TBX20 loss-of-function variants in families with left ventricular non-compaction cardiomyopathy.

TBX20 encodes a cardiac transcription factor that is associated with atrial septal defects. Recent studies implicate loss-of-function TBX20 variants with left ventricular non-compaction cardiomyopathy (LVNC), although clinical and genetic data in families are limited. We report four families with TBX20 loss-of-function variants that segregate with LVNC. Genetic testing using genome or exome sequencing was performed in index cases, variants were validated with Sanger sequencing, and cascade genetic testing was performed in family members. A multi-exon deletion, small deletion, essential splice site variant and nonsense variant in TBX20 were found in four families. The index cases in two families were symptomatic children with identical congenital heart diseases and LVNC who developed different cardiomyopathy phenotypes with one developing heart failure requiring transplantation. In another family, the child index case had LVNC and congestive heart failure requiring heart transplantation. In the fourth family, the index case was a symptomatic adult with LVNC. In all families, the variants segregated in relatives with isolated LVNC, or with congenital heart disease or cardiomyopathy. Family members displayed a clinical spectrum from asymptomatic to severe presentations including heart failure. Our data strengthen TBX20 loss-of-function variants as a rare cause of LVNC and support TBX20 inclusion in genetic testing of LVNC.

Scaling national and international improvement in virtual gene panel curation via a collaborative approach to discordance resolution.

Clinical validity assessments of gene-disease associations underpin analysis and reporting in diagnostic genomics, and yet wide variability exists in practice, particularly in use of these assessments for virtual gene panel design and maintenance. Harmonization efforts are hampered by the lack of agreed terminology, agreed gene curation standards, and platforms that can be used to identify and resolve discrepancies at scale. We undertook a systematic comparison of the content of 80 virtual gene panels used in two healthcare systems by multiple diagnostic providers in the United Kingdom and Australia. The process was enabled by a shared curation platform, PanelApp, and resulted in the identification and review of 2,144 discordant gene ratings, demonstrating the utility of sharing structured gene-disease validity assessments and collaborative discordance resolution in establishing national and international consensus.

Gene selection for genomic newborn screening: Moving toward consensus?

PURPOSE: Gene selection for genomic newborn screening (gNBS) underpins the validity, acceptability, and ethical application of this technology. Existing gNBS gene lists are highly variable despite being based on shared principles of gene-disease validity, treatability, and age of onset. This study aimed to curate a gNBS gene list that builds upon existing efforts and provide a core consensus list of gene-disease pairs assessed by multiple expert groups worldwide. METHODS: Our multidisciplinary expert team curated a gene list using an open platform and multiple existing curated resources. We included severe treatable disorders with age of disease onset <5 years with established gene-disease associations and reliable variant detection. We compared the final list with published lists from 5 other gNBS projects to determine consensus genes and to identify areas of discrepancy. RESULTS: We reviewed 1279 genes and 604 met our inclusion criteria. Metabolic conditions comprised the largest group (25%), followed by immunodeficiencies (21%) and endocrine disorders (15%). We identified 55 consensus genes included by all 6 gNBS research projects. Common reasons for discrepancy included variable definitions of treatability and strength of gene-disease association. CONCLUSION: We have identified a consensus gene list for gNBS that can be used as a basis for systematic harmonization efforts internationally.

A national education program for rapid genomics in pediatric acute care: Building workforce confidence, competence, and capability.

PURPOSE: To develop and evaluate a scalable national program to build confidence, competence and capability in the use of rapid genomic testing (rGT) in the acute pediatric setting. METHODS: We used theory-informed approaches to design a modular, adaptive program of blended learning aimed at diverse professional groups involved in acute pediatric care. The program comprised 4 online learning modules and an online workshop and was centered on case-based learning. We evaluated the program using the Kirkpatrick 4-level model of training evaluation and report our findings using the Reporting Item Standards for Education and its Evaluation (RISE2) guidelines for genomics education and evaluation. RESULTS: Two hundred and two participants engaged with at least 1 component of the program. Participants self-reported increased confidence in using rGT, (P < .001), and quiz responses objectively demonstrated increased competence (eg, correct responses to a question on pretest counseling increased from 30% to 64%; P < .001). Additionally, their capability in applying genomic principles to simulated clinical cases increased (P < .001), as did their desire to take on more responsibility for performing rGT. The clinical interpretation of more complex test results (such as negative results or variants of uncertain significance) appeared to be more challenging, indicating a need for targeted education in this area. CONCLUSION: The program format was effective in delivering multidisciplinary and wide-scale genomics education in the acute care context. The modular approach we have developed now lends itself to application in other medical specialties or areas of health care.

