Guidelines for Genetic Testing of Inherited Cardiac Disorders

Sudden cardiac death in sports: could we save Pheidippides?

Hereditary diseases under the age of 35 are the most common underlying heart disease, leading to sudden cardiac death (SCD) in competitive sports, while in older people, atherosclerotic coronary artery disease (CAD) is the main cause. The following preventive measures are recommended: (a) The pre-participation cardiovascular screening, (b) the genetic testing, (c) the use of implantable cardioverter-defibrillator (ICD), (d) the prohibition of doping in sports, (e) the prevention of 'exercise-induced' cardiac complications, (f) the reduction of high-risk factors for CAD, and (g) the use of cardiopulmonary resuscitation. The cost-effectiveness of the electrocardiograms in the pre-participation screening programs remains questionable. Genetic testing is recommended in borderline cases and positive family history. Athletes with ICD can, under certain conditions, participate in competitive sports. Excessive endurance exercise appears to harm the endothelium, promotes inflammatory processes and leads to fibrosis in the myocardium, and calcium deposition in the coronary vessels. Cardiac arrest may be reversed if cardiopulmonary resuscitation is performed and a defibrillator is immediately used. Thus, equipping all fields with automatic external defibrillators are recommended.

Development and evaluation of decision aids to guide families' predictive testing choices for children at risk for arrhythmia or cardiomyopathy

BACKGROUND

Assessing the issues surrounding predictive genetic testing for children at risk of an inherited arrythmia or cardiomyopathy is complex. The objective of this study was to design and evaluate four cardiac decision aids. The decision aids were developed to assist families with a genetic diagnosis of long QT syndrome, hypertrophic cardiomyopathy, dilated cardiomyopathy or arrhythmogenic right ventricular cardiomyopathy in deciding between predictive genetic testing and cardiac screening for their children.

METHOD/RESULTS

The decision aids were developed using the International Patient Decision Aid Standards framework and revised based on feedback from individuals with lived experience, genetic counsellors and other healthcare professionals. Response to the decision aids was positive and acceptability and understandability scores were high.

CONCLUSION

The decision aids can be used before, during or following a genetic counselling appointment as a resource or to guide discussion. These tools permit a balanced and consistent approach to the decision-making process, with a focus on the importance families place on the advantages and disadvantages of each option.

Cardiovascular magnetic resonance in women with cardiovascular disease: position statement from the Society for Cardiovascular Magnetic Resonance (SCMR)

This document is a position statement from the Society for Cardiovascular Magnetic Resonance (SCMR) on recommendations for clinical utilization of cardiovascular magnetic resonance (CMR) in women with cardiovascular disease. The document was prepared by the SCMR Consensus Group on CMR Imaging for Female Patients with Cardiovascular Disease and endorsed by the SCMR Publications Committee and SCMR Executive Committee. The goals of this document are to (1) guide the informed selection of cardiovascular imaging methods, (2) inform clinical decision-making, (3) educate stakeholders on the advantages of CMR in specific clinical scenarios, and (4) empower patients with clinical evidence to participate in their clinical care. The statements of clinical utility presented in the current document pertain to the following clinical scenarios: acute coronary syndrome, stable ischemic heart disease, peripartum cardiomyopathy, cancer therapy-related cardiac dysfunction, aortic syndrome and congenital heart disease in pregnancy, bicuspid aortic valve and aortopathies, systemic rheumatic diseases and collagen vascular disorders, and cardiomyopathy-causing mutations. The authors cite published evidence when available and provide expert consensus otherwise. Most of the evidence available pertains to translational studies involving subjects of both sexes. However, the authors have prioritized review of data obtained from female patients, and direct comparison of CMR between women and men. This position statement does not consider CMR accessibility or availability of local expertise, but instead highlights the optimal utilization of CMR in women with known or suspected cardiovascular disease. Finally, the ultimate goal of this position statement is to improve the health of female patients with cardiovascular disease by providing specific recommendations on the use of CMR.

