The molecular autopsy: an indispensable step following sudden cardiac death in the young?

Cardiovascular-related death in infancy and childhood: a clinicopathological study of two referral institutions in England

To review post-mortem findings among deaths presenting as sudden and/or unexpected deaths in two centers in the UK during a 16-year period in order to identify those related to cardiovascular conditions. The post-mortem databases of two tertiary referral institutions were searched, and all reports were reviewed. Histological features and results of ancillary investigations were noted. All cases of sudden and/or unexpected cardiac deaths (SCD) between 2003 and 2018 were identified. The study was PRISMA compliant and approved by clinical governance. 68/1129 cases of SCD (6.0%) were identified in one center and 83/753 cases (11%) in the other. These 151 cases constituted the study cohort. The mean annual incidence of SCD was 0.3 per 100,000 persons/annum. The three most prevalent groups of cardiac pathology were cardiac malformations (51/151; 33.8%), cardiomyopathies (32/151; 21.2%), and myocarditis (31/151; 20.5%). Mean age at death was 3.4 years. Prematurity was predominantly associated with deaths related to cardiac malformations (p < 0.001). Symptoms had been present for a mean of 3.8, 3.0, and 3.5 days before death for myocarditis, cardiomyopathy, and cardiac malformations/complications post-surgery. This retrospective comparative study represents the largest autopsy series of SCD in infants and children in the UK. Some entities are very infrequent. Several diseases could have been identified earlier in life allowing for the possibility of intervention. Limitation includes the retrospective nature of the study and that, as arrhythmogenic gene mutations are not yet routinely performed in unexplained deaths, the incidence of SCD in infants and children is most likely underestimated.

Sudden arrhythmic death and cardiomyopathy are important causes of sudden cardiac death in the UK: results from a national coronial autopsy database

AIMS

Sudden cardiac death (SCD) is defined as natural unexpected death in witnessed cases occurring < 1 h and in unwitnessed cases as last seen alive < 24 h. SCD due to ischaemic heart disease (IHD) is frequent in older age groups; in younger people genetic cardiac causes, including channelopathies and cardiomyopathies, are more frequent. This study aimed to present the causes of SCD from a large specialist pathology registry.

METHODS AND RESULTS

Cases were examined macroscopically and microscopically by two expert cardiac pathologists. The hearts from 7214 SCD cases were examined between 1994 and 2021. Sudden arrhythmic death syndrome (SADS), a morphologically normal heart, which can be underlaid by cardiac channelopathies, is most common (3821, 53%) followed by the cardiomyopathies (1558, 22%), then IHD (670, 9%), valve disease (225, 3%), congenital heart disease (213, 3%) and myocarditis/sarcoidosis (206, 3%). Hypertensive heart disease (185, 3%), aortic disease (129, 2%), vascular disease (97, 1%) and conduction disease (40, 1%) occur in smaller proportions.

DISCUSSION

To our knowledge, this is the largest SCD cohort with autopsy findings ever reported from one country. SADS and cardiomyopathies predominate. This study highlights the importance of the autopsy in SCD, which is a significant public health concern in all age groups. Knowing the true incidence in our population will improve risk stratification and develop preventative strategies for family members. There is now a national pilot study integrating molecular autopsy and family screening into the assessment of SCD victims.

Análisis clínico e histopatológico de la prevalencia de enfermedades cardiacas en muerte súbita. Estudio en autopsias

