From rare events to systematic data collection: the RESCUED registry for sudden cardiac death in the young in Germany.

BACKGROUND: Approximately one-third of sudden cardiac deaths in the young (SCDY) occur due to a structural cardiac disease. Forty to fifty percent of SCDY cases remain unexplained after autopsy (including microscopic and forensic-toxicological analyses), suggesting arrhythmia syndromes as a possible cause of death. Due to the possible inheritability of these diseases, blood relatives of the deceased may equally be carriers of the causative genetic variations and therefore may have an increased cardiac risk profile. A better understanding of the forensic, clinical, and genetic data might help identify a subset of the general population that is at increased risk of sudden cardiac death. STUDY DESIGN: The German registry RESCUED (REgistry for Sudden Cardiac and UnExpected Death) comprises information about SCDY fatalities and clinical and genetic data of both the deceased and their biological relatives. The datasets collected in the RESCUED registry will allow for the identification of leading causes of SCDY in Germany and offer unique possibilities of scientific analyses with the aim of detecting unrecognized trends, risk factors, and clinical warning signs of SCDY. In a pilot phase of 24 months, approximately 180 SCDY cases (< 50 years of age) and 500 family members and clinical patients will be included. CONCLUSION: RESCUED is the first registry in Germany collecting comprehensive data of SCDY cases and clinical data of the biological relatives reviewed by cardiac experts. RESCUED aims to improve individual risk assessment and public health approaches by directing resources towards early diagnosis and evidence-based, personalized therapy and prevention in affected families. Trial registration number (TRN): DRKS00033543.

Suitable biomarkers for post-mortem differentiation of cardiac death causes: Quantitative analysis of miR-1, miR-133a and miR-26a in heart tissue and whole blood.

Cardiovascular diseases are the most common causes of death worldwide. Cardiac death can occur as reaction to myocardial infarction (MI). A diagnostic challenge arises for sudden unexpected death (SUD) cases with structural abnormalities (SA) or without any structural abnormalities (without SA). Therefore, the identification of reliable biomarkers to differentiate cardiac cases from each other is necessary. In the current study, the potential of different microRNAs (miRNAs) as biomarkers in tissue and blood samples of cardiac death cases was analyzed. Blood and tissue samples of 24 MI, 21 SUD and 5 control (C) cases were collected during autopsy. Testing for significance and receiver operating characteristic analysis (ROC) were performed. The results show that miR-1, miR-133a and miR-26a possess a high diagnostic power to discriminate between different cardiac death causes in whole blood and in tissue.

Telemedical monitoring in patients with inborn cardiac disease - experience of a tertiary care centre.

BACKGROUND: The number of cardiologically relevant genetic findings will continue to increase. This is due to the use of high-throughput sequencing techniques and the critical role of incidental findings in cardiac disease genes. Telemedicine can be a useful diagnostic tool to monitor the heart rhythm of patients with inborn cardiac diseases. METHODS: Patients were screened once they had been referred to our outpatient department for rare cardiac diseases between January 2020 and May 2022. Those patients who underwent genetic testing and were consequently diagnosed with a genetic disorder were included in this study. Their medical records were evaluated regarding implanted cardiac electronic devices and findings in the telemedical monitoring. RESULTS: 304 patients were seen in our outpatient department for rare cardiac diseases in the mentioned period. In 100 cases, genetic testing was performed. 10 patients (10%) with an identified inborn cardiac disease were monitored via telemedicine until the end of May 2022. 4 patients were monitored by implantable loop recorders (ILR), 4 patients were monitored by Implantable Cardioverter Defibrillators (ICD), and 2 patients received both devices. Clinical relevant arrhythmias making medical intervention necessary were identified in 4 cases. In two cases, data interpretation was hampered by sinus tachycardia caused by physical exercise. DISCUSSION: Telemonitoring of the heart rhythm by medical devices is beneficial for patients with monogenic heart diseases. Especially, when the indication for an ICD is not clear, implantation of a telemonitored ILR can be a suitable choice. However, rhythm analysis can be challenging in young patients who are physically active.

Variant interpretation in molecular autopsy: a useful dilemma.