Clinical Insights Into Heritable Cardiomyopathies

Cardiomyopathies (CMs) encompass a heterogeneous group of structural and functional abnormalities of the myocardium. The phenotypic characteristics of these myocardial diseases range from silent to symptomatic heart failure, to sudden cardiac death due to malignant tachycardias. These diseases represent a leading cause of cardiovascular morbidity, cardiac transplantation, and death. Since the discovery of the first locus associated with hypertrophic cardiomyopathy 30 years ago, multiple loci and molecular mechanisms have been associated with these cardiomyopathy phenotypes. Conversely, the disparity between the ever-growing landscape of cardiovascular genetics and the lack of awareness in this field noticeably demonstrates the necessity to update training curricula and educational pathways. This review summarizes the current understanding of heritable CMs, including the most common pathogenic gene variants associated with the morpho-functional types of cardiomyopathies: dilated, hypertrophic, arrhythmogenic, non-compaction, and restrictive. Increased understanding of the genetic/phenotypic associations of these heritable diseases would facilitate risk stratification to leveraging appropriate surveillance and management, and it would additionally provide identification of family members at risk of avoidable cardiovascular morbidity and mortality.

Investigation of current models of care for genetic heart disease in Australia: A national clinical audit

BACKGROUND

This sub-study of the Australian Genomics Cardiovascular Genetic Disorders Flagship sought to conduct the first nation-wide audit in Australia to establish the current practices across cardiac genetics clinics.

METHOD

An audit of records of patients with a suspected genetic heart disease (cardiomyopathy, primary arrhythmia, autosomal dominant congenital heart disease) who had a cardiac genetics consultation between 1st January 2016 and 31 July 2018 and were offered a diagnostic genetic test.

RESULTS

This audit included 536 records at multidisciplinary cardiac genetics clinics from 11 public tertiary hospitals across five Australian states. Most genetic consultations occurred in a clinic setting (90%), followed by inpatient (6%) and Telehealth (4%). Queensland had the highest proportion of Telehealth consultations (9% of state total). Sixty-six percent of patients had a clinical diagnosis of a cardiomyopathy, 28% a primary arrhythmia, and 0.7% congenital heart disease. The reason for diagnosis was most commonly as a result of investigations of symptoms (73%). Most patients were referred by a cardiologist (85%), followed by a general practitioner (9%) and most genetic tests were funded by the state Genetic Health Service (73%). Nationally, 29% of genetic tests identified a pathogenic or likely pathogenic gene variant; 32% of cardiomyopathies, 26% of primary arrhythmia syndromes, and 25% of congenital heart disease.

CONCLUSION

We provide important information describing the current models of care for genetic heart diseases throughout Australia. These baseline data will inform the implementation and impact of whole genome sequencing in the Australian healthcare landscape.

Genetics-Related Activities in Everyday Practice of Family Physicians in Slovenia

INTRODUCTION

Development of genomic technologies has an important impact on patient management in medicine. Nevertheless, translation of new advances of genomic medicine in primary care is challenging and needs to be adapted to the needs of health systems.

OBJECTIVE

The objective of this study was to analyze the current state of the use and the level of confidence in genetic management activities in everyday clinical practice of family practitioners (FPs) in Slovenia.

METHODS

We used a cross-sectional observational study design. The dataset was obtained through a questionnaire containing demographics, questions about the use of genetics in everyday practice, and a scale for measuring the responders' confidence in their ability to carry out basic genetic activities during patient treatment. The questionnaire was sent by regular mail to every FP in Slovenia (N = 950).

RESULTS

The questionnaire was completed by a total of 271 physicians (response rate 28.5%), with an average physicians' age of 45.5 ± 10.6 years. In their everyday clinical practice, the majority of Slovenian FPs report to encounter genetic conditions more than once a month (241, 91.2%). Family medical history is the most commonly used among all activities related to genetic management of patients. Only 5.9% of Slovenian FPs are confident in their ability to carry out basic activities related to genetic patient management. Most of them believe they are only competent enough to obtain family medical history and identify a positive family history. The FPs who reported a lower degree of confidence are those with the lowest level of education in the field of medical genetics and older physicians (age >50 years).

CONCLUSIONS

Slovenian family physicians commonly encounter patients with genetic conditions but are not confident in their ability to carry out basic medical genetic tasks. Therefore, additional education is necessary.

The Multifaced Perspectives of Genetic Testing in Pediatric Cardiomyopathies and Channelopathies

Pediatric inherited cardiomyopathies (CMPs) and channelopathies (CNPs) remain important causes of death in this population, therefore, there is a need for prompt diagnosis and tailored treatment. Conventional evaluation fails to establish the diagnosis of pediatric CMPs and CNPs in a significant proportion, prompting further, more complex testing to make a diagnosis that could influence the implementation of lifesaving strategies. Genetic testing in CMPs and CNPs may help unveil the underlying cause, but needs to be carried out with caution given the lack of uniform recommendations in guidelines about the precise time to start the genetic evaluation or the type of targeted testing or whole-genome sequencing. A very diverse etiology and the scarce number of randomized studies of pediatric CMPs and CNPs make genetic testing of these maladies far more particular than their adult counterpart. The genetic diagnosis is even more puzzling if the psychological impact point of view is taken into account. This review aims to put together different perspectives, state-of-the art recommendations-synthetizing the major indications from European and American guidelines-and psychosocial outlooks to construct a comprehensive genetic assessment of pediatric CMPs and CNPs.