Introducción: un evento de muerte súbita supone un gran impacto para la sociedad, siendo importante su estudio para aportar conocimiento y fortalecer estrategias de promoción y prevención. Objetivo: determinar la prevalencia de los diagnósticos anatomopatológicos cardiacos definitivos y los hallazgos histopatológicos asociados con la muerte súbita de origen cardíaco en los pacientes sometidos a autopsias clínicas realizadas en el Hospital de San José de Bogotá DC, Colombia, durante el período 2015 a 2018. Métodos: estudio descriptivo de corte transversal retrospectivo en pacientes a quienes se les realizó autopsia con diagnóstico de muerte súbita de origen cardiovascular en el servicio de patología del Hospital de San José, Bogotá DC, Colombia. Resultados: se incluyeron 178 autopsias con diagnóstico de muerte súbita cardíaca. El promedio global de edad fue 56.1 años (DE: 15.06) con una relación hombre-mujer de 3:1. El hallazgo macroscópico más frecuente fue cardiomegalia (promedio 428.1 g (DE 112.8), acompañado de la presencia de coronariopatía esclerótica (p=0.000) con obstrucción de la luz de las arterias coronarias mayores de 80% (p=0.037). Conclusiones: los diagnósticos anatomopatológicos definitivos prevalentes en la muerte súbita cardiaca fueron cardiopatía isquémica crónica complicada (65%) e infarto agudo de miocardio (16%), datos similares a los reportados a nivel mundial. La cardiomegalia es un hallazgo frecuente que debe valorarse en forma cuidadosa.

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.

Effects of Extended Postmortem Interval on Microbial Communities in Organs of the Human Cadaver

Human thanatomicrobiota studies have shown that microorganisms inhabit and proliferate externally and internally throughout the body and are the primary mediators of putrefaction after death. Yet little is known about the source and diversity of the thanatomicrobiome or the underlying factors leading to delayed decomposition exhibited by reproductive organs. The use of the V4 hypervariable region of bacterial 16S rRNA gene sequences for taxonomic classification ("barcoding") and phylogenetic analyses of human postmortem microbiota has recently emerged as a possible tool in forensic microbiology. The goal of this study was to apply a 16S rRNA barcoding approach to investigate variation among different organs, as well as the extent to which microbial associations among different body organs in human cadavers can be used to predict forensically important determinations, such as cause and time of death. We assessed microbiota of organ tissues including brain, heart, liver, spleen, prostate, and uterus collected at autopsy from criminal casework of 40 Italian cadavers with times of death ranging from 24 to 432 h. Both the uterus and prostate had a significantly higher alpha diversity compared to other anatomical sites, and exhibited a significantly different microbial community composition from non-reproductive organs, which we found to be dominated by the bacterial orders MLE1-12, Saprospirales, and Burkholderiales. In contrast, reproductive organs were dominated by Clostridiales, Lactobacillales, and showed a marked decrease in relative abundance of MLE1-12. These results provide insight into the observation that the uterus and prostate are the last internal organs to decay during human decomposition. We conclude that distinct community profiles of reproductive versus non-reproductive organs may help guide the application of forensic microbiology tools to investigations of human cadavers.

An international telemedicine program for diagnosis of genetic disorders: Partnership of pediatrician and geneticist

There is a shortage of genetics providers worldwide and access is limited to large academic centers. Telemedicine programs can facilitate access to genetic services to patients living in remote locations. The goal of this study was to improve access to genetic services in the Dominican Republic by creating a partnership model between a pediatrician and geneticist. This approach has been used within the United States but not in the setting of two different countries, healthcare system, and cultures. Patients were referred to the Centro de Obstetricia y Ginecologia program if a syndromic or genetic etiology was suspected by their local provider. Pediatrician first evaluated all patients prior to telemedicine appointment to review family and medical history. All genetic visits were scheduled within 2 weeks of referral in collaboration with telehealth program at Cincinnati Children's Hospital Medical Center. A total of 66 individuals were evaluated during a period of 5 years. Fifty-seven individuals underwent genetic studies, and a molecular diagnosis was made in 39 individuals. Exome sequencing was the most common first line test when differential diagnosis was broad (n = 40). The most common inheritance was autosomal recessive in 15 individuals, followed by 13 individuals with autosomal dominant disorders, 7 individuals X-linked disorders, and 4 individuals with chromosomal abnormalities. This study provides data to support utility of geneticist and pediatrician partnership to provide outreach telemedicine diagnostics and management services for rare diseases in an international setting.

