Prospective, population-based long QT molecular autopsy study of postmortem negative sudden death in 1 to 40 year olds

Concealed cardiomyopathy as an emerging cause of sudden cardiac arrest and sudden cardiac death

The inherited cardiomyopathies exhibit a broad spectrum of disease, with some patients remaining asymptomatic throughout life, while, for others, the first symptom of disease is sudden cardiac death at a young age. The risk of malignant ventricular arrhythmia in these conditions has traditionally been linked to the degree of structural myocardial abnormalities and functional impairment. However, recent advances in genetic testing and knowledge of the genetic basis of the diseases have led to the identification of concealed cardiomyopathy, in which sudden cardiac arrest or sudden cardiac death occurs in the absence of observable clinical features of cardiomyopathy, with a diagnosis being made only after the identification of a causative genetic variant. Increased awareness of concealed cardiomyopathy, a better understanding of mechanisms of arrhythmia and identification of risk modulators will be vital to improve care for families with concealed cardiomyopathy.

Autopsy of all young sudden death cases is important to increase survival in family members left behind

Sudden cardiac death (SCD) is an important public health problem worldwide, accounting for an estimated 6-20% of total mortality. A significant proportion of SCD is caused by inherited heart disease, especially among the young. An autopsy is crucial to establish a diagnosis of inherited heart disease, allowing for subsequent identification of family members who require cardiac evaluation. Autopsy of cases of unexplained sudden death in the young is recommended by both the European Society of Cardiology and the American Heart Association. Overall autopsy rates, however, have been declining in many countries across the globe, and there is a lack of skilled trained pathologists able to carry out full autopsies. Recent studies show that not all cases of sudden death in the young are autopsied, likely due to financial, administrative, and organizational limitations as well as awareness among police, legal authorities, and physicians. Consequently, diagnoses of inherited heart disease are likely missed, along with the opportunity for treatment and prevention among surviving relatives. This article reviews the evidence for the role of autopsy in sudden death, how the cardiologist should interpret the autopsy-record, and how this can be integrated and implemented in clinical practice. Finally, we identify areas for future research along with potential for healthcare reform aimed at increasing autopsy awareness and ultimately reducing mortality from SCD.

Sudden cardiac death in the young: A qualitative study of experiences of family members with cardiogenetic evaluation

Sudden cardiac death (SCD) is a devastating event for the family and the community, especially when it occurs in a young person (<45 years). Genetic heart diseases, including cardiomyopathies and primary arrhythmia syndromes, are an important cause of SCD in the young. Although cardiogenetic evaluation, that is, clinical evaluation, genetic testing, and psychological support, is increasingly performed after SCD, it is unknown how suddenly bereaved family members experience the process. We aimed to explore the experiences of family members with cardiogenetic evaluation after SCD, and their perception of the process and care received. In-depth interviews were conducted with 18 family members of young people (<45 years old) who died suddenly, including parents, siblings, and partners. The interviews were thematically analyzed by two researchers independently. In total, 18 interviews were conducted from 17 families. The following themes were identified: (1) Experiences with postmortem genetic testing including managing expectations and psychological impact, (2) appreciation of care such as access to genetic counseling and relief following cardiac evaluation of relatives, and (3) need for support including unmet psychological support needs and better coordination of care immediately after the death. Although participants appreciated the opportunity for cardiogenetic evaluation, they also experienced a lack of coordination of cardiogenetic and psychological care. Our findings stress the importance of access to expert multidisciplinary teams, including psychological care, to adequately support these families after a SCD in a young family member.

Novel combinations of variations in KCNQ1 were associated with patients with long QT syndrome or Jervell and Lange-Nielsen syndrome

OBJECTIVES

Long QT syndrome (LQTS) is one of the primary causes of sudden cardiac death (SCD) in youth. Studies have identified mutations in ion channel genes as key players in the pathogenesis of LQTS. However, the specific etiology in individual families remains unknown.

METHODS

Three unrelated Chinese pedigrees diagnosed with LQTS or Jervell and Lange-Nielsen syndrome (JLNS) were recruited clinically. Whole exome sequencing (WES) was performed and further validated by multiplex ligation-dependent probe amplification (MLPA) and Sanger sequencing.

RESULTS

All of the probands in our study experienced syncope episodes and featured typically prolonged QTc-intervals. Two probands also presented with congenital hearing loss and iron-deficiency anemia and thus were diagnosed with JLNS. A total of five different variants in KCNQ1, encoding a subunit of the voltage-gated potassium channel, were identified in 3 probands. The heterozygous variants, KCNQ1 c.749T > C was responsible for LQTS in Case 1, transmitting in an autosomal dominant pattern. Two patterns of compound heterozygous variants were responsible for JLNS, including a large deletion causing loss of the exon 16 and missense variant c.1663 C > T in Case 2, and splicing variant c.605-2 A > G and frame-shift variant c.1265del in Case 3. To our knowledge, the compound heterozygous mutations containing a large deletion and missense variant were first reported in patients with JLNS.

CONCLUSION

Our study expanded the LQTS genetic spectrum, thus favoring disease screening and diagnosis, personalized treatment, and genetic consultation.

Handle with Care: A Narrative Review of Infant Safe Sleep Practices across Clinical Guidelines and Social Media to Reduce SIDS

Sudden Infant Death Syndrome (SIDS) is a leading cause of infant mortality across the United States and the world. There are multiple environmental and behavioral determinants of sudden infant death which are modifiable risk factors and potential targets for intervention. In this increasingly digital era, health education and communication on SIDS have taken many forms, which extend to social media. Current published studies on coverage of infant safe sleep practices are scant and were published well before the newly revised guidelines of the American Academy of Pediatrics that review ways to prevent infant sleep-related deaths based on evidence-based SIDS-reduction measures. In this Perspective: Review of a Pediatric Field, the current state of published knowledge and coverage on a range of infant safe sleep considerations across social media are reviewed. We delineate gaps in the knowledge and practice as well as the central differences between the 2016 and 2022 AAP Safe Sleep guidelines. We also present recommendations for further research and practice which support coverage of future content on the revised guidelines across social media as the basis to present the most up-to-date and evidence-based information for reducing sudden infant death from sleep-related causes. Tapping into the potential of social media as a learning modality in health promotion also contributes towards the larger goal of the World Health Organization, United Nations International Children's Emergency Fund (UNICEF), and Healthy People 2030 to reduce infant mortality on both global and national levels.