Establishment of Specialized Clinical Cardiovascular Genetics Programs: Recognizing the Need and Meeting Standards: A Scientific Statement From the American Heart Association

Cardiovascular genetics is a rapidly evolving subspecialty within cardiovascular medicine, and its growth is attributed to advances in genome sequencing and genetic testing and the expanding understanding of the genetic basis of multiple cardiac conditions, including arrhythmias (channelopathies), heart failure (cardiomyopathies), lipid disorders, cardiac complications of neuromuscular conditions, and vascular disease, including aortopathies. There have also been great advances in clinical diagnostic methods, as well as in therapies to ameliorate symptoms, slow progression of disease, and mitigate the risk of adverse outcomes. Emerging challenges include interpretation of genetic test results and the evaluation, counseling, and management of genetically at-risk family members who have inherited pathogenic variants but do not yet manifest disease. With these advances and challenges, there is a need for specialized programs combining both cardiovascular medicine and genetics expertise. The integration of clinical cardiovascular findings, including those obtained from physical examination, imaging, and functional assessment, with genetic information allows for improved diagnosis, prognostication, and cascade family testing to identify and to manage risk, and in some cases to provide genotype-specific therapy. This emerging subspecialty may ultimately require a new cardiovascular subspecialist, the genetic cardiologist, equipped with these combined skills, to permit interpretation of genetic variation within the context of phenotype and to extend the utility of genetic testing. This scientific statement outlines current best practices for delivering cardiovascular genetic evaluation and care in both the pediatric and the adult settings, with a focus on team member expertise and conditions that most benefit from genetic evaluation.

Practical Aspects in Genetic Testing for Cardiomyopathies and Channelopathies

Genetic testing has an increasingly important role in the diagnosis and management of cardiac disorders, where it confirms the diagnosis, aids prognostication and risk stratification and guides treatment. A genetic diagnosis in the proband also enables clarification of the risk for family members by cascade testing. Genetics in cardiac disorders is complex where epigenetic and environmental factors might come into interplay. Incomplete penetrance and variable expressivity is also common. Genetic results in cardiac conditions are mostly probabilistic and should be interpreted with all available clinical information. With this complexity in cardiac genetics, testing is only indicated in patients with a strong suspicion of an inheritable cardiac disorder after a full clinical evaluation. In this review we discuss the genetics underlying the major cardiomyopathies and channelopathies, and the practical aspects of diagnosing these conditions in the laboratory.

Genetic Testing for Inherited Cardiac Arrhythmias: Current State-of-the-Art and Future Avenues

The seminal discovery that sequence variation in genes encoding cardiac ion channels was behind the inherited cardiac arrhythmic syndromes has led to major advances in understanding the functional biological mechanisms of cardiomyocyte depolarization and repolarization. The cost and speed with which these genes can now be sequenced have allowed for genetic testing to become a major component of clinical care and have led to important ramifications, yet interpretation of specific variants needs to be performed within the context of the clinical findings in the proband and extended family. As technology continues to advance, the promise of therapeutic manipulation of certain genetic pathways grows ever more real.

Practice Variation among an International Group of Genetic Counselors on when to Offer Predictive Genetic Testing to Children at Risk of an Inherited Arrhythmia or Cardiomyopathy

Cascade predictive genetic testing is available for many families as a means to identify individuals at risk of long QT syndrome (LQTS), catecholaminergic polymorphic ventricular tachycardia (CPVT), hypertrophic cardiomyopathy (HCM), and arrhythmogenic right ventricular cardiomyopathy (ARVC). The general issue of offering predictive genetic testing to minors has been an area of ethical debate among genetic counselors and other healthcare professionals for many years. An online questionnaire was circulated to four international genetic counseling associations to assess the views of cardiac genetic counselors regarding when to offer predictive genetic testing to children at risk of LQTS, CPVT, HCM, and ARVC. Analysis was both quantitative and qualitative. The study sample comprised 98 respondents. The majority reported that they offer predictive genetic testing before 5 years of age to children at risk of LQTS (83%) and CVPT (75%) and before 10 years of age to children at risk of HCM (66%) or ARVC (70%). Influencing factors included country of practice, clinical setting, and years of experience. The rationale provided for when to offer predictive genetic testing is encompassed by the ethical principles of beneficence, non-maleficence, autonomy, and informed consent. In conclusion, significant practice variation exists among cardiac genetic counselors regarding predictive genetic testing for children at risk of an inherited cardiomyopathy. These variations call for more research in the area to assist with the development of evidence-based guidelines.

