL with unstructured data in clinical notes.

Preliminary results

Thus far, 828 individuals with a median age of 57 years have been included, 58% of whom are male. All data are captured in a temporal sequence amounting to a total of 18,565 electrocardiograms, 3619 echocardiograms, data from over 20,000 radiological examinations and 650,000 individual laboratory measurements.

Conclusion

Integration of routine electronic health care in a research data platform allows efficient data collection, including all investigations in chronological sequence. Trials embedded in the electronic health record are now possible, providing cost-effective ways to answer clinical questions. We explicitly welcome national and international collaboration and have provided our protocols and other materials on www.unravelrdp.nl.

Prevalence and cardiac phenotype of patients with a phospholamban mutation

Pathogenic mutations in the phospholamban (PLN) gene may give rise to inherited cardiomyopathies due to its role in calcium homeostasis. Several PLN mutations have been identified, with the R14del mutation being the most prevalent cardiomyopathy-related mutation in the Netherlands. It is present in patients diagnosed with arrhythmogenic cardiomyopathy as well as dilated cardiomyopathy. Awareness of the phenotype of this PLN mutation is of great importance, since many carriers remain to be identified. Patients with the R14del mutation are characterised by older age at onset, low-voltage electrocardiograms and a high frequency of ventricular arrhythmias. Additionally, these patients have a poor prognosis often with left ventricular dysfunction and early-onset heart failure. Therefore, when there is a suspicion of a PLN mutation, cardiac and genetic screening is strongly recommended.

NGS panel analysis in 24 ectopia lentis patients; a clinically relevant test with a high diagnostic yield

BACKGROUND

Several genetic causes of ectopia lentis (EL), with or without systemic features, are known. The differentiation between syndromic and isolated EL is crucial for further treatment, surveillance and counseling of patients and their relatives. Next generation sequencing (NGS) is a powerful tool enabling the simultaneous, highly-sensitive analysis of multiple target genes.

OBJECTIVE

The aim of this study was to evaluate the diagnostic yield of our NGS panel in EL patients. Furthermore, we provide an overview of currently described mutations in ADAMTSL4, the main gene involved in isolated EL.

METHODS

A NGS gene panel was analysed in 24 patients with EL.

RESULTS

A genetic diagnosis was confirmed in 16 patients (67%). Of these, four (25%) had a heterozygous FBN1 mutation, 12 (75%) were homozygous or compound heterozygous for ADAMTSL4 mutations. The known European ADAMTSL4 founder mutation c.767_786del was most frequently detected.

CONCLUSION

The diagnostic yield of our NGS panel was high. Causative mutations were exclusively identified in ADAMTSL4 and FBN1. With this approach the risk of misdiagnosis or delayed diagnosis can be reduced. The value and clinical implications of establishing a genetic diagnosis in patients with EL is corroborated by the description of two patients with an unexpected underlying genetic condition.

Arrhythmogenic cardiomyopathy: diagnosis, genetic background, and risk management

Arrhythmogenic cardiomyopathy (AC), also known as arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C), is a hereditary disease characterised by ventricular arrhythmias, right ventricular and/or left ventricular dysfunction, and fibrofatty replacement of cardiomyocytes. Patients with AC typically present between the second and the fourth decade of life with ventricular tachycardias. However, sudden cardiac death (SCD) may be the first manifestation, often at young age in the concealed stage of disease. AC is diagnosed by a set of clinically applicable criteria defined by an international Task Force. The current Task Force Criteria are the essential standard for a correct diagnosis in individuals suspected of AC. The genetic substrate for AC is predominantly identified in genes encoding desmosomal proteins. In a minority of patients a non-desmosomal mutation predisposes to the phenotype. Risk stratification in AC is imperfect at present. Genotype-phenotype correlation analysis may provide more insight into risk profiles of index patients and family members. In addition to symptomatic treatment, prevention of SCD is the most important therapeutic goal in AC. Therapeutic options in symptomatic patients include antiarrhythmic drugs, catheter ablation, and ICD implantation. Furthermore, patients with AC and also all pathogenic mutation carriers should be advised against practising competitive and endurance sports.

