Penetrance and Prognosis of MYH7 Variant-Associated Cardiomyopathies: Results From a Dutch Multicenter Cohort Study.

BACKGROUND: MYH7 variants cause hypertrophic cardiomyopathy (HCM), noncompaction cardiomyopathy (NCCM), and dilated cardiomyopathy (DCM). Screening of relatives of patients with genetic cardiomyopathy is recommended from 10 to 12 years of age onward, irrespective of the affected gene. OBJECTIVES: This study sought to study the penetrance and prognosis of MYH7 variant-associated cardiomyopathies. METHODS: In this multicenter cohort study, penetrance and major cardiomyopathy-related events (MCEs) were assessed in carriers of (likely) pathogenic MYH7 variants by using Kaplan-Meier curves and log-rank tests. Prognostic factors were evaluated using Cox regression with time-dependent coefficients. RESULTS: In total, 581 subjects (30.1% index patients, 48.4% male, median age 37.0 years [IQR: 19.5-50.2 years]) were included. HCM was diagnosed in 226 subjects, NCCM in 70, and DCM in 55. Early penetrance and MCEs (age <12 years) were common among NCCM-associated variant carriers (21.2% and 12.0%, respectively) and DCM-associated variant carriers (15.3% and 10.0%, respectively), compared with HCM-associated variant carriers (2.9% and 2.1%, respectively). Penetrance was significantly increased in carriers of converter region variants (adjusted HR: 1.87; 95% CI: 1.15-3.04; P = 0.012) and at age ≤1 year in NCCM-associated or DCM-associated variant carriers (adjusted HR: 21.17; 95% CI: 4.81-93.20; P < 0.001) and subjects with a family history of early MCEs (adjusted HR: 2.45; 95% CI: 1.09-5.50; P = 0.030). The risk of MCE was increased in subjects with a family history of early MCEs (adjusted HR: 1.82; 95% CI: 1.15-2.87; P = 0.010) and at age ≤5 years in NCCM-associated or DCM-associated variant carriers (adjusted HR: 38.82; 95% CI: 5.16-291.88; P < 0.001). CONCLUSIONS: MYH7 variants can cause cardiomyopathies and MCEs at a young age. Screening at younger ages may be warranted, particularly in carriers of NCCM- or DCM-associated variants and/or with a family history of MCEs at <12 years.

A Systematic Analysis of the Clinical Outcome Associated with Multiple Reclassified Desmosomal Gene Variants in Arrhythmogenic Right Ventricular Cardiomyopathy Patients.

The presence of multiple pathogenic variants in desmosomal genes (DSC2, DSG2, DSP, JUP, and PKP2) in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC) has been linked to a severe phenotype. However, the pathogenicity of variants is reclassified frequently, which may result in a changed clinical risk prediction. Here, we present the collection, reclassification, and clinical outcome correlation for the largest series of ARVC patients carrying multiple desmosomal pathogenic variants to date (n = 331). After reclassification, only 29% of patients remained carriers of two (likely) pathogenic variants. They reached the composite endpoint (ventricular arrhythmias, heart failure, and death) significantly earlier than patients with one or no remaining reclassified variant (hazard ratios of 1.9 and 1.8, respectively). Periodic reclassification of variants contributes to more accurate risk stratification and subsequent clinical management strategy. Graphical Abstract.

MYH7 p.(Arg1712Gln) is pathogenic founder variant causing hypertrophic cardiomyopathy with overall relatively delayed onset.