Genetic evaluation of cardiomyopathy: a clinical practice resource of the American College of Medical Genetics and Genomics (ACMG)

PURPOSE

The purpose of this document is to provide updated guidance for the genetic evaluation of cardiomyopathy and for an approach to manage secondary findings from cardiomyopathy genes. The genetic bases of the primary cardiomyopathies (dilated, hypertrophic, arrhythmogenic right ventricular, and restrictive) have been established, and each is medically actionable; in most cases established treatments or interventions are available to improve survival, reduce morbidity, and enhance quality of life.

METHODS

A writing group of cardiologists and genetics professionals updated guidance, first published in 2009 for the Heart Failure Society of America (HFSA), in a collaboration with the American College of Medical Genetics and Genomics (ACMG). Each recommendation was assigned to teams of individuals by expertise, literature was reviewed, and recommendations were decided by consensus of the writing group. Recommendations for family history, phenotype screening of at-risk family members, referral to expert centers as needed, genetic counseling, and cardiovascular therapies, informed in part by phenotype, are presented in the HFSA document.

RESULTS

A genetic evaluation of cardiomyopathy is indicated with a cardiomyopathy diagnosis, which includes genetic testing. Guidance is also provided for clinical approaches to secondary findings from cardiomyopathy genes. This is relevant as cardiomyopathy is the phenotype associated with 27% of the genes on the ACMG list for return of secondary findings. Recommendations herein are considered expert opinion per current ACMG policy as no systematic approach to literature review was conducted.

CONCLUSION

Genetic testing is indicated for cardiomyopathy to assist in patient care and management of at-risk family members.

Genetic Evaluation of Cardiomyopathy-A Heart Failure Society of America Practice Guideline

This guideline describes the approach and expertise needed for the genetic evaluation of cardiomyopathy. First published in 2009 by the Heart Failure Society of America (HFSA), the guideline has now been updated in collaboration with the American College of Medical Genetics and Genomics (ACMG). The writing group, composed of cardiologists and genetics professionals with expertise in adult and pediatric cardiomyopathy, reflects the emergence and increased clinical activity devoted to cardiovascular genetic medicine. The genetic evaluation of cardiomyopathy is a rapidly emerging key clinical priority, because high-throughput sequencing is now feasible for clinical testing and conventional interventions can improve survival, reduce morbidity, and enhance quality of life. Moreover, specific interventions may be guided by genetic analysis. A systematic approach is recommended: always a comprehensive family history; an expert phenotypic evaluation of the proband and at-risk family members to confirm a diagnosis and guide genetic test selection and interpretation; referral to expert centers as needed; genetic testing, with pre- and post-test genetic counseling; and specific guidance as indicated for drug and device therapies. The evaluation of infants and children demands special expertise. The approach to managing secondary and incidental sequence findings as recommended by the ACMG is provided.

Development of a communication aid for explaining hypertrophic cardiomyopathy genetic test results

Background

Large gene panels are now commonplace for hypertrophic cardiomyopathy (HCM), increasing the yield of uncertain genetic findings. Few resources exist which aim to facilitate communication of HCM genetic test results. We sought to develop, pilot, and refine a communication aid for probands receiving HCM genetic test results.

Methods

Development was a multi-step process involving expertise of a multidisciplinary team, literature review, and empirical experience. The aid went through an iterative revision process throughout the piloting phase to incorporate feedback. HCM probands attending a specialized multidisciplinary HCM clinic, aged ≥ 18 years and genetic test results available for disclosure between May and August 2016, or recently received their gene results (January–April 2015) were eligible. A purposive sampling strategy was employed, recruiting those attending clinic during the study period or those who could attend without difficulty.