Otocephaly-Dysgnathia Complex: Description of Four Cases and Confirmation of the Role of OTX2

Otocephaly-dysgnathia complex is characterized by mandibular hypo- or aplasia, ear abnormalities, microstomia, and microglossia. Mutations in the orthodenticle homeobox 2 (OTX2) and paired related homeobox 1 (PRRX1) genes have recently been identified in some cases. We screened 4 otocephalic cases for these 2 genes and identified OTX2 mutations in 2 of them, thus confirming OTX2 is implicated in otocephaly. No PRRX1 mutation was identified. Interestingly, ocular involvement is not a constant feature in otocephalic cases with an OTX2 mutation. In one case, the mutation was inherited from a microphthalmic mother. The mechanism underlying this intrafamilial phenotypic variability remains unclear, but other genetic factors are likely to be necessary for the manifestation of the otocephalic phenotype.

Recurrent and founder mutations in the Netherlands: the cardiac phenotype of DES founder mutations p.S13F and p.N342D

Background

Desmin-related myopathy (DRM) is an autosomally inherited skeletal and cardiac myopathy, mainly caused by dominant mutations in the desmin gene (DES). We describe new families carrying the p.S13F or p.N342D DES mutations, the cardiac phenotype of all carriers, and the founder effects.

Methods

We collected the clinical details of all carriers of p.S13F or p.N342D. The founder effects were studied using genealogy and haplotype analysis.

Results

We identified three new index patients carrying the p.S13F mutation and two new families carrying the p.N342D mutation. In total, we summarised the clinical details of 39 p.S13F carriers (eight index patients) and of 21 p.N342D carriers (three index patients). The cardiac phenotype of p.S13F carriers is fully penetrant and severe, characterised by cardiac conduction disease and cardiomyopathy, often with right ventricular involvement. Although muscle weakness is a prominent and presenting symptom in p.N342D carriers, their cardiac phenotype is similar to that of p.S13F carriers. The founder effects of p.S13F and p.N342D were demonstrated by genealogy and haplotype analysis.

Conclusion

DRM may occur as an apparently isolated cardiological disorder. The cardiac phenotypes of the DES founder mutations p.S13F and p.N342D are characterised by cardiac conduction disease and cardiomyopathy, often with right ventricular involvement.

Electronic supplementary material

The online version of this article (doi:10.1007/s12471-011-0233-y) contains supplementary material, which is available to authorized users.

Superior mesenteric artery aneurysm in a 9-year-old boy with classical Ehlers-Danlos syndrome

A 9-year-old boy with the classical type of Ehlers-Danlos syndrome (EDS) developed a symptomatic aneurysm of the superior mesenteric artery. His EDS diagnosis had been confirmed biochemically and genetically. Vascular complications are known to be associated with the vascular type of EDS, but this is the first report of a child with classical EDS who developed a major vascular complication. Clinicians should be aware that severe vascular complications albeit rare, can also occur in classical EDS.

Founder mutations in hypertrophic cardiomyopathy patients in the Netherlands

In this part of a series on cardiogenetic founder mutations in the Netherlands, we review the Dutch founder mutations in hypertrophic cardiomyopathy (HCM) patients. HCM is a common autosomal dominant genetic disease affecting at least one in 500 persons in the general population. Worldwide, most mutations in HCM patients are identified in genes encoding sarcomeric proteins, mainly in the myosin-binding protein C gene (MYBPC3, OMIM #600958) and the beta myosin heavy chain gene (MYH7, OMIM #160760). In the Netherlands, the great majority of mutations occur in the MYBPC3, involving mainly three Dutch founder mutations in the MYBPC3 gene, the c.2373_2374insG, the c.2864_2865delCT and the c.2827C>T mutation. In this review, we describe the genetics of HCM, the genotype-phenotype relation of Dutch founder MYBPC3 gene mutations, the prevalence and the geographic distribution of the Dutch founder mutations, and the consequences for genetic counselling and testing. (Neth Heart J 2010;18:248-54.).

