Sudden Cardiac Death and Copy Number Variants: What Do We Know after 10 Years of Genetic Analysis?

Appropriate time interval to update ambiguous genetic diagnosis in inherited arrhythmogenic syndromes

Genetic analysis identified the cause of the disease in inherited arrhythmogenic syndromes. A clinically actionable genetic diagnosis requires an accurate interpretation following the current guidelines. Practically half of the genetic diagnoses remain inconclusive due to the identification of variants of uncertain significance. An update can help shed light on uncertain results. No specific time frame has been set for updating an ambiguous diagnosis. We carried out an analysis of the available reclassification/reinterpretation data concerning genetic diagnosis in inherited arrhythmogenic syndromes. We aim to determine an appropriate interval for updating a conclusive classification. Genetic diagnoses achieved without following current guidelines should be updated immediately. An ambiguous result obtained following the current guidelines should be updated no more than 5 years after the first analysis. There are still questions to be resolved regarding the legal responsibility or who should assume the economic cost of updating a genetic diagnosis.

Unique Genetic Profiles in Hypertrophic Cardiomyopathy Patients From São Miguel Island (Azores, Portugal)

To investigate the clinical features and mutational spectrum underlying hypertrophic cardiomyopathy (HCM) in São Miguel Island (Azores, Portugal), we analyzed 37 adult patients (12 sporadic, 25 familial) with positive genetic tests. Seven disease-causing variants were identified, being two novels, in three sarcomeric genes (MYH7, TNNT2, and MYBPC3) and one non-sarcomeric gene (ALPK3). The novel variants, classified as likely pathogenic (LP), involved large multi-exon deletions in MYBPC3 (exons 26-32 and 28-33). These deletions were found in heterozygosity in two young males who remained clinically stable, though early onset may predict a more severe prognosis. Segregation analysis in a consanguineous family revealed two new genotypes: a digenic heterozygous for MYH7:c.1750G>C (p.Gly584Arg; P) and TNNT2:c.842A>T (p.Asn281Ile; LP) variants, and a homozygous for the TNNT2 variant. The 70-year-old homozygous patient remained stable and without arrhythmic events, challenging the belief that homozygous variants have a worse prognosis. This study is the first molecular and clinical analysis of HCM in the Azores.

Exploring transcriptomic signatures in sudden unexplained death (SUD) cases

BACKGROUND

Molecular autopsy in sudden unexplained death (SUD) has successfully identified pathogenic variants in cardiovascular genes in a substantial proportion of cases, contributing to prevention strategies in family members. However, many SUD cases remain genetically unresolved, prompting investigations into other omics technologies to better understand the pathogenic mechanisms leading to a sudden death event. In this study, whole transcriptome sequencing was performed on heart samples from 43 SUD cases and 17 heart-healthy controls, with the aim to identify disease-specific transcriptome signatures in sudden unexplained death.

RESULTS

PCA based on the top 500 genes with the highest variance among the samples showed no clear separation between SUD and controls or among the three SUD subgroups. DESeq2 identified 1,676 differentially expressed genes between SUD and controls with significantly upregulated genes involved in biological processes such as angiogenesis, blood vessel development, vasculogenesis and cell adhesion. Pathway analysis of the differentially expressed genes showed that most were downregulated and involved in amide/peptide biosynthesis and fatty acid metabolism. Additional analysis of SUD subgroups revealed unique gene expression patterns and highlighted differentially expressed genes within each subgroup.

CONCLUSION

Gene expression analysis of SUD heart tissue is a promising approach to identify cardiac disease-related pathways to further understand the pathological mechanisms leading to a sudden death event. However, due to the heterogeneity of the SUD cases and the unclear phenotype, further studies in larger cohorts are needed.

Copy Number Variants in Cardiac Channelopathies: Still a Missed Part in Routine Arrhythmic Diagnostics

