Assisting Black Patients With Decision-Making for Implantable Cardioverter Defibrillator Therapy: Qualitative Findings From the Videos to Reduce Racial Disparities in ICD Therapy via Innovative Designs (VIVID) Trial

BACKGROUND

The VIVID (Videos for Addressing Racial Disparities in Implantable Cardioverter Defibrillator Therapy via Innovative Designs) study was a multicenter, randomized controlled trial aimed at evaluating the effectiveness of a video-based decision support tool in enhancing informed consent for implantable cardioverter defibrillator (ICD) implantation among Black patients who met guideline criteria for primary prevention ICDs. Within the broader VIVID randomized trial, a qualitative investigation was conducted to elucidate the decisional factors among Black individuals considering ICD implantation for the primary prevention of sudden cardiac arrest.

METHODS

Between October 2016 and July 2019, in-depth interviews were conducted at 2 time points from randomization, ≈7 days (time interval for the decision) and at 90 days; the time interval for determining ICD implantation. Interview findings were categorized by randomized groups, those assigned to 1 of the 2 encounter-based video decision support tools or standard care (without video). Interview participants were purposefully selected to ensure diversity across gender, age, educational background, research site, and randomization group; participants were sampled from 14 academic and community-based electrophysiology clinics in the United States. Data analysis employed applied thematic analysis techniques.

RESULTS

A diverse sample of Black individuals were interviewed at 1 week (n=59; female, 37.3%) and 90 days (n=48; female, 39.6%). The primary factors influencing the decisions of Black individuals considering a primary prevention ICD implantation were (1) their clinicians' recommendations for ICD implantation; (2) their perception of their cardiac health status; and (3) a desire to prolong their lives for the sake of their families.

CONCLUSIONS

These findings offer valuable insights that may guide clinicians in their communication with Black patients during shared decision-making encounters related to ICD implantation.

Arrhythmias and ion channelopathies causing sudden cardiac death in Hispanic/Latino and Indigenous populations

The limited literature and increasing interest in studies on cardiac electrophysiology, explicitly focusing on cardiac ion channelopathies and sudden cardiac death in diverse populations, has prompted a comprehensive examination of existing research. Our review specifically targets Hispanic/Latino and Indigenous populations, which are often underrepresented in healthcare studies. This review encompasses investigations into genetic variants, epidemiology, etiologies, and clinical risk factors associated with arrhythmias in these demographic groups. The review explores the Hispanic paradox, a phenomenon linking healthcare outcomes to socioeconomic factors within Hispanic communities in the United States. Furthermore, it discusses studies exemplifying this observation in the context of arrhythmias and ion channelopathies in Hispanic populations. Current research also sheds light on disparities in overall healthcare quality in Indigenous populations. The available yet limited literature underscores the pressing need for more extensive and comprehensive research on cardiac ion channelopathies in Hispanic/Latino and Indigenous populations. Specifically, additional studies are essential to fully characterize pathogenic genetic variants, identify population-specific risk factors, and address health disparities to enhance the detection, prevention, and management of arrhythmias and sudden cardiac death in these demographic groups.

Socioeconomic deprivation and racialised disparities in competitive athletes with sudden cardiac arrest from the USA

OBJECTIVE

To explore the association of socioeconomic deprivation and racialised outcomes in competitive athletes with sudden cardiac arrest (SCA) in the USA.

METHODS

SCA cases from the National Center for Catastrophic Sports Injury Research (July 2014 to June 2021) were included. We matched Area Deprivation Index (ADI) scores (17 metrics to grade socioeconomic conditions) to the 9-digit zip codes for each athlete's home address. ADI is scored 1-100 with higher scores indicating greater neighbourhood socioeconomic deprivation. Analysis of variance was used to assess differences in mean ADI by racial groups. Tukey post hoc testing was used for pairwise comparisons.

RESULTS

391 cases of SCA in competitive athletes (85.4% male; 16.9% collegiate, 68% high school, 10.7% middle school, 4.3% youth) were identified via active surveillance. 79 cases were excluded due to missing data (19 race, 60 ADI). Of 312 cases with complete data, 171 (54.8%) were white, 110 (35.3%) black and 31 (9.9%) other race. The mean ADI was 40.20 (95% CI 36.64, 43.86) in white athletes, 57.88 (95% CI 52.65, 63.11) in black athletes and 40.77 (95% CI 30.69, 50.86) in other race athletes. Mean ADI was higher in black versus white athletes (mean difference 17.68, 95% CI 10.25, 25.12; p=0.0036) and black versus other race athletes (mean difference 17.11, 95% CI 4.74, 29.47; p<0.0001).