Critical appraisal of the revised Ghent criteria for diagnosis of Marfan syndrome

Marfan syndrome (MFS) is a connective tissue disorder with major features in cardiovascular, ocular and skeletal systems. Recently, diagnostic criteria were revised where more weight was given to the aortic root dilatation. We applied the revised Marfan nosology in an established adult Marfan population to define practical repercussions of novel criteria for clinical practice and individual patients. Out of 180 MFS patients, in 91% (n = 164) the diagnosis of MFS remained. Out of 16 patients with rejected diagnosis, four patients were diagnosed as MASS (myopia, mitral valve prolapse, borderline non-progressive aortic root dilatation, skeletal findings and striae) phenotype, three as ectopia lentis syndrome and in nine patients no alternative diagnosis was established. In 13 patients, the diagnosis was rejected because the Z-score of the aortic root was <2, although the aortic diameter was larger than 40 mm in six of them. In three other patients, the diagnosis of MFS was rejected because dural ectasia was given less weight in the revised nosology. Following the revised Marfan nosology, the diagnosis of MFS was rejected in 9% of patients, mostly because of the absence of aortic root dilatation defined as Z-score ≥2. Currently used Z-scores seem to underestimate aortic root dilatation, especially in patients with large body surface area (BSA). We recommend re-evaluation of criteria for aortic root involvement in adult patients with a suspected diagnosis of MFS.

Desmin-related myopathy

Desmin-related myopathy (DRM) is an autosomally inherited skeletal and cardiac myopathy, mainly caused by dominant mutations in the desmin gene (DES). We provide (i) a literature review on DRM, including clinical manifestations, inheritance, molecular genetics, myopathology and management and (ii) a meta-analysis of reported DES mutation carriers, focusing on their clinical characteristics and potential genotype-phenotype correlations. Meta-analysis: DES mutation carriers (n = 159) with 40 different mutations were included. Neurological signs were present in 74% and cardiological signs in 74% of carriers (both neurological and cardiological signs in 49%, isolated neurological signs in 22%, and isolated cardiological signs in 22%). More than 70% of carriers exhibited myopathy or muscular weakness, with normal creatine kinase levels present in one third of them. Up to 50% of carriers had cardiomyopathy and around 60% had cardiac conduction disease or arrhythmias, with atrioventricular block as an important hallmark. Symptoms generally started during the 30s; a quarter of carriers died at a mean age of 49 years. Sudden cardiac death occurred in two patients with a pacemaker, suggesting a ventricular tachyarrhythmia as cause of death. The majority of DES mutations were missense mutations, mostly located in the 2B domain. Mutations in the 2B domain were predominant in patients with an isolated neurological phenotype, whereas head and tail domain mutations were predominant in patients with an isolated cardiological phenotype.

[Cardiogenetics: the importance of identifying patients with hereditary heart disease]

During the past decade, developments in the field of DNA diagnostics have resulted in the confirmation of the genetic nature of several cardiac diseases. In a cardiogenetics outpatient clinic, a cardiologist and a clinical geneticist together evaluate persons with a (possible) hereditary cardiac disease. It is of utmost importance that patients with hereditary cardiac diseases be recognised and subsequently referred for genetic counselling as several preventive and therapeutic options are available.

GENCOR: a national registry for patients and families suffering from a familial heart disease in the Netherlands

INTRODUCTION

Developments in DNA-diagnostic techniques allow us to identify a significant proportion of patients with gene mutations causing familial heart diseass (arrhythmia syndromes, cardiomyopathies etc.) and to identify family members in early stages of the disease and/or even before symptoms occur. Early treatment can prevent sudden cardiac death and disease progression. However, data on long-term outcome in unselected genotyped patients are scarce due to a lack of large registries. In 2005, a national internet-based registry for familial heart diseases in the Netherlands, named GENCOR, was developed in collaboration with the Interuniversity Cardiology Institute of the Netherlands (ICIN).

OBJECTIVES

GENCOR aims to assess the prevalence of familial heart diseases in patients and families in the Netherlands and to facilitate research to improve the quality of diagnostics and therapy in familial heart diseases.

METHODS

Patients who visit the (cardio)genetic outpatient clinic are informed about GENCOR and asked to consent to the storage of information about cardiac examinations, family history and DNA diagnostics from all their visits. Patient data are entered into the internet-based GENCOR database by the cardiologist or clinical geneticist in attendance. Additional information can be stored for scientific research.

RESULTS

Four university hospitals are actively obtaining informed consent from the patients, which resulted in the inclusion of more than 300 patients. In 2006, more university hospitals will start using GENCOR and the aim is that all university hospitals will participate. Three research projects have already started using GENCOR.