The role of genetic testing in the prevention, diagnosis, and prognosis of sudden cardiac arrest in children

Background

Determining the pathogenesis of sudden cardiac arrest (SCA) in children is crucial for its management and prognosis. Our aim is to analyze the role of broad genetic testing in the prevention, diagnosis, and prognosis of SCA in Children.

Methods

ECG, 12-lead holter, exercise testing, cardiac imaging, familial study, and genetic testing were used to study 29 families, in whom a child experienced SCA.

Results

After a thorough clinical and genetic evaluation a positive diagnosis was reached in 24/29 (83%) families. Inherited channelopathies (long QT syndrome and catecholaminergic polymorphic ventricular tachycardia) were the most prevalent 20/29 (69%) diagnosis, followed by cardiomyopathy 3/29 (10%). Broad genetic testing was positive in 17/24 (71%) cases. Using the Mann-Whitney test, we found that genetic testing (effect size = 0.625, p = 0.003), ECG (effect size = 0.61, p = 0.009), and exercise test (effect size = 0.63, p = 0.047) had the highest yield in reaching the final diagnosis. Genetic testing was the only positive test available for five (17%) families. Among 155 family members evaluated through cascade screening, 73 (47%) had a positive clinical evaluation and 64 (41%) carried a pathologic mutation. During 6 ± 4.8 years of follow-up, 58% of the survived children experienced an arrhythmic event. Of nine family members who had an ICD implant for primary prevention, four experienced appropriate ICD shock.

Conclusions

The major causes of SCA among children are genetic etiology, and genetic testing has a high yield. Family screening has an additional role in both the diagnosis and preventing of SCA.

Risk factors of sudden cardiac death in Egyptian patients younger than 40 years

BACKGROUND

Sudden cardiac death in young people is a major problem. The causes are well known; however, they may not be discovered before the episode of sudden death. A challenge for the future is identifying patients at risk before an episode of sudden cardiac death. Development of preventive and educational programs is required to identify sudden cardiac death/sudden cardiac arrest (SCD/SCA) risk factors, causes and characteristics. We aimed to study the characteristics of SCD/SCA in a cohort of young Egyptian population. Our retrospective cohort study included 246 patients of SCD/SCA who were collected from 5000 records of arrhythmia patients from January 2010 till January 2020. The records of the specialized arrhythmia clinic were reviewed to collect the families of SCD/SCA. All patients and/or their first-degree relatives were subjected to thorough history taking and clinical evaluation and investigations. Comparisons were done regarding age group and presence of positive family history of SCD.

RESULTS

Males constituted 56.9% of the study population. Mean age was 26.6 ± 12.73 years. Positive family history was present in 202 (82.1%) cases. Sixty-one percent of the cases had history of syncopal attacks. SCD/SCA during non-exertion or sleep occurred in 50.4% of cases. Hypertrophic cardiomyopathy was the most common cause of SCD/SCA (20.3%), followed by dilated cardiomyopathy (19.1%), long QT Syndrome (11.4%), complete heart block (8.5%), and Brugada syndrome (6.8%). In the older age group of 18-40 years, hypertrophic cardiomyopathy was responsible for SCD in 44 patients (25.3%) versus 6 patients (8.3%) in younger age group (p-value: 0.003). DCM was also dominant in older age group (42 patients; 24.1%) versus 5 patients (6.9%) in younger age group. Hypertrophic cardiomyopathy was more prevalent in positive family history group (46 patients; 22.8%) versus 4 patients (9.1%) in negative family history group (p-value: 0.041).

CONCLUSION

Family history of SCD was the most common risk factor of SCD. The most common cause of SCD in young Egyptian patients below 40 years was hypertrophic cardiomyopathy, followed by dilated cardiomyopathy. Both diseases were more common in the age group between 18 and 40 years. Hypertrophic cardiomyopathy was more common in patients with positive family history of SCD/SCA.

Molecular autopsy: Twenty years of post-mortem diagnosis in sudden cardiac death

In the forensic medicine field, molecular autopsy is the post-mortem genetic analysis performed to attempt to unravel the cause of decease in cases remaining unexplained after a comprehensive forensic autopsy. This negative autopsy, classified as negative or non-conclusive, usually occurs in young population. In these cases, in which the cause of death is unascertained after a thorough autopsy, an underlying inherited arrhythmogenic syndrome is the main suspected cause of death. Next-generation sequencing allows a rapid and cost-effectives genetic analysis, identifying a rare variant classified as potentially pathogenic in up to 25% of sudden death cases in young population. The first symptom of an inherited arrhythmogenic disease may be a malignant arrhythmia, and even sudden death. Early identification of a pathogenic genetic alteration associated with an inherited arrhythmogenic syndrome may help to adopt preventive personalized measures to reduce risk of malignant arrhythmias and sudden death in the victim's relatives, at risk despite being asymptomatic. The current main challenge is a proper genetic interpretation of variants identified and useful clinical translation. The implications of this personalized translational medicine are multifaceted, requiring the dedication of a specialized team, including forensic scientists, pathologists, cardiologists, pediatric cardiologists, and geneticists.

Causes of sudden cardiac death according to age and sex in persons aged 1-49 years

BACKGROUND

Knowledge of causes of sudden cardiac death (SCD) according to age is important in clinical decision making and to lower the risk of SCD in family members of the deceased.

OBJECTIVE

The purpose of this study was to report overall and sex-stratified causes of SCD according to age in persons aged 1-49 years.

METHODS

The study population consisted of all persons in Denmark aged 1-35 years in 2000-2009 and 36-49 years in 2007-2009, which equals 27.1 million person-years. Danish death certificates, discharge summaries, autopsy reports, and data from nationwide registries were used to identify all SCD cases. The SCD cases were divided into 5-year age groups.

RESULTS

In the 10-year study period, there were 14,294 deaths, of which 1362 (10%) were classified as SCD. Potentially inherited cardiac disease accounted for a high proportion (43%-78%) of autopsied SCD in all age groups. A significant proportion (19%-54%) of SCD was caused by sudden arrhythmic death syndrome in all age groups. Autopsy rates in both sudden unexpected death cases and SCD cases declined significantly with increasing age (74% in the youngest age group vs 35% in the oldest).