INTRODUCTION: The MYH7 c.5135G > A p.(Arg1712Gln) variant has been identified in several patients worldwide and is classified as pathogenic in the ClinVar database. We aimed to delineate its associated phenotype and evaluate a potential founder effect. METHODS: We retrospectively collected clinical and genetic data of 22 probands and 74 family members from an international cohort. RESULTS: In total, 53 individuals carried the MYH7 p.(Arg1712Gln) variant, of whom 38 (72%) were diagnosed with hypertrophic cardiomyopathy (HCM). Mean age at HCM diagnosis was 48.8 years (standard deviation: 18.1; range: 8-74). The clinical presentation ranged from asymptomatic HCM to arrhythmias (atrial fibrillation and malignant ventricular arrhythmias). Aborted sudden cardiac death (SCD) leading to the diagnosis of HCM occurred in one proband at the age of 68 years, and a family history of SCD was reported by 39% (5/13) probands. Neither heart failure deaths nor heart transplants were reported. Women had a generally later-onset disease, with 14% of female carriers diagnosed with HCM at age 50 years compared with 54% of male carriers. In both sexes, the disease was fully penetrant by age 75 years. Haplotypes were reconstructed for 35 patients and showed a founder effect in a subset of patients. CONCLUSION: MYH7 p.(Arg1712Gln) is a pathogenic founder variant with a consistent HCM phenotype that may present with delayed penetrance. This suggested that clinical follow-up should be pursued after the seventh decade in healthy carriers and that longer intervals between screening may be justified in healthy women < 30 years.

Beneficial Effects of Cardiomyopathy-Associated Genetic Variants on Physical Performance: A Hypothesis-Generating Scoping Review.

BACKGROUND: Genetic variants associated with cardiomyopathies (CMPs) are prevalent in the general population. In young athletes, CMPs account for roughly a quarter of sudden cardiac death, with further unexplained clustering in specific sports. Consequently, most CMPs form a contraindication for competitive sports. We hypothesized that genetic variants might (paradoxically) improve physical performance early in life while impairing cardiac function later in life. METHODS: Systematic PubMed search was done to investigate whether genetic variants in genes associated with CMPs could be related to beneficial performance phenotypes. SUMMARY: In a limited number of studies (n = 6), 2,860 individuals/subjects with genetic variants were able to outperform those without said variants, as measured by running speed (∼38 m/min in heterozygous [HET] mice, n = 6, vs. ∼32 m/min in wild type [WT] mice, n = 7, p = 0.004) and distance (966 ± 169 km HET mice vs. 561 ± 144 km WT mice, p = 0.0035, n = 10), elite athlete status in endurance athletes (n = 1,672, p = 1.43 × 10-8), maximal oxygen uptake in elite athletes (absolute difference not provided, n = 32, p = 0.005), maximal oxygen uptake in unrelated individuals (n = 473, p = 0.0025), personal records in highly trained marathon runners (2:26:28 ± 0:06:23 min HET, n = 32, vs. 2:28:53 ± 0:05:50 min without polymorphism, n = 108, p = 0.020), and peripheral muscle force contraction in patients following a cardiac rehabilitation program (absolute values not provided, n = 260). Key Message: Beneficial effects in genetic variants associated with CMPs could hypothetically play a role in the selection of young athletes, consequently explaining the prevalence of such genetic variants in athletes and the general population.

Case series, chemotherapy-induced cardiomyopathy: mind the family history!

BACKGROUND: Cardiotoxicity presenting as cardiomyopathy is a common side effect in cancer treatment especially with anthracyclines. The role of genetic predisposition is still being investigated. CASE SUMMARY: Four unrelated patients with a familial burden for cardiac disease, who developed cardiomyopathy after anthracycline treatment are presented. Case 1 received chemotherapy for breast cancer and developed a dilated left ventricle just after treatment. Her father had died unexpectedly while being screened for heart transplant. Case 2 was known with a family history of sudden cardiac death prior to her breast cancer diagnosis. She received anthracycline-containing chemotherapy treatment twice in 5 years due to recurrence of breast cancer. During that period, two brothers developed a cardiomyopathy. Eighteen years later, a genetic predisposition for cardiomyopathy was ascertained and at screening an asymptomatic non-ischaemic cardiomyopathy was established. Case 3 was diagnosed with a dilated cardiomyopathy 1 year after chemotherapy treatment for breast cancer. Her mother had developed a dilated cardiomyopathy several years before. Case 4 received chemotherapy treatment for Non-Hodgkin's lymphoma and developed dilated cardiomyopathy 1 year later. His brother died from congestive heart failure which he developed after chemotherapy for Non-Hodgkin's lymphoma and a grandmother had died suddenly during child delivery. In all four cases, genetic screening showed (likely) pathogenic variants in cardiomyopathy-associated genes. DISCUSSION: Current guidelines recommend cardiac evaluation in cancer patients receiving chemotherapy based on the presence of cardiovascular risk factors at the start of treatment. This series emphasizes the importance of including a thorough family history in this process.

