Second opinion system for sudden cardiac death cases in forensic practice

Exploratory DNA methylation analysis in post-mortem heart tissue of sudden unexplained death

BACKGROUND

Sudden unexplained death (SUD) is a devastating event in the young. Despite efforts to identify causal genetic variants, many cases remain unexplained after genetic screening. This study aimed to investigate an alternative potential contributor to SUD by studying the human methylome using the MethylationEPIC v2.0 BeadChip kit in heart tissue from SUD cases. The genome-wide methylation results of the SUD cases were compared to the results of a control cohort. The SUD cases were divided into three main groups based on their autopsy reports, heart morphology and histopathology (primaryN: macroscopically and histologically normal heart; primaryCM: macroscopically or histologically abnormal heart, suspected cardiomyopathies; and secondary: myocardial damage due to other underlying conditions). The main focus of this study was to identify differentially methylated regions (DMRs) between the case groups and the control cohort.

RESULTS

We identified DMRs for both the primaryN and primaryCM groups, whereas the secondary group yielded no such results. In the primaryN cases, the corresponding genes for each DMR led to the identification of genes with common biological pathways. Some were associated with heart morphology (e.g. heart outflow tract morphogenesis or trabecular morphogenesis), but the majority belonged to more general cellular regulatory pathways (e.g. transcription coactivator activity, long non-coding RNAs, etc.). Although no common pathways were found for the primaryCM group, some common regulatory molecular functions were identified, such as p53 binding and transcription coactivator activity.

CONCLUSIONS

Our study is the first to investigate the whole human methylome in heart tissue of SUD cases. We propose that there are observable differences in the methylation patterns of the case groups that may have contributed to SUD. Still, further studies are required to improve our understanding of the impact of methylation levels on SUD risk and to pinpoint methylation-based screening opportunities for SUD relatives.

Reviewing hereditary connective tissue disorders: Proposals of harmonic medicolegal assessments

Hereditary connective tissue disorders (HCTDs) are a heterogeneous group of inherited diseases. These disorders show genetic mutations with loss of function of primary components of connective tissue, such as collagen and elastic fibers. There are more than 200 conditions that involve hereditary connective tissue disorders, while the most known are Marfan syndrome, Osteogenesis Imperfecta, and Ehlers-Danlos syndromes. These disorders need continuous updates, multidisciplinary skills, and specific methodologic evaluations sharing many medicolegal issues. Marfan syndrome and Ehlers-Danlos syndromes show a high risk of early sudden death. As a consequence of this, postmortem genetic testing can identify novel genotype-phenotype correlations which help the clinicians to assess personalized cardiovascular screening programs among the ill subjects. Genetic testing is also essential to identify children suffering from Osteogenesis Imperfecta, especially when a physical abuse is clinically suspected. However, this is a well-known clinical problem even though there are still challenges to interpret genetic data and variants of unknown significance due to the current extensive use of new genetic/genomic techniques. Additionally, the more significant applications and complexities of genomic testing raise novel responsibilities on the clinicians, geneticists, and forensic practitioners as well, increasing potential liability and medical malpractice claims. This systematic review provides a detailed overview on how multidisciplinary skills belonging to clinicians, medicolegal consultants, radiologists, and geneticists can cooperate to manage HCTDs from autopsy or clinical findings to genetic testing. Thus, technical aspects need to be addressed to the medicolegal community since there is no consensus works or guidelines which specifically discuss these issues.

HIF-1α expression by immunohistochemistry and mRNA-210 levels by real time polymerase chain reaction in post-mortem cardiac tissues: A pilot study

INTRODUCTION

The postmortem diagnosis of acute myocardial ischemia (AMI) represents a challenging issue in forensic practice. Immunohistochemical studies and gene expression studies are becoming a promising field of research in forensic pathology. The present study aims to evaluate HIF-1α expression through immunohistochemistry (IHC), and mRNA-210 level using real-time polymerase chain reaction (RT-PCR), in order to define if HIF-1α and mRNA-210 in post-mortem myocardium could be adopted in the diagnosis of AMI.

