Sudden cardiac death in children and young adults - epidemiology and prevention

Characterization of electrocardiographic findings in young students

INTRODUCTION AND OBJECTIVES

The resting 12-lead electrocardiogram (ECG) has been used in the evaluation of young asymptomatic individuals to detect pre-existing heart disease, but systematic ECG use is controversial and there are no data on this population in our environment. We aimed to determine the prevalence and spectrum of electrocardiographic findings in a population of secondary school students.

METHODS

We conducted an observational, cross-sectional study of resting ECG findings in all 13 to 14-year-old secondary school students in a region of the province of Gerona between 2009 and 2017. ECG findings were classified into 3 groups according to the modified criteria of Corrado et al.: normal ECG findings, ECG findings suggestive of adaptive changes, and pathologic findings. Students with pathologic ECG findings were referred to a tertiary hospital, and complementary tests were performed according to a pre-established protocol.

RESULTS

A total of 1911 ECGs were obtained, with a participation rate of 79% of all high school students. In all, 1321 students (69%) had a normal ECG, 554 (29%) showed ECG findings suggestive of adaptive changes, and 36 (2%) had pathologic ECG findings. Among the group with pathologic findings, 5 (14%) had cardiovascular disease. The prevalence of heart disease in this group of asymptomatic secondary school students was 0.3%.

CONCLUSIONS

One third of the students had ECG findings that were mostly suggestive of physiological adaptation. One seventh of the students with pathologic ECG findings had pre-existing heart disease, although the overall prevalence of pre-existing heart disease was low.

Feasibility of analysis of the SCN5A gene in paraffin embedded samples in sudden infant death cases at the Pretoria Medico-Legal Laboratory, South Africa

To determine variations in the SCN5A gene linked to inherited cardiac arrhythmogenic disorders in sudden, unexplained infant death (SUID) cases examined at the Pretoria Medico-Legal Laboratory, South Africa. A retrospective study was conducted on SUID cases and controls, analyzing DNA extracted from archived formalin-fixed, paraffin-embedded (FFPE) myocardial tissue samples as well as blood samples. A total of 48 FFPE tissue samples (cases), 10 control FFPE tissue samples and nine control blood samples were included. DNA extracted from all samples was used to test for variations in the SCN5A gene by using high resolution melt (HRM) real-time PCR and sequencing. Genetic analysis showed 31 different single nucleotide variants in the entire study population (n = 67). Five previously reported variants of known pathogenic significance, and 14 variants of benign clinical significance, were identified. The study found 12 different variants in the cases that were not published in any database or literature and were considered novel. Of these novel variants, two were predicted as "probably damaging" with a high level of certainty (found in four case samples), one (identified in another case sample) was predicted to be "possibly damaging" with a 50% chance of being disease-causing, and nine were predicted to be benign. This study shows the significant added value of using genetic testing in determining the cause of death in South African SUID cases. Considering the high heritability of these arrhythmic disorders, post mortem genetic testing could play an important role in the understanding of the pathogenesis thereof and could also aid in the diagnosis and treatment of family members at risk, ultimately preventing similar future cases.

Long QT syndrome and sudden unexpected infant death

Long QT syndrome (LQTS) is an inheritable primary electric disease of the heart characterised by abnormally long QT intervals and a propensity to develop atrial and ventricular tachyarrhythmias. It is caused by an inherited channelopathy responsible for sudden cardiac death in individuals with structurally normal hearts. Long QT syndrome can present early in life, and some studies suggest that it may be associated with up to 20% of sudden unexplained infant death (SUID), particularly when associated with external stressors such as asphyxia, which is commonly seen in many infant death scenes. With an understanding of the genetic defects, it has now been possible to retrospectively analyse samples from infants who have presented to forensic pathology services with a history of unexplained sudden death, which may, in turn, enable the implementation of preventative treatment for siblings previously not known to have pathogenic genetic variations. In this viewpoint article, we will discuss SUID, LQTS and postmortem genetic analysis.