CONCLUSION

The proportion of SCD cases that were identified with a potentially inherited cardiac disease postmortem was high in all studied age groups, while autopsy rates in sudden and unexpected death cases declined markedly with increasing age. Our findings indicate that diagnoses of inherited heart disease are likely missed in some SCD cases, along with the opportunity for treatment and prevention in surviving relatives.

Ten-year-old boy with congenital long QT syndrome type 2 (LQTS2) and life-threatening electrical storm: a case report of successful treatment with mexiletine

We present a case of a boy with long QT syndrome type 2, who was admitted after an out of hospital cardiac arrest due to ventricular fibrillation. Subsequently, all treatments - intravenous magnesium, optimisation of electrolytes, an isoproterenol infusion - failed to terminate his electrical storm. As a last option before left-sided cardiac sympathetic denervation, mexiletine was started and the electrical storm resolved completely.

1029 genomes of self-declared healthy individuals from India reveal prevalent and clinically relevant cardiac ion channelopathy variants

BACKGROUND

The prevalence and genetic spectrum of cardiac channelopathies exhibit population-specific differences. We aimed to understand the spectrum of cardiac channelopathy-associated variations in India, which is characterised by a genetically diverse population and is largely understudied in the context of these disorders.

RESULTS

We utilised the IndiGenomes dataset comprising 1029 whole genomes from self-declared healthy individuals as a template to filter variants in 36 genes known to cause cardiac channelopathies. Our analysis revealed 186,782 variants, of which we filtered 470 variants that were identified as possibly pathogenic (440 nonsynonymous, 30 high-confidence predicted loss of function ). About 26% (124 out of 470) of these variants were unique to the Indian population as they were not reported in the global population datasets and published literature. Classification of 470 variants by ACMG/AMP guidelines unveiled 13 pathogenic/likely pathogenic (P/LP) variants mapping to 19 out of the 1029 individuals. Further query of 53 probands in an independent cohort of cardiac channelopathy, using exome sequencing, revealed the presence of 3 out of the 13 P/LP variants. The identification of p.G179Sfs*62, p.R823W and c.420 + 2 T > C variants in KCNQ1, KCNH2 and CASQ2 genes, respectively, validate the significance of the P/LP variants in the context of clinical applicability as well as for large-scale population analysis.

CONCLUSION

A compendium of ACMG/AMP classified cardiac channelopathy variants in 1029 self-declared healthy Indian population was created. A conservative genotypic prevalence was estimated to be 0.9-1.8% which poses a huge public health burden for a country with large population size like India. In the majority of cases, these disorders are manageable and the risk of sudden cardiac death can be alleviated by appropriate lifestyle modifications as well as treatment regimens/clinical interventions. Clinical utility of the obtained variants was demonstrated using a cardiac channelopathy patient cohort. Our study emphasises the need for large-scale population screening to identify at-risk individuals and take preventive measures. However, we suggest cautious clinical interpretation to be exercised by taking other cardiac channelopathy risk factors into account.

Family Screening After Sudden Death in a Population-Based Study of Children

In a US population-based registry of sudden death in the young, this study performed familial evaluation of surviving relatives.

A review of the causes and risk factors for sudden unexpected death in the young

Sudden unexpected death in the young (SUDY) is a tragic event resulting in the fatality of seemingly healthy individuals between the ages of one and 40 years. Whilst studies have been performed on sudden unexpected death in infants, children, and adults respectively, little is known about trends in risk factors and causes of death of SUDY cases. Understanding the factors surrounding these deaths could lead to targeted interventions for at-risk individuals. Hence, a systematic approach to investigate the reported possible causes of SUDY was employed using three major databases and Primo, wherein 67 relevant articles were identified and 2 additional guidelines were read. Sudden unexpected death in epilepsy and sudden cardiac events were well-established causes of death with risk factors such as male predominance, substance use and a familial history identified. It was acknowledged that while the cause of death is established following post-mortem examination in many cases, some remain non-specific or undetermined. Considering the genetic etiology, these cases would be ideal candidates for molecular autopsies in the future. Thus, this review emphasized the significance of acquiring the relevant information to aid in resolving cause of death of these SUDY cases and subsequently highlighted the potential for further studies on risk factors and the value of molecular autopsies.

The Outcome of Long QT Syndrome, a Korean Single Center Study

Congenital long QT syndrome is an inherited cardiac channelopathy, causing fatal arrhythmia. In this study, we conducted a retrospective cohort study on 105 congenital LQTS patients and its outcome in a tertiary center. The 10-year event free survival rate was 73.2%, and the outcome was different according to the genotypes. With treatment, all survived except one. The genetic analysis and risk stratification may be essential for better outcome and further nationwide and large scaled studies are required.

Background and Objectives

Although long QT syndrome (LQTS) is a potentially life-threatening inherited cardiac channelopathy, studies documenting the long-term clinical data of Korean patients with LQTS are scarce.

Methods

This retrospective cohort study included 105 patients with LQTS (48 women; 45.7%) from a single tertiary center. The clinical outcomes were analyzed for the rate of freedom from breakthrough cardiac events (BCEs), additional treatment needed, and death.

Results

LQTS was diagnosed at a median age of 11 (range, 0.003–80) years. Genetic testing was performed on 90 patients (yield, 71.1%). The proportions of genetically confirmed patients with LQTS types 1, 2, 3, and others were 34.4%, 12.2%, 12.2%, and 12.2%, respectively. In the symptomatic group (n=70), aborted cardiac arrest was observed in 30% of the patients. Treatments included medications in 60 patients (85.7%), implantable cardioverter-defibrillators in 27 (38.6%; median age, 17 years; range, 2–79 years), and left cardiac sympathetic denervation surgery in 7 (10%; median age, 13 years; range, 2–34). The 10-year BCE-free survival rate was 73.2%. By genotype, significant differences were observed in BCEs despite medication (p<0.001). The 10-year BCE-free survival rate was the highest in patients with LQTS type 1 (81.8%) and the lowest in those with multiple LQTS-associated mutations (LQTM). All patients with LQTS survived, except for one patient who had LQTM.

Conclusions

Good long-term outcomes can be achieved by using recently developed genetically tailored management strategies for patients with LQTS.

