Nationwide (Denmark) study of symptoms preceding sudden death due to arrhythmogenic right ventricular cardiomyopathy

Incidence, risk assessment and prevention of sudden cardiac death in cardiomyopathies

Cardiomyopathies are a significant contributor to cardiovascular morbidity and mortality, mainly due to the development of heart failure and increased risk of sudden cardiac death (SCD). Despite improvement in survival with contemporary treatment, SCD remains an important cause of mortality in cardiomyopathies. It occurs at a rate ranging between 0.15% and 0.7% per year (depending on the cardiomyopathy), which significantly surpasses SCD incidence in the age- and sex-matched general population. The risk of SCD is affected by multiple factors including the aetiology, genetic basis, age, sex, physical exertion, the extent of myocardial disease severity, conduction system abnormalities, and electrical instability, as measured by various metrics. Over the past decades, the knowledge on the mechanisms and risk factors for SCD has substantially improved, allowing for a better-informed risk stratification. However, unresolved issues still challenge the guidance of SCD prevention in patients with cardiomyopathies. In this review, we aim to provide an in-depth discussion of the contemporary concepts pertinent to understanding the burden, risk assessment and prevention of SCD in cardiomyopathies (dilated, non-dilated left ventricular, hypertrophic, arrhythmogenic right ventricular, and restrictive). The review first focuses on SCD incidence in cardiomyopathies and then summarizes established and emerging risk factors for life-threatening arrhythmias/SCD. Finally, it discusses validated approaches to the risk assessment and evidence-based measures for SCD prevention in cardiomyopathies, pointing to the gaps in evidence and areas of uncertainties that merit future clarification.

Risk stratification of sudden cardiac death: a review

Sudden cardiac death (SCD) is responsible for several millions of deaths every year and remains a major health problem. To reduce this burden, diagnosing and identification of high-risk individuals and disease-specific risk stratification are essential. Treatment strategies include treatment of the underlying disease with lifestyle advice and drugs and decisions to implant a primary prevention implantable cardioverter-defibrillator (ICD) and perform ablation of the ventricles and novel treatment modalities such as left cardiac sympathetic denervation in rare specific primary electric diseases such as long QT syndrome and catecholaminergic polymorphic ventricular tachycardia. This review summarizes the current knowledge on SCD risk according to underlying heart disease and discusses the future of SCD prevention.

Family History and Warning Symptoms Precede Sudden Cardiac Death in Arrhythmogenic Right Ventricular Cardiomyopathy (from a Nationwide Study in Sweden)

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited cardiac disease explaining about 4% of sudden cardiac death (SCD) cases in the young in Sweden. This study aimed to describe the circumstances preceding SCD in all victims <35 years of age who received an autopsy-confirmed diagnosis of ARVC from January 1, 2000, to December 31, 2010, in Sweden (n = 22). Data on demographics, medical and family history, circumstances of death, and anatomopathological findings were collected from several compulsory national health registries, clinical records, family interviews, and autopsy reports. Registry-based data were compared with age-matched, gender-matched, and geographically-matched population controls. During the 6 months preceding SCD, 15 cases (68%) had experienced symptoms of cardiac origin, mainly syncope or presyncope (54%) and chest discomfort (27%). A total of 8 cases (36%) had sought medical care because of cardiac symptoms. The occurrence of hospital visits was significantly increased in cases compared with controls (odds ratio 4.62 [1.35 to 15.8]). A total of 10 cases (45%) had a family history of SCD. The most common activity at the time of death was exercise (41%). A complete cardiac investigation was seldom performed; only 1 case was diagnosed with ARVC before death. In conclusion, in this nationwide study, we observed a high prevalence of symptoms of cardiac origin, healthcare use, and family history of SCD preceding SCD in the young caused by ARVC. Increased awareness of these warning signals in younger patients is critical to improving risk stratification and early disease detection.

Sex Disparities in Sudden Cardiac Death

The overall incidence of sudden cardiac death is considerably lower among women than men, reflecting significant and often under-recognized sex differences. Women are older at time of sudden cardiac death, less likely to have a prior cardiac diagnosis, and less likely to have coronary artery disease identified on postmortem examination. They are more likely to experience their death at home, during sleep, and less likely witnessed. Women are also more likely to present in pulseless electrical activity or systole rather than ventricular fibrillation or ventricular tachycardia. Conversely, women are less likely to receive bystander cardiopulmonary resuscitation or receive cardiac intervention post-arrest. Underpinning sex disparities in sudden cardiac death is a paucity of women recruited to clinical trials, coupled with an overall lack of prespecified sex-disaggregated evidence. Thus, predominantly male-derived data form the basis of clinical guidelines. This review outlines the critical sex differences concerning epidemiology, cause, risk factors, prevention, and outcomes. We propose 4 broad areas of importance to consider: physiological, personal, community, and professional factors.

