Prospective Countywide Surveillance and Autopsy Characterization of Sudden Cardiac Death: POST SCD Study

Cardiac arrest and sudden cardiac death registries: a systematic review of global coverage

Background

Sudden cardiac death (SCD) is a major global health problem, accounting for up to 20% of deaths in Western societies. Clinical quality registries have been shown in a range of disease conditions to improve clinical management, reduce variation in care and improve outcomes.

Aim

To identify existing cardiac arrest (CA) and SCD registries, characterising global coverage and methods of data capture and validation.

Methods

Biomedical and public search engines were searched with the terms ‘registry cardio*’; ‘sudden cardiac death registry’ and ‘cardiac arrest registry’. Registries were categorised as either CA, SCD registries or ‘other’ according to prespecified criteria. SCD registry coordinators were contacted for contemporaneous data regarding registry details.

Results

Our search strategy identified 49 CA registries, 15 SCD registries and 9 other registries (ie, epistries). Population coverage of contemporary CA and SCD registries is highly variable with registries densely concentrated in North America and Western Europe. Existing SCD registries (n=15) cover a variety of age ranges and subpopulations, with some enrolling surviving patients (n=8) and family members (n=5). Genetic data are collected by nine registries, with the majority of these (n=7) offering indefinite storage in a biorepository.

Conclusions

Many CA registries exist globally, although with inequitable population coverage. Comprehensive multisource surveillance SCD registries are fewer in number and more challenging to design and maintain. Challenges identified include maximising case identification and case verification.

Trial registration number

CRD42019118910.

Unexpected High Prevalence of Cardiovascular Disease Risk Factors and Psychiatric Disease Among Young People With Sudden Cardiac Arrest

Background

It is believed that most sudden cardiac arrests (SCAs) in young people occur in previously healthy people with rare risk factors for sudden death. Few studies have investigated large populations with complete ascertainment. Our objective was to use multisource records to identify and classify all out‐of‐hospital cardiac arrests in the Greater Toronto Area (population 6.6 million) in people aged 2 to 45 years from 2009 to 2012.

Methods and Results

Expert reviewers employed a systematic process, with emergency medical services, in‐hospital and coroner records, to adjudicate the cause of death as SCA from cardiac or noncardiac causes. We report the adjudicated etiologies, circumstances, triggers, and characteristics of the SCA cohort. Of 2937 eligible out‐of‐hospital cardiac arrest cases, 608 (20.7%) SCAs had an adjudicated etiology of cardiac cause (120 survivors and 488 nonsurvivors). Two thirds of these SCA patients had a history of cardiovascular disease, and over 50% had been diagnosed with ≥1 cardiovascular disease risk factor. Moreover, 20.1% of SCAs were diagnosed with psychiatric disease and 30% had central nervous system drugs prescribed. Over 30% of SCA patients had central nervous system active drugs, including drugs of abuse detected postmortem, with opioids and ethanol being detected most frequently. Potentially heritable structural cardiac diseases accounted for only 6.9% of SCA events, with acquired cardiac diseases comprising the rest.

Conclusions

The underlying causes of SCA, in people aged 2 to 45 years, often occur in those with previously diagnosed cardiovascular diseases, and are associated with contributory factors including prescribed medications, recreational drugs, and a concomitant psychiatric history.

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Sudden Arrhythmic Death at the Higher End of the Heart Failure Spectrum

The risk of sudden cardiac death (SCD) is high in heart failure (HF) patients. Sudden arrhythmic death (SAD) is a frequent cause of exit in HF patients at the lower end of the HF spectrum, and implantable cardioverter–defibrillators have been recommended to prevent these life-threatening rhythm disturbances in select patients. However, less is known regarding the cause of SCD in patients at the upper end of the HF spectrum, despite the fact that the majority of out-of-hospital SCD victims have unknown or near-normal/normal left ventricular ejection fraction (LVEF). In this review, we report the epidemiology, summarize the mechanisms, discuss the diagnostic challenges, and propose a stepwise approach for the prevention of SAD in HF with near-normal/normal LVEF.

