The usual suspects in sudden cardiac death of the young: a focus on inherited arrhythmogenic diseases

[Adult advanced life support]

These European Resuscitation Council Advanced Life Support guidelines are based on the 2020 International Consensus on Cardiopulmonary Resuscitation Science with Treatment Recommendations. This section provides guidelines on the prevention of and ALS treatments for both in-hospital cardiac arrest and out-of-hospital cardiac arrest.

European Resuscitation Council Guidelines 2021: Adult advanced life support

These European Resuscitation Council Advanced Life Support guidelines, are based on the 2020 International Consensus on Cardiopulmonary Resuscitation Science with Treatment Recommendations. This section provides guidelines on the prevention of and ALS treatments for both in-hospital cardiac arrest and out-of-hospital cardiac arrest.

Prevented Sudden Cardiac Death and Neurologic Recovery in Inherited Heart Diseases

Introduction: Inherited cardiovascular diseases are an important cause of sudden cardiac death (SD). The use of risk scores identify high risk patients who would benefit from an implantable cardioverter-defibrillators (ICDs). The development of automated devices for out-of-hospital cardiac arrest improves early resuscitation. The objective of the study is to quantify prevented SD and the neurological recovery of patients with inherited cardiovascular diseases. Methods: Two hundred fifty-seven cases of SD (age 42 ± 18 years, 79.4% men) of non-ischemic cardiac cause were prospectively collected during the study period (2009-17). Fifty three (20.6%) had a resuscitated cardiac arrest (RCA) (age 40 ± 18 years, 64.2% male). Epidemiological, clinical and autopsy aspects were analyzed. Prevented SD was defined as a combination of RCA and appropriate ICD therapy cases. Results: An autopsy was performed in 157/204 (77.0%) cases who died. There were 19 (12.1%) cases with a negative autopsy. The diagnosis of cardiomyopathy and channelopathy was 58.0 and 18.7%, respectively. Female sex and confirmed or suspected channelopathy were associated with successful resuscitation. The percentage of prevented SD remained low during the study period (mean 35.6%). 60.4% of RCA cases presented good neurological outcome. There was no association between neurological recovery and therapeutic hypothermia, but there was association with time of resuscitation (min). Conclusion: A fifth part of non-ischemic cardiac arrests were resuscitated. Female sex and channelopathies were more prevalent among RCA. Two thirds of RCA had a good neurological recovery.

Death in childhood and adolescence: Accident!

In childhood and adolescence periods, individuals encounter many dangerous situations caused by not completing their biological and psychological development. Some of them are pathological deaths such as accidents, poisoning, and traumatic actions for children. Awareness of the number and causes of death is an indicator that reflects the health status of our society. It is also vital in-service planning for both preventive and therapeutic medical professions. The purpose of this article is to evaluate death cases between the ages of 0-18 in terms of forensic medicine. As a result, it has been understood that accidents are an important cause of death in childhood. In particular, developing policies to protect against common accidents will reduce the mortality rates of children.

The Emergence of Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes (hiPSC-CMs) as a Platform to Model Arrhythmogenic Diseases

There is a need for improved in vitro models of inherited cardiac diseases to better understand basic cellular and molecular mechanisms and advance drug development. Most of these diseases are associated with arrhythmias, as a result of mutations in ion channel or ion channel-modulatory proteins. Thus far, the electrophysiological phenotype of these mutations has been typically studied using transgenic animal models and heterologous expression systems. Although they have played a major role in advancing the understanding of the pathophysiology of arrhythmogenesis, more physiological and predictive preclinical models are necessary to optimize the treatment strategy for individual patients. Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have generated much interest as an alternative tool to model arrhythmogenic diseases. They provide a unique opportunity to recapitulate the native-like environment required for mutated proteins to reproduce the human cellular disease phenotype. However, it is also important to recognize the limitations of this technology, specifically their fetal electrophysiological phenotype, which differentiates them from adult human myocytes. In this review, we provide an overview of the major inherited arrhythmogenic cardiac diseases modeled using hiPSC-CMs and for which the cellular disease phenotype has been somewhat characterized.

Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes as Models for Cardiac Channelopathies: A Primer for Non-Electrophysiologists

Life threatening ventricular arrhythmias leading to sudden cardiac death are a major cause of morbidity and mortality. In the absence of structural heart disease, these arrhythmias, especially in the younger population, are often an outcome of genetic defects in specialized membrane proteins called ion channels. In the heart, exceptionally well-orchestrated activity of a diversity of ion channels mediates the cardiac action potential. Alterations in either the function or expression of these channels can disrupt the configuration of the action potential, leading to abnormal electrical activity of the heart that can sometimes initiate an arrhythmia. Understanding the pathophysiology of inherited arrhythmias can be challenging because of the complexity of the disorder and lack of appropriate cellular and in vivo models. Recent advances in human induced pluripotent stem cell technology have provided remarkable progress in comprehending the underlying mechanisms of ion channel disorders or channelopathies by modeling these complex arrhythmia syndromes in vitro in a dish. To fully realize the potential of induced pluripotent stem cells in elucidating the mechanistic basis and complex pathophysiology of channelopathies, it is crucial to have a basic knowledge of cardiac myocyte electrophysiology. In this review, we will discuss the role of the various ion channels in cardiac electrophysiology and the molecular and cellular mechanisms of arrhythmias, highlighting the promise of human induced pluripotent stem cell-cardiomyocytes as a model for investigating inherited arrhythmia syndromes and testing antiarrhythmic strategies. Overall, this review aims to provide a basic understanding of the electrical activity of the heart and related channelopathies, especially to clinicians or research scientists in the cardiovascular field with limited electrophysiology background.

Genetic testing and cascade screening in pediatric long QT syndrome and hypertrophic cardiomyopathy

BACKGROUND

The efficacy of cascade screening for the inherited heart conditions long QT syndrome (LQTS) and hypertrophic cardiomyopathy (HCM) is incompletely characterized.

OBJECTIVE

The purpose of this study was to examine the use of genetic testing and yield of cascade screening across diverse regions in the United States and to evaluate obstacles to screening in multipayer systems.

METHODS

An institutional review board-approved 6 United States pediatric center retrospective chart review of LQTS and HCM patients from 2008-2014 was conducted for (1) genetic test completion and results and (2) family cascade screening acceptance, methods, results, and barriers.

RESULTS

The families of 315 index patients (mean age 9.0 ± 5.8 years) demonstrated a 75% (254) acceptance of cascade screening. The yield of relative screening was 39% (232/601), an average of 0.91 detected per family. Genetic testing was less utilized in HCM index patients and relatives. Screening participation was greater in families of gene-positive index patients (88%) (P <.001) compared to gene-negative patients (53%). Cascade method utilization: Cardiology-only 45%, combined genetic and cardiology 39%, and genetic only 16%. Screening yield by method: combined 57%, genetic-only 29%, and cardiology-only 20%. Family decisions were the leading barriers to cascade screening (26% lack of followthrough and 26% declined), whereas insurance (6%) was the least cited barrier.

CONCLUSION

Family participation in cascade screening is high, but the greatest barriers are family mediated (declined, lack of followthrough). Positive proband genetic testing led to greater participation. Cardiology-only screening was the most utilized method, but combined cardiology and genetic screening had the highest detection.

Genetic risk stratification in cardiac arrhythmias

PURPOSE OF REVIEW

The current article provides a concise summary of the possibilities and limitations of genotype-based risk stratification of cardiac arrhythmias. We will outline the most important findings of the recent years in the light of their chronological and conceptual development.

RECENT FINDINGS

Genotype-phenotype association studies in families with single-gene disorders as well as in the general population led to the discovery of several DNA variants significantly associated with the risk of sudden death or life-threatening arrhythmias. In genetic (monogenic) diseases, the disease-causing mutations modulate the risk of events and response to antiarrhythmic therapy according to the specific gene involved, to their position of the mutation and to their functional effects. These causal relationships have been quite well characterized in the case of long QT syndrome but are still less defined in the case of other inherited conditions. Quantitatively, the risk associated with a single genetic variant is large for DNA variants that cause monogenic inherited arrhythmias. Much different is the case of more common variants associated with the risk of arrhythmias in the general population as they are generally associated with a small effect size.

SUMMARY

Genetic profiling identifies arrhythmogenic risk even if a complete picture allowing high-granularity risk stratification is yet to come.

Post mortem pro life - Should we analyse the implantable devices after death? A systematic review

AIM

Post-mortem interrogation of the cardiac implantable electronic devices (CIEDs) in combination with autopsy findings can provide additional information regarding device functioning after implantation or the mechanism of death. The aim of the study is to review the available data on the post-mortem interrogation of CIEDs and its possible clinical implications.

