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Introduction: There is limited data on the experience with insertable cardiac monitors (ICMs) in patients with Brugada syndrome. Objective: To evaluate the outcome of ICM in symptomatic patients with Brugada syndrome who are at suspected low risk of sudden cardiac death (SCD). Methods: We conducted a prospective single-center cohort study including all symptomatic patients with Brugada syndrome who received an ICM (Reveal LINQ) between July 2014 and October 2019. The main indication for monitoring was to exclude ventricular arrhythmias as the cause of symptoms and to establish a symptom-rhythm relationship. Results: A total of 20 patients (mean age, 39 ± 12 years; 55% male) received an ICM during the study period. Nine patients (45%) had a history of syncope (presumed nonarrhythmogenic), and 5 patients had a recent syncope (<6 months). During a median follow-up of 32 months (interquartile range, 11-36 months), 3 patients (15%) experienced an episode of nonsustained ventricular arrhythmia. No patient died suddenly or experienced a sustained ventricular arrhythmia, and no p

Introduction: Biallelic damaging variants in ALPK3, encoding alpha-protein kinase 3, cause pediatric-onset cardiomyopathy with manifestations that are incompletely defined. Methods and Results: We analyzed clinical manifestations of damaging biallelic ALPK3 variants in 19 pediatric patients, including nine previously published cases. Among these, 11 loss-of-function (LoF) variants, seven compound LoF and deleterious missense variants, and one homozygous deleterious missense variant were identified. Among 18 live-born patients, 8 exhibited neonatal dilated cardiomyopathy (44.4%; 95% CI: 21.5%-69.2%) that subsequently transitioned into ventricular hypertrophy. The majority of patients had extracardiac phenotypes, including contractures, scoliosis, cleft palate, and facial dysmorphisms. We observed no association between variant type or location, disease severity, and/or extracardiac manifestations. Myocardial histopathology showed focal cardiomyocyte hypertrophy, subendocardial fibroelastosis in patients under 4 years of age, and myofibrillar disarray in adults. Rare heterozygous ALPK3 variants were also assessed in adult-onset cardiomyopathy patients. Among 1548 Dutch patients referred for initial genetic analyses, we identified 39 individuals with rare heterozygous ALPK3 variants (2.5%; 95% CI: 1.8%-3.4%), including 26 missense and 10 LoF variants. Among 149 U.S. patients without pathogenic variants in 83 cardiomyopathy-related genes, we identified six missense and nine LoF ALPK3 variants (10.1%; 95% CI: 5.7%-16.1%). LoF ALPK3 variants were increased in comparison to matched controls (Dutch cohort, P = 1.6×10−5; U.S. cohort, P = 2.2×10−13). Conclusion: Biallelic damaging ALPK3 variants cause pediatric cardiomyopathy manifested by DCM transitioning to hypertrophy, often with poor contractile function. Additional extracardiac features occur in most patients, including musculoskeletal abnormalities and cleft palate. Heterozygous LoF ALPK3 variants are enriched in adult

Cardiovascular disease (CVD) is the leading cause of death and disability in the world. Lifestyle and environmental factors greatly influence the risk for CVD. However, over the years it has become clear that genetic factors also substantially contribute to its pathogenesis. The majority of CVD are thought to result from multifactorial inheritance, involving a complex interplay between multiple susceptibility genes and environmental factors. Despite extensive research efforts, the molecular mechanisms underlying these complex forms of CVD remain poorly understood. In this thesis, we focus on monogenic forms of CVD in a

Simultaneous analysis of multiple genes using next-generation sequencing (NGS) technology has become widely available. Copy-number variations (CNVs) in disease-associated genes have emerged as a cause for several hereditary disorders. CNVs are, however, not routinely detected using NGS analysis. The aim of this study was to assess the diagnostic yield and the prevalence of CNVs using our panel of Hereditary Thoracic Aortic Disease (H-TAD)-associated genes. Eight hundred ten patients suspected of H-TAD were analyzed by targeted NGS analysis of 21 H-TAD associated genes. In addition, the eXome hidden Markov model (XHMM; an algorithm to identify CNVs in targeted NGS data) was used to detect CNVs in these genes. A pathogenic or likely pathogenic variant was found in 66 of 810 patients (8.1%). Of these 66 pathogenic or likely pathogenic variants, six (9.1%) were CNVs not detectable by routine NGS analysis. These CNVs were four intragenic (multi-)exon deletions in MYLK, TGFB2, SMAD3, and PRKG1, respectively. In addition, a large duplication including NOTCH1 and a large deletion encompassing SCARF2 were detected. As confirmed by additional analyses, both CNVs indicated larger chromosomal abnormalities, which could explain the phenotype in both patients. Given the clinical relevance of the identification of a genetic cause, CNV analysis using a method such as XHMM should be incorporated into the clinical diagnostic care for H-TAD patients.

