Sudden cardiac death in the young: a genetic destiny?

Causes of sudden cardiac arrest and death and the diagnostic yield of sport preparticipation screening in children

OBJECTIVE

Evidence on the increased risk of sports-related sudden cardiac arrest and death (SCA/D) and the potential benefit of cardiovascular preparticipation screening (PPS) in children is limited. We assessed the burden and circumstances of SCA/D and the diagnostic yield of cardiovascular PPS in children aged 8-15 years.

METHODS

Data on the incidence and causes of SCA/D from 2011 to 2020 were obtained from the Veneto region (Italy) sudden death registry, hospital records and local press. During the same period, we assessed the results of annual PPS in 25 251 young competitive athletes aged 8-15 years who underwent 58 185 evaluations (mean 2.3/athlete) in Padua, Italy.

RESULTS

Over 10 years, 26 SCA/D occurred in children aged 8-15 years in the Veneto region: 6 in athletes (incidence 0.7/100 000/year, all ≥12 years) versus 20 in non-athletes (0.7/100 000/year, 17/20 ≥12 years). In total, 4/6 athletes versus 1/20 non-athletes survived. The cause of SCA/D remained unexplained in four athletes and in nine non-athletes. No athlete suffered SCA/D from structural diseases potentially identifiable by PPS. The incidence of SCA/D in athletes and non-athletes was 0.2/100 000/year in the 8-11 years group versus 1.3/100 000/year in the 12-15 years group. PPS identified 26 new diagnoses of cardiovascular diseases (CVDs) at risk of SCA/D, more often in children ≥12 years old (0.06%/evaluation) than <12 years old (0.02%/evaluation, p=0.02). Among athletes with a negative PPS, two suffered unexplained SCA/D during follow-up, one during exercise.

CONCLUSIONS

In children aged 8-15 years, the incidence of SCA/D and the yield of PPS for identifying at-risk CVD were both substantially higher in those ≥12 years, suggesting that systematic PPS may be more useful beyond this age.

Primary myocardial fibrosis - a distinct entity characterized by heterogeneous histology

Primary myocardial fibrosis (PMF), defined as myocardial fibrosis in the absence of identifiable causes, may represent a common alternative phenotype in various cardiomyopathies and contribute to sudden cardiac death (SCD). No previous definitions of histopathological characteristics exist for PMF. We aimed to evaluate whether common features of fibrosis could be identified. PMF cases (n = 28) were selected from the FinGesture cohort consisting of 5,869 SCD victims that underwent a medicolegal autopsy. Twelve trauma controls and 10 ischemic heart disease cases were selected as reference groups. Further 3 PMF cases and 5 ischemic heart disease cases from autopsies performed in the University of Copenhagen, Denmark, were selected for a validation substudy. Relative area of fibrosis, amount of diffuse and perivascular fibrosis, and location of fibrosis were assessed from left ventricle myocardial samples stained with Masson trichrome. Further evaluations were performed with alpha-smooth muscle actin (α-SMA), vimentin, and CD68 stainings. Mean relative area of fibrosis was 5.8 ± 10.7%, 1.0 ± 0.7%, and 7.0 ± 7.4% in PMF, trauma controls, and ischemic cases, respectively. Fibrosis in the PMF group was mostly located in other sites than the endocardium. Most cases with fibrosis had vimentin-positive but α-SMA-negative stromal cells within fibrotic areas. Histopathologically, PMF represents a heterogeneous entity with variable fibrotic lesions affecting the whole myocardium and a suggested significant role of fibroblasts. These findings may bring validation to PMF being a common manifestation of cardiomyopathies. Evidently, PMF stands out as a particular entity demanding special attention as a cause of SCD.