Inherited cardiac channelopathies are major causes of sudden cardiac death (SCD) in young people. Genetic testing is focused on the identification of single-nucleotide variants (SNVs) by Next-Generation Sequencing (NGS). However, genetically elusive cases can carry copy number variants (CNVs), which need specific detection tools. We underlie the utility of identifying CNVs by investigating the literature data and internally analyzing cohorts with CNVs in KCNQ1, KCNH2, SCN5A, and RYR2. CNVs were reported in 119 patients from the literature and 21 from our cohort. Young patients with CNVs in KCNQ1 show a Long QT (LQT) phenotype > 480 ms and a higher frequency of syncope. None of them had SCD. All patients with CNV in KCNH2 had a positive phenotype for QT > 480 ms. CNVs in SCN5A were represented by the Brugada pattern, with major cardiac events mainly in males. Conversely, adult females show more supraventricular arrhythmias. RYR2-exon3 deletion showed a broader phenotype, including left ventricular non-compaction (LVNC) and catecholaminergic polymorphic ventricular tachycardia (CPVT). Pediatric patients showed atrial arrhythmias and paroxysmal atrial fibrillation. Relatively higher syncope and SCA were observed in young females. The detection of CNVs can be of greater yield in two groups: familial channelopathies and patients with suspected Jervell and Lange-Nielsen syndrome or CPVT. The limited number of reported individuals makes it mandatory for multicentric studies to give future conclusive results.

Investigating cardiac genetic background in sudden infant death syndrome (SIDS)

Sudden infant death syndrome (SIDS) is still the leading cause of death for newborns in developed countries. The pathophysiological mechanisms have not been fully clarified, but in some of SIDS cases variants of genes associated with inherited cardiac conditions are found. In this study, an analysis of SCD-related genes was performed to determine the prevalence of rare pathogenic (P) or likely pathogenic (LP) variants that could provide an unambiguous explanation for the fatal event. A cohort of 76 SIDS cases underwent Next-Generation Sequencing (NGS) analysis with a custom panel of SCD-related genes. Rare variants were classified according to the guidelines provided by the American College of Medical Genetics and Genomics (ACMG) and the specifications of the ClinGen association. Post-mortem genetic testing identified 50 (65.8%) carriers of at least one variant in SCD genes. 104 rare genetic variants were found, 65.4% in genes encoding structural proteins. Only 4 out of 76 cases (5.3%) hosted at least a P or LP variant found in genes with structural or structural/arrhythmogenic functions (SLC22A5, SCN5A, MYL3and TTN). 99 variants were classified as of uncertain significance (VUS). The difference in the distribution of variants between gene groups by function was not statistically significant (chi square, p = 0,219). Despite this, most of the variants concerned structural genes that were supposed to have a close interaction with ion channels, thus providing an explanation for the arrhythmic event. Segregation analysis, reclassification of VUS variants and identification of new associated genes could clarify the implications of the current findings.

Clinical Relevance of the Systematic Analysis of Copy Number Variants in the Genetic Study of Cardiomyopathies

Cardiomyopathies (CMs), one of the main causes of sudden death among the young population, are a heterogeneous group of myocardial diseases, usually with a genetic cause. Next-Generation Sequencing (NGS) has expanded the genes studied for CMs; however, the yield is still around 50%. The systematic study of Copy Number Variants (CNVs) could contribute to improving our diagnostic capacity. These alterations have already been described as responsible for cardiomyopathies in some cases; however, their impact has been rarely assessed. We analyzed the clinical significance of CNVs in cardiomyopathies by studying 11,647 affected patients, many more than those considered in previously published studies. We evaluated the yield of the systematic study of CNVs in a production context using NGS and a novel CNV detection software tool v2.0 that has demonstrated great efficacy, maximizing sensitivity and avoiding false positives. We obtained a CNV analysis yield of 0.8% that fluctuated depending on the type of cardiomyopathy studied (0.29% HCM, 1.41% DCM, 1.88% ARVC, 1.8% LVNC, 1.45% RCM), and we present the frequency of occurrence for 18 genes that agglutinate the 95 pathogenic/likely pathogenic CNVs detected. We conclude the importance of including in diagnostic tests a systematic study of these genetic alterations for the different cardiomyopathies.

Phenotypic spectrum of the first Belgian MYBPC3 founder: a large multi-exon deletion with a varying phenotype

Background

Variants in the MYBPC3 gene are a frequent cause of hypertrophic cardiomyopathy (HCM) but display a large phenotypic heterogeneity. Founder mutations are often believed to be more benign as they prevailed despite potential negative selection pressure. We detected a pathogenic variant in MYBPC3 (del exon 23-26) in several probands. We aimed to assess the presence of a common haplotype and to describe the cardiac characteristics, disease severity and long-term outcome of mutation carriers.

Methods

Probands with HCM caused by a pathogenic deletion of exon 23-26 of MYBPC3 were identified through genetic screening using a gene panel encompassing 59 genes associated with cardiomyopathies in a single genetic center in Belgium. Cascade screening of first-degree relatives was performed, and genotype positive relatives were further phenotyped. Clinical characteristics were collected from probands and relatives. Cardiac outcomes included death, heart transplantation, life-threatening arrhythmia, heart failure hospitalization or septal reduction therapy. Haplotype analysis, using microsatellite markers surrounding MYBPC3, was performed in all index patients to identify a common haplotype. The age of the founder variant was estimated based on the size of the shared haplotype using a linkage-disequilibrium based approach.