Sudden cardiac death (SCD) in adolescents and young adults may be the first manifestation of an inherited arrhythmic syndrome. Thus identification of a genetic origin in sudden death cases deemed inconclusive after a comprehensive autopsy and may help to reduce the risk of lethal episodes in the remaining family. Using next-generation sequencing (NGS), a large number of variants of unknown significance (VUS) are detected. In the majority of cases, there is insufficient evidence of pathogenicity, representing a huge dilemma in current genetic investigations. Misinterpretation of such variants may lead to inaccurate genetic diagnoses and/or the adoption of unnecessary and/or inappropriate therapeutic approaches. In our study, we applied current (ACMG) recommendations for variant classification in post-mortem genetic screening of a cohort of 56 SCD victims. We identified a total 53 rare protein-altering variants (MAF < 0.2%) classified as VUS or worse. Twelve percent of the cases exhibited a clinically actionable variant (pathogenic, likely pathogenic or VUS - potentially pathogenic) that would warrant cascade genetic screening in relatives. Most of the variants detected by means of the post-mortem genetic investigations were VUS. Thus, genetic testing by itself might be fairly meaningless without supporting background data. This data reinforces the need for an experienced multidisciplinary team for obtaining reliable and accountable interpretations of variant significance for elucidating potential causes for SCDs in the young. This enables the early identification of relatives at risk or excludes family members as genetic carriers. Also, development of adequate forensic guidelines to enable appropriate interpretation of rare genetic variants is fundamental.

Genetic analysis of sudden unexpected death cases: Evaluation of library preparation methods to handle heterogeneous sample material.

Over the past years, next-generation sequencing (NGS) technologies revolutionized the possibilities in a broad range of application areas. Also in the field of forensic genetics, NGS continuously gained in importance and attentiveness. A significant number of sudden cardiac deaths (SCD) in the young is due to heritable arrhythmia syndromes emphasizing the need of examining the genetic basis in these cases also with regard to the identification of relatives and/or patients being at risk. As a result, high-throughput methods became of increasing value in molecular autopsy investigations enabling the analysis of a broad spectrum of genes. Most standard protocols are optimized for high-quality samples and frequently not directly applicable to challenging forensic sample material. In the present study, we intended to examine a comprehensive gene panel associated with SCD and inherited arrhythmogenic disorders. We compared three different hybridization-based library preparation technologies in order to implement a suitable NGS workflow for heterogeneous, forensic as well as diagnostic sample material. The results obtained indicated, that the Illumina technologies Nextera DNA Flex and TruSeq were compatible with samples exhibiting varying levels of degradation. In comparison, the TruSight method also resulted in good sequencing data, but seemed to be more dependent on DNA integrity. The preparation protocols evaluated in our study are not restricted to molecular autopsy investigations and might be helpful for and transferrable to further forensic research applications.

Post-mortem genetic investigation of cardiac disease-associated genes in sudden infant death syndrome (SIDS) cases.

The sudden infant death syndrome (SIDS) is one of the leading causes of postneonatal infant death. It has been shown that there exists a complex relationship between SIDS and inherited cardiac disease. Next-generation sequencing and surveillance of cardiac channelopathy and cardiomyopathy genes represent an important tool for investigating the cause of death in SIDS cases. In the present study, targeted sequencing of 80 genes associated with genetic heart diseases in a cohort of 31 SIDS cases was performed. To determine the spectrum and prevalence of genetic heart disease associated mutations as a potential monogenic basis for SIDS, a stringent variant classification was applied and the percentage of rare (minor allele frequency ≤ 0.2%) and ultra-rare variants (minor allele frequency ≤ 0.005%) in these genes was assessed. With a minor allele frequency of ≤ 0.005%, about 20% of the SIDS cases exhibited a variant of uncertain significance (VUS), but in only 6% of these cases, gene variants proved to be "potentially informative." The present study shows the importance of careful variant interpretation. Applying stringent criteria misinterpretations are avoided, as the results of genetic analyses may have an important impact of the family members involved.

Characterization of an N-terminal Nav1.5 channel variant - a potential risk factor for arrhythmias and sudden death?

BACKGROUND: Alterations in the SCN5A gene encoding the cardiac sodium channel Nav1.5 have been linked to a number of arrhythmia syndromes and diseases including long-QT syndrome (LQTS), Brugada syndrome (BrS) and dilative cardiomyopathy (DCM), which may predispose to fatal arrhythmias and sudden death. We identified the heterozygous variant c.316A > G, p.(Ser106Gly) in a 35-year-old patient with survived cardiac arrest. In the present study, we aimed to investigate the functional impact of the variant to clarify the medical relevance. METHODS: Mutant as well as wild type GFP tagged Nav1.5 channels were expressed in HEK293 cells. We performed functional characterization experiments using patch-clamp technique. RESULTS: Electrophysiological measurements indicated, that the detected missense variant alters Nav1.5 channel functionality leading to a gain-of-function effect. Cells expressing S106G channels show an increase in Nav1.5 current over the entire voltage window. CONCLUSION: The results support the assumption that the detected sequence aberration alters Nav1.5 channel function and may predispose to cardiac arrhythmias and sudden cardiac death.