CONCLUSIONS

Black athletes with SCA come from areas with higher neighbourhood socioeconomic deprivation than white or other race athletes with SCA. Our findings suggest that socioeconomic deprivation may be associated with racialised disparities in athletes with SCA.

Risk Factors for Sudden Cardiac Arrest Among Hispanic or Latino Adults in Southern California: Ventura PRESTO and HCHS/SOL

Background Out-of-hospital sudden cardiac arrest (SCA) is a leading cause of mortality, making prevention of SCA a public health priority. No studies have evaluated predictors of SCA risk among Hispanic or Latino individuals in the United States. Methods and Results In this case-control study, adult SCA cases ages 18-85 (n=1,468) were ascertained in the ongoing Ventura Prediction of Sudden Death in Multi-Ethnic Communities (PRESTO) study (2015-2021) in Ventura County, California. Control subjects were selected from 3033 Hispanic or Latino participants who completed Visit 2 examinations (2014-2017) at the San Diego site of the HCHS/SOL (Hispanic Community Health Survey/Study of Latinos). We used logistic regression to evaluate the association of clinical factors with SCA. Among Hispanic or Latino SCA cases (n=295) and frequency-matched HCHS/SOL controls (n=590) (70.2% men with mean age 63.4 and 61.2 years, respectively), the following clinical variables were associated with SCA in models adjusted for age, sex, and other clinical variables: chronic kidney disease (odds ratio [OR], 7.3 [95% CI, 3.8-14.3]), heavy drinking (OR, 4.5 [95% CI, 2.3-9.0]), stroke (OR, 3.1 [95% CI, 1.2-8.0]), atrial fibrillation (OR, 3.7 [95% CI, 1.7-7.9]), coronary artery disease (OR, 2.9 [95% CI, 1.5-5.9]), heart failure (OR, 2.5 [95% CI, 1.2-5.1]), and diabetes (OR, 1.5 [95% CI, 1.0-2.3]). Conclusions In this first population-based study, to our knowledge, of SCA risk predictors among Hispanic or Latino adults, chronic kidney disease was the strongest risk factor for SCA, and established cardiovascular disease was also important. Early identification and management of chronic kidney disease may reduce SCA risk among Hispanic or Latino individuals, in addition to prevention and treatment of cardiovascular disease.

Evaluation of Sudden Cardiac Arrest by Race/Ethnicity Among Residents of Ventura County, California, 2015-2020

Importance

Sudden cardiac arrest (SCA) is a major public health problem. Owing to a lack of population-based studies in multiracial/multiethnic communities, little information is available regarding race/ethnicity-specific epidemiologic factors of SCA.

Objective

To evaluate the association of race/ethnicity with burden, outcomes, and clinical profile of individuals experiencing SCA.

Design, Setting, and Participants

A 5-year prospective, population-based cohort study of out-of-hospital SCA was conducted from February 1, 2015, to January 31, 2020, among residents of Ventura County, California (2018 population, 848 112: non-Hispanic White [White], 45.8%; Hispanic/Latino [Hispanic], 42.4%; Asian, 7.3%; and Black, 1.7% individuals). All individuals with out-of-hospital SCA of likely cardiac cause and resuscitation attempted by emergency medical services were included.

Exposures

Data on circumstances and outcomes of SCA from prehospital emergency medical services records and data on demographics and pre-SCA clinical history from detailed archived medical records, death certificates, and autopsies.

Main Outcomes and Measures

Annual age-adjusted SCA incidence by race and ethnicity and SCA circumstances and outcomes by ethnicity. Clinical profile (cardiovascular risk factors, comorbidity burden, and cardiac history) by ethnicity, overall, and stratified by sex.

Results

A total of 1624 patients with SCA were identified (1059 [65.2%] men; mean [SD] age, 70.9 [16.1] years). Race/ethnicity data were available for 1542 (95.0%) individuals, of whom 1022 (66.3%) were White, 381 (24.7%) were Hispanic, 86 (5.6%) were Asian, 31 (2.0%) were Black, and 22 (1.4%) were other race/ethnicity. Annual age-adjusted SCA rates per 100 000 residents of Ventura County were similar in White (37.5; 95% CI, 35.2-39.9), Hispanic (37.6; 95% CI, 33.7-41.5; P = .97 vs White), and Black (48.0; 95% CI, 30.8-65.2; P = .18 vs White) individuals, and lower in the Asian population (25.5; 95% CI, 20.1-30.9; P = .006 vs White). Survival to hospital discharge following SCA was similar in the Asian (11.8%), Hispanic (13.9%), and non-Hispanic White (13.0%) (P = .69) populations. Compared with White individuals, Hispanic and Asian individuals were more likely to have hypertension (White, 614 [76.3%]; Hispanic, 239 [79.1%]; Asian, 57 [89.1%]), diabetes (White, 287 [35.7%]; Hispanic, 178 [58.9%]; Asian, 37 [57.8%]), and chronic kidney disease (White, 231 [29.0%]; Hispanic, 123 [40.7%]; Asian, 33 [51.6%]) before SCA. Hispanic individuals were also more likely than White individuals to have hyperlipidemia (White, 380 [47.2%]; Hispanic, 165 [54.6%]) and history of stroke (White, 107 [13.3%]; Hispanic, 55 [18.2%]), but less likely to have a history of atrial fibrillation (White, 251 [31.2%]; Hispanic, 59 [19.5%]).