MATERIALS AND METHODS

Thirty-five deceased individuals, who underwent forensic autopsy at the Legal Medicine Service of the University of Parma, between 2010 and 2018, were investigated. The cohort was divided into two groups according to the cause of death (sudden deaths caused by AMI vs control cases). Cardiac specimens were collected during autopsy, then samples were processed for morphological evaluation using haematoxylin-eosin staining, for IHC, and for RT-PCR. HIF-1α expression and mRNA-210 levels were investigated.

RESULTS

Statistical evaluation demonstrated statistically significant differences in terms of number of IHC positive vessels, leukocytes, and cardiomyocytes between the two groups. Moreover, in the majority of cases, immunostaining positivity was observed only in myocardial and subendocardial samples. With reference to mRNA-210, the difference between the two groups proved to be statistically significant.

CONCLUSIONS

The present study indicates that HIF-1α and mRNA-210 in post-mortem cardiac specimens could represent appropriate biomarkers in the diagnosis of AMI. The current study was primarily limited by the scarcity of the cohort, so further research is required to confirm these preliminary observations.

Exome analysis focusing on epilepsy-related genes in children and adults with sudden unexplained death

PURPOSE

Genetic studies in sudden infant death syndrome (SIDS) and sudden unexplained death (SUD) cohorts have indicated that cardiovascular diseases might have contributed to sudden unexpected death in 20-35 % of autopsy-negative cases. Sudden unexpected death can also occur in people with epilepsy, termed as sudden unexpected death in epilepsy (SUDEP). The pathophysiological mechanisms of SUDEP are not well understood, but are likely multifactorial, including seizure-induced hypoventilation and arrhythmias as well as genetic risk factors. The sudden death of some of the SIDS/SUD victims might also be explained by genetic epilepsy, therefore this study aimed to expand the post-mortem genetic analysis of SIDS/SUD cases to epilepsy-related genes.

METHODS

Existing whole-exome sequencing data from our 155 SIDS and 45 SUD cases were analyzed, with a focus on 365 epilepsy-related genes. Nine of the SUD victims had a known medical history of epilepsy, seizures or other underlying neurological conditions and were therefore classified as SUDEP cases.

RESULTS

In our SIDS and SUD cohorts, we found epilepsy-related pathogenic/likely pathogenic variants in the genes OPA1, RAI1, SCN3A, SCN5A and TSC2.

CONCLUSION

Post-mortem analysis of epilepsy-related genes identified potentially disease-causing variants that might have contributed to the sudden death events in our SIDS/SUD cases. However, the interpretation of identified variants remains challenging and often changes over time as more data is gathered. Overall, this study contributes insight in potentially pathophysiological epilepsy-related mechanisms in SIDS, SUD and SUDEP victims and underlines the importance of sensible counselling on the risk and preventive measures in genetic epilepsy.

Postmortem biochemistry in deaths from ischemic heart disease

Ischemic heart disease (IHD) is one of the leading causes of morbidity and sudden cardiac death worldwide and is an important public health problem. The presence of ischemia in clinical applications can be detected by ECG, biochemical markers, and radiological methods. Myocardial infarction is also frequently encountered in forensic autopsies. Postmortem diagnosis is determined as a result of histopathological examinations and additional exclusionary examinations (toxicology, microbiology, etc.). However, routine histopathological examinations are insufficient, especially when death occurs in the early period of ischemia. It creates a problem for forensic pathologists and forensic medicine specialists in such cases of sudden cardiac death. Postmortem biochemistry is one of the important and promising disciplines in which forensic applications work in order to diagnose these cases correctly. The issue of whether biomarkers used in the diagnosis of myocardial infarction in clinical studies can be used reliably in postmortem cases has been discussed by forensic medicine researchers for some time. This manuscript aims to review and summarize biomarkers belonging to various categories that have been studied in IHD-related deaths, in biological fluids taken at autopsy, or in animal experiments. Our study shows that the postmortem use of biochemical markers in the diagnosis of IHD yields promising results. However, it should not be forgotten that postmortem biochemistry is different from clinical applications due to its dynamics and that the body causes unpredictable changes in markers in the postmortem process. Therefore, comprehensive studies are needed to evaluate the postmortem stability of these markers in different biological fluids, their significance among various causes of death, and whether they are affected by any variable (Cardiopulmonary resuscitation, Postmortem interval, medications, etc.) before they are routinely applied. It is suggested by the authors that the cut-off values of biomarkers whose significance has been proven by these studies should be determined and that they should be used in this way in routine applications.