Genetic variants of uncertain significance: How to match scientific rigour and standard of proof in sudden cardiac death?

In many SCD cases, in particular in pediatric age, autopsy can be completely negative and then a post-mortem genetic testing (molecular autopsy) is indicated. In NGS era finding new/rare variants is extremely frequent and, when only variants of unknown significance are found, molecular autopsy fails to find a cause of death. We describe the emblematic case of the sudden death of a 7-year-old girl. We performed a full-body micro-CT analysis, an accurate autopsy, a serum tryptase test and toxicological tests. Since the only macroscopic abnormality we found was a myocardial bridging (length: 1,1 cm, thickness: 0,5 cm) of the left anterior descending coronary artery, a molecular autopsy has been performed. NGS analysis on victim DNA detected rare variants in DPP6, MYH7, SCN2B and NOTCH1 and segregation analysis was then achieved. On the basis of ACMG/AMP (clinical) guidelines, all the found variants were classified as of unknown significance. In other words, both the macroscopic and genetic anomalies we found were of uncertain significance and then the autopsy failed to find the cause of the death. Our case raises three main discussion points: (a) economical, ethical and legal limitations of genetic investigation; (b) risk that genetic testing does not succeed in finding a certain cause of the death; (c) absence of specific guidelines to face the problem of VUS in forensic cases.

[Molecular autopsy in sudden cardiac death]

Currently, there are a significant percentage of autopsies left without a conclusive diagnosis of death, especially when this lethal event occurs suddenly. Genetic analysis has been recently incorporated into the field of forensic medicine, especially in patients with sudden death and where no conclusive cause of death is identified after a complete medical-legal autopsy. Inherited arrhythmogenic diseases are the main cause of death in these cases. To date, more than 40 genes have been associated with arrhythmogenic disease, and causing sudden cardiac death has been described. The main arrhythmogenic diseases are Long QT Syndrome, Catecholaminergic Polymorphic Ventricular Tachycardia, Brugada Syndrome, and Short QT Syndrome. These post-mortem genetic studies, not only allow a diagnosis of the cause of death, but also allow a clinical translation in relatives, focusing on the early identification of individuals at risk of syncope, as well as adopting personalised therapeutic measures for the prevention of a lethal arrhythmic episode.

Sudden unexplained cardiac deaths in young adults: a call for multidisciplinary approach

The investigation of death in young (<35 years), previously fit individuals, calls for a detailed autopsy with emphasis placed upon the examination of the heart. In most instances, the cause of cardiac death can be identified during autopsy. However, a large percentage of sudden deaths remain unexplained even after comprehensive medicolegal investigation, including autopsy, and are labelled as autopsy-negative sudden unexplained cardiac death (SUD). Still, when you look to the law, an autopsy, a much needed truth-finding-instrument, usually is not mandatory and is left up to the discretion of various medical or legal authorities, which when making a decision, balance various, often conflicting interests of the state and society on the one hand and of the deceased and his family on the other. Cardiac molecular autopsy calls for a close cooperation between medical examiner, pathologist, family physician, cardiologist, geneticist, and the relatives. Multidisciplinary approach and the identification of genetic cause of SUD enable proper genetic counselling for surviving relatives as well as for implementing specific preventive/therapeutic strategies, e.g. implantable cardioverter-defibrillator (ICD) implantation.

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.

Relevance of molecular testing in patients with a family history of sudden death

Sudden cardiac death (SCD) is a major cause of death in industrial countries. Although SCD occurs mainly in adults, it may also affect young persons, where genetic cardiac disorders comprise at least half of these cases. This includes primary arrhythmogenic disorders such as long QT syndrome and inherited cardiomyopathies. However, in many cases, postmortem examinations provide no conclusive results explaining the cause of death. Since family members of the deceased may eventually have inherited the same disease, they are at risk of SCD. In the present study, 28 patients with a family history of sudden unexplained death (SUD), of survived cardiac arrest and with a clinical diagnosis of an inherited cardiac disease were screened using phenotype-guided molecular analysis of genes associated with arrhythmogenic cardiac diseases. In 64% of the cases, gene variants with potentially pathogenic cardiac effects were detected suggesting that an arrhythmia syndrome may have caused the death of the deceased family member. Therefore, we recommend that relatives of SUD victims should undergo extended cardiac examination and, depending on the clinical diagnosis, a targeted genetic analysis should follow, which is crucial to identify family members at risk.