Conclusions and Relevance

The results of this study suggest that the burden of SCA was similar in Hispanic and White individuals and lower in Asian individuals. The Asian and Hispanic populations had shared SCA risk factors, which were different from those of the White population. These findings underscore the need for an improved understanding of race/ethnicity-specific differences in SCA risk.

Prevalence of Abnormal Heart Weight After Sudden Death in People Younger than 40 Years of Age

Background After sudden cardiac death in people aged <40 years, heart weight is a surrogate for cardiomegaly and a marker for cardiomyopathy. However, thresholds for cardiomegaly based on heart weight have not been validated in a cohort of cases of sudden cardiac death in young people. Methods and Results We surveyed medical examiner offices to determine which tools were used to assess heart weight norms. The survey determined that there was no gold standard for cardiomegaly (52 centers reported 22 different methods). We used a collection of heart weight data from sudden deaths in the Northwestern Sudden Death Collaboration (NSDC) to test the 22 methods. We found that the methods reported in our survey had little consistency: they classified between 18% and 81% of NSDC hearts with cardiomegaly. Therefore, we obtained biometric and postmortem data from a reference population of 3398 decedents aged <40 years. The reference population was ethnically diverse and had no known cardiac pathology on autopsy or histology. We derived and validated a multivariable regression model to predict normal heart weights and a threshold for cardiomegaly (upper 95% CI limit) in the young reference population (the Chicago model). Using the new model, the prevalence of cardiomegaly in hearts from the NSDC was 19%. Conclusions Medical examiner offices use a variety of tools to classify cardiomegaly. These approaches produce inconsistent results, and many overinterpret cardiomegaly. We recommend the model proposed to classify postmortem cardiomegaly in cases of sudden cardiac death in young people.

Bringing Critical Race Praxis Into the Study of Electrophysiological Substrate of Sudden Cardiac Death: The ARIC Study

Background Race is an established risk factor for sudden cardiac death (SCD). We sought to determine whether the association of electrophysiological substrate with SCD varies between black and white individuals. Methods and Results Participants from the ARIC (Atherosclerosis Risk in Communities) study with analyzable ECGs (n=14 408; age, 54±6 years; 74% white) were included. Electrophysiological substrate was characterized by ECG metrics. Two competing outcomes were adjudicated: SCD and non-SCD. Interaction of ECG metrics with race was studied in Cox proportional hazards and Fine-Gray competing risk models, adjusted for prevalent cardiovascular disease, risk factors, and incident nonfatal cardiovascular disease. At the baseline visit, adjusted for age, sex, and study center, blacks had larger spatial ventricular gradient magnitude (0.30 mV; 95% CI, 0.25-0.34 mV), sum absolute QRST integral (18.4 mV*ms; 95% CI, 13.7-23.0 mV*ms), and Cornell voltage (0.30 mV; 95% CI, 0.25-0.35 mV) than whites. Over a median follow-up of 24.4 years, SCD incidence was higher in blacks (2.86 per 1000 person-years; 95% CI, 2.50-3.28 per 1000 person-years) than whites (1.37 per 1000 person-years; 95% CI, 1.22-1.53 per 1000 person-years). Blacks with hypertension had the highest rate of SCD: 4.26 (95% CI, 3.66-4.96) per 1000 person-years. Race did not modify an association of ECG variables with SCD, except QRS-T angle. Spatial QRS-T angle was associated with SCD in whites (hazard ratio, 1.38; 95% CI, 1.25-1.53) and hypertension-free blacks (hazard ratio, 1.52; 95% CI, 1.09-2.12), but not in blacks with hypertension (hazard ratio, 1.15; 95% CI, 0.99-1.32) (P-interaction=0.004). Conclusions Race did not modify associations of electrophysiological substrate with SCD and non-SCD. Electrophysiological substrate does not explain racial disparities in SCD rate.

