A comprehensive evaluation of the genetic architecture of sudden cardiac arrest.

Aims: Sudden cardiac arrest (SCA) accounts for 10% of adult mortality in Western populations. We aim to identify potential loci associated with SCA and to identify risk factors causally associated with SCA. Methods and results: We carried out a large genome-wide association study (GWAS) for SCA (n = 3939 cases, 25 989 non-cases) to examine common variation genome-wide and in candidate arrhythmia genes. We also exploited Mendelian randomization (MR) methods using cross-trait multi-variant genetic risk score associations (GRSA) to assess causal relationships of 18 risk factors with SCA. No variants were associated with SCA at genome-wide significance, nor were common variants in candidate arrhythmia genes associated with SCA at nominal significance. Using cross-trait GRSA, we established genetic correlation between SCA and (i) coronary artery disease (CAD) and traditional CAD risk factors (blood pressure, lipids, and diabetes), (ii) height and BMI, and (iii) electrical instability traits (QT and atrial fibrillation), suggesting aetiologic roles for these traits in SCA risk. Conclusions: Our findings show that a comprehensive approach to the genetic architecture of SCA can shed light on the determinants of a complex life-threatening condition with multiple influencing factors in the general population. The results of this genetic analysis, both positive and negative findings, have implications for evaluating the genetic architecture of patients with a family history of SCA, and for efforts to prevent SCA in high-risk populations and the general community.

Circulating N-Linked Glycoprotein Acetyls and Longitudinal Mortality Risk.

RATIONALE: Circulating glycoprotein N-acetyl glucosamine residues have recently been associated with incident cardiovascular disease and diabetes mellitus. OBJECTIVE: Using a plasma glycan biosignature (GlycA) to identify circulating N-acetyl glycan groups, we examined the longitudinal association between GlycA and mortality among initially healthy individuals. METHODS AND RESULTS: We quantified GlycA by 400 MHz (1)H nuclear magnetic resonance spectroscopy in 27,524 participants in the Women's Health Study (NCT00000479). The primary outcome was all-cause mortality. We replicated the findings in an independent cohort of 12,527 individuals in the Justification for the Use of statins in Prevention: an Intervention Trial Evaluating Rosuvastatin (JUPITER) trial (NCT00239681). We also undertook secondary examination of cardiovascular disease and cancer mortality in the Women's Health Study. In the Women's Health Study, during 524,515 person-years of follow-up (median, 20.5 years), there were 3523 deaths. Risk factor-adjusted multivariable Cox proportional hazard ratio (95% confidence interval) per SD increment in GlycA for all-cause mortality was significantly increased at 5 years (1.21 [1.06-1.40]) and during maximal follow-up (1.14 [1.09-1.16]). Similar risk for all-cause mortality was observed in the replication cohort (1.33 [1.21-1.45]). In the Women's Health Study, risk of cardiovascular disease mortality was increased at 5 years (1.43 [1.05-1.95]) and during maximal follow-up (1.15 [1.04-1.26]) and of cancer mortality at 5 years (1.23 [1.02-1.47]) and during maximal follow-up (1.08 [1.01-1.16]). Examination of correlations and mortality associations adjusted for high-sensitivity C-reactive protein, fibrinogen, and intercellular adhesion molecule-1, suggested that GlycA reflects summative risk related to multiple pathways of systemic inflammation. CONCLUSIONS: Among initially healthy individuals, elevated baseline circulating glycoprotein N-acetyl methyl groups were associated with longitudinal risk of all-cause, cardiovascular, and cancer mortality.

A common variant at 9p21 is associated with sudden and arrhythmic cardiac death.