Sporadic and rapidly progressive arrhythmogenic right ventricular cardiomyopathy in a 12-year-old boy who was diagnosed with epilepsy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is one of the leading causes of sudden cardiac death amongst young people and athletes. In this genetic disease, arrhythmia and fibro-fatty changes in the right ventricular myocardium are the main characteristics of the disease. Here, we report a case of ARVC in a 12-year-old boy who was previously diagnosed with epilepsy, the patient's condition manifested sporadically and was complicated by rapid progression, and unfortunate fatal deterioration after admission into the pediatric emergency room due to fatigue, dizziness and palpitation. A diagnosis of ARVC was established, even though a family history was absent. Due to possible rapid deterioration, as described in this case, we recommend immediate primary and secondary prevention of arrhythmias in these patients, and to take in consideration of the potential risks of using sodium valproate in these patients.

Risk Stratification in Arrhythmogenic Right Ventricular Cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC), also called arrhythmogenic right ventricular dysplasia or arrhythmogenic cardiomyopathy, is a genetic disease characterised by progressive myocyte loss with replacement by fibrofatty tissue. This structural change leads to the prominent features of ARVC of ventricular arrhythmia and increased risk for sudden cardiac death (SCD). Emphasis should be placed on determining and stratifying the patient’s risk of ventricular arrhythmia and SCD. ICDs should be used to treat the former and prevent the latter, but ICDs are not benign interventions. ICDs come with their own complications in this overall young population of patients. This article reviews the literature regarding the factors that contribute to the assessment of risk stratification in ARVC patients.

Symptoms Preceding Sports-Related Sudden Cardiac Death in Persons Aged 1-49 Years

PURPOSE OF REVIEW

Sports-related sudden cardiac death (Sr-SCD) is a leading natural cause of death in young athletes. To prevent Sr-SCD in athletes, it is important to identify individuals at risk. This review sought to summarize the current knowledge of symptoms prior to Sr-SCD in athletes aged 1-49 years.

RECENT FINDINGS

Cardiovascular screening of athletes is a subject of interest. However, the cost of ECG screening in a young population is relatively high compared to potential benefits, and systematic screening of athletes is heavily debated. In the background population, both cardiac and non-specific symptoms are often present prior to SCD. Both cardiac and non-specific symptoms are present in up to 74% prior to Sr-SCD. The main symptoms are syncope, chest pain, palpitations and dizziness. Knowledge of symptoms could potentially be used in combination with non-invasive prediction models to prevent Sr-SCD and treat athletes at risk.

Symptoms and healthcare contact preceding sudden cardiac death in persons aged 1-49 years

Sudden Cardiac Death (SCD) is a leading cause of death among persons in their youth and early middle-age. To prevent SCD it is crucial to identify persons at high-risk of SCD. Knowledge of symptoms and medical contact prior to SCD could potentially aid in the identification of high-risk persons in the general population who would benefit from further investigation. This review aims to summarize the current knowledge of symptoms and healthcare contact preceding SCD in persons aged 1-49 years, and to explore how the symptoms differ according to SCD cause and age of the deceased. There was a high frequency of both cardiac and non-specific symptoms prior to SCD. Additionally, many SCD victims contacted the healthcare system prior to death on the basis of their symptoms and only a few were diagnosed with cardiovascular disease. This information underlines that young persons reporting potential cardiac symptoms should also be thoroughly examined. Furthermore, such symptoms could be used in combination with other easily accessible information in non-invasive prediction models aiming at identifying persons at high risk of SCD that would benefit from further investigation and possibly treatment.

Sudden cardiac death caused by myocarditis in persons aged 1-49 years: a nationwide study of 14 294 deaths in Denmark

Myocarditis is associated with an increased risk of sudden cardiac death (SCD) in the young. However, information on nationwide burden of SCD caused by myocarditis (SCD-myocarditis) is sparse. For this study all deaths among persons in Denmark aged 1–35 years in 2000–2009 and 36–49 years in 2007–2009 (27.1 million person-years) were included. Autopsy reports, death certificates, discharge summaries, and nationwide registries were used to identify all cases of SCD-myocarditis. In the 10-year study period, there were 14 294 deaths, of which we identified 1 363 (10%) SCD. Among autopsied SCD (n = 753, 55%), cause of death was myocarditis in 42 (6%) cases corresponding to an SCD-myocarditis incidence of 0.16 (95%CI: 0.11–0.21) per 100 000 person-years. Males had significantly higher incidence rates of SCD-myocarditis compared to females with an incidence rate ratio of 2.2 (95%CI: 1.1–4.1). Myocarditis was not registered as cause of death in any of the non-autopsied SCD (n = 610, 45%). In conclusion, after nationwide unselected inclusion of 14 294 deaths, we found that 6% of all autopsied SCD was caused by myocarditis. No cases of SCD-myocarditis were reported in the non-autopsied SCD, which could reflect underdiagnosing of myocarditis in non-autopsied SCD. Furthermore, our data suggest a female protection towards SCD-myocarditis.