Sudden Cardiac Death in Women

BACKGROUND

Despite recent progress in profiling of risk for sudden cardiac death (SCD) and prevention and intervention of cardiac diseases, SCD remains a major cause of death. Among women, the incidence of SCD is significant, but lower than in men, particularly in the premenopausal and early postmenopausal years. Possibly, as a consequence of the difference in population burden, the mechanisms and risk markers of SCD are not as well defined for women. The aim of this study was to determine the autopsy findings and causes of death among women in a large SCD population. Additionally, we sought to classify prior ECG characteristics in male and female subjects with SCD.

METHODS

The Fingesture study has systematically collected clinical and autopsy data from subjects with SCD in Northern Finland between 1998 and 2017. The cohort consists of 5869 subjects with SCD. Previously recorded ECGs were available and analyzed in 1101 subjects (18.8% of total population; and in 25.3% of women).

RESULTS

Female subjects with SCD were significantly older than men: 70.1±13.1 years versus 63.5±11.8 years (mean ± standard deviation, P<0.001). The most frequently identified cause of death was ischemic heart disease in both sexes: 71.7% among women versus 75.7% among men, P=0.005. In contrast, women were more likely to have nonischemic cause of SCD than men (28.3% versus 24.3%, P=0.005). The prevalence of primary myocardial fibrosis was higher among women (5.2%, n=64) than in men (2.6%, n=120; P<0.001). Female subjects with SCD were more likely to have normal prior ECG tracings (22.2% versus 15.3% in men, P<0.001). A normal ECG was even more common among nonischemic female subjects with SCD (27.8% versus 16.2% in men, P=0.009). However, ECG markers of left ventricular hypertrophy, with or without repolarization abnormalities, were more common among women (8.2%; 17.9%) than in men (4.9%; 10.6%, P=0.036; P<0.001, respectively).

CONCLUSIONS

Women were considerably older at the time of SCD and more commonly had nonischemic causes. Women were also more likely to have a prior normal ECG than men, but an increased marker for SCD risk based on ECG criteria for left ventricular hypertrophy with repolarization abnormalities was more commonly observed in women.

Sudden cardiac death in the Kazakh and Han peoples of Xinjiang, China: A comparative cross-sectional study

Sudden cardiac death (SCD) is a major cause of mortality in China. This study collected reference data for future programs of prevention of SCD among the ethnic Kazakh and Han populations in Xinjiang, China.From January 1, 2015 to December 31, 2015, 2 monitoring locations in northern Xinjiang China were utilized. These locations were selected based on the geographic, economic, and administrative structures of the ethnic Kazakh settlements in Xinjiang. Investigators were trained to investigate SCDs in Kazakh and Han people, a study population totaling more than 400,000. The populations were compared for SCD incidence.The average age of the Han population was significantly higher than that of the Kazakh. During the year 2015, there were 135 SCDs, specifically 67 and 68 in the Han and Kazakh populations, respectively, incidences of 37.94 and 36.2 per 100,000. After standardizing for age, the incidence in these populations was 29.36 and 51.85 per 100,000. Among those who experienced SCD, the prevalence of hypertension was higher in the Kazakh group than in the Han. The multivariate analysis of populations with SCD showed that, among the patients with coronary heart disease, the Kazakh were more likely to have SCD than the Han (odds ratio: 3.58, confidence interval: 1.18-10.95).Among the elderly, the incidence of SCD was much higher in the Kazakh population than in the Han population. Basic medical services and health education should be strengthened in the Kazakh pastoral areas.

Cardiac Arrest and Cardiopulmonary Resuscitation Outcome Reports: Update of the Utstein Resuscitation Registry Template for In-Hospital Cardiac Arrest: A Consensus Report From a Task Force of the International Liaison Committee on Resuscitation (American Heart Association, European Resuscitation Council, Australian and New Zealand Council on Resuscitation, Heart and Stroke Foundation of Canada, InterAmerican Heart Foundation, Resuscitation Council of Southern Africa, Resuscitation Council of Asia)

Utstein-style reporting templates provide a structured framework with which to compare systems of care for cardiac arrest. The 2004 Utstein reporting template encompassed both out-of-hospital and in-hospital cardiac arrest. A 2015 update of the Utstein template focused on out-of-hospital cardiac arrest, which makes this update of the in-hospital template timely. Representatives of the International Liaison Committee on Resuscitation developed an updated in-hospital Utstein reporting template iteratively by meeting face-to-face, by teleconference, and by online surveys between 2013 and 2018. Data elements were grouped by hospital factors, patient variables, pre-event factors, cardiac arrest and postresuscitation processes, and outcomes. Elements were classified as core or supplemental by use of a modified Delphi process. Variables were described as core if they were considered essential. Core variables should enable reasonable comparisons between systems and are considered essential for quality improvement programs. Together with core variables, supplementary variables are considered useful for research.