Evidence-Based Assessment of Genes in Dilated Cardiomyopathy.

BACKGROUND: Each of the cardiomyopathies, classically categorized as hypertrophic cardiomyopathy, dilated cardiomyopathy (DCM), and arrhythmogenic right ventricular cardiomyopathy, has a signature genetic theme. Hypertrophic cardiomyopathy and arrhythmogenic right ventricular cardiomyopathy are largely understood as genetic diseases of sarcomere or desmosome proteins, respectively. In contrast, >250 genes spanning >10 gene ontologies have been implicated in DCM, representing a complex and diverse genetic architecture. To clarify this, a systematic curation of evidence to establish the relationship of genes with DCM was conducted. METHODS: An international panel with clinical and scientific expertise in DCM genetics evaluated evidence supporting monogenic relationships of genes with idiopathic DCM. The panel used the Clinical Genome Resource semiquantitative gene-disease clinical validity classification framework with modifications for DCM genetics to classify genes into categories on the basis of the strength of currently available evidence. Representation of DCM genes on clinically available genetic testing panels was evaluated. RESULTS: Fifty-one genes with human genetic evidence were curated. Twelve genes (23%) from 8 gene ontologies were classified as having definitive (BAG3, DES, FLNC, LMNA, MYH7, PLN, RBM20, SCN5A, TNNC1, TNNT2, TTN) or strong (DSP) evidence. Seven genes (14%; ACTC1, ACTN2, JPH2, NEXN, TNNI3, TPM1, VCL) including 2 additional ontologies were classified as moderate evidence; these genes are likely to emerge as strong or definitive with additional evidence. Of these 19 genes, 6 were similarly classified for hypertrophic cardiomyopathy and 3 for arrhythmogenic right ventricular cardiomyopathy. Of the remaining 32 genes (63%), 25 (49%) had limited evidence, 4 (8%) were disputed, 2 (4%) had no disease relationship, and 1 (2%) was supported by animal model data only. Of the 16 evaluated clinical genetic testing panels, most definitive genes were included, but panels also included numerous genes with minimal human evidence. CONCLUSIONS: In the curation of 51 genes, 19 had high evidence (12 definitive/strong, 7 moderate). It is notable that these 19 genes explain only a minority of cases, leaving the remainder of DCM genetic architecture incompletely addressed. Clinical genetic testing panels include most high-evidence genes; however, genes lacking robust evidence are also commonly included. We recommend that high-evidence DCM genes be used for clinical practice and that caution be exercised in the interpretation of variants in variable-evidence DCM genes.

Publisher Correction: Relevance of Titin Missense and Non-Frameshifting Insertions/Deletions Variants in Dilated Cardiomyopathy.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

A mutation update for the FLNC gene in myopathies and cardiomyopathies.