CONCLUSION

GENCOR is already a success, regarding the number of included patients and the related research projects set up within a limited period of time. GENCOR provides easy internet-based access for authorised cardiologists, clinical geneticists and scientists throughout the country.

Can parents adjust to the idea that their child is at risk for a sudden death?: Psychological impact of risk for long QT syndrome

Can a parent adjust to the idea that its child is at risk for a sudden death? This question is raised by a diagnostic procedure in which children were tested for an inherited Long QT Syndrome (LQTS). This potentially life-threatening but treatable cardiac arrhythmia syndrome may cause sudden death, especially in children and young adults. The long-term psychological effects are described for parents whose children were tested for inherited LQTS. The adverse short-term impact of such testing has been described previously. The goal of this investigation is to determine whether this distress endures. Thirty-six parents completed measures of psychological distress. With the twenty-four parents of carrier children, a semi-structured interview was held 18 months after DNA disclosure. Parents of carrier children reported more distress than parents of non-carrier children. Parents of carrier children remained vulnerable to high levels of distress; up to one-third of these parents showed clinically relevant high levels of distress. High levels of distress were reported by parents of carrier children who (1) were highly distressed at previous assessments, (2) were familiar with the disease for a longer time, (3) had experienced a sudden death in the family, (4) were lesser educated, and who (5) were unsatisfied with the given information. Parents were particularly concerned about possible hazardous behavior during puberty. We conclude that the continuous threat of developing LQTS symptoms despite prophylactic treatment affected the psychological well-being of the parents for a long time. In light of the tempetuous developments in the areas of cardiac genetics, periodical information on new insight and developments may act as a buffer for the parents' (growing) concerns about their child's inherited disorder.

An extended family suddenly confronted with a life-threatening hereditary arrhythmia

OBJECTIVE

This exploratory study serves to illustrate the psychological impact on an extended family in the process of genetic counselling and testing for a potentially life-threatening arrhythmia, the long-QT syndrome (LQTS).

METHOD

All members of the third generation and their partners (n=11) were interviewed, the mutation carriers with partners twice. In addition they completed measures for anxiety and depression three times in 18 months.

RESULTS

During the interviews these family members emphasised the damaged solidarity when the family is divided into carriers and noncarriers of a mutation in a LQTS predisposing gene. This demonstrates one way in which a family can react to the reality of being at risk of a potentially severe disease. Rewriting family history and mourning early death seem other ways to deal with this. The distress scores, especially of the women, were moderate to clinically high, not because of their own chance of having an arrhythmia but more due to their children's risk.

CONCLUSION

Mothers need educational even more than emotional support, because the lifestyle of their carrier children is in need of radical change. The setting of a combined outpatient cardiogenetic clinic with a medical and psychosocial staff meets such needs efficiently.

Neonatal lactic acidosis, complex I/IV deficiency, and fetal cerebral disruption

Cerebral developmental abnormalities occur in various inborn errors of metabolism including peroxisomal deficiencies, pyruvate dehydrogenase complex deficiency and others. Associations with abnormalities of the respiratory chain are rare. Here we report male and female siblings with microcephaly, a complex neuromigrational disorder including ependymal cysts, leptomeningeal and subcortical heterotopia, polymicrogyria, multifocal cerebral calcifications, agenesis of the corpus callosum, and spongiform changes in brainstem and cerebellum. Intractable lactic acidosis, causing death on the first day of life, was associated with severely reduced activities of complex I and complex IV. The neuropathological and biochemical findings are closely similar to those reported previously. The findings confirm a distinct genetic syndrome of disrupted brain development with TORCH-like calcifications, and a complex neuronal migration disorder associated with a multicomplex disorder of the respiratory chain.

High Distress in Parents Whose Children Undergo Predictive Testing for Long QT Syndrome

OBJECTIVES

To assess the psychological effect of predictive testing in parents of children at risk for long QT syndrome (LQTS) in a prospective study.

METHODS

After their child was clinically screened by electrocardiography and blood was taken for DNA analysis, and shortly after delivery of the DNA test result, 36 parents completed measures of psychological distress.

RESULTS

24 parents were informed that at least one of their children is a mutation carrier. Up to 50% of the parents of carrier children showed clinically relevant high levels of distress. Parents who were familiar with the disease for a longer time, who had more experiences with the disease in their family and who received positive test results for all their children were most distressed.

