Anders G. Holst

Risk Factors for Venous Thromboembolism Results From the Copenhagen City Heart Study

Background— Studies have suggested a link between risk factors for atherosclerotic disease and venous thromboembolism (VTE), but results are heterogeneous. We sought to identify risk factors for VTE with a focus on risk factors for atherosclerotic disease. Methods and Results— Data were taken from the Copenhagen City Heart Study, a prospective cohort study of a random, age-stratified sample of people living in a defined area in Copenhagen, Denmark, started in 1976 with follow-up until 2007. First VTE (deep vein thrombosis and pulmonary embolism) diagnosis was retrieved from electronic national registries from study baseline to 2007. Of 18 954 subjects (median follow-up, 19.5 years) representing 360 399 person-years of follow-up, 969 subjects experienced at least 1 VTE, corresponding to a crude incidence rate of 2.69 (95% confidence interval [CI], 2.52 to 2.86) per 1000 person-years. The variables found to be significantly associated with VTE in a multivariable model adjusted for age and calendar time were as follows: body mass index (hazard ratio [HR] for ≥35 versus <20=2.10 [95% CI, 1.39 to 3.16]); smoking (HR for ≥25 g tobacco per day versus never smoker=1.52 [95% CI, 1.15 to 2.01]); gender (HR for men versus women=1.24 [95% CI, 1.08 to 1.42]); household income (HR for medium versus low=0.82 [95% CI, 0.70 to 0.95]); and diastolic blood pressure (HR for >100 versus <80 mm Hg=1.34 [95% CI, 1.08 to 1.66]). Other cardiovascular risk factors including total/high-density lipoprotein/low-density lipoprotein cholesterol levels, triglyceride levels, and diabetes mellitus were not associated with VTE. Conclusions— Obesity and smoking were both found to be important risk factors for VTE whereas total/high-density lipoprotein/low-density lipoprotein cholesterol levels, triglyceride levels, and diabetes mellitus were not.

New population-based exome data are questioning the pathogenicity of previously cardiomyopathy-associated genetic variants

Cardiomyopathies are a heterogeneous group of diseases with various etiologies. We focused on three genetically determined cardiomyopathies: hypertrophic (HCM), dilated (DCM), and arrhythmogenic right ventricular cardiomyopathy (ARVC). Eighty-four genes have so far been associated with these cardiomyopathies, but the disease-causing effect of reported variants is often dubious. In order to identify possible false-positive variants, we investigated the prevalence of previously reported cardiomyopathy-associated variants in recently published exome data. We searched for reported missense and nonsense variants in the NHLBI-Go Exome Sequencing Project (ESP) containing exome data from 6500 individuals. In ESP, we identified 94 variants out of 687 (14%) variants previously associated with HCM, 58 out of 337 (17%) variants associated with DCM, and 38 variants out of 209 (18%) associated with ARVC. These findings correspond to a genotype prevalence of 1:4 for HCM, 1:6 for DCM, and 1:5 for ARVC. PolyPhen-2 predictions were conducted on all previously published cardiomyopathy-associated missense variants. We found significant overrepresentation of variants predicted as being benign among those present in ESP compared with the ones not present. In order to validate our findings, seven variants associated with cardiomyopathy were genotyped in a control population and this revealed frequencies comparable with the ones found in ESP. In conclusion, we identified genotype prevalences up to more than one thousand times higher than expected from the phenotype prevalences in the general population (HCM 1:500, DCM 1:2500, and ARVC 1:5000) and our data suggest that a high number of these variants are not monogenic causes of cardiomyopathy.

High prevalence of genetic variants previously associated with LQT syndrome in new exome data.

To date, hundreds of variants in 13 genes have been associated with long QT syndrome (LQTS). The prevalence of LQTS is estimated to be between 1:2000 and 1:5000. The knowledge of genetic variation in the general population has until recently been limited, but newly published data from NHLBI GO Exome Sequencing Project (ESP) has provided important knowledge on this topic. We aimed to investigate the prevalence of previously LQTS-associated variants in ESP (5400 individuals), in order to identify possible false-positive LQTS variants. With this aim, we performed a search for previously published LQTS-associated variants in ESP. In addition, a PolyPhen-2 prediction was conducted, and the four most prevalent LQTS-associated variants with significant functional effects present in ESP were genotyped in a second control population. We identified 33 missense variants previously associated with LQTS in ESP. These 33 variants affected 173 alleles and this corresponded to a LQTS prevalence of 1:31 in the ESP population. PolyPhen-2 predicted 30% of the 33 variants present in ESP to be benign compared with 13% among LQTS-associated variants not present in ESP (P=0.019). Genotyping of the four variants KCNH2 P347S; SCN5A: S216L, V1951L; and CAV3 T78M in the control population (n=704) revealed prevalences comparable to those of ESP. Thus, we identified a much higher prevalence of previously LQTS-associated variants than expected in exome data from population studies. Great caution regarding the possible disease causation of some of these variants has to be taken, especially when used for risk stratification in family members.