Results

We developed and pilot tested a genetic counsellor-led communication aid. Based on clinical expertise, the aid addresses (a) what genetic testing is, (b) implications for the patient, (c) reasoning for variant classification, and (d) implications for the family. Pilot data were sought to assess knowledge, feasibility, and acceptability using a self-report survey 2 weeks post-intervention. Twelve of 13 participants completed the follow-up questionnaire. Participants valued the individualised nature of the aid, recommended use of the aid, and indicated genetic knowledge, and family communication was better facilitated. Iterative modification of images helped to more simply depict important genetic concepts.

Conclusions

We have developed a tool that is feasible, acceptable, and helpful to patients receiving genetic results. This is an important first step, and trial of the aid to assess effectiveness compared to usual care will follow.

Genetic Testing in Inherited Heart Diseases: Practical Considerations for Clinicians

PURPOSE OF REVIEW

Genetic testing has become an important element in the care of patients with inherited cardiac conditions (ICCs). The purpose of this review is to provide clinicians with insights into the utility of genetic testing as well as challenges associated with interpreting results.

RECENT FINDINGS

Genetic testing may be indicated for individuals who are affected with or who have family histories of various ICCs. Various testing options are available and determining the most appropriate test for any given clinical scenario is key when interpreting results. Newly published guidelines as well as various publicly accessible tools are available to clinicians to help with interpretation of genetic findings; however the subjectivity with respect to variant classification can make accurate assessment challenging. Genetic information can provide highly useful and relevant information for patients, their family members, and their healthcare providers. Given the potential ramifications of variant misclassification, expertise in both clinical phenotyping and molecular genetics is imperative in order to provide accurate diagnosis, management recommendations, and family risk assessment for this patient population.

Clinical and genetic features of Australian families with long QT syndrome: A registry-based study

BACKGROUND

Familial long QT syndrome (LQTS) is a primary arrhythmogenic disorder caused by mutations in ion channel genes. The phenotype ranges from asymptomatic individuals to sudden cardiac arrest and death. LQTS is a rare but significant health problem for which global data should exist. This study sought to provide the first clinical and genetic description of Australian families with LQTS.

METHODS

We performed a cross-sectional study to evaluate clinical and genetic features of families with LQTS. We recruited individuals from the Australian Genetic Heart Disease Registry and Genetic Heart Disease Clinic, in Sydney, Australia, and included those with a diagnosis of LQTS according to the most recent consensus statement.

RESULTS

Among 108 families with LQTS, 173 individuals were affected. Twenty-five (32%) probands had a sudden cardiac death (SCD) event (including appropriate implantable cardioverter defibrillator [ICD] therapy, or resuscitated cardiac arrest). There were 64 (82%) probands who underwent genetic testing, and 34 (53%) had a pathogenic or likely pathogenic mutation in. Having a family history of LQTS was significantly associated with identification of a pathogenic result (79% versus 14%, p<0.0001). There were 16 (9%) participants who experienced delay to diagnosis of at least 12 months.

CONCLUSIONS

This is the first clinical and genetic study in a large cohort of Australian families with LQTS. Findings from this study suggest that the clinical and genetic features in this population are not dissimilar to those described in North American, European, and Asian cohorts. Global-scale information about families with LQTS is an important initiative to ensure diagnostic and management approaches are applicable to different populations and ethnicities.

Enhancing Literacy in Cardiovascular Genetics: A Scientific Statement From the American Heart Association

Advances in genomics are enhancing our understanding of the genetic basis of cardiovascular diseases, both congenital and acquired, and stroke. These advances include finding genes that cause or increase the risk for childhood and adult-onset diseases, finding genes that influence how patients respond to medications, and the development of genetics-guided therapies for diseases. However, the ability of cardiovascular and stroke clinicians to fully understand and apply this knowledge to the care of their patients has lagged. This statement addresses what the specialist caring for patients with cardiovascular diseases and stroke should know about genetics; how they can gain this knowledge; how they can keep up-to-date with advances in genetics, genomics, and pharmacogenetics; and how they can apply this knowledge to improve the care of patients and families with cardiovascular diseases and stroke.

Genetic testing for inheritable cardiac channelopathies

Cardiac channelopathies are linked to an increased risk of ventricular arrhythmia and sudden death. This article reviews the clinical characteristics and genetic basis of common cardiac ion-channel diseases, highlights some genotype–phenotype correlations, and summarizes genetic testing for inheritable cardiac channelopathies.