The Risk of Sudden Unexpected Cardiac Death in Children: Epidemiology, Clinical Causes, and Prevention

"Sudden unexplained death (SUD) is a tragic event for both the family and community, particularly when it occurs in young individuals. Sudden cardiac death (SCD) represents the leading form of SUD and is defined as an unexpected event without an obvious extracardiac cause, occurring within 1 hour after the onset of symptoms. In children, the main causes of SCD are inherited cardiac disorders, whereas coronary artery diseases (congenital or acquired), congenital heart diseases, and myocarditis are rare. The present review examines the current state of knowledge regarding SCD in children, discussing the epidemiology, clinical causes, and prevention strategies."

Molecular Autopsy of Sudden Cardiac Death in the Genomics Era

Molecular autopsy is the process of investigating sudden death through genetic analysis. It is particularly useful in cases where traditional autopsy is negative or only shows non-diagnostic features, i.e., in sudden unexplained deaths (SUDs), which are often due to an underlying inherited arrhythmogenic cardiac disease. The final goal of molecular autopsy in SUD cases is to aid medico-legal inquiries and to guide cascade genetic screening of the victim’s relatives. Early attempts of molecular autopsy relied on Sanger sequencing, which, despite being accurate and easy to use, has a low throughput and can only be employed to analyse a small panel of genes. Conversely, the recent adoption of next-generation sequencing (NGS) technologies has allowed exome/genome wide examination, providing an increase in detection of pathogenic variants and the discovery of newer genotype-phenotype associations. NGS has nonetheless brought new challenges to molecular autopsy, especially regarding the clinical interpretation of the large number of variants of unknown significance detected in each individual.

Sudden Death in Adults: A Practical Flow Chart for Pathologist Guidance

The medico-legal term "sudden death (SD)" refers to those deaths that are not preceded by significant symptoms. SD in apparently healthy individuals (newborn through to adults) represents a challenge for medical examiners, law enforcement officers, and society as a whole. This review aims to introduce a useful flowchart that should be applied in all cases of SD. Particularly, this flowchart mixes the data obtained through an up-to-date literature review and a revision of the latest version of guidelines for autopsy investigation of sudden cardiac death (SCD) in order to support medico-legal investigation. In light of this review, following the suggested flowchart step-by-step, the forensic pathologist will be able to apply all the indications of the scientific community to real cases. Moreover, it will be possible to answer all questions relative to SD, such as: death may be attributable to cardiac disease or to other causes, the nature of the cardiac disease (defining whether the mechanism was arrhythmic or mechanical), whether the condition causing SD may be inherited (with subsequent genetic counseling), the assumption of toxic or illicit drugs, traumas, and other unnatural causes.

Genetic investigations of 100 inherited cardiac disease-related genes in deceased individuals with schizophrenia

Cardiac diseases and sudden cardiac death (SCD) are more prevalent in individuals diagnosed with schizophrenia compared to the general population, with especially coronary artery disease (CAD) as the major cardiovascular cause of death. Antipsychotic medications, genetics, and lifestyle factors may contribute to the increased SCD in individuals with schizophrenia. The role of antipsychotic medications and lifestyle factors have been widely investigated, while the genetic predisposition to inherited cardiac diseases in schizophrenia is poorly understood. In this study, we examined 100 genes associated with inherited cardiomyopathies and cardiac channelopathies in 97 deceased individuals diagnosed with schizophrenia for the prevalence of genetic variants associated with SCD. The deceased individuals had various causes of death and were included in the SURVIVE project, a prospective, autopsy-based study of mentally ill individuals in Denmark. This is the first study of multiple inherited cardiac disease-related genes in deceased individuals with diagnosed schizophrenia to shed light on the genetic predisposition to SCD in individuals with schizophrenia. We found no evidence for an overrepresentation of rare variants with high penetrance in inherited cardiac diseases, following the American College of Medical Genetics and Genomics and the Association for Molecular Pathology (ACMG) consensus guidelines. However, we found that the deceased individuals had a statistically significantly increased polygenic burden caused by variants in the investigated heart genes compared to the general population. This indicates that common variants with smaller effects in heart genes may play a role in schizophrenia.

Global approaches to cardiogenetic evaluation after sudden cardiac death in the young: A survey among health care professionals

BACKGROUND

Thorough investigation of sudden cardiac death (SCD) in those aged 1-40 years commonly reveals a heritable cause, yet access to postmortem genetic testing is variable.

OBJECTIVE

The purpose of this study was to explore practices of postmortem genetic testing and attitudes of health care professionals worldwide.

METHODS

A survey was administered among health care professionals recruited through professional associations, social media, and networks of researchers. Topics included practices around postmortem genetic testing, level of confidence in health care professionals' ability, and attitudes toward postmortem genetic testing practices.

RESULTS

There were 112 respondents, with 93% from North America, Europe, and Australia/New Zealand, and 7% from South America, Asia and Africa. Only 30% reported autopsy as mandatory, and overall practices were largely case by case and not standardized. North American respondents (87%) more often perceived practices as ineffective compared to those from Europe (58%) and Australia/New Zealand (48%; P = .002). Where a heritable cause is suspected, 69% considered postmortem genetic testing and 61% offered genetic counseling to surviving family members. Financial resources varied widely. Half of participants believed practices in their countries perpetuated health inequalities.

CONCLUSION

Postmortem genetic testing is not consistently available in the investigation of young SCD despite being a recommendation in international guidelines. Access to postmortem genetic testing, which is critical in ascertaining a cause of death in many cases, must be guided by well-resourced, multidisciplinary teams.

The Postmortem Interpretation of Cardiac Genetic Variants of Unknown Significance in Sudden Death in the Young: A Case Report and Review of the Literature

Sudden cardiac death (SCD) in adolescents and young adults is a major traumatic event for families and communities. In these cases, it is not uncommon to have a negative autopsy with structurally and histologically normal heart. Such SCD cases are generally attributed to channelopathies, which include long QT syndrome, short QT syndrome, Brugada syndrome, and catecholaminergic polymorphic ventricular tachycardia. Our understanding of the causes for SCDs has changed significantly with the advancements in molecular and genetic studies, where many mutations are now known to be associated with certain channelopathies. Postmortem analysis provides great value in informing decision-making with regard to screening tests and prophylactic measures that should be taken to prevent sudden death in first degree relatives of the decedent. As this is a rapidly advancing field, our ability to identify genetic mutations has surpassed our ability to interpret them. This led to a unique challenge in genetic testing called variants of unknown significance (VUS). VUSs present a diagnostic dilemma and uncertainty for clinicians and patients with regard to next steps. Caution should be exercised when interpreting VUSs since misinterpretation can result in mismanagement of patients and their families. A case of a young adult man with drowning as his proximate cause of death is presented in circumstances where cardiac genetic testing was indicated and undertaken. Eight VUSs in genes implicated in inheritable cardiac dysfunction were identified and the interpretation of VUSs in this scenario is discussed.