Results

We identified 24 probands with HCM harbouring the MYBPC3 exon 23-26 deletion. Probands were on average 51 ± 16 years old at time of clinical HCM diagnosis and 62 ± 10 years old at time of genetic diagnosis. A common haplotype of 1.19 Mb was identified in all 24 probands, with 19 of the probands sharing a 13.8 Mb haplotype. The founder event was estimated to have happened five generations, or 175-200 years ago, around the year 1830 in central Flanders. Through cascade screening, 59 first-degree relatives were genetically tested, of whom 37 (62.7%) were genotype positive (G+) and 22 (37.3%) genotype negative (G-). They were on average 38 ± 19 years old at time of genetic testing. Subsequent clinical assessment revealed a HCM phenotype in 19 (51.4%) G+ relatives. Probands were older (63 ± 10 vs. 42 ± 21 years; p < 0.001) and had more severe phenotypes than G+ family members, presenting with more symptoms (50% vs. 13.5%; p = 0.002), arrhythmia (41.7% vs. 12.9%, p = 0.014), more overt hypertrophy and left ventricular outflow tract obstruction (43.5% vs. 3.0%; p < 0.001). Male G+ relatives more often had a HCM phenotype (78.6% vs. 34.8%; p = 0.010) and were more severely affected than females. At the age of 50, a penetrance of 78.6% was observed, defined as the presence of HCM in 11 of 14 G+ relatives with age ≥50 years. Overall, 20.3% of all variant carriers developed one of the predefined cardiac outcomes after a median follow-up of 5.5 years with an average age of 50 (±21) years.

Conclusion

A Belgian founder variant, an exon 23-26 deletion in MYBPC3, was identified in 24 probands and 37 family members. The variant is characterized by a high penetrance of 78.6% at the age of 50 years but has variable phenotypic expression. Adverse outcomes were observed in 20.3% of patients during follow-up.

Analysis of the Association between Copy Number Variation and Ventricular Fibrillation in ST-Elevation Acute Myocardial Infarction

Sudden cardiac death due to ventricular fibrillation (VF) during ST-elevation acute myocardial infarction (STEAMI) significantly contributes to cardiovascular-related deaths. Although VF has been linked to genetic factors, variations in copy number variation (CNV), a significant source of genetic variation, have remained largely unexplored in this context. To address this knowledge gap, this study performed whole exome sequencing analysis on a cohort of 39 patients with STEAMI who experienced VF, aiming to elucidate the role of CNVs in this pathology. The analysis revealed CNVs in the form of duplications in the PARP2 and TTC5 genes as well as CNVs in the form of deletions in the MUC15 and PPP6R1 genes, which could potentially serve as risk indicators for VF during STEAMI. The analysis also underscores notable CNVs with an average gene copy number equal to or greater than four in DEFB134, FCGR2C, GREM1, PARM1, SCG5, and UNC79 genes. These findings provide further insight into the role of CNVs in VF in the context of STEAMI.

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.

What can autopsy say about COVID-19? A case series of 60 autopsies

INTRODUCTION

Autopsies in SARS-CoV-2 infected cadavers are mainly performed to distinguish patients who died with SARS-CoV-2 infection from those who died of COVID-19. The aim of the current study is to assess the most frequent autopsy findings in patients who died of COVID-19 and to establish an association with clinical records.

MATERIALS AND METHODS

60 patients died between April 2020 and March 2021 after SARS-CoV-2 infection underwent a full autopsy performed at Fondazione Policlinico Universitario Agostino Gemelli IRCCS (Rome). Ante-mortem diagnosis of SARS-CoV-2 infection was microbiologically confirmed.

RESULTS

55 (92%) of cases had at least a comorbidity. At microscopic examination, 40 (67%) of the patients presented pulmonary intravascular coagulation with an inflammatory pattern. Pulmonary microangiopathy was a rare finding (n = 8; 13%). Myocardiosclerosis was the main heart finding (n = 44; 73%). Liver involvement with congestion and hypotrophy was found in 33 (55%) of cadavers. Renal tubular epithelial exfoliation (n = 12; 20%) and intravascular coagulation (n = 4; 7%) were frequent observations. During hospitalization 31% of patients (n = 19) developed acute kidney injury (AKI).