Videos to reduce racial disparities in ICD therapy Via Innovative Designs (VIVID) trial: Rational, design and methodology

BACKGROUND

Despite a higher prevalence of sudden cardiac death (SCD), black individuals are less likely than whites to have an implantable cardioverter defibrillator (ICD) implanted. Racial differences in ICD utilization is in part explained by higher refusal rates in black individuals. Decision support can assist with treatment-related uncertainty and prepare patients to make well-informed decisions.

METHODS

The Videos to reduce racial disparities in ICD therapy Via Innovative Designs (VIVID) study will randomize 350 black individuals with a primary prevention indication for an ICD to a racially concordant/discordant video-based decision support tool or usual care. The composite primary outcome is (1) the decision for ICD placement in the combined video groups compared with usual care and (2) the decision for ICD placement in the racially concordant relative to discordant video group. Additional outcomes include knowledge of ICD therapy and SCD risk; decisional conflict; ICD receipt at 90 days; and a qualitative assessment of ICD decision making in acceptors, decliners, and those undecided.

CONCLUSIONS

In addition to assessing the efficacy of decision support on ICD acceptance among black individuals, VIVID will provide insight into the role of racial concordance in medical decision making. Given the similarities in the root causes of racial/ethnic disparities in care across health disciplines, our approach and findings may be generalizable to decision making in other health care settings.

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.

Epidemiological investigation of sudden cardiac death in multiethnic Xinjiang Uyghur autonomous region in Northwest China

BACKGROUND

The epidemiological characteristics of sudden cardiac death (SCD) in the autonomous region of Xinjiang Uygur have been largely unknown. This study aimed to evaluate the incidence and demographic risk factors of SCD in Xinjiang, China.

METHODS

This retrospective study reviewed medical records from 11 regions in Xinjiang with different geography (north and south of the Tian Shan mountain range), gross domestic product, and ethnicity (Han, Uyghur, Kazakh, and Hui). SCD was defined as unexpected death due to cardiac reasons within 1 hour after the onset of acute symptoms, including sudden death, unexpected death, and nonviolent death. Monitoring was conducted throughout 2015. Demographic and mortality data were recorded and age-adjusted standardized risk ratio (SRR) was analyzed.

RESULTS

Among 3,224,103 residents, there were 13,308 all-cause deaths and 1244 events of SCD (784 men and 460 women; overall incidence 38.6 per 100,000 residents). SCD was associated with age (χ2 = 2105.3), but not geography. Men had an increased risk of SCD compared with women (SRR: 1.75, 95% CI: 1.10-2.79). The risk of SCD was highest in residents of the Uyghur (SRR: 1.59, 95% CI: 1.05-2.42) and Kazakh (SRR: 1.92, 95% CI: 1.29-2.87) compared with those of the Han. Poor economic development was associated with elevated risk of SCD (SRR: 1.55, 95% CI: 1.02-2.38).

CONCLUSION

SCD is an important public health issue in China. Our understanding of the demographic differences on SCD in Xinjiang, China may improve the risk stratification and management to reduce the incidence and lethality of SCD.

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.

Associations between common ion channel single nucleotide polymorphisms and sudden cardiac death in adults: A MOOSE-compliant meta-analysis

BACKGROUND

We sought to identify common ion channel single nucleotide polymorphisms (SNPs) associated with the occurrence of sudden cardiac death (SCD) to predict the incidence of SCD in clinical settings.

METHODS

This study involved a systematic review and meta-analysis of ion channel SNPs and risk of SCD in adults. We searched public databases for studies published up to September 19, 2017. We examined relationships between SNPs in common ion channel genes and the incidence of SCD.

RESULTS

We collected data for 22 trials that included a total of 4149 patients who experienced SCD or had a high risk of SCD and assessed these data in our meta-analysis. An allelic model showed that rs11720524 in SCN5A clearly protected against SCD (odds ratio [OR]: 0.76; 95% confidence interval [95% CI]: 0.67-0.85; P < .001). Subgroup analysis showed that rs11720524 in SCN5A protected against SCD in Europeans and Caucasians but not in Koreans. The allelic model indicated that rs12296050 in KCNQ1 also had significant protective effects against SCD (OR: 0.85; 95% CI: 0.76-0.96; P = .007). Moreover, this model demonstrated that rs2283222 in KCNQ1 had a significant negative relationship with SCD (OR: 0.73; 95% CI: 0.62-0.85; P < .001). Rs12296050 in KCNQ1 protected against SCD in Koreans and Americans. Our results also showed that rs790896 in RYR2 was negatively associated with SCD in a dominant model (OR: 0.66; 95% CI: 0.45-0.97; P = .033).