What Are the Causes of Death among Patients Admitted to a Contemporary Tertiary-Level Cardiology Department? An Analysis of 10 Years of Morbidity and Mortality Meetings

Despite the efforts to deliver the best evidence-based care, in-hospital death is an inevitable event among some patients hospitalized in cardiology departments. We conducted a retrospective evaluation of mortality events from inpatient admissions to the cardiology department between 2010 and 2019. Data were collected from morbidity and mortality meeting presentations that evaluated comorbidities, medical history, treatments, and causes of death for the overall cohort and according to age group and sex. There were 1182 registered deaths. The most common causes of death among patients were acute myocardial infarction (AMI, 53.0%), heart failure (HF, 11.7%), cardiac arrest (CA, 6.6%), HF with complication/defined cardiomyopathy (6.3%), and sepsis (4.4%). We observed a decline in deaths from AMI from 61.9% in 2010 to 46.7% in 2019, while there was a clear increase in deaths from HF (11.1% in 2010 to 25.9% in 2019). Compared to patients ≥65 years, younger patients were more likely to have died from CA (15.7% vs. 4.3%, p < 0.001) and other cardiac reasons (3.0% vs. 0.4%, p < 0.001). The majority of deaths were due to AMI, HF, and CA. We observed a significant declining trend in the proportion of deaths due to AMI in recent years, with an increase in deaths due to HF.

Autopsy and sudden death

Our story dates back in the late 70s, when a series of juvenile sudden death (SD) occurred in the Veneto region, north east of Italy. A successful application for a prospective study on young people dying suddenly (<35-year-old, sudden infant death syndrome excluded) was submitted to the regional health authorities, thus implementing a network of collaboration with local anatomic and forensic pathologists, to collect all such events and to gather demographic data. The project is still in progress, and since then, we studied hundreds of consecutive juvenile SD cases, allowing to identify the culprit diseases in the various organs and cardiac structures (aorta, coronary arteries, myocardium, valves, and conduction system). The long-standing Veneto region experience clearly shows that autopsy still plays a pivotal role in the study and prevention of SD and should be carried out regularly. With time, the investigation of SD moved from the classic post-mortem study to molecular autopsy, especially in cases of SD with structurally normal heart. Sudden death prevention in the young has to be faced by an interdisciplinary team, including pathologists, cardiologists, sport physicians, and geneticists, the clinicopathologic correlation method still being the polar star. The game in the fight against SD is still played in the anatomical theatre, the place where 'death enjoys to save lives'.

Metagenomic analysis of viral genes integrated in whole genome sequencing data of Thai patients with Brugada syndrome

Brugada syndrome (BS) is an autosomal dominant inheritance cardiac arrhythmia disorder associated with sudden death in young adults. Thailand has the highest prevalence of BS worldwide, and over 60% of patients with BS still have unclear disease etiology. Here, we performeda new viral metagenome analysis pipeline called VIRIN and validated it with whole genome sequencing (WGS) data of HeLa cell lines and hepatocellular carcinoma. Then the VIRIN pipelinewas applied to identify viral integration positions from unmapped WGS data of Thai males, including 100 BS patients (case) and 100 controls. Even though the sample preparation had noviral enrichment step, we can identify several virus genes from our analysis pipeline. The predominance of human endogenous retrovirus K (HERV-K) viruses was found in both cases andcontrols by blastn and blastx analysis. This study is the first report on the full-length HERV-Kassembled genomes in the Thai population. Furthermore, the HERV-K integration breakpointpositions were validated and compared between the case and control datasets. Interestingly,Brugada cases contained HERV-K integration breakpoints at promoters five times more oftenthan controls. Overall, the highlight of this study is the BS-specific HERV-K breakpoint positionsthat were found at the gene coding region "NBPF11" (n = 9), "NBPF12" (n = 8) and longnon-coding RNA (lncRNA) "PCAT14" (n = 4) region. The genes and the lncRNA have been reported to be associated with congenital heart and arterial diseases. These findings provide another aspect of the BS etiology associated with viral genome integrations within the humangenome.

Perspectives in Sports Genomics

Human athletic performance is a complex phenotype influenced by environmental and genetic factors, with most exercise-related traits being polygenic in nature. The aim of this article is to outline some of the challenge faced by sports genetics as this relatively new field moves forward. This review summarizes recent advances in sports science and discusses the impact of the genome, epigenome and other omics (such as proteomics and metabolomics) on athletic performance. The article also highlights the current status of gene doping and examines the possibility of applying genetic knowledge to predict athletes’ injury risk and to prevent the rare but alarming occurrence of sudden deaths during sporting events. Future research in large cohorts of athletes has the potential to detect new genetic variants and to confirm the previously identified DNA variants believed to explain the natural predisposition of some individuals to certain athletic abilities and health benefits. It is hoped that this article will be useful to sports scientists who seek a greater understanding of how genetics influences exercise science and how genomic and other multi-omics approaches might support performance analysis, coaching, personalizing nutrition, rehabilitation and sports medicine, as well as the potential to develop new rationale for future scientific investigation.