Cardiac Arrest and Cardiopulmonary Resuscitation Outcome Reports: Update of the Utstein Resuscitation Registry Template for In-Hospital Cardiac Arrest: A Consensus Report From a Task Force of the International Liaison Committee on Resuscitation (American Heart Association, European Resuscitation Council, Australian and New Zealand Council on Resuscitation, Heart and Stroke Foundation of Canada, InterAmerican Heart Foundation, Resuscitation Council of Southern Africa, Resuscitation Council of Asia)

Utstein-style reporting templates provide a structured framework with which to compare systems of care for cardiac arrest. The 2004 Utstein reporting template encompassed both out-of-hospital and in-hospital cardiac arrest. A 2015 update of the Utstein template focused on out-of-hospital cardiac arrest, which makes this update of the in-hospital template timely. Representatives of the International Liaison Committee on Resuscitation developed an updated in-hospital Utstein reporting template iteratively by meeting face-to-face, by teleconference, and by online surveys between 2013 and 2018. Data elements were grouped by hospital factors, patient variables, pre-event factors, cardiac arrest and postresuscitation processes, and outcomes. Elements were classified as core or supplemental by use of a modified Delphi process. Variables were described as core if they were considered essential. Core variables should enable reasonable comparisons between systems and are considered essential for quality improvement programs. Together with core variables, supplementary variables are considered useful for research.

Implications of Initial Recorded Rhythm on Cardioverter-Defibrillator Insertion and Subsequent All-Cause Mortality in Sudden Cardiac Arrest Survivors

Sudden cardiac arrest (SCA) rhythms have been traditionally divided into shockable [ventricular tachycardia (VT)/ventricular fibrillation (VF)] and nonshockable [(asystole (ASY)/pulseless electrical activity (PEA)] rhythms. It is unclear if the specific rhythm has implications on patient management and outcomes. We evaluated 1,433 patients who were admitted with SCA from 2000 to 2012 and were discharged alive. Of those, 1,123 patients had a recorded initial SCA rhythm. Subjects included were >18 years of age, and without an implantable cardioverter-defibrillator (ICD) in place at the time of the event. The likelihood of receiving an ICD for each SCA rhythm and the time to death were analyzed. Of the overall cohort of 1,123 SCA survivors (age of 62 ± 15 years; 39.2% women; 56.3% in-hospital SCA; 83% white; 67% coronary artery disease), 355 (31.6%) received an ICD, and 493 (43.9%) died over a mean follow-up of 3.8 ± 3.2 years. Patients with VF (n = 254, 43.6%) or VT (n = 83, 43.9%) were more likely to receive ICD therapy compared with those with ASY (n = 9, 5.3%) or PEA (n = 9, 4.8%; p <0.001). All-cause mortality was lower in VF patients compared with the other groups (p <0.0001). ICD therapy was associated with lower risk of death in the VF group (hazard ratio [HR] 0.61 [0.45 to 0.83]; p = 0.002) and strong trends toward less mortality in patients with VT (HR 0.64 [0.40 to 1.03]; p = 0.07) and ASY (HR 0.39 [0.12 to 1.31]; p = 0.13) but not in those with PEA (HR 0.93 [0.39 to 2.23]; p = 0.88). In conclusion, long-term survival in post-SCA patients is influenced by initial SCA rhythm. Although SCA survivors with shockable rhythms were more likely to receive ICDs, the ICD was associated with lower risk of death in most patients, including those with ASY. In conclusion, our data suggest that a more detailed SCA rhythm classification has important implications to patient management and long-term survival in this population.

Sudden cardiac death in families with premature cardiovascular disease

Objective

Sudden cardiac death (SCD) in families with premature atherosclerosis (PAS) is generally attributed to lethal arrhythmias during myocardial infarction. Yet, such arrhythmias may also arise from non-ischaemic inherited susceptibility. We aimed to test the hypothesis that Brugada syndrome is prevalent among families with PAS in which SCD occurred.