METHODS AND RESULTS

A systematic review of the published studies has been performed. Out of 762 unique citations 14 have been retained for final analysis. Post-mortem CIED interrogation reliably detects both serious device malfunctions and lead disorders but also improper device programming. As the need for CIED implantation is growing in the low-income countries, currently available data on battery longevity of devices explanted and destined for re-use have been reviewed.

CONCLUSIONS

Post-mortem CIED interrogation provides a unique opportunity to explore different mechanisms of death, often unavailable for distinction during regular in-hospital observation or in autopsy analysis.

Sudden Arrhythmic Death During Exercise: A Post-Mortem Genetic Analysis

BACKGROUND

Sudden cardiac death is a natural and unexpected death that occurs within 1 h of the first symptom. Most sudden cardiac deaths occur during exercise, mostly as a result of myocardial infarction. After autopsy, some cases, especially in the young, are diagnosed as cardiomyopathies or remain without a conclusive cause of death. In both situations, genetic alterations may explain the arrhythmia.

OBJECTIVE

Our aim was to identify a genetic predisposition to sudden cardiac death in a cohort of post-mortem cases of individuals who died during exercise, with a structurally normal heart, and were classified as arrhythmogenic death.

METHODS

We analyzed a cohort of 52 post-mortem samples from individuals <50 years old who had a negative autopsy. Next-generation sequencing technology was used to screen genes associated with sudden cardiac death.

RESULTS

Our cohort showed a male prevalence (12:1). Half of the deaths occurred in individuals 41-50 years of age. Running was the most common exercise activity during the fatal event, accounting for 46.15% of cases. Genetic analysis identified 83 rare variants in 37 samples (71.15% of all samples). Of all rare variants, 36.14% were classified as deleterious, being present in 53.84% of all cases.

CONCLUSIONS

A comprehensive analysis of sudden cardiac death-related genes in individuals who died suddenly while exercising enabled the identification of potentially causative variants. However, many genetic variants remain of indeterminate significance, thus further work is needed before clinical translation. Nonetheless, comprehensive genetic analysis of individuals who died during exercise enables the detection of potentially causative variants and helps to identify at-risk relatives.

Sudden cardiac death among the young in Sweden from 2000 to 2010: an autopsy-based study

Aims

To study the incidence and aetiology of sudden cardiac death (SCD) in 1- to 35-year-olds in Sweden from 2000 to 2010.

Methods and results

We used the database of the Swedish National Board of Forensic Medicine and the Swedish Cause of Death Registry and identified SCD cases by review of forensic files and death certificates. We identified 552 individuals with SCD in 1- to 35-year-olds; 156 (28%) were women. In 393 (71%), a forensic autopsy had been performed; in 131 (24%), a clinical autopsy had been performed; in 28 (5%) with no autopsy, a cardiac disease was diagnosed before death. The incidence of SCD per 100 000 person-years was 1.3 in 1- to 35-year-olds and 1.8 in 15- to 35-year-olds. In women, the incidence rates yearly decreased during the study period by 11% (95% confidence interval 6.6-14.2). The most common aetiology in 1- to 35-year-olds was sudden arrhythmic death syndrome (31%) and coronary artery disease (15%). In cases with forensic autopsy, death occurred during daily activity (48%), sleep (38%), and physical activity (14%); death was unwitnessed in 60%. Co-morbidity in 15- to 35-year-olds, e.g. psychiatric disorder, obesity, or diabetes, was present in 93/340 (27%) (73 men).

Conclusion

The incidence of SCD among 1- to 35-year-olds in Sweden during 2000-10 was 1.3 per 100 000 person-years (28% women); incidence was decreasing in women. Sudden arrhythmic death syndrome was the most common diagnosis. Co-morbidity such as psychiatric disorders and obesity was common among men.

Heart rate variability as predictive factor for sudden cardiac death

Sudden cardiac death (SCD) represents about 25% of deaths in clinical cardiology. The identification of risk factors for SCD is the philosopher's stone of cardiology and the identification of non-invasive markers of risk of SCD remains one of the most important goals for the scientific community.The aim of this review is to analyze the state of the art around the heart rate variability (HRV) as a predictor factor for SCD.HRV is probably the most analyzed index in cardiovascular risk stratification technical literature, therefore an important number of models and methods have been developed.Nowadays, low HRV has been shown to be independently predictive of increased mortality in post- myocardial infarction patients, heart failure patients, in contrast with the data of the general population.Contrariwise, the relationship between HRV and SCD has received scarce attention in low-risk cohorts. Furthermore, in general population the attributable risk is modest and the cost/benefit ratio is not always convenient.The HRV evaluation could become an important tool for health status in risks population, even though the use of HRV alone for risk stratification of SCD is limited and further studies are needed.