Clinical and laboratory reporting impact of ACMG-AMP and modified ClinGen variant classification frameworks in MYH7-related cardiomyopathy.

PURPOSE: ClinGen provides gene-specific guidance for interpretation of sequence variants in MYH7. We assessed laboratory and clinical impact of reclassification by the American College of Medical Genetics and Genomics-Association for Molecular Pathology (ACMG-AMP) and ClinGen recommendations in 43 MYH7 variants reported by a diagnostic laboratory between 2013 and 2017. METHODS: Fifty-two proband reports containing MYH7 variants were reinterpreted by original ACMG-AMP and ClinGen guidelines. Evidence items were compared across schemes and reasons for classification differences recorded. Laboratory impact was assessed by number of recommended report reissues, and reclassifications coded as clinically "actionable" or "equivalent." Available pedigrees were reviewed to describe projected cascade impact. RESULTS: ClinGen produced a higher proportion of diagnostic classifications (65% of variants) compared with ACMG-AMP (54%) and fewer variants of uncertain significance (30% versus 42%). ClinGen classification resulted in actionable changes in 18% of variants with equal upgrades and downgrades from original report. ClinGen's revisions to PM1 and PS4 contributed to classification differences in 21% and 19% of variants respectively. Each classification change per proband report impacted, on average, 3.1 cascade reports with a further 6.3 first- and second-degree relatives potentially available for genotyping per family. CONCLUSION: ClinGen's gene-specific criteria provide expert-informed guidance for interpretation of MYH7 sequence variants. Periodic re-evaluation improves diagnostic confidence and should be considered by clinical and laboratory teams.

Professional regulation for Australasian genetic counselors.

As a result of the ongoing global expansion of genetic counseling, the need to formalize a system of professional regulation for genetic counselors was identified in Australasia. In June 2017, under the auspices of the Human Genetics Society of Australasia (HGSA), a working party was convened. The purpose of the working party was to provide strategic leadership for the profession of Australasian genetic counselors with a goal to formalize a national regulatory framework for genetic counselors across both Australian and New Zealand jurisdictions. This was ultimately achieved in Australia through full membership with the National Alliance of Self-Regulating Health Professions (NASRHP) while the profession of genetic counseling in New Zealand is utilizing this framework to establish their regulation pathway. Regulation has a number of implications for genetic counselors, their employers, and the wider community, with the primary purpose of regulation being protection of the public from harm. This paper details the process of formalizing self-regulation for genetic counselors in Australasia, by defining professional regulation; outlining the purpose of regulation and the status of regulation for genetic counselors in Australasia and internationally, as well as health professionals more broadly; exploring the challenges of establishing regulation in Australasia; and the next steps for regulation in Australasia. Through detailing this process, the intention is to provide a framework to support genetic counseling colleagues internationally as well as other health professions in Australasia to explore and achieve regulation through their respective jurisdiction.

Expanding the clinical and genetic spectrum of ALPK3 variants: Phenotypes identified in pediatric cardiomyopathy patients and adults with heterozygous variants.

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 adults with cardiomyopathy and may contribute to their cardiomyopathy. Adults with ALPK3 LoF variants therefore warrant evaluations for cardiomyopathy.

Genetic Testing in Inherited Heart Diseases.