High Prevalence of Long QT Syndrome Associated SCN5A Variants in Patients with Early-Onset Lone Atrial Fibrillation

Background—Atrial fibrillation (AF) is the most common cardiac arrhythmia. The cardiac sodium channel, NaV1.5, plays a pivotal role in setting the conduction velocity and the initial depolarization of the cardiac myocytes. We hypothesized that early-onset lone AF was associated with genetic variation in SCN5A. Methods and Results—The coding sequence of SCN5A was sequenced in 192 patients with early-onset lone AF. Eight nonsynonymous mutations (T220I, R340Q, T1304M, F1596I, R1626H, D1819N, R1897W, and V1951M) and 2 rare variants (S216L in 2 patients and F2004L) were identified. Of 11 genopositive probands, 6 (3.2% of the total population) had a variant previously associated with long QT syndrome type 3 (LQTS3). The prevalence of LQTS3-associated variants in the patients with lone AF was much higher than expected, compared with the prevalence in recent exome data (minor allele frequency, 1.6% versus 0.3%; P=0.003), mainly representing the general population. The functional effects of the mutations were analyzed by whole cell patch clamp in HEK293 cells; for 5 of the mutations previously associated with LQTS3, patch-clamp experiments showed an increased sustained sodium current, suggesting a mechanistic overlap between LQTS3 and early-onset lone AF. In 9 of 10 identified mutations and rare variants, we observed compromised biophysical properties affecting the transient peak current. Conclusions—In a cohort of patients with early-onset lone AF, we identified a high prevalence of SCN5A mutations previously associated with LQTS3. Functional investigations of the mutations revealed both compromised transient peak current and increased sustained current.

Right bundle branch block: prevalence, risk factors, and outcome in the general population: results from the Copenhagen City Heart Study

AIMS To determine the prevalence, predictors of newly acquired, and the prognostic value of right bundle branch block (RBBB) and incomplete RBBB (IRBBB) on a resting 12-lead electrocardiogram in men and women from the general population. METHODS AND RESULTS We followed 18 441 participants included in the Copenhagen City Heart Study examined in 1976-2003 free from previous myocardial infarction (MI), chronic heart failure, and left bundle branch block through registry linkage until 2009 for all-cause mortality and cardiovascular outcomes. The prevalence of RBBB/IRBBB was higher in men (1.4%/4.7% in men vs. 0.5%/2.3% in women, P < 0.001). Significant predictors of newly acquired RBBB were male gender, increasing age, high systolic blood pressure, and presence of IRBBB, whereas predictors of newly acquired IRBBB were male gender, increasing age, and low BMI. Right bundle branch block was associated with significantly increased all-cause and cardiovascular mortality in both genders with age-adjusted hazard ratios (HR) of 1.31 [95% confidence interval (CI), 1.11-1.54] and 1.87 (95% CI, 1.48-2.36) in the gender pooled analysis with little attenuation after multiple adjustment. Right bundle branch block was associated with increased risk of MI with an HR of 1.67 (95% CI, 1.16-2.42) and pacemaker insertion with an HR of 2.17 (95% CI, 1.22-3.86), but not with chronic heart failure (HR 1.37; 95% CI, 0.96-1.94), atrial fibrillation (HR 1.10; 95% CI, 0.73-1.67), or chronic obstructive pulmonary disease (HR 0.99; 95% CI, 0.60-1.62). The presence of IRBBB was not associated with any adverse outcome. CONCLUSION In this cohort study, RBBB and IRBBB were two to three times more common among men than women. Right bundle branch block was associated with increased cardiovascular risk and all-cause mortality, whereas IRBBB was not. Contrary to common perception, RBBB in asymptomatic individuals should alert clinicians to cardiovascular risk.

Strategy for clinical evaluation and screening of sudden cardiac death relatives.

Sudden cardiac death (SCD) may be the first and final manifestation of several heart diseases. In the young, SCD is often caused by a hereditary cardiac disease. As the most frequently seen inherited cardiac diseases have an autosomal‐dominant pattern of inheritance, half of the first‐degree relatives are at risk of having or developing the same disease. Therefore, screening of these high‐risk relatives is a rational approach to reduce the incidence of SCD. To offer family screening and counseling, the cause of death should be carefully established. Autopsy is only performed in a limited number of cases. We advocate for systematic autopsies in SCD, because positive findings are crucial for choosing the optimal screening program for the relatives. A negative autopsy makes identification of at‐risk population difficult. However, this finding also provides clues to the cardiologist, because a limited number of inherited cardiac diseases associated with SCD are without any structural changes. In other cases, the autopsy may reveal noncardiac causes of death, which is also important for reassuring the relatives. However, in cases with no autopsy or negative findings, thorough clinical examinations and selective genetic screening of relatives may identify a likely diagnosis in more than 50% of affected families. There is a need for consensus regarding routine evaluation of SCD cases and the ethical and legal framework related to postmortem testing. We propose an algorithm that narrows the diagnostic possibilities in apparently healthy relatives of young SCD victims. Molecular autopsy may play an important role.