Sex-Related Differences in Cardiac Channelopathies: Implications for Clinical Practice

Sex-related differences in prevalence, clinical presentation, and outcome of cardiac channelopathies are increasingly recognized, despite their autosomal transmission and hence equal genetic predisposition among sexes. In congenital long-QT syndrome, adult women carry a greater risk for Torsades de pointes and sudden cardiac death than do men. In contrast, Brugada syndrome is observed predominantly in adult men, with a considerably higher risk of arrhythmic sudden cardiac death in adult men than in women. In both conditions, the risk for arrhythmias varies with age. Sex-associated differences appear less evident in other cardiac channelopathies, likely a reflection of their rare(r) occurrence and our limited knowledge. In several cardiac channelopathies, sex-specific predictors of outcome have been identified. Together with genetic and environmental factors, sex hormones contribute to the sex-related disparities in cardiac channelopathies through modulation of the expression and function of cardiac ion channels. Despite these insights, essential knowledge gaps exist in the mechanistic understanding of these differences, warranting further investigation. Precise application of the available knowledge may improve the individualized care of patients with cardiac channelopathies. Promoting the reporting of sex-related phenotype and outcome parameters in clinical and experimental studies and advancing research on cardiac channelopathy animal models should translate into improved patient outcomes. This review provides a critical digest of the current evidence for sex-related differences in cardiac channelopathies and emphasizes their clinical implications and remaining gaps requiring further research.

Comprehensive Analysis of Genes Associated With Sudden Infant Death Syndrome

Background: Sudden infant death syndrome (SIDS) is a tragic incident which remains a mystery even after post-mortem investigation and thorough researches. Methods: This comprehensive review is based on the genes reported in the molecular autopsy studies conducted on SIDS so far. A total of 20 original studies and 7 case reports were identified and included in this analysis. The genes identified in children or adults were not included. Most of the genes reported in these studies belonged to cardiac channel and cardiomyopathy. Cardiac channel genes in SIDS were scrutinized for further analysis. Results: After screening and removing the duplicates, 42 unique genes were extracted. When the location of these genes was assessed, it was observed that most of these belonged to Chromosomes 11, 1 and 3 in sequential manner. The pathway analysis shows that these genes are involved in the regulation of heart rate, action potential, cardiac muscle cell contraction and heart contraction. The protein-protein interaction network was also very big and highly interactive. SCN5A, CAV3, ALG10B, AKAP9 and many more were mainly found in these cases and were regulated by many transcription factors such as MYOG C2C1 and CBX3 HCT11. Micro RNA, "hsa-miR-133a-3p" was found to be prevalent in the targeted genes. Conclusions: Molecular and computational approaches are a step forward toward exploration of these sad demises. It is so far a new arena but seems promising to dig out the genetic cause of SIDS in the years to come.

Sudden cardiac death among persons with diabetes aged 1-49 years: a 10-year nationwide study of 14 294 deaths in Denmark

AIMS

The aim of this study was to compare nationwide incidence rate (IR) of sudden cardiac death (SCD) in persons aged 1-49 years with and without diabetes mellitus (DM).

METHODS AND RESULTS

The study population consisted of all persons in Denmark aged 1-49 years in 2000-09, which equals 27.1 million person-years. All 14 294 deaths in the 10-year period were included. By using the highly descriptive Danish death certificates, 1698 cases of sudden and unexpected death were identified. Through review of autopsy reports, discharge summaries, and the Danish registries, we identified 1363 cases of SCD. The Danish Register of Medicinal Product Statistics was used to identify persons with type 1 DM and type 2 DM. Among the 14 294 decedents, there were 669 with DM, of which 118 suffered SCD (9% of all SCD), making SCD the leading cause of death among young persons with DM. Among those aged 1-35 years, the IR of SCD-DM was 21.9 per 100 000 person-years compared to 2.6 per 100 000 person-years among persons without DM [IR ratio 8.6, 95% confidence interval (CI) 5.8-28.6]. Within the age range 36-49 years, the IR among persons with DM was 119.8 per 100 000 person-years compared to 19.7 per 100 000 person-years among persons without DM (IR ratio 6.1, 95% CI 4.7-7.8).

CONCLUSION

We found that young persons with DM aged 1-35 years had >8-fold higher SCD IR compared to young persons without DM. Our study highlights the need for early cardiovascular risk monitoring and assessment in young persons with DM.

The yield of postmortem genetic testing in sudden death cases with structural findings at autopsy

Sudden cardiac death (SCD) is often associated with structural abnormalities of the heart during autopsy. This study sought to compare the diagnostic yield of postmortem genetic testing in (1) cases with structural findings of uncertain significance at autopsy to (2) cases with autopsy findings diagnostic of cardiomyopathy. We evaluated 57 SCD cases with structural findings at cardiac autopsy. Next-generation sequencing using a panel of 77 primary electrical disorder and cardiomyopathy genes was performed. Pathogenic and likely pathogenic variants were classified using American College of Medical Genetics (ACMG) consensus guidelines. In 29 cases (51%) autopsy findings of uncertain significance were identified whereas in 28 cases (49%) a diagnosis of cardiomyopathy was established. We identified a pathogenic or likely pathogenic variant in 10 cases (18%); in 1 (3%) case with non-specific autopsy findings compared with 9 (32%) cases with autopsy findings diagnostic of cardiomyopathy (p = 0.0054). The yield of genetic testing in SCD cases with autopsy findings consistent with cardiomyopathy is comparable with the yield in cardiomyopathy patients that are alive. Genetic testing in cases with findings of uncertain significance offers lower clinical utility than in cardiomyopathy, with lower yields than detected previously. This highlights the need for stringent evaluation of variant pathogenicity.