CONCLUSIONS

Lungs and kidneys have been shown to play a pivotal role in COVID-19. The gradual worsening of renal function and AKI might be the result of the progressive collapse of cardiopulmonary system.

Detection of the Copy Number Variants of Genes in Patients with Familial Cardiac Diseases by Massively Parallel Sequencing

INTRODUCTION

The implication of copy number variations in familial heart disease is known, although in-depth knowledge is lacking; hence, more studies are needed to further our understanding. Massively parallel sequencing, thanks to its recent surge in use, is emerging as a valid tool for the detection of this type of variant, through the use of appropriate software.

METHODS

We conducted a study with 182 patients diagnosed with mendelian cardiovascular diseases who underwent sequencing using a cardiac gene panel and then a specific calling process for copy number variations (CNVs) with ExomeDepth software, which provides us with a Bayes factor (BF), a score of the probability that a CNV detected is true.

RESULTS

After a rigorous CNV prioritization process, we confirmed the variants obtained by MLPA or SNP-based array, finding three real CNVs in five individuals in the MYH11, FBN1 and PDMI7 genes.

CONCLUSION

The confirmed CNVs present in all cases BF values > 60, thus establishing a threshold to consider real CNVs in the calling process carried out by ExomeDepth on our gene panel.

Eosinophilic Infiltration of the Sino-Atrial Node in Sudden Cardiac Death Caused by Long QT Syndrome

Sudden death is defined as the unexpected death of a healthy person that occurs within the first hour of the onset of symptoms or within 24 h of the victim being last seen alive. In some of these cases, rare deleterious variants of genes associated with inherited cardiac disorders can provide a highly probable explanation for the fatal event. We report the case of a 21-year-old obese woman who lost consciousness suddenly in a public place and was pronounced dead after hospital admission. Clinical autopsy showed an inconclusive gross examination, while in the histopathological analysis an eosinophilic inflammatory focus and interstitial fibrosis in the sino-atrial node were found. Molecular autopsy revealed an intronic variant in the KCNQ1 gene (c.683 + 5G > A), classified as likely pathogenic for long QT syndrome according to the guidelines provided by the American College of Medical Genetics and Genomics. Therefore, there were many anomalies that could have played a role in the causation of the sudden death, such as the extreme obesity, the cardiac anomalies and the KNCQ1 variant. This case depicts the difficult interpretation of rare cardiac structural abnormalities in subjects carrying rare variants responsible for inherited arrhythmic disorders and the challenge for the forensic pathologist to make causal inferences in the determinism of the unexpected decease.

Structural Heart Alterations in Brugada Syndrome: Is it Really a Channelopathy? A Systematic Review

Brugada syndrome (BrS) is classified as an inherited cardiac channelopathy attributed to dysfunctional ion channels and/or associated proteins in cardiomyocytes rather than to structural heart alterations. However, hearts of some BrS patients exhibit slight histologic abnormalities, suggesting that BrS could be a phenotypic variant of arrhythmogenic cardiomyopathy. We performed a systematic review of the literature following Preferred Reporting Items for Systematic Reviews and Meta-Analyses Statement (PRISMA) criteria. Our comprehensive analysis of structural findings did not reveal enough definitive evidence for reclassification of BrS as a cardiomyopathy. The collection and comprehensive analysis of new cases with a definitive BrS diagnosis are needed to clarify whether some of these structural features may have key roles in the pathophysiological pathways associated with malignant arrhythmogenic episodes.

Systematic Bioinformatics Analysis Based on Public and Second-Generation Sequencing Transcriptome Data: A Study on the Diagnostic Value and Potential Mechanisms of Immune-Related Genes in Acute Myocardial Infarction

Acute myocardial infarction (AMI) is one of the most serious cardiovascular diseases worldwide. Advances in genomics have provided new ideas for the development of novel molecular biomarkers of potential clinical value for AMI.

Novel Indel Variation of NPC1 Gene Associates With Risk of Sudden Cardiac Death

Background and Aims: Sudden cardiac death (SCD) was defined as an unexpected death from cardiac causes during a very short duration. It has been reported that Niemann-Pick type C1 (NPC1) gene mutations might be related to cardiovascular diseases. The purpose of the study is to investigate whether common genetic variants of NPC1 is involved in SCD susceptibility.