Filamin C (FLNC) variants are associated with cardiac and muscular phenotypes. Originally, FLNC variants were described in myofibrillar myopathy (MFM) patients. Later, high-throughput screening in cardiomyopathy cohorts determined a prominent role for FLNC in isolated hypertrophic and dilated cardiomyopathies (HCM and DCM). FLNC variants are now among the more prevalent causes of genetic DCM. FLNC-associated DCM is associated with a malignant clinical course and a high risk of sudden cardiac death. The clinical spectrum of FLNC suggests different pathomechanisms related to variant types and their location in the gene. The appropriate functioning of FLNC is crucial for structural integrity and cell signaling of the sarcomere. The secondary protein structure of FLNC is critical to ensure this function. Truncating variants with subsequent haploinsufficiency are associated with DCM and cardiac arrhythmias. Interference with the dimerization and folding of the protein leads to aggregate formation detrimental for muscle function, as found in HCM and MFM. Variants associated with HCM are predominantly missense variants, which cluster in the ROD2 domain. This domain is important for binding to the sarcomere and to ensure appropriate cell signaling. We here review FLNC genotype-phenotype correlations based on available evidence.

Arrhythmogenic Right Ventricular Cardiomyopathy-Associated Desmosomal Variants Are Rarely De Novo.

BACKGROUND: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is associated with pathogenic/likely pathogenic (P/LP) variants in genes encoding the cardiac desmosomal proteins. Origin of these variants, including de novo mutation rate and extent of founder versus recurrent variants has implications for variant adjudication and clinical care, yet this has never been systematically investigated. METHODS: We identified arrhythmogenic right ventricular cardiomyopathy probands who met 2010 Task Force Criteria and had undergone genotyping that included sequencing of the desmosomal genes (PKP2, DSP, DSG2, DSC2, and JUP) from 3 arrhythmogenic right ventricular cardiomyopathy registries in America and Europe. We classified the desmosomal variants, defined the contribution of unique versus nonunique (ie, not family-specific) P/LP variants, and identified the frequency and characteristics of de novo variants. Next, we haplotyped nonunique variants to determine how often they likely represent a single mutation event in a common ancestor (implied by shared haplotypes) versus multiple mutation events at the same genetic location. RESULTS: Of 501 arrhythmogenic right ventricular cardiomyopathy probands, 322 (64.3%) carried 327 desmosomal P/LP variants. Most variants (n=247, 75.6%, in 245 patients) were identified in more than one proband and, therefore, considered nonunique. For 212/327 variants (64.8%) genetic cascade screening was performed extensively enough to identify the parental origin of the P/LP variant. Only 3 variants were de novo, 2 of which were whole gene deletions. For 24 nonunique P/LP PKP2 variants, haplotyping was conducted in 183 available families. For all 24 variants, multiple seemingly unrelated families sharing identical haplotypes were identified, suggesting that these variants originate from common founders. CONCLUSIONS: Most desmosomal P/LP variants are inherited, nonunique, and originate from ancient founders. Two of 3 de novo variants were large deletions. These observations inform genetic testing, cascade screening, and variant adjudication.

Dutch genome diagnostic laboratories accelerated and improved variant interpretation and increased accuracy by sharing data.

Each year diagnostic laboratories in the Netherlands profile thousands of individuals for heritable disease using next-generation sequencing (NGS). This requires pathogenicity classification of millions of DNA variants on the standard 5-tier scale. To reduce time spent on data interpretation and increase data quality and reliability, the nine Dutch labs decided to publicly share their classifications. Variant classifications of nearly 100,000 unique variants were catalogued and compared in a centralized MOLGENIS database. Variants classified by more than one center were labeled as "consensus" when classifications agreed, and shared internationally with LOVD and ClinVar. When classifications opposed (LB/B vs. LP/P), they were labeled "conflicting", while other nonconsensus observations were labeled "no consensus". We assessed our classifications using the InterVar software to compare to ACMG 2015 guidelines, showing 99.7% overall consistency with only 0.3% discrepancies. Differences in classifications between Dutch labs or between Dutch labs and ACMG were mainly present in genes with low penetrance or for late onset disorders and highlight limitations of the current 5-tier classification system. The data sharing boosted the quality of DNA diagnostics in Dutch labs, an initiative we hope will be followed internationally. Recently, a positive match with a case from outside our consortium resulted in a more definite disease diagnosis.