[Meaningful diagnostics: genetics]

Molecular genetic analysis is an important component in the diagnostics of some cardiovascular diseases; however, genetic testing should not be used as a screening technique as the diagnostic value strongly depends on anamnestic and clinical factors, such as a positive family history and the disease phenotype. In cardiovascular diseases with high mutation detection rates, e.g. hypertrophic cardiomyopathy and primary arrhythmia syndromes (long QT syndrome, catecholaminergic polymorphic ventricular tachycardia) genetic testing should be included in the diagnostic work-up. Family screening of first-degree relatives (cascade screening) is a particularly important application of genetic diagnostics for a timely identification of asymptomatic mutation carriers and initiation of preventive treatment. A molecular autopsy, also known as postmortem molecular genetic DNA testing, is a special indication for genetic diagnostics. It is particularly useful in the analysis of sudden cardiac death victims for the identification of disease-specific gene mutations. Therefore, given a selective use and a thorough evaluation of the test results, molecular genetic analyses can make a meaningful diagnostic and prognostic contribution. Potential applications of genetic analyses in the future are polygenic cardiovascular diseases. The use of new high-throughput technologies enables the analysis of multiple genetic variants, which can then be included in the calculation of a polygenic risk score for the prediction of the probability of a specific disease.

Reference frame and emotions may contribute to discrepancies in patient and clinician risk estimates in Long QT syndrome

OBJECTIVE

Patients and clinicians need to have similar understandings of cardiac risk, so patients can make informed decisions. The aim of this study was to assess the concordance of risk estimates between Long-QT-Syndrome (LQTS) patients and an experienced clinician.

METHODS

This cross-sectional study included 86 LQTS patients recruited from a clinical registry. Participants completed two questions on their risk of cardiac arrest; likelihood (1=very-unlikely to 5=very-likely), and chance (%), and an experienced clinician computed the same based on risk factors.

RESULTS

30% and 55% of patients had concordant perceptions with the clinician estimate on the chance and likelihood questions respectively. The patients who overestimated their risk (%) had significantly greater emotional responses and concerns about their LQTS. 22 (29%) patients reported a risk of 50% or greater, in contrast to the clinician's risk estimates not exceeding 30%.

CONCLUSION

Many LQTS patients had discordant risk perceptions to the clinician's. Patients and clinicians may have different frames of reference, and patients' estimates are linked with emotions.

PRACTICAL IMPLICATIONS

Clinicians need to take into account LQTS patients' different frame of reference when discussing risk information. This will support shared decision making.

Cardiac Evaluation of Children With a Family History of Sudden Death

BACKGROUND

After sudden death occurs in the young, first-degree family members should undergo clinical screening for occult cardiac disease, but the diagnostic yield from screening is not well-defined in the United States.

OBJECTIVES

The purpose of this study was to determine the clinical predictors of cardiac diagnosis in children referred for evaluation following a sudden death in the family.

METHODS

Patients referred for a family history of sudden death were evaluated in a retrospective review from a tertiary pediatric referral center.

RESULTS

Among 419 pediatric relatives of 256 decedents, 27% of patients were diagnosed with a disease or had a clinical finding of uncertain significance. Patients were diagnosed with heritable cardiac disease in 39 cases (9.3%). Nonheritable cardiac disease was diagnosed in another 5.5% of patients. Clinical findings of uncertain significance were present in 52 patients (12.4%), including abnormal electrophysiological test results (41 of 52) or imaging test results (11 of 52). Among patients diagnosed with a heritable cardiac disease, the nearest affected relative was almost always a first-degree relative (37 of 39, 95%). The strongest predictors for a successful diagnosis in the patient were an abnormal electrocardiogram and a first-degree relationship to the nearest affected relative (odds ratios: 24.2 and 18.8, respectively).

CONCLUSIONS

Children referred for a family history of sudden death receive cardiac disease diagnoses (14%), but clinical findings of uncertain significance increase the challenge of clinical management. The importance of a diagnosis in first-degree affected relatives supports the clinical practice of testing intervening family members first when patients are second- or higher-degree relatives to the decedent.

Next-generation sequencing using microfluidic PCR enrichment for molecular autopsy

Background

We aimed to determine the mutation yield and clinical applicability of “molecular autopsy” following sudden arrhythmic death syndrome (SADS) by validating and utilizing low-cost high-throughput technologies: Fluidigm Access Array PCR-enrichment with Illumina HiSeq 2000 next generation sequencing (NGS).

Methods

We validated and optimized the NGS platform with a subset of 46 patients by comparison with Sanger sequencing of coding exons of major arrhythmia risk-genes (KCNQ1, KCNH2, SCN5A, KCNE1, KCNE2, RYR2). A combined large multi-ethnic international SADS cohort was sequenced utilizing the NGS platform to determine overall molecular yield; rare variants identified by NGS were subsequently reconfirmed by Sanger sequencing.

Results

The NGS platform demonstrated 100% sensitivity for pathogenic variants as well as 87.20% sensitivity and 99.99% specificity for all substitutions (optimization subset, n = 46). The positive predictive value (PPV) for NGS for rare substitutions was 16.0% (27 confirmed rare variants of 169 positive NGS calls in 151 additional cases). The overall molecular yield in 197 multi-ethnic SADS cases (mean age 22.6 ± 14.4 years, 68% male) was 5.1% (95% confidence interval 2.0–8.1%), representing 10 cases carrying pathogenic or likely pathogenic risk-mutations.

Conclusions

Molecular autopsy with Fluidigm Access Array and Illumina HiSeq NGS utilizing a selected panel of LQTS/BrS and CPVT risk-genes offers moderate diagnostic yield, albeit requiring confirmatory Sanger-sequencing of mutational variants.

Electronic supplementary material

The online version of this article (10.1186/s12872-019-1154-8) contains supplementary material, which is available to authorized users.

Sudden Arrhythmic Death During Exercise: A Post-Mortem Genetic Analysis

BACKGROUND

Sudden cardiac death is a natural and unexpected death that occurs within 1 h of the first symptom. Most sudden cardiac deaths occur during exercise, mostly as a result of myocardial infarction. After autopsy, some cases, especially in the young, are diagnosed as cardiomyopathies or remain without a conclusive cause of death. In both situations, genetic alterations may explain the arrhythmia.

OBJECTIVE

Our aim was to identify a genetic predisposition to sudden cardiac death in a cohort of post-mortem cases of individuals who died during exercise, with a structurally normal heart, and were classified as arrhythmogenic death.