Methods: Based on a candidate-gene-based approach and systematic screening strategy, this study analyzed an 8-bp insertion/deletion polymorphism (rs150703258) within downstream of NPC1 for the association with SCD risk in Chinese populations using 158 SCD cases and 524 controls. The association of rs150703258 and SCD susceptibility was analyzed using logistic regression. Genotype-phenotype correlation analysis was performed using public database including 1000G, expression quantitative trait loci (eQTL), and further validated by human heart tissues using PCR. Dual-luciferase assay was used to explore the potential regulatory role of rs150703258. Gene expression profiling interactive analysis and transcription factors prediction were performed.

Results: Logistic regression analysis exhibited that the deletion allele of rs150703258 significantly increased the risk of SCD [odds ratio (OR) = 1.329; 95% confidence interval (95%CI):1.03–1.72; p = 0.0289]. Genotype-phenotype correlation analysis showed that the risk allele was significantly associated with higher expression of NPC1 at mRNA and protein expressions level in human heart tissues. eQTL analysis showed NPC1 and C18orf8 (an adjacent gene to NPC1) are both related to rs150703258 and have higher expression level in the samples with deletion allele. Dual-luciferase activity assays indicate a significant regulatory role for rs150703258. Gene expression profiling interactive analysis revealed that NPC1 and C18orf8 seemed to be co-regulated in human blood, arteries and heart tissues. In silico analysis showed that the rs150703258 deletion variant may create transcription factor binding sites. In addition, a rare 12-bp allele (4-bp longer than the insertion allele) of rs150703258 was discovered in the current cohort.

Conclusion: In summary, our study revealed that rs150703258 might contribute to SCD susceptibility by regulating NPC1 and C18orf8 expression. This indel may be a potential marker for risk stratification and molecular diagnosis of SCD. Validations in different ethnic groups with larger sample size and mechanism explorations are warranted to confirm our findings.

Clinical Genetics of Inherited Arrhythmogenic Disease in the Pediatric Population

Sudden death is a rare event in the pediatric population but with a social shock due to its presentation as the first symptom in previously healthy children. Comprehensive autopsy in pediatric cases identify an inconclusive cause in 40-50% of cases. In such cases, a diagnosis of sudden arrhythmic death syndrome is suggested as the main potential cause of death. Molecular autopsy identifies nearly 30% of cases under 16 years of age carrying a pathogenic/potentially pathogenic alteration in genes associated with any inherited arrhythmogenic disease. In the last few years, despite the increasing rate of post-mortem genetic diagnosis, many families still remain without a conclusive genetic cause of the unexpected death. Current challenges in genetic diagnosis are the establishment of a correct genotype-phenotype association between genes and inherited arrhythmogenic disease, as well as the classification of variants of uncertain significance. In this review, we provide an update on the state of the art in the genetic diagnosis of inherited arrhythmogenic disease in the pediatric population. We focus on emerging publications on gene curation for genotype-phenotype associations, cases of genetic overlap and advances in the classification of variants of uncertain significance. Our goal is to facilitate the translation of genetic diagnosis to the clinical area, helping risk stratification, treatment and the genetic counselling of families.

Epidemiology of sudden infant death syndrome in Mexico, 2005-2020

BACKGROUND

Sudden Infant Death Syndrome (SIDS) constitutes one of the main causes of mortality in children under one year of age in developed countries; it's frequency to varies geographically. In Mexico the real incidence of SIDS is not known.

METHODS

National databases of deaths in children under one year of age, from 2005 to 2020, were analyzed, due to Sudden Unexpected Infant Death (SUID) [SIDS (R95), accidental suffocation in a sleeping environment (W75), and other ill-defined and unspecified causes of mortality (R99), according to the International Classification of Diseases, tenth revision (ICD 10)]. Mortality rates per year of occurrence due to SUID and their subcategories were calculated. Simple frequencies of SIDS were obtained per year and month of occurrence, state of residence, age, place of death, and access to social security services.

RESULTS

In the study period 473,545 infant deaths occurred; 7,714 (1.62%) deaths were due to SUID; of these, 6,489 (84%) were due to SIDS, which is among the 10 leading causes of infant death in Mexico. The average mortality rate for SUID was 22.4/100,000 live births, for SIDS was 18.8/100,000 live births. Mortality rates within the states were variable, ranging from 2.4/100,000 to 105.1/100,000 live births. In 81% of SIDS records there was no autopsy; 38% of deaths due to SIDS occurred in infants under one month of age, up to 87% of deaths occurred in families without social security services or it was unknown, and 76.2% of deaths occurred at home. Deaths were more frequent during the last months of autumn and during winter.