Use of potassium ion channel and spliceosome proteins as diagnostic biomarkers for sudden unexplained death in schizophrenia

Sudden unexplained death in schizophrenia (SUD-SCZ) is not uncommon and its incidence is approximately three times higher than that in the general population. However, diagnosis of SUD-SCZ remains a great challenge in forensic pathology. This study designed a two-phase study to investigate whether three proteins, namely two potassium ion channel proteins (KCNJ3 and KCNAB1) and one spliceosome protein (SF3B3) that were identified in our previous work, could be applied in the postmortem diagnosis of SUD-SCZ. Immunohistochemical staining of the three biomarkers, followed by a rigorous quantitative analysis, was performed on heart specimens from both SUD-SCZ and control groups. A diagnostic software based on the logistic regression formula derived from the test phase data was then constructed. In the test phase, we found that the staining intensities of KCNJ3, KCNAB1, and SF3B3 were all significantly lower in the SUD-SCZ group (n = 20) as compared with the control group that died from non-natural causes (n = 25), with fold-changes being 14.85 (p < 0.001), 4.13 (p = 0.028) and 2.12 (p = 0.048), respectively. Receiver operating characteristic analysis further illustrated that combination of the three biomarkers achieved the optimal diagnostic specificity (92%) and area under the curve (0.886). In the validation phase, the diagnostic software was confirmed to be a promising tool for predicting the risk of SUD-SCZ in authentic cases. Our study provided a valid strategy towards the practical diagnosis of SUD-SCZ by using KCNJ3, KCNAB1, and SF3B3 proteins as diagnostic biomarkers.

Post-mortem genetic investigation in sudden cardiac death victims: complete exon sequencing of forty genes using next-generation sequencing

Sudden cardiac death (SCD) in young people is predominantly caused by genetic causes as cardiomyopathies. Hypertrophic cardiomyopathy is the most common genetic cardiovascular disease and is responsible for the major proportion of SCD in the young. The purpose of this study was to identify the genetic variants present in young SCD victims with HCM characteristics. From the Portuguese records of autopsies performed at the National Institute of Legal Medicine and Forensic Sciences, North Delegation, 16 young (16-50 years) SCD victims whose death was suspected to be a manifestation of HCM were selected. Using next-generation sequencing, the coding regions of 40 genes associated with HCM, candidates, or strongly related to HCM-phenocopies were investigated. The victims included in this study were all males, with a mean age of 33.4 ± 11.7 years, left ventricle mean thickness of 21.5 ± 6.28 mm, and the majority of deaths occurred during sleep (36%). A pathogenic or likely pathogenic variant was identified in six out of 16 (37.5%) victims, in the most common HCM genes (MYBPC3 and MYH7). Our results indicate that molecular autopsy of SCD victims contributes to a more precise identification of a cause of death, and this can be used in the prevention of SCD cases through family screening of first relatives who may carry the same pathogenic variant.

Re-evaluation of single nucleotide variants and identification of structural variants in a cohort of 45 sudden unexplained death cases