CONCLUSIONS

Rs11720524 in SCN5A is negatively related to SCD in Europeans and Caucasians, and rs12296050 and rs2283222 in KCNQ1 and rs790896 in RYR2 clearly have protective effects against SCD.

Relation of Early Repolarization (J Point Elevation) to Mortality in Blacks (from the Jackson Heart Study)

Conflicting data exist regarding the associations of early repolarization (ER) with electrocardiogram (ECG) and clinical outcomes in blacks. We examined the association of ER defined by J point elevation (JPE) and all-cause mortality, and heart failure (HF) hospitalization in blacks in the Jackson Heart Study (JHS) cohort. We included JHS participants with ECGs from the baseline visit coding JPE and excluded participants with paced rhythms or QRS duration ≥120 ms. We compared the cumulative incidence of 10-year all-cause mortality and 8-year HF hospitalization by presence of JPE ≥0.1 mV in any ECG lead at baseline using Kaplan-Meier estimates and multivariable Cox models. Of the 4,978 participants, 1,410 (28%) had JPE at baseline: anterior leads 97.8%, lateral leads 8.3%, and inferior leads 2.9%. Compared with participants without JPE, those with JPE were younger, more likely to be male and current smokers, and less likely to have hypertension. Over a median follow-up of 8 years, there were no significant differences in the cumulative incidence or multivariable-adjusted hazards of all-cause mortality or HF hospitalization in participants with and without JPE in any lead (adjusted hazard ratio 0.97, 95% confidence interval 0.89 to 1.52, and adjusted hazard ratio 1.18, 95% confidence interval 0.9 to 1.54, respectively). Of the 2,523 participants who completed Exam 3 without JPE at baseline, 246 (10%) developed JPE over follow-up. In conclusion, JPE on ECG was not associated with long-term mortality or HF hospitalization in a large prospective black community cohort, suggesting that ER may represent a benign ECG finding in blacks.

Critical Roles of Xirp Proteins in Cardiac Conduction and Their Rare Variants Identified in Sudden Unexplained Nocturnal Death Syndrome and Brugada Syndrome in Chinese Han Population

BACKGROUND

Sudden unexplained nocturnal death syndrome (SUNDS) remains an autopsy negative entity with unclear etiology. Arrhythmia has been implicated in SUNDS. Mutations/deficiencies in intercalated disc components have been shown to cause arrhythmias. Human cardiomyopathy-associated 1 (XIRP1) and 3 (XIRP2) are intercalated disc-associated, Xin repeats-containing proteins. Mouse Xirp1 is necessary for the integrity of intercalated disc and for the surface expression of transient outward and delayed rectifier K+ channels, whereas mouse Xirp2 is required for Xirp1 intercalated disc localization. Thus, XIRP1 and XIRP2 may be potentially causal genes for SUNDS.

METHODS AND RESULTS

We genetically screened XIRP genes in 134 sporadic SUNDS victims and 22 Brugada syndrome (BrS) cases in a Chinese Han population. We identified 16 rare variants (6 were in silico predicted as deleterious) in SUNDS victims, including a novel variant, XIRP2-E215K. There were also four rare variants (2 were in silico predicted as deleterious) detected in BrS cases, including a novel variant, XIRP2-L2718P. Interestingly, among these 20 variants, we detected 2 likely pathogenic variants: a nonsense variant (XIRP2-Q2875*) and a frameshift variant (XIRP2-T2238QfsX7). Analyzing available Xirp2 knockout mice, we further found that mouse hearts without Xirp2 exhibited prolonged PR and QT intervals, slow conduction velocity, atrioventricular conduction block, and an abnormal infranodal ventricular conduction system. Whole-cell patch-clamp detected altered ionic currents in Xirp2-/- cardiomyocytes, consistent with the observed association between Xirp2 and Nav1.5/Kv1.5 in co-immunoprecipitation.

CONCLUSIONS

This is the first report identifying likely pathogenic XIRP rare variants in arrhythmogenic disorders such as SUNDS and Brugada syndrome, and showing critical roles of Xirp2 in cardiac conduction.

Ethnic Differences in Genetic Ion Channelopathies Associated with Sudden Cardiac Death: A Systematic Review and Meta-Analysis

BACKGROUND AND AIMS

Reports of allele frequencies encoding ion channel, or their interacting proteins associated with sudden cardiac death among different ethnic groups have been inconsistent. Here, we aimed to characterize the distribution of these genes and their alleles among various ethnicities through meta-analysis.