CONCLUSIONS

Predictive ECG testing together with DNA testing has a profound impact on parents whose minors undergo predictive testing for LQTS.

[Arrhythmogenic right-ventricular cardiomyopathy: different manifestations as precursors of sudden death which might be prevented]

Two men aged 47 and 56 and one woman aged 21 presented at our cardiology department with presyncope, heart failure and exercise induced palpitations, respectively. Using the criteria of McKenna et al., a diagnosis of arrhythmogenic right-ventricular cardiomyopathy (ARVC) was made. Following implantation of a defibrillator, one of the men experienced seven appropriate interventions within six months and also developed psychological problems. The other man was problem-free and the woman recovered reasonably well, having only one appropriate intervention from the defibrillator one year after implantation. Indications of ARVC were also found in her mother but not in any other family members. Because ARVC manifests itself in various different ways it is difficult to diagnose. It is important to consider ARVC in patients with exercise-induced palpitations, presyncope, and unexplained cardiomyopathies or arrhythmias, especially if there is a family history of unexpected deaths. ARVC is a potentially life-threatening disease, that may require implantation of a cardioverter defibrillator. Furthermore, since genetics play an important role and ARVC can be asymptomatic, evaluation of close relatives for preclinical symptoms is important.

[Implantable cardioverter-defibrillator in the treatment of two patients with an increased risk of sudden cardiac death]

A 23-year-old female with familial long-QT syndrome and a 48-year-old male with familial dilated cardiomyopathy were given an implantable cardioverter-defibrillator (ICD) as prophylaxis. About half a year after the implantation, there was an appropriate and successful ICD-discharge in both patients in connection with ventricular tachycardia. Treatment with an ICD can be life-saving in patients with cardiac rhythm disorders. The most common indication is ventricular tachycardia or fibrillation due to ischaemic heart disease, but an ICD may also be indicated in patients with cardiomyopathy, congenital heart disease, hereditary arrhythmia or a planned heart transplantation.

A large family characterised by nocturnal sudden death

BACKGROUND

We recently identified a novel mutation in large family characterised by premature nocturnal sudden death. In the present paper we provide an overview of the findings in this family.

METHODS

From 1958 onwards, when the first patient presented, we collected clinical data on as many family members as possible. After identification in 1998 of the underlying genetic disorder (SCN5A, 1795insD), genotyping was performed diagnostically.

RESULTS

Since 1905 unexplained sudden death occurred in 26 family members, 17 of whom died during the night. Besides sudden death, symptomatology was rather limited; only six patients reported syncopal attacks. In one of them, a 13-year-old boy, asystolic episodes up to nine seconds were documented. Until now, the mutation has been found in 114 family members (57 males, 57 females). Carriers of the mutant gene exhibited bradycardia-dependent QT-prolongation, intrinsic sinus node dysfunction, generalised conduction abnormalities, a paucity of ventricular ectopy, and the Brugada sign. Cardiomyopathy or other structural abnormalities were not found in any of the carriers. Electrophysiological studies showed that mutant channels were characterised by markedly reduced I_Na amplitude, a positive shift of voltage-dependence of activation and a substantial negative shift of voltage-dependence of inactivation of I_Na. From 1978 onwards, a pacemaker for anti-brady pacing was implanted for prevention of sudden death. In patients in whom a prophylactic pacemaker was implanted no unexplained sudden death occurred, whereas 5 sudden deaths occurred in the group of patients who did not receive a pacemaker.

CONCLUSION

We have described a large family with a SCN5A-linked disorder (1795insD) with features of LQT₃, Brugada syndrome and familial conduction system disease. Anti-brady pacing was successful in preventing sudden death. The mode of death is possibly bradycardic.