METHODS

We analyzed a cohort of 52 post-mortem samples from individuals <50 years old who had a negative autopsy. Next-generation sequencing technology was used to screen genes associated with sudden cardiac death.

RESULTS

Our cohort showed a male prevalence (12:1). Half of the deaths occurred in individuals 41-50 years of age. Running was the most common exercise activity during the fatal event, accounting for 46.15% of cases. Genetic analysis identified 83 rare variants in 37 samples (71.15% of all samples). Of all rare variants, 36.14% were classified as deleterious, being present in 53.84% of all cases.

CONCLUSIONS

A comprehensive analysis of sudden cardiac death-related genes in individuals who died suddenly while exercising enabled the identification of potentially causative variants. However, many genetic variants remain of indeterminate significance, thus further work is needed before clinical translation. Nonetheless, comprehensive genetic analysis of individuals who died during exercise enables the detection of potentially causative variants and helps to identify at-risk relatives.

Plakophilin-2 Truncation Variants in Patients Clinically Diagnosed With Catecholaminergic Polymorphic Ventricular Tachycardia and Decedents With Exercise-Associated Autopsy Negative Sudden Unexplained Death in the Young

OBJECTIVES

This study determined if radical plakophilin-2 (PKP2) variants might underlie some cases of clinically diagnosed catecholaminergic polymorphic ventricular tachycardia (CPVT) and exercise-associated, autopsy-negative sudden unexplained death in the young (SUDY).

BACKGROUND

Pathogenic variants in PKP2 cause arrhythmogenic right ventricular cardiomyopathy (ARVC). Recently, a cardiomyocyte-specific PKP2 knockout mouse model revealed that loss of PKP2 markedly reduced expression of genes critical in intracellular calcium handling. The mice with structurally normal hearts exhibited isoproterenol-triggered polymorphic ventricular arrhythmias that mimicked CPVT.

METHODS

A PKP2 gene mutational analysis was performed on DNA from 18 unrelated patients (9 males; average age at diagnosis: 19.6 ± 12.8 years) clinically diagnosed with CPVT but who were RYR2-, CASQ2-, KCNJ2-, and TRDN-negative, and 19 decedents with SUDY during exercise (13 males; average age at death: 14 ± 3 years). Only radical (i.e., frame-shift, canonical splice site, or nonsense) variants with a minor allele frequency of ≤0.00005 in the genome aggregation database (gnomAD) were considered pathogenic.

RESULTS

Radical PKP2 variants were identified in 5 of 18 (27.7%) CPVT patients and 1 of 19 (5.3%) exercise-related SUDY cases compared with 96 of 138,632 (0.069%) individuals in gnomAD (p = 3.1 × 10^-13). Cardiac imaging or autopsy demonstrated a structurally normal heart in all patients at the time of their CPVT diagnosis or sudden death.

CONCLUSIONS

Our data suggested that the progression of the PKP2-dependent electropathy can be independent of structural perturbations and can precipitate exercise-associated sudden cardiac arrest or sudden cardiac death before the presence of overt cardiomyopathy, which clinically mimics CPVT, similar to the PKP2 knockout mouse model. Thus, CPVT and SUDY genetic test panels should now include PKP2.

Molecular autopsy in a cohort of infants died suddenly at rest

Sudden infant death syndrome is the leading cause of death during the first year of life. A large part of cases remains without a conclusive cause of death after complete autopsy. In these situations, cardiac arrhythmia of genetic origin is suspected as the most plausible cause of death. Our aim was to ascertain whether genetic variants associated with sudden cardiac death might be the cause of death in a cohort of infants died suddenly. We analyzed 108 genes associated with sudden cardiac death in 44 post-mortem samples of infants less than 1 year old of age who died at rest. Definite cause of death was not conclusive in any case after a complete autopsy. Genetic analysis identified at least one rare variant in 90.90% of samples. A total of 121 rare genetic variants were identified. Of them, 33.05% were novel and 39.66% were located in genes encoding ion channels or associated proteins. A comprehensive genetic analysis in infants who died suddenly enables the unraveling of potentially causative cardiac variants in 2045% of cases. Molecular autopsy should be included in forensic protocols when no conclusive cause of death is identified. Large part genetic variants remain of uncertain significance, reinforcing the crucial role of genetic interpretation before clinical translation but also in early identification of relatives at risk.

Long QT molecular autopsy in sudden unexplained death in the young (1-40 years old): Lessons learnt from an eight year experience in New Zealand

BACKGROUND

To review long QT syndrome molecular autopsy results in sudden unexplained death in young (SUDY) between 2006 and 2013 in New Zealand.

METHODS

Audit of the LQTS molecular autopsy results, cardiac investigations and family screening data from gene-positive families.

RESULTS

During the study period, 365 SUDY cases were referred for molecular autopsy. 128 cases (35%) underwent LQTS genetic testing. 31 likely pathogenic variants were identified in 27 cases (21%); SCN5A (14/31, 45%), KCNH2 (7/31, 22%), KCNQ1 (4/31, 13%), KCNE2 (3/31, 10%), KCNE1 (2/31, 7%), KCNJ2 (1/31, 3%). Thirteen variants (13/128, 10%) were ultimately classified as pathogenic. Most deaths (63%) occurred during sleep. Gene variant carriage was more likely with a positive medical history (mostly seizures, 63% vs 36%, p = 0.01), amongst females (36% vs 12%, p = 0.001) and whites more than Maori (31% vs 0, p = 0.0009). Children 1-12 years were more likely to be gene-positive (33% vs 14%, p = 0.02). Family screening identified 42 gene-positive relatives, 18 with definitive phenotypic expression of LQTS/Brugada. 76% of the variants were maternally inherited (p = 0.007). Further family investigations and research now support pathogenicity of the variant in 13/27 (48%) of gene-positive cases.

CONCLUSION

In New Zealand, variants in SCN5A and KCNH2, with maternal inheritance, predominate. A rare variant in LQTS genes is more likely in whites rather than Maori, females, children 1-12 years and those with a positive personal and family history of seizures, syncope or SUDY. Family screening supported the diagnosis in a third of the cases. The changing classification of variants creates a significant challenge.