METHODS

We conducted a systematic review and meta-analysis to assess the mean allele frequencies of channelopathy genes SCN5A, NOS1AP, KCNH2, KCNE1, and KCNQ1 among the Black, Caucasian, Asian, and Hispanic ethnicities. Searches in PubMed, Google Scholar, and Web of Science resulted in 18 reports published before July 2015 that met the eligible criteria. Allele frequencies were averaged by weight, and pooled values were calculated by inverse variance. Fixed-effects and random-effects models were used to pool effect sizes within each study and across different studies, respectively. Moreover, to extend our findings, we used sequenced genomic data from the Exome Aggregation Consortium to compare allele frequencies between different ethnicities.

RESULTS

Meta-analysis of published studies supports that Asians had the highest overall mean allele frequencies of NOS1AP (0.36%, 95% CI: 0.30, 0.43; P<0.001), and SCN5A frequencies (0.17%, 95% CI: 0.07, 0.27, P=0.001), and whereas Caucasians had the highest KCNH2 frequency (0.21%, 95% CI: 0.16, 0.25; P<0.001), and Hispanics the highest KCNQ1 frequency (0.16%). Analysis of the Exome Aggregation Consortium also provided consistent data in agreement the meta-analysis.

CONCLUSION

Overall, Asians carried the most alleles of genes associated with sudden cardiac death. The meta-analysis reveals significant differences in allele distribution of channelopathy-associated genes among different ethnic groups.

Comparison of QRS Duration and Associated Cardiovascular Events in American Indian Men Versus Women (The Strong Heart Study)

Electrocardiographic QRS duration at rest is associated with sudden cardiac death and death from coronary heart disease in the general population. However, its relation to cardiovascular events in American Indians, a population with persistently high cardiovascular disease mortality, is unknown. The relation of QRS duration to incident cardiovascular disease during 17.2 years of follow-up was assessed in 1,851 male and female Strong Heart Study participants aged 45 to 74 years without known cardiovascular disease at baseline. Cox regression with robust standard error estimates was used to determine the association between quintiles of QRS duration and incident cardiovascular disease in gender-stratified analyses, adjusted for age, systolic blood pressure, hypertension, antihypertensive medication use, body mass index, current smoking, diabetes, total cholesterol, high-density lipoprotein cholesterol, and albuminuria. In women only, QRS duration in the highest quintile (≥105 ms) conferred significantly higher risk of cardiovascular disease than QRS duration in the lowest quintile (64 to 84 ms) (hazard ratio 1.6, 95% CI 1.1 to 2.4) likely because of higher risks of coronary heart disease (hazard ratio 1.8, 95% CI 1.1 to 3.1) and myocardial infarction (hazard ratio 2.1, 95% CI 1.0 to 4.7). Furthermore, when added to the Strong Heart Study Coronary Heart Disease Risk Calculator, QRS duration significantly improved prediction of future coronary heart disease events in women (Net Reclassification Index 0.17, 95% CI 0.06 to 0.47). In conclusion, QRS duration is an independent predictor of cardiovascular disease in women in the Strong Heart Study cohort and may have value in estimating risk in populations with similar risk profiles and a high lifetime incidence of cardiovascular disease.

Long-Term Prognosis of Patients with an Implantable Cardioverter-Defibrillator in Korea

PURPOSE

The objective of this study was to elucidate the long-term prognosis of patients with implantable cardioverter-defibrillators (ICDs) in Korea.

MATERIALS AND METHODS

We enrolled 405 patients (age, 57.7±16.7 years; 311 men) who had undergone ICD implantation. The patients were divided into three groups: heart failure (HF) and ICD for primary (group 1, n=118) and secondary prevention (group 2, n=93) and non-HF (group 3, n=194). We compared appropriate and inappropriate ICD therapy delivery among the groups and between high- (heart rate ≥200 /min) and low-rate (<200 /min) ICD therapy zones.

RESULTS

During the follow-up period (58.9±49.8 months), the annual appropriate ICD therapy rate was higher in group 2 (10.4%) than in groups 1 and 3 (6.1% and 5.9%, respectively, p<0.001). There were no significant differences in annual inappropriate ICD therapy rate among the three groups. In group 1, the annual appropriate ICD therapy rate was significantly lower in patients with a high-rate versus a low-rate therapy zone (4.5% and 9.6%, respectively, p=0.026). In group 3, the annual inappropriate ICD therapy rate was significantly lower in patients with a high-rate versus a low-rate therapy zone (3.1% and 4.0%, respectively, p=0.048).

CONCLUSION

Appropriate ICD therapy rates are not low in Korean patients with ICD, relative to prior large-scale studies in Western countries. Appropriate and inappropriate ICD therapy could be reduced by a high-rate therapy zone in patients with HF and ICD for primary prevention, as well as non-HF patients, respectively.

Echocardiographic Predictors of Sudden Cardiac Death: The Atherosclerosis Risk in Communities Study and Cardiovascular Health Study

BACKGROUND

This study assessed the echocardiographic predictors of sudden cardiac death (SCD) within 2 population-based cohorts.