Incomplete Penetrance and Variable Expressivity: Hallmarks in Channelopathies Associated with Sudden Cardiac Death

Sudden cardiac death is defined as an unexpected decease of cardiac origin. In individuals under 35 years old, most of these deaths are due to familial arrhythmogenic syndromes of genetic origin, also known as channelopathies. These familial cardiac syndromes commonly follow an autosomal dominant pattern of inheritance. Diagnosis, however, can be difficult, mainly due to incomplete penetrance and variable expressivity, which are hallmarks in these syndromes. The clinical manifestation of these diseases can range from asymptomatic to syncope but sudden death can sometimes be the first symptom of disease. Early identification of at-risk individuals is crucial to prevent a lethal episode. In this review, we will focus on the genetic basis of channelopathies and the effect of genetic and non-genetic modifiers on their phenotypes.

Cardiac Channelopathies and Sudden Death: Recent Clinical and Genetic Advances

Sudden cardiac death poses a unique challenge to clinicians because it may be the only symptom of an inherited heart condition. Indeed, inherited heart diseases can cause sudden cardiac death in older and younger individuals. Two groups of familial diseases are responsible for sudden cardiac death: cardiomyopathies (mainly hypertrophic cardiomyopathy, dilated cardiomyopathy, and arrhythmogenic cardiomyopathy) and channelopathies (mainly long QT syndrome, Brugada syndrome, short QT syndrome, and catecholaminergic polymorphic ventricular tachycardia). This review focuses on cardiac channelopathies, which are characterized by lethal arrhythmias in the structurally normal heart, incomplete penetrance, and variable expressivity. Arrhythmias in these diseases result from pathogenic variants in genes encoding cardiac ion channels or associated proteins. Due to a lack of gross structural changes in the heart, channelopathies are often considered as potential causes of death in otherwise unexplained forensic autopsies. The asymptomatic nature of channelopathies is cause for concern in family members who may be carrying genetic risk factors, making the identification of these genetic factors of significant clinical importance.

Is There a Role for Genetics in the Prevention of Sudden Cardiac Death?

The identification of patients at risk for sudden cardiac death (SCD) is fundamental for both acquired cardiovascular diseases (such as coronary artery diseases, CAD) and inherited arrhythmia syndromes (such as the long-QT syndrome, LQTS). Genetics may play a role in both situations, although the potential to exploit this information to reduce the burden of SCD varies among these two groups. Concerning acquired cardiovascular diseases, which affect most of the general population, preliminary data suggest an association between genetics and the risk of dying suddenly. The maximal utility, instead, is reached in inherited arrhythmia syndromes, where the discovery of monogenic diseases such as LQTS tracked the way for the first genotype-phenotype correlations. The aim of this review is to provide a general overview focusing on the current genetic knowledge and on the present and future applicability for prevention in these two populations at risk for SCD.

Genetics of inherited arrhythmias in pediatrics

PURPOSE OF REVIEW

Recent international expert consensus statements have updated the clinical and genetic diagnoses of patients suffering from arrhythmogenic diseases. However, a lack of genotype-phenotype correlations has hampered the development of a risk stratification scale for sudden cardiac death.

RECENT FINDINGS

The improvement in the field of genetics has prompted the discovery of new genes associated with sudden cardiac death. Sudden cardiac death is a socially devastating event, especially when it occurs in the pediatric population. Physical activity can often trigger the arrhythmia and sudden death may be the first symptom. These inherited cardiac diseases may be difficult to diagnose, leaving family members also at risk. Thanks to the development of new high-throughput technologies, genetics may be used in the diagnosis of these diseases and even cases that remain unexplained after a comprehensive autopsy. Genetic testing cannot only identify the causative genetic variant in the index case, but it enables the detection of relatives at risk of sudden death, despite remaining clinically asymptomatic.

SUMMARY

We review the recent advances in the genetics of inherited arrhythmias associated with sudden cardiac death. We focus on the pediatric population, the main group of people suffering from lethal inherited arrhythmias.