BACKGROUND: Although a heritable basis for sudden cardiac death (SCD) is suggested by the impact of family history on SCD risk, common genetic determinants have been difficult to identify. We hypothesized that a common variant at chromosome 9p21 related to myocardial infarction would influence SCD risk. METHODS AND RESULTS: This was a prospective, nested, case-control analysis among individuals of European ancestry enrolled in 6 prospective cohort studies. Study subjects were followed up for development of SCD, and genotypes for rs10757274 were determined for 492 sudden and/or arrhythmic deaths and 1460 controls matched for age, sex, cohort, history of cardiovascular disease, and follow-up time. Conditional logistic regression with fixed-effects meta-analysis assuming an additive model was used to test for associations. When individual study results were combined in the meta-analysis, each increasing copy of the G allele at rs10757274 conferred a significantly elevated age-adjusted odds ratio for SCD of 1.21 (95% confidence interval, 1.04 to 1.40; P=0.01). Controlling for cardiovascular and lifestyle risk factors strengthened these relationships (odds ratio, 1.29 per G-allele copy; 95% confidence interval, 1.09 to 1.53; P=0.003). These results were not materially altered in sensitivity analyses limited to definite SCD, in models that further controlled for the development of interim cardiovascular disease, or when the highly correlated variant rs2383207 was tested. CONCLUSIONS: The major allele of a single-nucleotide polymorphism previously associated with increased risk of coronary artery disease events is associated with increased risk of SCD in individuals of European ancestry. Study of the mechanism underlying this association may improve our understanding of lethal cardiovascular disease.

Rare Genetic Variants Associated With Sudden Cardiac Death in Adults.

BACKGROUND: Sudden cardiac death occurs in ∼220,000 U.S. adults annually, the majority of whom have no prior symptoms or cardiovascular diagnosis. Rare pathogenic DNA variants in any of 49 genes can pre-dispose to 4 important causes of sudden cardiac death: cardiomyopathy, coronary artery disease, inherited arrhythmia syndrome, and aortopathy or aortic dissection. OBJECTIVES: This study assessed the prevalence of rare pathogenic variants in sudden cardiac death cases versus controls, and the prevalence and clinical importance of such mutations in an asymptomatic adult population. METHODS: The authors performed whole-exome sequencing in a case-control cohort of 600 adult-onset sudden cardiac death cases and 600 matched controls from 106,098 participants of 6 prospective cohort studies. Observed DNA sequence variants in any of 49 genes with known association to cardiovascular disease were classified as pathogenic or likely pathogenic by a clinical laboratory geneticist blinded to case status. In an independent population of 4,525 asymptomatic adult participants of a prospective cohort study, the authors performed whole-genome sequencing and determined the prevalence of pathogenic or likely pathogenic variants and prospective association with cardiovascular death. RESULTS: Among the 1,200 sudden cardiac death cases and controls, the authors identified 5,178 genetic variants and classified 14 as pathogenic or likely pathogenic. These 14 variants were present in 15 individuals, all of whom had experienced sudden cardiac death-corresponding to a pathogenic variant prevalence of 2.5% in cases and 0% in controls (p < 0.0001). Among the 4,525 participants of the prospective cohort study, 41 (0.9%) carried a pathogenic or likely pathogenic variant and these individuals had 3.24-fold higher risk of cardiovascular death over a median follow-up of 14.3 years (p = 0.02). CONCLUSIONS: Gene sequencing identifies a pathogenic or likely pathogenic variant in a small but potentially important subset of adults experiencing sudden cardiac death; these variants are present in ∼1% of asymptomatic adults.

A common variant in the ß2-adrenergic receptor and risk of sudden cardiac death.

BACKGROUND: Homozygosity for a common nonsynonymous single nucleotide polymorphism (Gln27Glu) in the ß(2)-adrenergic receptor gene (ADRB2) has been inconsistently associated with sudden cardiac death (SCD) in individual studies of small sample size. OBJECTIVE: The purpose of this study was to examine the association between the Gln27Glu polymorphism and SCD in a large combined sample of SCD cases. METHODS: Nested case-control analysis was performed for individuals of Caucasian ancestry enrolled in six prospective cohort studies. Genotypes for the Gln27Glu variant were determined for 492 cases of SCD and 1,388 controls matched for age, sex, cohort, follow-up time, and history of cardiovascular disease (CVD) and at the time of the blood draw. Individual studies were combined with conditional logistic regression with fixed effects meta-analysis assuming a recessive model. RESULTS: Homozygosity for the Gln27 allele conferred a nonsignificant elevation of the age-adjusted odds ratio (OR 1.22, 95% confidence interval [CI] 0.98-1.53, P = .08) for SCD, which became marginally significant after controlling for multiple cardiac risk factors (OR 1.30, 95% CI 1.01-1.67, P = .046). In secondary analyses using controls additionally matched for the development of nonfatal CVD after the blood draw, results were attenuated (OR 1.19, 95% CI 0.92-1.52, P = .19). When the results of the primary analysis were combined in meta-analysis with published reports, a significant association between ADRB2 genotype and SCD emerged (OR 1.35, 95% CI 1.15-1.60, P = .0003). CONCLUSION: These data from a large prospective case-control series, when combined with published studies, provide further evidence for an association between ADRB2 genotype and SCD. The mechanism is unknown but appears to be partly mediated by development of CVD.