Methods

We investigated all patients who underwent Ajmaline testing to screen them for Brugada syndrome because of unexplained familial SCD in the Amsterdam University Medical Centers between 2004 and 2017. We divided the cohort into two groups based on a positive family history for PAS. All individuals with a positive Ajmaline test were screened for SCN5A-mutation.

Results

In families with SCD and PAS, the prevalence of positive Ajmaline test was similar to families with SCD alone (22% vs 19%). The number of SCD cases in families with SCD and PAS was higher (2.34 vs 1.63, p<0.001) and SCD occurred at older age in families with SCD and PAS (42 years vs 36 years, p<0.001), while the prevalence of SCN5A mutations was lower (3% vs 18%, p<0.05).

Conclusions

Brugada syndrome has a similar prevalence in families with SCD and PAS as in families with SCD alone, although SCD in families with SCD and PAS occurs in more family members and at older age, while SCN5A mutations in these families are rare. This suggests that the SCD occurring in families with PAS could be related to an underlying genetic predisposition of arrhythmias, with a different genetic origin. It could be considered to screen families with SCD and PAS for Brugada syndrome.

Arrhythmogenic cardiomyopathy with left ventricular involvement versus ischemic heart disease: lessons learned from the family study and the reviewed autopsy of a young male

Ischemic heart disease (IHD) is the leading cause of sudden cardiac death (SCD) and often non-thrombosed severe coronary stenoses with or without myocardial scars are detected. Left dominant arrhythmogenic cardiomyopathy (LDAC) is a life-threating rare disease which has been more thoroughly studied in the last 10 years. The macroscopic study of an SCD victim was conducted and re-evaluated 9 years later. The cardiological work-up in his first-degree relatives initially comprised an electrocardiogram (ECG) and an echocardiogram. When they were re-evaluted 9 years later, a cardiac magnetic resonance, an ECG-monitoring, an exercise testing and a genetic study were performed and the pedigree was extended accordingly. In 2008, an IHD was suspected in the sports-triggered SCD of a 37-year-old man upon the postmortem (75% stenosis of the left main and circumflex coronary arteries; the subepicardial left ventricular fibrofatty infiltration with mild myocardial degeneration was assumed to be a past myocardial infarction). No cardiomyopathy was identified in any of the two proband’s sisters. Nine years thereafter, distant relatives were diagnosed with LDAC due to a pathogenic desmoplakin mutation. The reanalysis of the two sisters showed ventricular arrhythmias in one of them without structural heart involvement and the reviewed postmortem of the proband was reclassified as LDAC based on the fibrofatty infiltration; both were mutation carriers. The completion of the family study on 19 family members yielded one SCD due to LDAC (the proband), three living patients diagnosed with LDAC (two with a defibrillator), one mutation carrier without structural ventricular involvement, and 14 healthy relatives (who were discharged) with a very good co-segregation of the mutation. Although rare, LDAC exists and sometimes its differential diagnosis with IHD has to be faced. Modifying previous postmortem misdiagnoses can help family screening to further prevent SCDs.

Evaluation of cardiac hypertrophy in the setting of sudden cardiac death

Ventricular hypertrophy is a common pathological finding at autopsy that can act as a substrate for arrhythmogenesis. Pathologists grapple with the significance of ventricular hypertrophy when assessing the sudden and unexpected deaths of young people and what it could mean for surviving family members. The pathological spectrum of left ventricular hypertrophy (LVH) is reviewed herein. This article is oriented to the practicing autopsy pathologist to help make sense of various patterns of increased heart muscle, particularly those that are not clearly cardiomyopathic, yet present in the setting of sudden cardiac death. The article also reviews factors influencing arrhythmogenesis as well as genetic mutations most commonly associated with ventricular hypertrophy, especially those associated with hypertrophic cardiomyopathy (HCM).

Refining the World Health Organization Definition: Predicting Autopsy-Defined Sudden Arrhythmic Deaths Among Presumed Sudden Cardiac Deaths in the POST SCD Study

BACKGROUND

Conventional definitions of sudden cardiac death (SCD) presume cardiac cause. We studied the World Health Organization-defined SCDs autopsied in the POST SCD study (Postmortem Systematic Investigation of SCD) to determine whether premortem characteristics could identify autopsy-defined sudden arrhythmic death (SAD) among presumed SCDs.