Evaluation of the Mayo Clinic Phenotype-Based Genotype Predictor Score in Patients with Clinically Diagnosed Hypertrophic Cardiomyopathy

Genetic testing for hypertrophic cardiomyopathy (HCM) can provide an important clinical marker for disease outcome and family screening. This study set out to validate our recently developed phenotype-based HCM genotype predictor score. Patients clinically diagnosed with HCM and evaluated by genetic counselors comprised the study cohort. Genotype score was derived based on clinical and echocardiographic variables. Total score was correlated with the yield of genetic testing. Of 564 HCM patients, 198 sought genetic testing (35 %; 55 % male; mean age at diagnosis, 50 ± 20 years). Of these, 101 patients (51 %) were genotype positive for a HCM-associated genetic mutation (55 % male; mean age at diagnosis, 42 ± 18 years). Cochran-Armitage analysis showed similar, statistically significant trends of increased yields for higher genotype scores for both the original and study cohort. Validated by the current study, this scoring system provides an easy-to-use, clinical tool to aid in determining the likelihood of a positive HCM genetic test.

Clinical benefits of a specialised clinic for hypertrophic cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is the most common monogenic cardiac condition, with a range of investigation and management options available. Recent research has recommended management within multidisciplinary-dedicated HCM centres.

AIM

To assess the clinical impact of attendance at a specialised clinic on the management of HCM.

METHODS

A retrospective study of patients attending the HCM Clinic @ The Alfred during the first 2 years of operation was performed. Outcome measures comprised improvements in management of HCM as a result of attending the clinic including risk stratification and further investigations, medication changes, referral for implantable cardioverter-defibrillators (ICD) and septal reduction therapy, and screening of first-degree relatives (FDR).

RESULTS

Following specialised clinic attendance, there was an increase in patients investigated with 24-h Holter monitoring by 39%, stress echocardiography by 21% and cardiac magnetic resonance imaging by 70%. Medications were optimised in 47% of patients. Six per cent of patients underwent ICD implantation and 13% underwent septal myectomy. Seventy new FDR were screened identifying 10 new cases of HCM.

CONCLUSIONS

Attendance at our specialised HCM clinic leads to facilitation of cardiac investigations, optimisation of medical therapy, streamlining of referrals for ICD implantation and septal reduction therapy, and improved family screening. Referral to a specialised clinic offering comprehensive management should be considered for all patients with HCM.

General Practitioners' knowledge and use of genetic counselling in managing patients with genetic cardiac disease in non-specialised settings

There have been over 40 cardiac diseases with a genetic cause identified to date. The management of most genetic cardiac diseases (GCDs) now necessitates multidisciplinary care, including the provision of genetic counselling. This study investigated the knowledge and management of GCDs by General Practitioners (GPs). Questionnaires were mailed out to 685 doctors working in general practice in Tasmania, Australia, with 144 responses (21 %) received. Results showed that the majority (77.8 %) of the responding doctors are managing at least one patient with GCD in their practice. However, GPs identified having limited confidence in the appropriate management of these conditions and indicated that they are very dependent on guidance from a cardiologist, including whether to refer a patient to genetic counselling. To our knowledge, this is the first Australian study that looks at the care of patients with GCD in the primary care sector. The knowledge gained will help us provide more appropriate care for patients who do not have immediate access to specialised services, particularly those outside metropolitan areas, and provides evidence for what resources can be offered to doctors working in general practice to help provide quality care for these patients.

Diagnosis, prevalence, and screening of familial dilated cardiomyopathy

INTRODUCTION

Dilated cardiomyopathy (DCM) is the most common cardiomyopathy and occurs often in families. As an inherited disease, understanding the significance of diagnostic procedures and genetic screening within families is of utmost importance.

AREAS COVERED

Genetic studies have shown that in 30-40% of familial DCM (FDC) cases a causative genetic mutation can be identified. Successful genetic analysis is highly dependent on close examination of patient and family history, and clinical guidelines exist recommending genetic testing to aid in the evaluation of family members at risk of developing FDC. Clinical genetic testing offers a resource for families to identify the etiology of their disease, and in some cases may provide clinical prognostic insight.

EXPERT OPINION

As an inherited disease, future FCD studies will focus on elucidating the remaining 60-70% of genetic causes in inherited cases and the pathogenic mechanisms leading to the phenotype. Specifically, a focus on regulatory regions, copy number variation, genetic and environmental modifiers and functional confirmatory investigations will be essential.