Cardiac Channelopathies and Sudden Death: Recent Clinical and Genetic Advances

Sudden cardiac death poses a unique challenge to clinicians because it may be the only symptom of an inherited heart condition. Indeed, inherited heart diseases can cause sudden cardiac death in older and younger individuals. Two groups of familial diseases are responsible for sudden cardiac death: cardiomyopathies (mainly hypertrophic cardiomyopathy, dilated cardiomyopathy, and arrhythmogenic cardiomyopathy) and channelopathies (mainly long QT syndrome, Brugada syndrome, short QT syndrome, and catecholaminergic polymorphic ventricular tachycardia). This review focuses on cardiac channelopathies, which are characterized by lethal arrhythmias in the structurally normal heart, incomplete penetrance, and variable expressivity. Arrhythmias in these diseases result from pathogenic variants in genes encoding cardiac ion channels or associated proteins. Due to a lack of gross structural changes in the heart, channelopathies are often considered as potential causes of death in otherwise unexplained forensic autopsies. The asymptomatic nature of channelopathies is cause for concern in family members who may be carrying genetic risk factors, making the identification of these genetic factors of significant clinical importance.

Genetic Insurance Discrimination in Sudden Arrhythmia Death Syndromes

Background—

There is virtually no information assessing the insurability of families affected with Sudden Arrhythmia Death Syndromes (SADS) for the determination of the nonclinical implications of genetic screening. It is important to identify the barriers and challenges faced by families as a result of genetic screening for SADS to enable equitable access to insurance coverage.

Methods and Results—

To explore the insurance coverage experiences of SADS-affected families, we administered a cross-sectional online survey across North America from April 28, 2012 to November 13, 2013. Participants included individuals with a SADS diagnosis and their relatives who have applied for insurance (health, life, travel, and disability) or have existing insurance coverage. Of 202 participants, 92% had a SADS diagnosis (92%) as either a proband (50%) or an affected relative (42%); 8% of participants were unaffected family members of a proband; and genetic confirmation was reported by 73%. Of the 54% of SADS respondents who applied for insurance, 60% were rejected by insurers. The preexisting SADS diagnosis was the major reason reported for rejection (57%). Most respondents (80%) had insurance coverage through a spouse/parent plan at the time of diagnosis; 14% experienced a subsequent negative effect on coverage. Thirty-nine percent of affected SADS respondents reported an increase in insurance premium rates.

Conclusions—

Increased genetic testing has negatively impacted insurability for SADS patients and affected family members. The challenges in obtaining life and health insurance are mainly because of the preexisting condition, even in the presence of protective laws in the United States.

Inherited arrhythmias: The cardiac channelopathies

Ion channels in the myocardial cellular membrane are responsible for allowing the cardiac action potential. Genetic abnormalities in these channels can predispose to life-threatening arrhythmias. We discuss the basic science of the cardiac action potential; outline the different clinical entities, including information regarding overlapping diagnoses, touching upon relevant genetics, new innovations in screening, diagnosis, risk stratification, and management. The special considerations of sudden unexplained death and sudden infant death syndrome are discussed. Scientists and clinicians continue to reconcile the rapidly growing body of knowledge regarding the molecular mechanisms and genetics while continuing to improve our understanding of the various clinical entities and their diagnosis and management in clinical setting. Two separate searches were run on the National Center for Biotechnology Information's website. The first using the term cardiac channelopathies was run on the PubMed database using filters for time (published in past 5 years) and age (birth-18 years), yielding 47 results. The second search using the medical subject headings (MeSH) database with the search terms “Long QT Syndrome” (MeSH) and “Short QT Syndrome” (MeSH) and “Brugada Syndrome” (MeSH) and “Catecholaminergic Polymorphic Ventricular Tachycardia” (MeSH), applying the same filters yielded 467 results. The abstracts of these articles were studied, and the articles were categorized and organized. Articles of relevance were read in full. As and where applicable, relevant references and citations from the primary articles where further explored and read in full.