METHODS

Between January 2, 2011, and January 4, 2016, we prospectively identified all 615 World Health Organization-defined SCDs (144 witnessed) 18 to 90 years in San Francisco County for medical record review and autopsy via medical examiner surveillance. Autopsy-defined SADs had no extracardiac or acute heart failure cause of death. We used 2 nested sets of premortem predictors-an emergency medical system set and a comprehensive set adding medical record data-to develop Least Absolute Selection and Shrinkage Operator models of SAD among witnessed and unwitnessed cohorts.

RESULTS

Of 615 presumed SCDs, 348 (57%) were autopsy-defined SAD. For witnessed cases, the emergency medical system model (area under the receiver operator curve 0.75 [0.67-0.82]) included presenting rhythm of ventricular tachycardia/fibrillation and pulseless electrical activity, while the comprehensive (area under the receiver operator curve 0.78 [0.70-0.84]) added depression. If only ventricular tachycardia/fibrillation witnessed cases (n=48) were classified as SAD, sensitivity was 0.46 (0.36-0.57), and specificity was 0.90 (0.79-0.97). For unwitnessed cases, the emergency medical system model (area under the receiver operator curve 0.68 [0.64-0.73]) included black race, male sex, age, and time since last seen normal, while the comprehensive (area under the receiver operator curve 0.75 [0.71-0.79]) added use of β-blockers, antidepressants, QT-prolonging drugs, opiates, illicit drugs, and dyslipidemia. If only unwitnessed cases <1 hour (n=59) were classified as SAD, sensitivity was 0.18 (0.13-0.22) and specificity was 0.95 (0.90-0.97).

CONCLUSIONS

Our models identify premortem characteristics that can better specify autopsy-defined SAD among presumed SCDs and suggest the World Health Organization definition can be improved by restricting witnessed SCDs to ventricular tachycardia/fibrillation or nonpulseless electrical activity rhythms and unwitnessed cases to <1 hour since last normal, at the cost of sensitivity.

Pathobiology of cardiovascular diseases: an update

This article introduces the Second Special Issue of Cardiovascular Pathology (CVP), the official journal of the Society for Cardiovascular Pathology (SCVP). This CVP Special Issue showcases a series of commemorative review articles in celebration of the 25th anniversary of CVP originally published in 2016 and now compiled into a virtual collection with online access for the cardiovascular pathology community. This overview also provides updates on the major categories of cardiovascular diseases from the perspective of cardiovascular pathologists, highlighting publications from CVP, as well as additional important review articles and clinicopathologic references.

Non-arrhythmic causes of sudden death: A comprehensive review

Sudden cardiac death (SCD) is a major public health issue in the United States and worldwide. It is estimated to affect between 1 and 1.5 million patients worldwide annually, with the global burden expected to rise due to the concomitant rise in coronary artery disease in the developing world. Although arrhythmic causes of SCD such as ventricular tachycardia and ventricular fibrillation are common and well-studied, non-arrhythmic causes are also important, with diverse etiologies from ischemia-related structural heart disease to non-ischemic heart diseases, non-atherosclerotic coronary pathologies, and inflammatory states. Recent research has also found that risk factors and/or demographics predispose certain individuals to a higher risk of non-arrhythmia-related SCD. This review discusses the epidemiology, mechanisms, etiologies, and management of non-arrhythmic SCD.

Sudden death related cardiomyopathies - Hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a form of inherited cardiomyopathy. Most individuals with HCM experience minimal symptoms throughout their lifetime. However, those with HCM are at risk of ventricular arrhythmias and sudden cardiac death (SCD), the most feared complication of HCM. Implantable cardioverter defibrillator (ICD) implantation has played a large role in transforming this disease from one with an ominous prognosis to one with mortality rates that are on par with the general public. Since the early 2000s, balance between SCD prevention and unnecessary ICD placement has been sought, this is reflected in the evolution of SCD risk stratification models for patients with HCM. This review discusses key concepts pertaining to HCM, with emphasis on prevention of SCD, and summarizes and compares the recommendations for ICD implantation in current guidelines.