Next generation sequencing challenges in the analysis of cardiac sudden death due to arrhythmogenic disorders

Inherited arrhythmogenic disorders is a relatively common cause of cardiac sudden death in young people. Diagnosis has been difficult so far due to the genetic heterogeneity of the disease. Next generation sequencing (NGS) is offering a new scenario for diagnosis. The purpose of our study was to validate NGS for the analysis of twenty-eight genes known to be associated with inherited arrhythmogenic disorders and therefore with sudden cardiac death. SureSelect hybridization was used to enrich DNA from 53 samples, prior to be sequenced with the SOLID™ System of Life Technologies. Depth of coverage, consistency of coverage across samples, and location of variants identified were assessed. All the samples showed a depth of coverage over 200×, except one of them discarded because of its coverage below 30×. Average percentage of target bp covered at least 20× was 96.45%. In the remaining samples, following a prioritization process 46 possible variants in 31 samples were found, of which 45 were confirmed by Sanger sequencing. After filtering variants according to their minor allele frequency in the Exome Sequencing Project 27 putative pathogenic variants in 20 samples remained. With the use of in silico tools, 13 variants in 11 samples were classified as likely pathogenic. In conclusion, NGS allowed us to accurately detect arrhythmogenic disease causing mutations in a fast and cost-efficient manner that is suitable for daily clinical and forensic practice of genetic testing of this type of disorders.

Characterization of a phenotype-based genetic test prediction score for unrelated patients with hypertrophic cardiomyopathy

OBJECTIVES

To determine the prevalence and spectrum of mutations and genotype-phenotype relationships in the largest hypertrophic cardiomyopathy (HCM) cohort to date and to provide an easy, clinically applicable phenotype-derived score that provides a pretest probability for a positive HCM genetic test result.

PATIENTS AND METHODS

Between April 1, 1997, and February 1, 2007, 1053 unrelated patients with the clinical diagnosis of HCM (60% male; mean ± SD age at diagnosis, 44.4 ± 19 years) had HCM genetic testing for the 9 HCM-associated myofilament genes. Phenotyping was performed by review of electronic medical records.

RESULTS

Overall, 359 patients (34%) were genotype positive for a putative HCM-associated mutation in 1 or more HCM-associated genes. Univariate and multivariate analyses identified the echocardiographic reverse curve morphological subtype, an age at diagnosis younger than 45 years, a maximum left ventricular wall thickness of 20 mm or greater, a family history of HCM, and a family history of sudden cardiac death as positive predictors of positive genetic test results, whereas hypertension was a negative predictor. A score, based on the number of predictors of a positive genetic test result, predicted a positive genetic test result ranging from 6% when only hypertension was present to 80% when all 5 positive predictor markers were present.

CONCLUSION

In this largest HCM cohort published to date, the overall yield of genetic testing was 34%. Although all the patients were diagnosed clinically as having HCM, the presence or absence of 6 simple clinical/echocardiographic markers predicted the likelihood of mutation-positive HCM. Phenotype-guided genetic testing using the Mayo HCM Genotype Predictor score provides an easy tool for an effective genetic counseling session.

Genetic testing in heritable cardiac arrhythmia syndromes: differentiating pathogenic mutations from background genetic noise

PURPOSE OF REVIEW

In this review, we summarize the basic principles governing rare variant interpretation in the heritable cardiac arrhythmia syndromes, focusing on recent advances that have led to disease-specific approaches to the interpretation of positive genetic testing results.

RECENT FINDINGS

Elucidation of the genetic substrates underlying heritable cardiac arrhythmia syndromes has unearthed new arrhythmogenic mechanisms and given rise to a number of clinically meaningful genotype-phenotype correlations. As such, genetic testing for these disorders now carries important diagnostic, prognostic, and therapeutic implications. Recent large-scale systematic studies designed to explore the background genetic 'noise' rate associated with these genetic tests have provided important insights and enhanced how positive genetic testing results are interpreted for these potentially lethal, yet highly treatable, cardiovascular disorders.

SUMMARY

Clinically available genetic tests for heritable cardiac arrhythmia syndromes allow the identification of potentially at-risk family members and contribute to the risk-stratification and selection of therapeutic interventions in affected individuals. The systematic evaluation of the 'signal-to-noise' ratio associated with these genetic tests has proven critical and essential to assessing the probability that a given variant represents a rare pathogenic mutation or an equally rare, yet innocuous, genetic bystander.

Clinical predictors of genetic testing outcomes in hypertrophic cardiomyopathy

PURPOSE

Genetic testing for hypertrophic cardiomyopathy has been commercially available for almost a decade; however, low mutation detection rate and cost have hindered uptake. This study sought to identify clinical variables that can predict probands with hypertrophic cardiomyopathy in whom a pathogenic mutation will be identified.