Identification and Functional Characterization of a Novel CACNA1C-Mediated Cardiac Disorder Characterized by Prolonged QT Intervals With Hypertrophic Cardiomyopathy, Congenital Heart Defects, and Sudden Cardiac Death

BACKGROUND

A portion of sudden cardiac deaths can be attributed to structural heart diseases, such as hypertrophic cardiomyopathy (HCM) or cardiac channelopathies such as long-QT syndrome (LQTS); however, the underlying molecular mechanisms are distinct. Here, we identify a novel CACNA1C missense mutation with mixed loss-of-function/gain-of-function responsible for a complex phenotype of LQTS, HCM, sudden cardiac death, and congenital heart defects.

METHODS AND RESULTS

Whole exome sequencing in combination with Ingenuity variant analysis was completed on 3 affected individuals and 1 unaffected individual from a large pedigree with concomitant LQTS, HCM, and congenital heart defects and identified a novel CACNA1C mutation, p.Arg518Cys, as the most likely candidate mutation. Mutational analysis of exon 12 of CACNA1C was completed on 5 additional patients with a similar phenotype of LQTS plus a personal or family history of HCM-like phenotypes and identified 2 additional pedigrees with mutations at the same position, p.Arg518Cys/His. Whole cell patch clamp technique was used to assess the electrophysiological effects of the identified mutations in CaV1.2 and revealed a complex phenotype, including loss of current density and inactivation in combination with increased window and late current.

CONCLUSIONS

Through whole exome sequencing and expanded cohort screening, we identified a novel genetic substrate p.Arg518Cys/His-CACNA1C, in patients with a complex phenotype including LQTS, HCM, and congenital heart defects annotated as cardiac-only Timothy syndrome. Our electrophysiological studies, identification of mutations at the same amino acid position in multiple pedigrees, and cosegregation with disease in these pedigrees provide evidence that p.Arg518Cys/His is the pathogenic substrate for the observed phenotype.

Genetic screening in sudden cardiac death in the young can save future lives

Background

Autopsy of sudden cardiac death (SCD) in the young shows a structurally and histologically normal heart in about one third of cases. Sudden death in these cases is believed to be attributed in a high percentage to inherited arrhythmogenic diseases. The purpose of this study was to investigate the value of performing post-mortem genetic analysis for autopsy-negative sudden unexplained death (SUD) in 1 to 35 year olds.

Methods and results

From January 2009 to December 2011, samples from 15 cases suffering SUD were referred to the Department of Clinical Genetics, Umeå University Hospital, Sweden, for molecular genetic evaluation. PCR and bidirectional Sanger sequencing of genes important for long QT syndrome (LQTS), short QT syndrome (SQTS), Brugada syndrome type 1 (BrS1), and catecholaminergic polymorphic ventricular tachycardia (CPVT) (KCNQ1, KCNH2, SCN5A, KCNE1, KCNE2, and RYR2) was performed. Multiplex ligation-dependent probe amplification (MLPA) was used to detect large deletions or duplications in the LQTS genes. Six pathogenic sequence variants (four LQTS and two CPVT) were discovered in 15 SUD cases (40 %). Ten first-degree family members were found to be mutation carriers (seven LQTS and three CPVT).

Conclusion

Cardiac ion channel genetic testing in autopsy-negative sudden death victims has a high diagnostic yield, with identification of the disease in 40 % of families. First-degree family members should be offered predictive testing, clinical evaluation, and treatment with the ultimate goal to prevent sudden death.