The pathogenicity of previously published disease-associated genes and variants is sometimes questionable. Large-scale, population-based sequencing studies have uncovered numerous false assignments of pathogenicity. Misinterpretation of sequence variants may have serious implications for the patients and families involved, as genetic test results are increasingly being used in medical decision making. In this study, we assessed the role of the calreticulin-3 gene (CALR3) in cardiomyopathy. CALR3 has been included in several cardiomyopathy gene panels worldwide. Its inclusion is based on a single publication describing two missense variants in patients with hypertrophic cardiomyopathy. In our national cardiomyopathy cohort (n = 6154), we identified 17 unique, rare heterozygous CALR3 variants in 48 probands. Overall, our patient cohort contained a significantly higher number of rare CALR3 variants compared to the ExAC population (p = 0.0036). However, after removing a potential Dutch founder variant, no statistically significant difference was found (p = 0.89). In nine probands, the CALR3 variant was accompanied by a disease-causing variant in another, well-known cardiomyopathy gene. In three families, the CALR3 variant did not segregate with the disease. Furthermore, we could not demonstrate calreticulin-3 protein expression in myocardial tissues at various ages. On the basis of these findings, it seems highly questionable that variants in CALR3 are a monogenic cause of cardiomyopathy.

Background: Thoracic aortic aneurysm (TAA) is a potentially life-threatening disorder with a strong genetic component. The number of genes implicated in TAA has increased exponentially over the last decade. Approximately 20% of patients with TAA have a positive family history. As most TAA remain asymptomatic for a long time, screening of at risk relatives is warranted to prevent complications. Existing international guidelines lack detailed instructions regarding genetic evaluation and family screening of TAA patients. We aimed to develop a consensus document to provide medical guidance for all health care professionals involved in the recognition, diagnosis and treatment of patients with thoracic aortic disease and their relatives. Methods: A multidisciplinary panel of experts including cardiologists, cardiothoracic surgeons, clinical geneticists and general practitioners, convened to review and discuss the current literature, guidelines and clinical practice on genetic testing and family screening in TAA. Results: There is a lack of high-quality evidence in the literature. This consensus statement, based on the available literature and expert opinions, summarizes our recommendations in order to standardize and optimize the cardiogenetic care for patients and families with thoracic aortic disease. In particular, we provide criteria to identify those patients most likely to have a genetic predisposition, and discuss the preferred modality and frequency of screening in their relatives. Conclusions: Age, family history, aortic size and syndromic features determine who is advised to have genetic testing as well as screening of first-degree relatives. There is a need for more prospective multicenter studies to optimize current recommendations.

Bicuspid aortic valve (BAV) is the most common congenital heart defect. Although many BAV patients remain asymptomatic, at least 20% develop thoracic aortic aneurysm (TAA). Historically, BAV-related TAA was considered as a hemodynamic consequence of the valve defect. Multiple lines of evidence currently suggest that genetic determinants contribute to the pathogenesis of both BAV and TAA in affected individuals. Despite high heritability, only very few genes have been linked to BAV or BAV/TAA, such as NOTCH1, SMAD6, and MAT2A. Moreover, they only explain a minority of patients. Other candidate genes have been suggested based on the presence of BAV in knockout mouse models (e.g., GATA5, NOS3) or in syndromic (e.g., TGFBR1/2, TGFB2/3) or non-syndromic (e.g., ACTA2) TAA forms. We hypothesized that rare genetic variants in these genes may be enriched in patients presenting with both BAV and TAA. We performed targeted resequencing of 22 candidate genes using Haloplex target enrichment in a strictly defined BAV/TAA cohort (n = 441; BAV in addition to an aortic root or ascendens diameter = 4.0 cm in adults, or a Z-score = 3 in children) and in a collection of healthy controls with normal echocardiographic evaluation (n = 183). After additional burden analysis against the Exome Aggregation Consortium database, the strongest candidate susceptibility gene was SMAD6 (p = 0.002), with 2.5% (n = 11) of BAV/TAA patients harboring causal variants, including two nonsense, one in-frame deletion and two frameshift mutations. All six missense mutations were located in the functionally important MH1 and MH2 domains. In conclusion, we report a significant contribution of SMAD6 mutations to the etiology of the BAV/TAA phenotype.

In the original article, we noted two mutation annotation errors. The correction of these two mistakes does not change the scientific conclusions in any way. The authors apologize for these nomenclature errors. Please find below the corrected annotations of those two mutations: (1) The correct RNA and protein annotations of the SMAD6 variant in P99 are c.455_461del and p.Pro152Profs*27, and not c.454_461del and p.Gly166Valfs*23. (2) The correct RNA and protein annotations of the SMAD6 variant in P128 are c.74_79del and p.Ser27_Gly28del, and not c.73_79del and p.Gly26_Ser27del. As a consequence, a correction has been made to RESULTS, Paragraphs 5 and 6: The SMAD6 c.726del variant leads to a frameshift (p.Lys242Asnfs*300) and a predicted protein with a C-terminal extension due to loss of the intended stop codon. The c.455_461del frameshift variant (p.Pro152Profs*27) causes the introduction of a premature stop codon, most likely resulting in haploinsufficiency due to nonsense-mediated mRNA decay (NMD). Also the two nonsense variants (p.Tyr279* and p.Tyr288*) are predicted to lead to NMD. All of the missense variants cluster in the functionally important MH1 and MH2 domains (Makkar et al., 2009) (amino acids 148-275 and 331-496, respectively), which is not the case for the sole missense variant (p.Ser130Leu) found in a control individual (Figure 2). All but one (p.Arg443His) of the identified variants were absent in the ExAC control cohort (v0.3.1; Supplementary Table 2). Moreover, the missense variants in the patient cohort (7/7) are enriched in the MH1 and MH2 domains when compared to ExAC controls (n = 228/430; p = 0.02).