METHODS

Probands attending specialized cardiac genetic clinics across Australia over a 10-year period (2002-2011), who met clinical diagnostic criteria for hypertrophic cardiomyopathy and who underwent genetic testing for hypertrophic cardiomyopathy were included. Clinical, family history, and genotype information were collected.

RESULTS

A total of 265 unrelated individuals with hypertrophic cardiomyopathy were included, with 138 (52%) having at least one mutation identified. The mutation detection rate was significantly higher in the probands with hypertrophic cardiomyopathy with an established family history of disease (72 vs. 29%, P < 0.0001), and a positive family history of sudden cardiac death further increased the detection rate (89 vs. 59%, P < 0.0001). Multivariate analysis identified female gender, increased left-ventricular wall thickness, family history of hypertrophic cardiomyopathy, and family history of sudden cardiac death as being associated with greatest chance of identifying a gene mutation. Multiple mutation carriers (n = 16, 6%) were more likely to have suffered an out-of-hospital cardiac arrest or sudden cardiac death (31 vs. 7%, P = 0.012).

CONCLUSION

Family history is a key clinical predictor of a positive genetic diagnosis and has direct clinical relevance, particularly in the pretest genetic counseling setting.

Poor psychological wellbeing particularly in mothers following sudden cardiac death in the young

AIMS

Sudden cardiac death (SCD) in the young is a devastating event and often due to an underlying genetic heart disease. Managing these families is complicated by uncertainty regarding clinical management and profound grief. This study sought to evaluate psychological wellbeing and experiences of at-risk relatives following SCD in the young.

METHODS

Relatives who attended a specialized clinic following the SCD of a relative were invited to complete the Hospital Anxiety and Depression Scale (HADS) and a series of open-ended questions. Primary outcome measures were the HADS anxiety and depression subscales and a thematic qualitative analysis of the open-ended responses was performed. Clinical and genetic data were collected from the medical record.

RESULTS

Fifty relatives from 29 families returned surveys. The mean time since death was 4±2 years (mean age at death 23±10 years, 79% males). There was significant impairment in mean anxiety (8.7±4.3, p<0.0001) and depression (5.8±3.6, p<0.0001) scores compared to the general population. Mothers showed significantly impaired anxiety (10.9±4.0, p=0.001) and depression (7.3±3.3, p=0.001) scores, with 53% having an anxiety score above 11 suggesting probable anxiety disorder. Participants revealed a number of factors that have helped and hindered their ability to cope with the death, and their decisions relating to clinical screening.

CONCLUSION

The SCD of a young relative has significant and long-term emotional implications for the family, particularly for the mother.

The mutations associated with dilated cardiomyopathy

Cardiomyopathy is an important cause of heart failure and a major indication for heart transplantation in children and adults. This paper describes the state of the genetic knowledge of dilated cardiomyopathy (DCM). The identification of the causing mutation is important since presymptomatic interventions of DCM have proven value in preventing morbidity and mortality. Additionally, as in general in genetic studies, the identification of the mutated genes has a direct clinical impact for the families and population involved. Identifying causative mutations immediately amplifies the possibilities for disease prevention through carrier screening and prenatal testing. This often lifts a burden of social isolation from affected families, since healthy family members can be assured of having healthy children. Identification of the mutated genes holds the potential to lead to the understanding of disease etiology, pathophysiology, and therefore potential therapy. This paper presents the genetic variations, or disease-causing mutations, contributing to the pathogenesis of hereditary DCM, and tries to relate these to the functions of the mutated genes.

New Genetic Insights into Congenital Heart Disease

There has been remarkable progress in understanding the genetic basis of cardiovascular malformations. Chromosome microarray analysis has provided a new tool to understand the genetic basis of syndromic cardiovascular malformations resulting from microdeletion or microduplication of genetic material, allowing the delineation of new syndromes. Improvements in sequencing technology have led to increasingly comprehensive testing for aortopathy, cardiomyopathy, single gene syndromic disorders, and Mendelian-inherited congenital heart disease. Understanding the genetic etiology for these disorders has improved their clinical recognition and management and led to new guidelines for treatment and family-based diagnosis and surveillance. These new discoveries have also expanded our understanding of the contribution of genetic variation, susceptibility alleles, and epigenetics to isolated congenital heart disease. This review summarizes the current understanding of the genetic basis of syndromic and non-syndromic congenital heart disease and highlights new diagnostic and management recommendations.