Mortality Risk Associated With Truncating Founder Mutations in Titin.

Background Truncating titin variants (TTNtv) are the most prevalent genetic cause of dilated cardiomyopathy, found in ≤25% of familial cases. Moreover, TTNtv associated with dilated cardiomyopathy are estimated to be present in 0.5% of the general population. The prognosis of asymptomatic carriers of TTNtv is poorly understood because TTNtv are associated with a highly variable phenotype. We aim to assess the natural history and clinical relevance of TTNtv by analyzing standardized mortality ratios (SMR) in multigenerational pedigrees and in close relatives of present-day patients. Methods Haplotype and genealogical analyses were performed on 3 recurrent TTNtv. Subsequently, the family tree mortality ratio method was used to compare all-cause mortality of subjects at an a priori 50% risk of carrying TTNtv to the general Dutch population. SMRs were stratified for sex, age, and calendar period. Subgroups were compared with Poisson regression. Similarly, SMRs were calculated in parents of 128 present-day dilated cardiomyopathy probands with TTNtv using the reverse parent-offspring method. Results The TTNtv were established as founder mutations and traced to 18th century ancestors. In 20 522 person-years, overall mortality was not significantly increased (SMR, 1.06; 95% CI, 0.95-1.18; P=0.162). However, mortality was significantly increased in subjects living after 1965 (SMR, 1.27; 95% CI, 1.04-1.53; P=0.009) and aged ≥60 years (SMR, 1.17; 95% CI, 1.01-1.35; P=0.02). The reverse parent-offspring analysis showed overall excess mortality (SMR, 1.26; 95% CI, 1.07-1.48; P=0.003), driven by subjects aged ≥60 years. Conclusions The natural history of the analyzed TTNtv shows a relatively mild disease course with significant excess mortality in elderly patients. With increasing life expectancy, TTNtv-associated morbidity and mortality will likely become more prevalent.

Relevance of Titin Missense and Non-Frameshifting Insertions/Deletions Variants in Dilated Cardiomyopathy.

Recent advancements in next generation sequencing (NGS) technology have led to the identification of the giant sarcomere gene, titin (TTN), as a major human disease gene. Truncating variants of TTN (TTNtv) especially in the A-band region account for 20% of dilated cardiomyopathy (DCM) cases. Much attention has been focused on assessment and interpretation of TTNtv in human disease; however, missense and non-frameshifting insertions/deletions (NFS-INDELs) are difficult to assess and interpret in clinical diagnostic workflow. Targeted sequencing covering all exons of TTN was performed on a cohort of 530 primary DCM patients from three cardiogenetic centres across Europe. Using stringent bioinformatic filtering, twenty-nine and two rare TTN missense and NFS-INDELs variants predicted deleterious were identified in 6.98% and 0.38% of DCM patients, respectively. However, when compared with those identified in the largest available reference population database, no significant enrichment of such variants was identified in DCM patients. Moreover, DCM patients and reference individuals had comparable frequencies of splice-region missense variants with predicted splicing alteration. DCM patients and reference populations had comparable frequencies of rare predicted deleterious TTN missense variants including splice-region missense variants suggesting that these variants are not independently causative for DCM. Hence, these variants should be classified as likely benign in the clinical diagnostic workflow, although a modifier effect cannot be excluded at this stage.

Lack of evidence for a causal role of CALR3 in monogenic cardiomyopathy.

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.

Genetics, Clinical Features, and Long-Term Outcome of Noncompaction Cardiomyopathy.