Sudden Cardiac Death Risk Distribution in the United States Population (from NHANES, 2005 to 2012)

Sudden cardiac death (SCD) accounts for more than half of all deaths from cardiovascular disease and is the first manifestation of heart disease in 50% of these subjects. We aimed to describe the distribution of predicted SCD risk in the general US population using a recently developed risk score. We previously developed a population-based, 10-year risk score for SCD using data from the multiracial Atherosclerosis Risk in Communities cohort, validated in the Framingham Study. We now estimate 10-year predicted SCD risk in National Health and Nutrition Examination Survey participants (pooled from cycles in 2005 to 2012) and evaluate the clinical profile of participants in lower risk (0 to 80th percentile of risk) or high risk (81st to 100th percentile of risk) strata. A total of 10,811 participants were included; the mean age of participants was 48 years, and 50% were women. The average predicted 10-year risk of SCD was 3.6% in high-risk participants (81st to 100th percentile), and 0.37% in low-risk participants (0 to 80th percentile). High-risk participants were older, had higher blood pressure, total cholesterol and body mass index, lower high-density lipoprotein, and were more likely to be men, black, smokers, and diabetic. In US adults free of cardiovascular disease, the majority of SCD risk appears confined to 10% to 20% of the population. This risk score, comprised of readily available clinical variables, identifies a subset of individuals in the population who are at an appreciably higher risk of SCD. This enriched cohort represents candidates for additional nuanced and selective screening techniques to further quantify SCD risk.

New Concepts in Sudden Cardiac Arrest to Address an Intractable Epidemic: JACC State-of-the-Art Review

Sudden cardiac arrest (SCA) is one of the largest causes of mortality globally, with an out-of-hospital survival below 10% despite intense research. This document outlines challenges in addressing the epidemic of SCA, along the framework of respond, understand and predict, and prevent. Response could be improved by technology-assisted orchestration of community responder systems, access to automated external defibrillators, and innovations to match resuscitation resources to victims in place and time. Efforts to understand and predict SCA may be enhanced by refining taxonomy along phenotypical and pathophysiological "axes of risk," extending beyond cardiovascular pathology to identify less heterogeneous cohorts, facilitated by open-data platforms and analytics including machine learning to integrate discoveries across disciplines. Prevention of SCA must integrate these concepts, recognizing that all members of society are stakeholders. Ultimately, solutions to the public health challenge of SCA will require greater awareness, societal debate and focused public policy.

A low end-tidal CO2/arterial CO2 ratio during cardiopulmonary resuscitation suggests pulmonary embolism

INTRODUCTION

Identifying reversible causes of cardiac arrest is challenging. The diagnosis of pulmonary embolism is often missed. Pulmonary embolism increases alveolar dead space resulting in low end-tidal CO2 (EtCO2) relative to arterial CO2 (PaCO2) tension. Thus, a low EtCO2/PaCO2 ratio during resuscitation may be a sign of pulmonary embolism.

METHODS

Post hoc analysis of data from two porcine studies comparing ultrasonographic measurements of right ventricular diameter during resuscitation from cardiac arrest of different causes. Pigs were grouped according to cause of arrest (pulmonary embolism, hypovolemia, primary arrhythmia, hypoxia, or hyperkalaemia) and EtCO2/PaCO2 ratios were compared.

RESULTS

Data from 54 pigs were analysed. EtCO2 levels at the third rhythm analysis were significantly lower when cardiac arrest was caused by pulmonary embolism than by primary arrhythmia, hypoxia and hyperkalaemia, but there was no significant difference between pulmonary embolism and hypovolemia. In contrast, PaCO2 levels were higher in cardiac arrest caused by pulmonary embolism than in the other causes of cardiac arrest. Consequently, the EtCO2/PaCO2 ratio was lower in pulmonary embolism 0.2 (95%CI 0.1-0.4), than in hypovolaemia 0.5 (95%CI 0.3-0.6), primary arrhythmia 0.7 (95%CI 0.7-0.8), hypoxia 0.5 (95%CI 0.4-0.6), and hyperkalaemia 0.6 (95%CI 0.6-0.7).

CONCLUSION

A low EtCO2/PaCO2 ratio during cardiopulmonary resuscitation suggests pulmonary embolism.

Who Benefits From a Defibrillator-Balancing the Risk of Sudden Versus Non-sudden Death

PURPOSE OF REVIEW

Treatment with a defibrillator can reduce the risk of sudden death by terminating ventricular arrhythmias. The identification of patient groups in whom this function reduces overall mortality is challenging. In this review, we summarise the evidence for who benefits from a defibrillator.