Common variants in cardiac ion channel genes are associated with sudden cardiac death.

BACKGROUND: Rare variants in cardiac ion channel genes are associated with sudden cardiac death in rare primary arrhythmic syndromes; however, it is unknown whether common variation in these same genes may contribute to sudden cardiac death risk at the population level. METHODS AND RESULTS: We examined the association between 147 single nucleotide polymorphisms (SNPs) (137 tag, 5 noncoding SNPs associated with QT interval duration, and 5 nonsynonymous SNPs) in 5 cardiac ion channel genes, KCNQ1, KCNH2, SCN5A, KCNE1, and KCNE2, and sudden and/or arrhythmic death in a combined nested case-control analysis among 516 cases and 1522 matched control subjects of European ancestry enrolled in 6 prospective cohort studies. After accounting for multiple testing, 2 SNPs (rs2283222 located in intron 11 in KCNQ1 and rs11720524 located in intron 1 in SCN5A) remained significantly associated with sudden/arrhythmic death (false discovery rate=0.01 and 0.03, respectively). Each increasing copy of the major T-allele of rs2283222 or the major C-allele of rs1172052 was associated with an odds ratio of 1.36 (95% confidence interval, 1.16 to 1.60; P=0.0002) and 1.30 (95% confidence interval, 1.12 to 1.51; P=0.0005), respectively. Control for cardiovascular risk factors and/or limiting the analysis to definite sudden cardiac death did not significantly alter these relationships. CONCLUSION: In this combined analysis of 6 prospective cohort studies, 2 common intronic variants in KCNQ1 and SCN5A were associated with sudden cardiac death in individuals of European ancestry. Further study in other populations and investigation into the functional abnormalities associated with noncoding variation in these genes may lead to important insights into predisposition to lethal arrhythmias.

Comparison of baseline characteristics and mortality experience of participants and nonparticipants in a randomized clinical trial: the Physicians' Health Study.

Although subjects randomized into clinical trials tend to have different mortality experiences from those not randomized, few studies have examined how baseline characteristics may explain these differences. We used the recruitment experience of the Physicians' Health Study (PHS) to describe and compare subgroups of subjects ultimately randomized - or not - into the PHS. A total of 112528 male physicians ages 40-84 years responded to letters of invitation and baseline questionnaires sent to 261248 subjects. Baseline information was collected on eligibility criteria, plus lifestyle and clinical risk factors. Total, cardiovascular, cancer, and other mortality were determined through the National Death Index after a mean follow-up of 5.39 years. Respondents had 19 and 19% lower total and cardiovascular mortality rates than nonrespondents. Similarly, willing respondents were 19 and 16% less likely to die than unwilling respondents. However, much of this difference in mortality was explained by disease and lifestyle factors. Respondents who were eligible for the PHS had significantly lower age-adjusted relative risks (RRs) that were attenuated but remained substantially below 1 upon multivariate adjustment in models for total (RRs from 0.48 to 0.79), cardiovascular (from 0.40 to 0.85), and cancer mortality (from 0.55 to 0.87). Finally, a nearly halving in the age-adjusted risk of total and cause-specific mortality among men completing a run-in and randomized into PHS compared with those not randomized was nominally altered upon adding all covariates into multivariate models. In conclusion, a difference in mortality rates according to willingness to participate in a trial was explained by disease and lifestyle factors. In contrast, diseases and risk factors explain some, but not all, of the lower mortality rates of physicians based on eligibility status and their ability to complete a run-in phase.