BACKGROUND: The clinical outcomes of noncompaction cardiomyopathy (NCCM) range from asymptomatic to heart failure, arrhythmias, and sudden cardiac death. Genetics play an important role in NCCM. OBJECTIVES: This study investigated the correlations among genetics, clinical features, and outcomes in adults and children diagnosed with NCCM. METHODS: A retrospective multicenter study from 4 cardiogenetic centers in the Netherlands classified 327 unrelated NCCM patients into 3 categories: 1) genetic, with a mutation in 32% (81 adults; 23 children) of patients; 2) probably genetic, familial cardiomyopathy without a mutation in 16% (45 adults; 8 children) of patients; or 3) sporadic, no family history, without mutation in 52% (149 adults; 21 children) of patients. Clinical features and major adverse cardiac events (MACE) during follow-up were compared across the children and adults. RESULTS: MYH7, MYBPC3, and TTN mutations were the most common mutations (71%) found in genetic NCCM. The risk of having reduced left ventricular (LV) systolic dysfunction was higher for genetic patients compared with the probably genetic and sporadic cases (p = 0.024), with the highest risk in patients with multiple mutations and TTN mutations. Mutations were more frequent in children (p = 0.04) and were associated with MACE (p = 0.025). Adults were more likely to have sporadic NCCM. High risk for cardiac events in children and adults was related to LV systolic dysfunction in mutation carriers, but not in sporadic cases. Patients with MYH7 mutations had low risk for MACE (p = 0.03). CONCLUSIONS: NCCM is a heterogeneous condition, and genetic stratification has a role in clinical care. Distinguishing genetic from nongenetic NCCM complements prediction of outcome and may lead to management and follow-up tailored to genetic status.

Yield and Pitfalls of Ajmaline Testing in the Evaluation of Unexplained Cardiac Arrest and Sudden Unexplained Death: Single-Center Experience With 482 Families.

OBJECTIVES: This study evaluated the yield of ajmaline testing and assessed the occurrence of confounding responses in a large cohort of families with unexplained cardiac arrest (UCA) or sudden unexplained death (SUD). BACKGROUND: Ajmaline testing to diagnose Brugada syndrome (BrS) is routinely used in the evaluation of SUD and UCA, but its yield, limitations, and appropriate dosing have not been studied in a large cohort. METHODS: We assessed ajmaline test response and genetic testing results in 637 individuals from 482 families who underwent ajmaline testing for SUD or UCA. RESULTS: Overall, 89 individuals (14%) from 88 families (18%) had a positive ajmaline test result. SCN5A mutations were identified in 9 of 86 ajmaline-positive cases (10%). SCN5A mutation carriers had positive test results at significantly lower ajmaline doses than noncarriers (0.75 [range: 0.64 to 0.98] mg/kg vs. 1.03 [range: 0.95 to 1.14] mg/kg, respectively; p < 0.01). In 7 of 88 families (8%), it was concluded that the positive ajmaline response was a confounder, either in the presence of an alternative genetic diagnosis accounting for UCA/SUD (5 cases) or noncosegregation of positive ajmaline response and arrhythmia (2 cases). The rate of confounding responses was significantly higher in positive ajmaline responses obtained at >1 mg/kg than in those obtained at ≤1 mg/kg (7 of 48 vs. 0 of 41 individuals; Fisher's exact test: p = 0.014). CONCLUSIONS: In line with previous, smaller studies, a positive ajmaline response was observed in a large proportion of UCA/SUD families. Importantly, our data emphasize the potential for confounding possibly false-positive ajmaline responses in this population, particularly at high doses, which could possibly lead to a misdiagnosis. Clinicians should consider all alternative causes in UCA/SUD and avoid ajmaline doses >1 mg/kg.

Truncating titin mutations are associated with a mild and treatable form of dilated cardiomyopathy.