RECENT FINDINGS

Recent evidence suggests that contemporary pharmacologic and non-defibrillator device therapies are altering the potential risks and benefits of a defibrillator. Who benefits from a defibrillator is determined by both the risk of sudden death and the competing risk of other, non-sudden causes of death. The balance of these risks is changing, which calls into question whether historic evidence for the use of defibrillators remains robust in the modern era.

Differences in Risk of Sudden Cardiac Death Between Blacks and Whites

BACKGROUND

Prior studies have consistently demonstrated that blacks have an approximate 2-fold higher incidence of sudden cardiac death (SCD) than whites; however, these analyses have lacked individual-level sociodemographic, medical comorbidity, and behavioral health data.

OBJECTIVES

The purpose of this study was to evaluate whether racial differences in SCD incidence are attributable to differences in the prevalence of risk factors or rather to underlying susceptibility to fatal arrhythmias.

METHODS

The Reasons for Geographic and Racial Differences in Stroke study is a prospective, population-based cohort of adults from across the United States. Associations between race and SCD defined per National Heart, Lung, and Blood Institute criteria were assessed.

RESULTS

Among 22,507 participants (9,416 blacks and 13,091 whites) without a history of clinical cardiovascular disease, there were 174 SCD events (67 whites and 107 blacks) over a median follow-up of 6.1 years (interquartile range: 4.6 to 7.3 years). The age-adjusted SCD incidence rate (per 1,000 person-years) was higher in blacks (1.8; 95% confidence interval [CI]: 1.4 to 2.2) compared with whites (0.7; 95% CI: 0.6 to 0.9), with an unadjusted hazard ratio of 2.35; 95% CI: 1.74 to 3.20. The association of black race with SCD risk remained significant after adjustment for sociodemographics, comorbidities, behavioral measures of health, intervening cardiovascular events, and competing risks of non-SCD mortality (hazard ratio: 1.97; 95% CI: 1.39 to 2.77).

CONCLUSIONS

In a large biracial population of adults without a history of cardiovascular disease, SCD rates were significantly higher in blacks as compared with whites. These racial differences were not fully explained by demographics, adverse socioeconomic measures, cardiovascular risk factors, and behavioral measures of health.

Wearable Cardioverter-Defibrillator after Myocardial Infarction

BACKGROUND

Despite the high rate of sudden death after myocardial infarction among patients with a low ejection fraction, implantable cardioverter-defibrillators are contraindicated until 40 to 90 days after myocardial infarction. Whether a wearable cardioverter-defibrillator would reduce the incidence of sudden death during this high-risk period is unclear.

METHODS

We randomly assigned (in a 2:1 ratio) patients with acute myocardial infarction and an ejection fraction of 35% or less to receive a wearable cardioverter-defibrillator plus guideline-directed therapy (the device group) or to receive only guideline-directed therapy (the control group). The primary outcome was the composite of sudden death or death from ventricular tachyarrhythmia at 90 days (arrhythmic death). Secondary outcomes included death from any cause and nonarrhythmic death.

RESULTS

Of 2302 participants, 1524 were randomly assigned to the device group and 778 to the control group. Participants in the device group wore the device for a median of 18.0 hours per day (interquartile range, 3.8 to 22.7). Arrhythmic death occurred in 1.6% of the participants in the device group and in 2.4% of those in the control group (relative risk, 0.67; 95% confidence interval [CI], 0.37 to 1.21; P=0.18). Death from any cause occurred in 3.1% of the participants in the device group and in 4.9% of those in the control group (relative risk, 0.64; 95% CI, 0.43 to 0.98; uncorrected P=0.04), and nonarrhythmic death in 1.4% and 2.2%, respectively (relative risk, 0.63; 95% CI, 0.33 to 1.19; uncorrected P=0.15). Of the 48 participants in the device group who died, 12 were wearing the device at the time of death. A total of 20 participants in the device group (1.3%) received an appropriate shock, and 9 (0.6%) received an inappropriate shock.

CONCLUSIONS

Among patients with a recent myocardial infarction and an ejection fraction of 35% or less, the wearable cardioverter-defibrillator did not lead to a significantly lower rate of the primary outcome of arrhythmic death than control. (Funded by the National Institutes of Health and Zoll Medical; VEST ClinicalTrials.gov number, NCT01446965 .).