CONCLUSION

In Mexico there is an underregistry of SIDS as cause of death, along with other SUID categories. Health workers need to be trained to improve diagnosis and data registration, including the practice of autopsies; additionally, it is necessary to implement a public health campaign.

The association between apolipoprotein A-1 plasma level and premature coronary artery disease: A systematic review and meta-analysis

BACKGROUND

Apolipoprotein A-1 (Apo A-1) is a constituent of high-density lipoprotein (HDL) and emerging evidences put forward a potential association between Apo A-1 plasma levels and premature coronary artery disease (pCAD). The aim of the present study is to gather relative literature and perform a systematic review and meta-analysis regarding the association between serum ApoA-1 levels and pCAD.

METHODS

Medline (via PubMed), Scopus, Embase and Web of Science databases were searched from the inception of databases until December 7, 2020. All articles reporting the plasma levels of ApoA-1 in patients with pCAD and the control group were included. A meta-analysis with pooled standardised mean difference (SMD) and 95% confidence interval (95% CI) was reported. Subgroup analyses were done based on the observed heterogeneity in results.

RESULTS

Seventeen case-control studies were included. ApoA-1 plasma level was calculated to be lower in pCAD patients compared with the control group (SMD: -0.67; 95% CI: -0.48 to -0.86; P < .001). The subgroup analysis and meta-regression showed that the variation in gender distribution, the development level of the target population's country and quality score of included studies were the main sources of heterogeneity. It was observed that the relationship was only significant in the developed countries (P < .001). Also, the heterogeneity was reduced when the analysis was limited to males (I² = 57.2%) and females only (I² = 26.0%).

CONCLUSION

In conclusion, there seems to be a significant association between the serum levels of ApoA-1 and pCAD. However, all of the included studies had a case-control design and since there is no good quality and prospective cohort studies included, reliability of the current evidence is debatable. Therefore, further well-designed cohort studies are required to assess the impact of serum ApoA-1 reduction on pCAD onset.

Sudden Death without a Clear Cause after Comprehensive Investigation: An Example of Forensic Approach to Atypical/Uncertain Findings

Sudden death (SD) is defined as the unexpected natural death occurred within an hour after the onset of symptoms or from the last moment the subject has been seen in a healthy condition. Brugada syndrome (BrS) is one of the most remarkable cardiac causes of SD among young people. We report the case of a 20-year-old man who suddenly died after reportedly having smoked cannabis. Autopsy, toxicology, and genetic testing were performed. Autopsy found a long and thick myocardial bridging (MB) at 2 cm from the beginning of the left anterior descending coronary artery. Furthermore, at the histopathological examination, fibrosis and disarray in myocardial area above the MB, fatty tissue in the right ventricle and fibrosis of the sino-atrial node area were found. Toxicology testing was inconclusive, while genetic testing found a rare missense variant of the TTN gene, classified as likely benign, and a variant of unknown significance in the SLMAP gene (a gene that can be associated with BrS). Hence, despite several atypical features were found, no inference on the cause of the death could be made under current evidence.

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.

Malignant Arrhythmogenic Role Associated with RBM20: A Comprehensive Interpretation Focused on a Personalized Approach

The RBM20 gene encodes the muscle-specific splicing factor RNA-binding motif 20, a regulator of heart-specific alternative splicing. Nearly 40 potentially deleterious variants in RBM20 have been reported in the last ten years, being found to be associated with highly arrhythmogenic events in familial dilated cardiomyopathy. Frequently, malignant arrhythmias can be a primary manifestation of disease. The early recognition of arrhythmic genotypes is crucial in avoiding lethal episodes, as it may have an impact on the adoption of personalized preventive measures. Our study performs a comprehensive update of data concerning rare variants in RBM20 that are associated with malignant arrhythmogenic phenotypes with a focus on personalized medicine.

Genetic Variants as Sudden-Death Risk Markers in Inherited Arrhythmogenic Syndromes: Personalized Genetic Interpretation

Inherited arrhythmogenic syndromes are the primary cause of unexpected lethal cardiac episodes in young people. It is possible that the first sign of the condition may be sudden death. Inherited arrhythmogenic syndromes are caused by genetic defects that may be analyzed using different technical approaches. A genetic alteration may be used as a marker of risk for families who carry the genetic alterations. Therefore, the early identification of the responsible genetic defect may help the adoption of preventive therapeutic measures focused on reducing the risk of lethal arrhythmias. Here, we describe the use of massive sequencing technologies and the interpretation of genetic analyses in inherited arrhythmogenic syndromes.

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.