Cardiac magnetic resonance in the diagnosis of the unusually detected acute myocarditis in the young people: a case report

Myocarditis is among the causes of arrhythmic sudden cardiac death (SCD) in young athletes, with viral infection being the most common cause worldwide. Myocarditis recently has been reported as one of the cardiac complications of coronavirus disease 2019 (COVID-19) in athletes. Here we present a case of a 20-year-old male recreational soccer player with an episode of loss of consciousness in the context of respiratory infection. The patient reports having woken up with symptoms of an upper respiratory tract infection, and after playing a soccer match, he developed dizziness and a headache. He then suffered vasovagal syncope without loss of sphincter control. Physical examination, heart auscultation, peripheral and carotid pulses, and blood, microbiological/serological tests result on admission were normal. Moreover, no jugular engorgement at 45º, malleolar edema, or other heart failure signs were found. The 12-lead electrocardiogram (ECG), echocardiogram, 24-hour Holter-ECG did not reveal any significant finding. A cardiac magnetic resonance (CMR) was finally performed, revealing an abnormal signal increase was observed at the apical level in the short-tau inversion-recovery (STIR) and 4-chamber sequences. In addition, a pattern of apical fibrosis was observed in 4- and 2-chamber and short-axis late enhancement sequences for assessment of myocardial viability confirming the diagnosis of myocarditis. In athletes with suspected myocarditis, CMR seems to be a useful diagnostic tool, with excellent sensitivity for detecting inflammation, myocardial edema, and/or focal scarring.

Update on the Diagnostic Pitfalls of Autopsy and Post-Mortem Genetic Testing in Cardiomyopathies

Inherited cardiomyopathies are frequent causes of sudden cardiac death (SCD), especially in young patients. Despite at the autopsy they usually have distinctive microscopic and/or macroscopic diagnostic features, their phenotypes may be mild or ambiguous, possibly leading to misdiagnoses or missed diagnoses. In this review, the main differential diagnoses of hypertrophic cardiomyopathy (e.g., athlete's heart, idiopathic left ventricular hypertrophy), arrhythmogenic cardiomyopathy (e.g., adipositas cordis, myocarditis) and dilated cardiomyopathy (e.g., acquired forms of dilated cardiomyopathy, left ventricular noncompaction) are discussed. Moreover, the diagnostic issues in SCD victims affected by phenotype-negative hypertrophic cardiomyopathy and the relationship between myocardial bridging and hypertrophic cardiomyopathy are analyzed. Finally, the applications/limits of virtopsy and post-mortem genetic testing in this field are discussed, with particular attention to the issues related to the assessment of the significance of the genetic variants.

The Hidden Fragility in the Heart of the Athletes: A Review of Genetic Biomarkers

Sudden cardiac death (SCD) is a devastating event which can also affect people in apparent good health, such as young athletes. It is known that intense and continuous exercise along with a genetic background that predisposes a person to the risk of fatal arrhythmias is a trigger for SCD. Therefore, knowledge of the athlete’s genetic conditions underlying the onset of SCD must be extended, in order to develop new effective prevention and/or therapeutic strategies. Arrhythmic features occur across a broad spectrum of cardiac diseases, sometimes presenting with overlapping phenotypes. The genetic basis of arrhythmogenic disorders has been greatly highlighted in the last 30 years, and has shown marked heterogeneity. The advent of next-generation sequencing has constantly updated our understanding of the genetic basis of arrhythmogenic diseases and is laying the foundation for precision medicine. With the exception of a few clinical cases involving a single athlete showing a highly suspected phenotype for the presence of a heart disease, there are few studies to date that analysed the applicability of genetic testing on cohorts of athletes. This evidence shows that genetic testing can contribute to the diagnosis of up to 13% of athletes; however, the presence of clinical markers is essential. This review aims to provide a reference collection on current knowledge of the genetic basis of sudden cardiac death in athletes and to review updated evidence on the effectiveness of genetic testing in early identification of athletes at risk for SCD.