Variants of an explicit kernel-split panel-based Nyström discretization scheme for Helmholtz boundary value problems

The incorporation of analytical kernel information is exploited in the construction of Nyström discretization schemes for integral equations modeling planar Helmholtz boundary value problems. Splittings of kernels and matrices, coarse and fine grids, high-order polynomial interpolation, product integration performed on the fly, and iterative solution are some of the numerical techniques used to seek rapid and stable convergence of computed fields in the entire computational domain.

Common polymorphisms in KCNJ5 [corrected] are associated with early-onset lone atrial fibrillation in Caucasians.

Objectives: The aim of this study was to screen lone atrial fibrillation (AF) patients for mutations in the genes KCNJ2, KCNJ3 and KCNJ5, all encoding potassium channels. Furthermore, we wanted to replicate the prior association of two single-nucleotide polymorphisms (SNPs) in KCNJ5, C171T (rs6590357) and G810T (rs7118824), with lone AF in Han Chinese. Methods: We sequenced the coding region and splice site of KCNJ2, KCNJ3 and KCNJ5 in 187 early-onset lone-AF patients screening for mutations and counting SNP frequencies for the two noted SNPs in KCNJ5. Results: No mutations were found in KCNJ2, KCNJ3 or KCNJ5. Both genotype distribution and allele frequencies of the SNPs rs6590357 and rs7118824 significantly differed between the AF and control group (pgenotype = 0.0067, pallele = 0.0021 and pgenotype = 0.014, pallele = 0.0101, respectively). On allele level, the OR for lone AF for rs6590357 was 1.77 (95% CI 1.16–2.73, p = 0.009) and for rs7118824 it was 1.71 (95% CI 1.13–2.57, p = 0.01) in a model adjusted for age and gender. Conclusions: Our findings indicate that rs6590357 and rs7118824 in KCNJ5 are associated with early-onset lone AF in Caucasians. No mutations were found in the exon or splice site of KCNJ2, KCNJ3 or KCNJ5.

A Novel SCN5A Mutation in a Patient with Coexistence of Brugada Syndrome Traits and Ischaemic Heart Disease

Brugada syndrome (BrS) is a primary electrical heart disease, which can lead to sudden cardiac death. In older patients with BrS, the disease may coexist with ischaemic heart disease (IHD) and recent studies support a synergistic proarrhythmic effect of the two disease entities. We report a case that illustrates this. The index patient was a middle-aged patient with BrS traits, IHD, and aborted sudden cardiac death. Mutation analysis discovered a novel mutation P468L in the NaV1.5 sodium channel. Surprisingly, voltage-clamp experiments on the wild-type and mutant NaV1.5 channels expressed in HEK cells revealed no functional effect of the mutation. In a patient like ours, the distinction between IHD and BrS as the cause of an aborted sudden cardiac death is hard to establish and mounting evidence shows that coexistence of the two may have a synergistic proarrhythmic effect.

Rare truncating variants in the sarcomeric protein titin associate with familial and early-onset atrial fibrillation

A family history of atrial fibrillation constitutes a substantial risk of developing the disease, however, the pathogenesis of this complex disease is poorly understood. We perform whole-exome sequencing on 24 families with at least three family members diagnosed with atrial fibrillation (AF) and find that titin-truncating variants (TTNtv) are significantly enriched in these patients (P = 1.76 × 10−6). This finding is replicated in an independent cohort of early-onset lone AF patients (n = 399; odds ratio = 36.8; P = 4.13 × 10−6). A CRISPR/Cas9 modified zebrafish carrying a truncating variant of titin is used to investigate TTNtv effect in atrial development. We observe compromised assembly of the sarcomere in both atria and ventricle, longer PR interval, and heterozygous adult zebrafish have a higher degree of fibrosis in the atria, indicating that TTNtv are important risk factors for AF. This aligns with the early onset of the disease and adds an important dimension to the understanding of the molecular predisposition for AF.Common genetic variants in structural proteins contribute to risk of atrial fibrillation (AF). Here, using whole-exome sequencing, the authors identify rare truncating variants in TTN that associate with familial and early-onset AF and show defects in cardiac sarcomere assembly in ttn.2-mutant zebrafish.