Novel KCNQ1 and HERG missense mutations in Dutch long-QT families

Congenital long QT syndrome (cLQTS) is electrocardiographically characterized by a prolonged QT interval and polymorphic ventricular arrhythmias (torsade de pointes). These cardiac arrhythmias may result in recurrent syncopes, seizure, or sudden death. LQTS can occur either as an autosomal dominant (Romano Ward) or as an autosomal recessive disorder (Jervell and Lange-Nielsen syndrome). Mutations in at least five genes have been associated with the LQTS. Four genes, encoding cardiac ion channels, have been identified. The most common forms of LQTS are due to mutations in the potassium-channel genes KCNQ1 and HERG. We have screened 24 Dutch LQTS families for mutations in KCNQ1 and HERG. Fourteen missense mutations were identified. Eight of these missense mutations were novel: three in KCNQ1 and five in HERG. Novel missense mutations in KCNQ1 were Y184S, S373P, and W392R and novel missense mutations in HERG were A558P, R582C, G604S, T613M, and F640L. The KCNQ1 mutation G189R and the HERG mutation R582C were detected in two families. The pathogenicity of the mutations was based on segregation in families, absence in control individuals, the nature of the amino acid substitution, and localization in the protein. Genotype-phenotype studies indicated that auditory stimuli as trigger of cardiac events differentiate LQTS2 and LQTS1. In LQTS1, exercise was the predominant trigger. In addition, a number of asymptomatic gene defect carriers were identified. Asymptomatic carriers are still at risk of the development of life-threatening arrhythmias, underlining the importance of DNA analyses for unequivocal diagnosis of patients with LQTS.

[Long QT-interval syndrome and investigation of heritability: psychological reactions in three generations in one family]

DNA diagnostics were carried out in a family after the long QT interval syndrome had been diagnosed in one of its members. The psychic reactions to this testing were different from those seen in other hereditary diseases such as Huntington's disease. This was probably due to the sudden and unexpected occurrence of the arrhythmia. The family members in whom clinical and DNA diagnostics gave purely negative findings were not relieved, owing to solidarity with the affected relatives. Their partners did not understand this response. The anxiety and concern of the gene carriers had nothing to do with their own health status but with that of their carrier children. These parents were in need of educational counselling and advice. The results of clinical and DNA diagnostics affected the family relationships: in carriers the feeling of closeness grew, while the non-carriers were afraid of loss of family closeness.

[Presymptomatic screening after a sudden cardiac death in the family]

Sudden cardiac death without ischaemic heart disease may be due to a hereditary heart disease with an autosomal dominant heredity. The occurrence, if any, of sudden death in such a family is a main indicator for the risk of sudden cardiac death in other family members. Cardiological and/or genetic investigation may reveal a hereditary disease in relatives without symptoms. Of some of these pathological conditions, the corresponding chromosomal localizations and sometimes the gene mutations have been identified. The psychic burden of family investigation and the socio-economic consequences (insurances, occupation, family relationships) are potentially heavy. Prophylactic treatment of asymptomatic persons in whom a gene mutation is established may comprise advice about lifestyle (e.g. avoidance of peak exercise in patients with hypertrophic cardiomyopathy), medication (e.g. beta-receptor blockers in patients with a long QT interval) or implantation of a pacemaker or internal defibrillator (e.g. in asymptomatic persons with the Brugada syndrome, a form of right bundle branch block). Presymptomatic investigation must be performed multidisciplinary.

Auditory stimuli as a trigger for arrhythmic events differentiate HERG-related (LQTS2) patients from KVLQT1-related patients (LQTS1)

OBJECTIVE

This study was performed to identify a possible relationship between genotype and phenotype in the congenital familial long QT syndrome (cLQTS).

BACKGROUND

The cLQTS, which occurs as an autosomal dominant or recessive trait, is characterized by QT-interval prolongation on the electrocardiogram and torsade de pointes arrhythmias, which may give rise to recurrent syncope or sudden cardiac death. Precipitators for cardiac events are exercise or emotion and occasionally acoustic stimuli.

METHODS

The trigger for cardiac events (syncope, documented cardiac arrhythmias, sudden cardiac death) was analyzed in 11 families with a familial LQTS and a determined genotype.

RESULTS

The families were subdivided in KVLQT1-related families (LQTS1, n = 5) and HERG (human ether-a-gogo-related gene)-related families (LQTS2, n = 6) based on single-strand conformation polymorphism analysis and sequencing. Whereas exercise-related cardiac events dominate the clinical picture of LQTS1 patients, auditory stimuli as a trigger for arrhythmic events were only seen in LQTS2 patients.

CONCLUSIONS

Arrhythmic events triggered by auditory stimuli may differentiate LQTS2 from LQTS1 patients.