Sudden unexplained death (SUD) takes up a considerable part in overall sudden death cases, especially in adolescents and young adults. During the past decade, many channelopathy- and cardiomyopathy-associated single nucleotide variants (SNVs) have been identified in SUD studies by means of postmortem molecular autopsy, yet the number of cases that remain inconclusive is still high. Recent studies had suggested that structural variants (SVs) might play an important role in SUD, but there is no consensus on the impact of SVs on inherited cardiac diseases. In this study, we searched for potentially pathogenic SVs in 244 genes associated with cardiac diseases. Whole-exome sequencing and appropriate data analysis were performed in 45 SUD cases. Re-analysis of the exome data according to the current ACMG guidelines identified 14 pathogenic or likely pathogenic variants in 10 (22.2%) out of the 45 SUD cases, whereof 2 (4.4%) individuals had variants with likely functional effects in the channelopathy-associated genes SCN5A and TRDN and 1 (2.2%) individual in the cardiomyopathy-associated gene DTNA. In addition, 18 structural variants (SVs) were identified in 15 out of the 45 individuals. Two SVs with likely functional impairment were found in the coding regions of PDSS2 and TRPM4 in 2 SUD cases (4.4%). Both were identified as heterozygous deletions, which were confirmed by multiplex ligation-dependent probe amplification. In conclusion, our findings support that SVs could contribute to the pathology of the sudden death event in some of the cases and therefore should be investigated on a routine basis in suspected SUD cases.

Cardiac hypertrophy at autopsy

Since cardiac hypertrophy may be considered a cause of death at autopsy, its assessment requires a uniform approach. Common terminology and methodology to measure the heart weight, size, and thickness as well as a systematic use of cut off values for normality by age, gender, and body weight and height are needed. For these reasons, recommendations have been written on behalf of the Association for European Cardiovascular Pathology. The diagnostic work up implies the search for pressure and volume overload conditions, compensatory hypertrophy, storage and infiltrative disorders, and cardiomyopathies. Although some gross morphologic features can point to a specific diagnosis, systematic histologic analysis, followed by possible immunostaining and transmission electron microscopy, is essential for a final diagnosis. If the autopsy is carried out in a general or forensic pathology service without expertise in cardiovascular pathology, the entire heart (or pictures) together with mapped histologic slides should be sent for a second opinion to a pathologist with such an expertise. Indication for postmortem genetic testing should be integrated into the multidisciplinary management of sudden cardiac death.

CircSLC8A1 and circNFIX can be used as auxiliary diagnostic markers for sudden cardiac death caused by acute ischemic heart disease

Sudden cardiac death (SCD) caused by acute ischemic heart disease (IHD) is a major cause of sudden death worldwide. Circular RNAs (circRNAs) are abundant in the heart and play important roles in cardiovascular diseases, but the role of circRNAs as biomarkers in the forensic diagnosis of SCD caused by acute IHD remains poorly characterized. To investigate the potential of two heart-enriched circRNAs, circNFIX and circSLC8A1, we explored the expression of these two circRNAs in different kinds of commonly used IHD models, and further verified their expressions in forensic autopsy cases. The results from both the IHD rat and H9c2 cell models revealed that circSlc8a1 level was upregulated, while the circNfix level was elevated in the early stage of ischemia and subsequently downregulated. The time-dependent expression patterns of the two circRNAs suggested their potential as SCD biomarkers. In autopsy cases, the results showed that the expression of these two circRNAs in the myocardium with acute IHD-related SCDs corresponded to the observations in the ischemic models. Further analysis related to myocardial ischemia indicated that circSLC8A1 showed high sensitivity and specificity for myocardial infarction and was positively correlated with creatine kinase MB in pericardial fluid. Downregulated circNFIX level could indicate the ischemic myocardial damage, and it was negatively correlated with the coronary artery stenosis grade. The combination of circSLC8A1 and circNFIX had better performance to discriminate IHD-related SCDs. The results suggested that circSLC8A1 and circNFIX may be used as auxiliary diagnostic markers for SCD caused by acute IHD in forensic medicine.

Mind the gap: Knowledge deficits in evaluating young sudden cardiac death

Sudden cardiac arrest affects around half a million people aged under 50 years old annually, with a 90% mortality rate. Despite high patient numbers and clear clinical need to improve outcomes, many gaps exist in the evidence underpinning patients' management. Domains identifying the greatest barriers to conducting trials are the prehospital and forensic settings, which also provide care to the majority of patients. Addressing gaps in evidence along each point of the cardiac arrest trajectory is a key clinical priority.