Sport and exercise genomics: the FIMS 2019 consensus statement update

Rapid advances in technologies in the field of genomics such as high throughput DNA sequencing, big data processing by machine learning algorithms and gene-editing techniques are expected to make precision medicine and gene-therapy a greater reality. However, this development will raise many important new issues, including ethical, moral, social and privacy issues. The field of exercise genomics has also advanced by incorporating these innovative technologies. There is therefore an urgent need for guiding references for sport and exercise genomics to allow the necessary advancements in this field of sport and exercise medicine, while protecting athletes from any invasion of privacy and misuse of their genomic information. Here, we update a previous consensus and develop a guiding reference for sport and exercise genomics based on a SWOT (Strengths, Weaknesses, Opportunities and Threats) analysis. This SWOT analysis and the developed guiding reference highlight the need for scientists/clinicians to be well-versed in ethics and data protection policy to advance sport and exercise genomics without compromising the privacy of athletes and the efforts of international sports federations. Conducting research based on the present guiding reference will mitigate to a great extent the risks brought about by inappropriate use of genomic information and allow further development of sport and exercise genomics in accordance with best ethical standards and international data protection principles and policies. This guiding reference should regularly be updated on the basis of new information emerging from the area of sport and exercise medicine as well as from the developments and challenges in genomics of health and disease in general in order to best protect the athletes, patients and all other relevant stakeholders.

Prevalence of sudden arrhythmic death syndrome-related genetic mutations in an Asian cohort of whole genome sequence

AIMS

Recently, the spectrum of background mutation in the genes implicated in sudden arrhythmic death syndrome (SADS), has been elucidated in the Caucasian populations. However, this information is largely unknown in the Asian populations.

METHODS AND RESULTS

We assessed the background rare variants (minor allele frequency < 0.01) of major SADS genes in whole genome sequence data of 1514 healthy Taiwanese subjects from the Taiwan Biobank. We found up to 45% of healthy subjects have a rare variant in at least one of the major SADS genes. Around 3.44% of healthy subjects had multiple mutations in one or multiple genes. The background mutation rates in long QT syndrome, catecholaminergic polymorphic ventricular tachycardia, and arrhythmogenic right ventricular cardiomyopathy genes were similar, but those in Brugada syndrome (BrS) (SCN5A) and hypertrophic cardiomyopathy (HCM) genes (MYBPC3, MYH7, and TNNT2) were higher, compared to those reported in the Caucasian populations. Furthermore, the rate of incidental pathogenic variant was highest in MYBPC3 gene. Finally, the number of variant was proportional to the exon length of the gene (R2 = 0.486, P = 0.0056) but not related to its functional or evolutionary importance (degree of evolutionary conservation) (R2 = 0.0008, P = 0.9218), suggesting that the mutation was random. The ratio of variant number over exon nucleotide length was highest in MYBPC3, MYH7, and TNNT2 genes.

CONCLUSION

Unique features of background SADS gene mutation in the Asian populations include higher prevalence of incidental variant in HCM, BrS, and long QT 3 (SCN5A) genes. HCM genes have the highest variant number per exon length.

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.

Myocarditis in the Athlete: Arrhythmogenic Substrates, Clinical Manifestations, Management, and Eligibility Decisions

Myocarditis is as an important cause of sudden cardiac death (SCD) among athletes. The incidence of SCD ascribed to myocarditis did not change after the introduction of pre-participation screening in Italy, due to the transient nature of the disease and problems in the differential diagnosis with the athlete's heart. The arrhythmic burden and the underlying mechanisms differ between the acute and chronic setting, depending on the relative impact of acute inflammation versus post-inflammatory myocardial fibrosis. In the acute phase, ventricular arrhythmias vary from isolated ventricular ectopic beats to complex tachycardias that can lead to SCD. Atrioventricular blocks are typical of specific forms of myocarditis, and supraventricular arrhythmias may be observed in case of atrial inflammation. Athletes with acute myocarditis should be temporarily restricted from physical exercise, until complete recovery. However, ventricular tachycardia may also occur in the chronic phase in the context of post-inflammatory myocardial scar.