Sudden Cardiac Death in Children and Adolescents

Sudden cardiac death (SCD) is a rare but devastating event in children and adolescents. Etiologies include congenital heart disease, cardiomyopathies, primary arrhythmia syndromes, and miscellaneous conditions. Challenges in the diagnosis and prevention of SCD in the young are reviewed.

Investigating the Genetic Causes of Sudden Unexpected Death in Children Through Targeted Next-Generation Sequencing Analysis

Background—

Inherited arrhythmia syndromes are responsible for a significant portion of autopsy-negative sudden unexpected death (SUD) cases, but molecular autopsy used to identify potentially causal variants is not routinely included in SUD investigations. We collaborated with a medical examiner's office to assist in finding a diagnosis for their autopsy-negative child SUD cases.

Methods and Results—

191 child SUD cases (<5 years of age) were selected for analyses. Our next generation sequencing panel incorporated 38 inherited arrhythmia syndrome candidate genes and another 33 genes not previously investigated for variants that may underlie SUDY pathophysiology. Overall, we identified 11 potentially causal disease-associated variants in 12 cases, for an overall yield of 6.3%. We also identified 31 variants of uncertain significance in 36 cases and 16 novel variants predicted to be pathogenic in silico in 15 cases. The disease-associated variants were reported to the medical examiner to notify surviving relatives and recommend clinical assessment.

Conclusions—

We have identified variants that may assist in the diagnosis of at least 6.3% of autopsy-negative child SUD cases and reduce risk of future SUD in surviving relatives. We recommend a cautious approach to variant interpretation. We also suggest inclusion of cardiomyopathy genes as well as other candidate SUD genes in molecular autopsy analyses.

Splice Site Variants in the KCNQ1 and SCN5A Genes: Transcript Analysis as a Tool in Supporting Pathogenicity

BACKGROUND

Approximately 75% of clinically definite long QT syndrome (LQTS) cases are caused by mutations in the KCNQ1, KCNH2 and SCN5A genes. Of these mutations, a small proportion (3.2-9.2%) are predicted to affect splicing. These mutations present a particular challenge in ascribing pathogenicity.

METHODS

Here we report an analysis of the transcriptional consequences of two mutations, one in the KCNQ1 gene (c.781_782delinsTC) and one in the SCN5A gene (c.2437-5C>A), which are predicted to affect splicing. We isolated RNA from lymphocytes and used a directed PCR amplification strategy of cDNA to show mis-spliced transcripts in mutation-positive patients.

RESULTS

The loss of an exon in each mis-spliced transcript had no deduced effect on the translational reading frame. The clinical phenotype corresponded closely with genotypic status in family members carrying the KCNQ1 splice variant, but not in family members with the SCN5A splice variant. These results are put in the context of a literature review, where only 20% of all splice variants reported in the KCNQ1, KCNH2 and SCN5A gene entries in the HGMDPro 2015.4 database have been evaluated using transcriptional assays.

CONCLUSIONS

Prediction programmes play a strong role in most diagnostic laboratories in classifying variants located at splice sites; however, transcriptional analysis should be considered critical to confirm mis-splicing. Critically, this study shows that genuine mis- splicing may not always imply clinical significance, and genotype/phenotype cosegregation remains important even when mis-splicing is confirmed.

Clinical and Genetic Diagnosis of Nonischemic Sudden Cardiac Death

INTRODUCTION AND OBJECTIVES

Nonischemic sudden cardiac death (SCD) is predominantly caused by cardiomyopathies and channelopathies. There are many diagnostic tests, including some complex techniques. Our aim was to analyze the diagnostic yield of a systematic diagnostic protocol in a specialized unit.

METHODS

The study included 56 families with at least 1 index case of SCD (resuscitated or not). Survivors were studied with electrocardiogram, advanced cardiac imaging, exercise testing, familial study, genetic testing and, in some cases, pharmacological testing. Families with deceased probands were studied using the postmortem findings, familial evaluation, and molecular autopsy with next-generation sequencing (NGS).

RESULTS

A positive diagnosis was obtained in 80.4% of the cases, with no differences between survivors and nonsurvivors (P=.53). Cardiac channelopathies were more prevalent among survivors than nonsurvivors (66.6% vs 40%, P=.03). Among the 30 deceased probands, the definitive diagnosis was given by autopsy in 7. A diagnosis of cardiomyopathy tended to be associated with a higher event rate in the family. Genetic testing with NGS was performed in 42 index cases, with a positive result in 28 (66.6%), with no differences between survivors and nonsurvivors (P=.21).

CONCLUSIONS

There is a strong likelihood of reaching a diagnosis in SCD after a rigorous protocol, with a more prevalent diagnosis of channelopathy among survivors and a worse familial prognosis in cardiomyopathies. Genetic testing with NGS is useful and its value is increasing with respect to the Sanger method.

Infant sudden death: Mutations responsible for impaired Nav1.5 channel trafficking and function

BACKGROUND

Two genetic variants in SCN5A, encoding the Nav1.5 Na⁺ channel α-subunit, were found in a 5-month-old girl who died suddenly in her sleep. The first variant is a missense mutation, resulting in an amino acid change (Q1832E), which has been described (but not characterized) in a patient with Brugada syndrome. The second is a nonsense mutation that produces a premature stop codon and a C-terminal truncation (R1944Δ).

METHODS AND RESULTS

To investigate their functional relevance with patch clamp experiments in transfected HEK-293 cells. The Q1832E mutation drastically reduced Nav1.5 current density. The R1944Δ C-terminal truncation had negligible effects on Nav1.5 current density. Neither of the mutations affected the voltage dependence of steady activation and inactivation or influenced the late Na⁺ current or the recovery from inactivation. Biochemical and immunofluorescent approaches demonstrated that the Q1832E mutation caused severe trafficking defects. Polymerase chain reaction cloning and sequencing the victim's genomic DNA allowed us to determine that the two variants were in trans. We investigated the functional consequences by coexpressing Nav1.5(Q1832E) and Nav1.5(R1944Δ), which led to a significantly reduced current amplitude relative to wild-type.

CONCLUSIONS

These sudden infant death syndrome (SIDS)-related variants caused a severely dysfunctional Nav1.5 channel, which was mainly due to trafficking defects caused by the Q1832E mutation. The decreased current density is likely to be a major contributing factor to arrhythmogenesis in Brugada syndrome and the sudden death of this SIDS victim.