Risk Stratification in Arrhythmogenic Right Ventricular Cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited cardiomyopathy characterized by ventricular arrhythmias and an increased risk of sudden cardiac death. Although structural abnormalities of the right ventricle predominate, it is well recognized that left ventricular involvement is common, particularly in advanced disease, and that left-dominant forms occur. The pathological characteristic of ARVC is myocyte loss with fibrofatty replacement. Since the first detailed clinical description of the disorder in 1982, significant advances have been made in understanding this disease. Once the diagnosis of ARVC is established, the single most important clinical decision is whether a particular patient's sudden cardiac death risk is sufficient to justify placement of an implantable cardioverter-defibrillator. The importance of this decision reflects the fact that ARVC is a common cause of sudden death in young people and that sudden death may be the first manifestation of the disease. This decision is particularly important because these are often young patients who are expected to live for many years. Although an implantable cardioverter-defibrillator can save lives in individuals with this disease, it is also well recognized that implantable cardioverter-defibrillator therapy is associated with both short- and long-term complications. Decisions about the placement of an implantable cardioverter-defibrillator are based on an estimate of a patient's risk of sudden cardiac death, as well as their preferences and values. The primary purpose of this article is to provide a review of the literature that concerns risk stratification in patients with ARVC and to place this literature in the framework of the 3 authors' considerable lifetime experiences in caring for patients with ARVC. The most important parameters to consider when determining arrhythmic risk include electric instability, including the frequency of premature ventricular contractions and sustained ventricular arrhythmia; proband status; extent of structural disease; cardiac syncope; male sex; the presence of multiple mutations or a mutation in TMEM43; and the patient's willingness to restrict exercise and to eliminate participation in competitive or endurance exercise.

Comparison of Features of Fatal Versus Nonfatal Cardiac Arrest in Patients With Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy

Once arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) is diagnosed, the incidence of sudden cardiac death (SCD) is rare and prognosis is favorable, highlighting the value of early disease recognition. To inform strategies to diagnose ARVD/C before SCD, we sought to characterize clinical, genetic, and family history features of ARVD/C cases first recognized after SCD or resuscitated SCD (sudden cardiac arrest [SCA]). We identified 66 ARVD/C cases submitted to the Johns Hopkins ARVD/C Registry in whom disease was first recognized after SCD (n = 45) or SCA (n = 21) and compared their clinical, genetic, and demographic features with 352 patients (227 probands) diagnosed with ARVD/C by 2010 Task Force Criteria before any arrest. SCD/SCA cases were 65% men and experienced their arrest at 29.3 ± 13.8 years. Exertion precipitated 72% of arrests. Family history was recognized before arrest in 11 cases (17%), and 24 cases (41%) had reported cardiac symptoms before arrest. The SCD/SCA cohort was disproportionately men (65% SCD/SCA vs 50% living, p = 0.03) and younger at both first reported symptom (27.7 ± 13.5 years SCD/SCA vs 33.0 ± 13.6 years living, p = 0.01) and first sustained ventricular arrhythmia (VA) (29.3 ± 13.8 years SCD/SCA vs 35.6 ± 12.9 years living, p <0.001). In addition, survival from first symptom to VA was significantly shorter in SCD/SCA cases (p <0.001). These results suggest that the natural history of ARVD/C may be accelerated in SCD/SCA cases. In conclusion, although symptoms or family history provide a window of opportunity for diagnosis before death, time to intervene after symptom onset is limited.

Influence of functional polymorphism in MIF promoter on sudden cardiac death in Chinese populations