AIMS: Truncating titin mutations (tTTN) occur in 25% of dilated cardiomyopathy (DCM) cases, but the phenotype and severity of disease they cause have not yet been systematically studied. We studied whether tTTN variants are associated with a clinically distinguishable form of DCM. METHODS AND RESULTS: We compared clinical data on DCM probands and relatives with a tTTN mutation (n = 45, n = 73), LMNA mutation (n = 28, n = 29), and probands who tested negative for both genes [idiopathic DCM (iDCM); n = 60]. Median follow-up was at least 2.5 years in each group. TTN subjects presented with DCM at higher age than LMNA subjects (probands 47.9 vs. 40.4 years, P = 0.004; relatives 59.8 vs. 47.0 years, P = 0.01), less often developed LVEF <35% [probands hazard ratio (HR) 0.38, P = 0.002], had higher age of death (probands 70.4 vs. 59.4 years, P < 0.001; relatives 74.1 vs. 58.4 years, P = 0.008), and had better composite outcome (malignant ventricular arrhythmia, heart transplantation, or death; probands HR 0.09, P < 0.001; relatives HR 0.21, P = 0.02) than LMNA subjects and iDCM subjects (HR 0.36, P = 0.07). An LVEF increase of at least 10% occurred in 46.9% of TTN subjects after initiation of standard heart failure treatment, while this only occurred in 6.5% of LMNA subjects (P < 0.001) and 18.5% of iDCM subjects (P = 0.02). This was confirmed in families with co-segregation, in which the 10% point LVEF increase occurred in 55.6% of subjects (P = 0.003 vs. LMNA, P = 0.079 vs. iDCM). CONCLUSIONS: This study shows that tTTN-associated DCM is less severe at presentation and more amenable to standard therapy than LMNA mutation-induced DCM or iDCM.

Best practice guidelines for the use of next-generation sequencing applications in genome diagnostics: a national collaborative study of Dutch genome diagnostic laboratories.

Next-generation sequencing (NGS) methods are being adopted by genome diagnostics laboratories worldwide. However, implementing NGS-based tests according to diagnostic standards is a challenge for individual laboratories. To facilitate the implementation of NGS in Dutch laboratories, the Dutch Society for Clinical Genetic Laboratory Diagnostics (VKGL) set up a working group in 2012. The results of their discussions are presented here. We provide best practice guidelines and criteria for implementing and validating NGS applications in a clinical setting. We introduce the concept of "diagnostic yield" as the main performance characteristic for evaluating diagnostic tests. We recommend that the laboratory procedures, including the tested genes, should be recorded in a publicly available document describing the complete "diagnostic routing." We also propose that laboratories should use a list of "core disease genes" for specific genetic diseases. This core list contains the essential genes for each disease, and they should all be included in a diagnostic test to establish a reliable and accurate molecular diagnosis. The guidelines will ensure a clear and standardized quality of care provided by genetic diagnostic laboratories. The best practice guidelines and criteria that are presented here were adopted by the VKGL in January 2013.

Targeted sequence capture and GS-FLX Titanium sequencing of 23 hypertrophic and dilated cardiomyopathy genes: implementation into diagnostics.

BACKGROUND: Genetic evaluation of cardiomyopathies poses a challenge. Multiple genes are involved but no clear genotype-phenotype correlations have been found so far. In the past, genetic evaluation for hypertrophic (HCM) and dilated (DCM) cardiomyopathies was performed by sequential screening of a very limited number of genes. Recent developments in sequencing have increased the throughput, enabling simultaneous screening of multiple genes for multiple patients in a single sequencing run. OBJECTIVE: Development and implementation of a next generation sequencing (NGS) based genetic test as replacement for Sanger sequencing. METHODS AND RESULTS: In order to increase the number of genes that can be screened in a shorter time period, we enriched all exons of 23 of the most relevant HCM and DCM related genes using on-array multiplexed sequence capture followed by massively parallel pyrosequencing on the GS-FLX Titanium. After optimisation of array based sequence capture it was feasible to reliably detect a large panel of known and unknown variants in HCM and DCM patients, whereby the unknown variants could be confirmed by Sanger sequencing. CONCLUSIONS: The rate of detection of (pathogenic) variants in both HCM and DCM patients was increased due to a larger number of genes studied. Array based target enrichment followed by NGS showed the same accuracy as Sanger sequencing. Therefore, NGS is ready for implementation in a diagnostic setting.