METHODS AND RESULTS

Echocardiograms were obtained on 2383 participants (1993-1995) from the ARIC study (Atherosclerosis Risk in Communities; 100% black) and 5366 participants (1987-1989 and 1994-1995) from the CHS (Cardiovascular Health Study). The main outcome was physician-adjudicated SCD. We used Cox proportional-hazards models with incident coronary heart disease and heart failure as time-dependent covariates to assess the association between echocardiographic variables and SCD, adjusting for Framingham risk score variables, coronary heart disease, and renal function. Cohort-specific results were meta-analyzed. During a median follow-up of 7.3 and 13.1 years, 44 ARIC study participants and 275 CHS participants had SCD, respectively. In the meta-analyzed results, the adjusted hazard ratios (95% confidence intervals) for predictors of SCD were 3.07 (2.29-4.11) for reduced left ventricular ejection fraction; 1.85 (1.36-2.52) for mitral annular calcification; 1.64 (1.07-2.51) for mitral E/A >1.5, and 1.52 (1.14-2.02) for mitral E/A <0.7 (versus mitral E/A 0.7-1.5); 1.30 (1.15-1.48) per 1 SD increase in left ventricular mass; and 1.15 (1.02-1.30) per 1 SD increase in left atrial diameter. A receiver-operating characteristic model for prediction of SCD using Framingham risk score variables had a C statistic of 0.61 for ARIC study and 0.67 for CHS; the full multivariable model including all echocardiographic variables had a C statistic of 0.76 for ARIC study and 0.74 for CHS.

CONCLUSIONS

In addition to reduced left ventricular ejection fraction, we identified other echocardiographic-derived variables predictive for SCD that provided incremental value compared with clinical risk factors.

Referral Patterns for Primary Prophylaxis Implantable Cardioverter Defibrillator Therapy for an Urban US Population

Implantable cardioverter defibrillators (ICDs) have been demonstrated to improve survival for both primary and secondary prevention of sudden cardiac arrest. However, studies suggest that ICD therapy is underused in appropriate candidates. Sex and racial disparities in ICD use have been suggested. We sought to characterize the referral patterns of high-risk patients for the primary prophylaxis of sudden cardiac arrest at a tertiary academic medical center serving a diverse population in an urban US setting. Electronic hospital databases were retrospective reviewed for patients meeting criteria for prophylactic ICD implantation. We evaluated the association of gender, age, race, and primary language with the referral and subsequent implantation of an ICD. We identified 1,055 patients satisfying prophylactic ICD criteria: 600 men, mean age 62.6 years, 27.6% black, 19.3% white, 23.3% Hispanic, and 49.8% primary language of English. Of the 673 patients (63.7%) referred for ICD evaluation, 345 underwent implantation, 125 declined, and 203 had significant co-morbidities that precluded implantation. Gender, race, and primary language were not associated with referral for ICD or with decision to proceed with implantation. Patients of increased age were less likely to be referred for ICD and were more likely to refuse implantation. ICD therapy was not considered in 146 patients eligible for prophylactic implantation. In conclusion, referral rates for ICD consideration were higher at our institution than in previous reports. Nonetheless, 14% of appropriate patients were not considered. This argues for the importance of increased education for patients and referring physicians.

Distinctive Clinical Profile of Blacks Versus Whites Presenting With Sudden Cardiac Arrest

BACKGROUND

Sudden cardiac arrest (SCA) is a major contributor to mortality, but data are limited among nonwhites. Identification of differences in clinical profile based on race may provide opportunities for improved SCA prevention.

METHODS AND RESULTS

In the ongoing Oregon Sudden Unexpected Death Study (SUDS), individuals experiencing SCA in the Portland, OR, metropolitan area were identified prospectively. Patient demographics, arrest circumstances, and pre-SCA clinical profile were compared by race among cases from 2002 to 2012 (for clinical history, n=126 blacks, n=1262 whites). Incidence rates were calculated for cases from the burden assessment phase (2002-2005; n=1077). Age-adjusted rates were 2-fold higher among black men and women (175 and 90 per 100 000, respectively) compared with white men and women (84 and 40 per 100 000, respectively). Compared with whites, blacks were >6 years younger at the time of SCA and had a higher prearrest prevalence of diabetes mellitus (52% versus 33%; P<0.0001), hypertension (77% versus 65%; P=0.006), and chronic renal insufficiency (34% versus 19%; P<0.0001). There were no racial differences in previously documented coronary artery disease or left ventricular dysfunction, but blacks had more prevalent congestive heart failure (43% versus 34%; P=0.04) and left ventricular hypertrophy (77% versus 58%; P=0.02) and a longer QTc interval (466±36 versus 453±41 milliseconds; P=0.03).