Sudden cardiac death (SCD) is defined as an unexpected natural death without any obvious non-cardiac causes that occurs within 1 h with witnessed symptom onset or within 24 h without witnessed symptom onset. Genetic studies conducted during the past decade have markedly illuminated the genetic basis of the cardiac disorders associated with SCD. Macrophage migration inhibitory factor (MIF) is an upstream immunoregulatory cytokine associated with the pathogenesis of many inflammatory diseases including atherosclerosis and myocardial infarction. Previous studies have reported that the functional −794(CATT)_5–8 polymorphism in MIF is unrelated to sudden infant death syndrome susceptibility. However, there are no reports concerning the association between the polymorphism and adult SCD susceptibility. In the current study, we investigated the association between the −794(CATT)_5–8 polymorphism and adult SCD susceptibility using 79 adult SCD cases and 313 healthy controls. All samples were analysed using a conventional polymerase chain reaction (PCR) technique. We found that CATT₆ and 5–6 were the most common allele and genotype in both groups, respectively, while no significant association was found between the −794(CATT)_5–8 polymorphism and SCD susceptibility. We also summarized the allele frequencies of −794(CATT)_5–8 in cohorts of healthy people from different countries and found that the allele frequency distributions of the polymorphism in Chinese populations were quite different from that of American and European populations (P = 0.005, P = 0.0001, respectively), but similar to Japanese populations (P = 0.827). In conclusion, this study indicates that the −794(CATT)_5–8 polymorphism may not be associated with adult SCD susceptibility in Chinese populations. Different allele frequency distributions of the polymorphism in multiple populations may provide a useful reference for further genetic association studies.

Symptoms Before Sudden Arrhythmic Death Syndrome: A Nationwide Study Among the Young in Denmark

INTRODUCTION

No studies in an unselected and nationwide setting have characterized the symptoms and medical history of patients with sudden arrhythmic death syndrome (SADS). The aim of this study was to identify and describe the symptoms and medical history of patients before the presentation of SADS.

METHODS AND RESULTS

We have previously identified all of the autopsied sudden cardiac deaths (SCD; n = 314) in Danes aged 1-35 years between 2000 and 2006. After comprehensive pathological and toxicological investigation did not reveal a cause of SCD, 136 of the patients were identified as SADS. The National Patient Registry was utilized to obtain information on all in- and outpatient activity in Danish hospitals. All medical records from hospitals and general practitioners, including death certificates and autopsy reports were reviewed. Before death, 48 (35%) SADS patients had cardiac symptoms; among these, 30 (22%) had contacted the healthcare system. Antecedent symptoms (symptoms >24 hours before death) were present in 34 (25%) patients. Prodromal symptoms (symptoms ≤24 hours before death) were present in 23 (17%) patients. Cardiac symptoms included chest pain (n = 16, 12%), dyspnea (n = 18, 13%), palpitations (n = 2, 1%), presyncope/syncope (n = 23, 17%), and aborted SCD (n = 2, 1%). In addition, seizures (n = 25, 18%) were prevalent. In 61 (45%) SADS cases, no previous medical history were recorded.

CONCLUSION

In this unselected, nationwide study of 136 young SADS patients, 35% had experienced cardiac symptoms before death, most commonly presyncope/syncope, but only one out of five had contacted a healthcare provider with cardiac symptoms.

Sudden death in young persons with uncontrolled asthma--a nationwide cohort study in Denmark

BACKGROUND

Asthma is a common chronic disease among young adults, and several studies have reported increased mortality rates in patients with asthma. However, no study has described sudden unexpected death in a nationwide setting in patients with uncontrolled asthma. We defined uncontrolled asthma as a previous hospital admittance because of asthma (of any severity) or when asthma was considered to have influenced the death according to the death certificate. The purpose of this study is to increase the medical focus on young persons with uncontrolled asthma and thereby hopefully aid in preventing sudden unexpected deaths. We therefore aimed to describe clinical characteristics, symptoms, causes of death, and contact with the healthcare system prior to sudden unexpected death in young persons with uncontrolled asthma.

METHODS

Through the review of death certificates, we found 625 sudden unexpected death cases in individuals aged 1-35 years in Denmark from 2000 to 2006. Of those, 49 persons with uncontrolled asthma were identified. Previous contacts with the healthcare system were identified, and available records from general practitioners were retrieved.

RESULTS

We identified 49 individuals who suffered from uncontrolled asthma. This corresponds to an incidence rate of 0.32 per 100,000 person-years. The cause of death in 31 cases (63%) was sudden cardiac death, and in 13 cases (27%), it was a fatal asthma attack. Symptoms (chest pain, dyspnea, seizures, general malaise, syncope, and palpitations) prior to death were reported in 41 (84%) of the cases. In 34 (69%) of the cases, antecedent symptoms (symptoms >24 hours before death) were present, and 28 (57%) patients had prodromal symptoms (symptoms <24 hours before death). The most common antecedent symptoms were dyspnea and chest pain, whereas the most common prodromal symptoms were dyspnea, general malaise, and/or fatigue. Twenty-eight patients (57%) sought medical advice from a general practitioner and/or emergency department due to these symptoms.

CONCLUSION

The cause of death was predominantly sudden cardiac death followed by fatal asthma attack. We found that 41 (84%) of patients suffered from symptoms prior to death and that 28 (57%) sought medical advice from the emergency department and/or general practitioners.