CONCLUSIONS

In this US community, the burden of SCA was significantly higher in blacks compared with whites. Blacks with SCA had a higher prearrest prevalence of risk factors beyond established coronary artery disease, providing potential targets for race-specific prevention.

Ethnic differences among implantable cardioverter defibrillators recipients in Israel

Heart failure is an increasingly common condition arising from a variety of different pathophysiological processes. Little is known about the unique features of Israeli Arabs who present with heart failure and who undergo cardiac device implantation. The study population comprised of 4,671 patients who were enrolled in the national Israeli Implantable Cardioverter Defibrillator registry. We compared demographic, clinical, and echocardiographic characteristics; device-related indications; and outcomes between Israeli Arabs (n = 733) and Jews (n = 3,938), who were enrolled in the registry from July 2010 through December 2013. Israeli Arabs constituted 15.7% of the study population. They were younger at presentation compared with Jews (57 ± 15 vs 66 ± 12 years, respectively; p <0.001), with a greater burden of co-morbidities, including diabetes mellitus and chronic obstructive lung disease and smoking. In addition, Arab patients had a greater frequency of non-ischemic cardiomyopathy (40.2% vs 24.6%, respectively; p <0.001), which was associated with a greater frequency of familial history of sudden cardiac death. During 15 ± 9 month follow-up, the mortality rates and appropriate device therapy were similar in both ethnic groups. In conclusion, Israeli Arab patients implanted with implantable cardioverter defibrillators display unique clinical features with greater prevalence of non-ischemic cardiomyopathy characterized by an early-onset and rapid deterioration.

Rationale and design of the Pan-African Sudden Cardiac Death survey: the Pan-African SCD study

BACKGROUND

The estimated rate of sudden cardiac death (SCD) in Western countries ranges from 300,000 to 400,000 annually, which represents 0.36 to 1.28 per 1 000 inhabitants in Europe and the United States. The burden of SCD in Africa is unknown. Our aim is to assess the epidemiology of SCD in Africa.

METHODS

The Pan-Africa SCD study is a prospective, multicentre, community-based registry monitoring all cases of cardiac arrest occurring in victims over 15 years old. We will use the definition of SCD as 'witnessed natural death occurring within one hour of the onset of symptoms' or 'unwitnessed natural death within 24 hours of the onset of symptoms'. After approval from institutional boards, we will record demographic, clinical, electrocardiographic and biological variables of SCD victims (including survivors of cardiac arrest) in several African cities. All deaths occurring in residents of districts of interest will be checked for past medical history, circumstances of death, and autopsy report (if possible). We will also analyse the employment of resuscitation attempts during the time frame of sudden cardiac arrest (SCA) in various patient populations throughout African countries.

CONCLUSION

This study will provide comprehensive, contemporary data on the epidemiology of SCD in Africa and will help in the development of strategies to prevent and manage cardiac arrest in this region of the world.

Prevalence and significance of early repolarisation in a black African population: data of 246 individuals with cardiovascular morbidity

BACKGROUND

Early repolarisation (ER) is commonly seen on electrocardiograms (ECG). Recent reports have described the relationship between ER and sudden cardiac death (SCD). The prevalence and significance of ER have not been studied in black Africans.

METHOD

We matched clinical and ECG records of subjects over 18 years of age who consulted a cardiac unit in two medical centres of Douala, Cameroon. A questionnaire focusing on past history of syncope or family history of sudden unexplained death (SUD) was filled in by each subject. A 12-lead ECG was recorded by a trained nurse and analysed by two independent physicians.

RESULTS

Of the 752 ECGs recorded, we studied 246 index cases. The mean age of subjects was 45 ± 16 years and 53% were female. Almost 57% had hypertension, 41% had palpitations and 18% reported a history of syncope. ER pattern was found in 20% [slurring in three (3%), notching in 13% and both in three (7%)]. ER subjects were younger than those without (41 ± 16 vs 49 ± 16 years, p = 0.0048). Lead localisation was predominantly the laterals for the slurring pattern, whereas the inferior and lateral leads were equally involved for the notching pattern. Negative T waves in the infero-lateral leads were associated with ER (p = 0.00025). Among the subjects with syncope, 41% displayed ER and 13% did not have ER (p = 0.00014). The notching pattern seemed to be associated with syncope (p = 0.00011).

CONCLUSION

Early repolarisation is frequent in black Africans, especially in the setting of cardiovascular morbidity. Early repolarisation may be associated with a past history of syncope, especially the notched pattern.