Inherited heart diseases include numerous conditions, from the more prevalent hypertrophic cardiomyopathy (HCM) and familial hypercholesterolaemia (FH), to the comparatively less common inherited arrhythmia syndromes, such as long QT syndrome (LQTS), catecholaminergic polymorphic ventricular tachycardia (CPVT) and Brugada syndrome (BrS). Genetic testing has evolved rapidly over the last decade and is now considered a mainstream component of clinical management of inherited heart diseases. Cardiac manifestations can also be part of wider syndromes, and genetic testing can play a critical role in clarifying the underlying aetiological basis of disease in some cases. The greatest utility of a genetic diagnosis, however, comes from the ability to elucidate disease risk amongst asymptomatic at-risk family members. Given the nuances and challenges, cardiac genetic testing is best performed in a multidisciplinary specialised clinic with access to cardiac genetic counselling.

Readiness of clinical genetic healthcare professionals to provide genomic medicine: An Australian census.

We aimed to determine capacity and readiness of Australian clinical genetic healthcare professionals to provide genomic medicine. An online survey was administered to individuals with genetic counseling or clinical genetics qualifications in Australia. Data collected included: education, certification, continuing professional development (CPD), employment, and genetic versus genomic clinical practice. Of the estimated 630 clinical genetic healthcare professionals in Australia, 354 completed the survey (56.2% response rate). Explanatory interviews were conducted with 5.5% of the genetic counselor respondents. Those working clinically reported being involved in aspects of whole exome or genome sequencing (48.6% genetic counselors, 88.6% clinical geneticists). Most genetic counselors (74.2%) and clinical geneticists (87.0%) had attended genomics CPD in the last two years, with 61.0% and 39.1% self-funding, respectively. Genetic counselors desire broad involvement in genomics, including understanding classifying and interpreting results to better counsel patients. The majority of respondents (89.9%) were satisfied with their job and 91.6% planned to work in genetics until retirement. However, 14.1% of the genetic counselors in clinical roles and 24.6% of the clinical geneticists planned to retire within 10 years. This is the first national audit of clinical genetic healthcare professionals, revealing the Australian workforce is motivated and prepared to embrace new models to deliver genomic medicine but consideration of education and training is required to meet demand.

A novel approach to offering additional genomic findings-A protocol to test a two-step approach in the healthcare system.

Internationally, the practice of offering additional findings (AFs) when undertaking a clinically indicated genomic test differs. In the USA, the recommendation is to include analysis for AFs alongside diagnostic analysis, unless a patient opts-out, whereas European and Canadian guidelines recommend opt-in models. These guidelines all consider the offer of AFs as an activity concurrent with the offer of diagnostic testing. This paper describes a novel two-step model for managing AFs within the healthcare system in Victoria, Australia and presents the study protocol for its evaluation. Adults who have received results of diagnostic whole exome sequencing undertaken within the healthcare system are invited to attend a genetic counseling appointment to consider reanalysis of their stored genomic data for AFs. The evaluation protocol addresses uptake, decision-making, understanding, counseling challenges, and explores preferences for future models of care. Recruitment commenced in November 2017 and will cease when 200 participants have been approached. When the study is concluded, the evaluation results will contribute to the evidence base guiding approaches to counseling and models of care for AFs.

Genetic Counseling in the Era of Genomics: What's all the Fuss about?

As genomic sequencing becomes more widely available in clinical settings for diagnostic purposes, a number of genetic counseling issues are gaining precedence. The ability to manage these issues will be paramount as genetic and non-genetic healthcare professionals navigate the complexities of using genomic technologies to facilitate diagnosis and inform patient management. Counseling issues arising when counseling for diagnostic genomic sequencing were identified by four genetic counselors with 10 years of collective experience providing genetic counseling in this setting. These issues were discussed and refined at a meeting of genetic counselors working in clinical genomics settings in Melbourne, Australia. Emerging counseling issues, or variations of established counseling issues, were identified from the issues raised. Illustrative cases were selected where pre- and post-test genetic counseling was provided in clinical settings to individuals who received singleton or trio WES with targeted analysis. Counseling issues discussed in this paper include a reappraisal of how genetic counselors manage hope in the genomic era, informed consent for secondary use of genomic data, clinical reanalysis of genomic data, unexpected or unsolicited secondary findings, and trio sequencing. The authors seek to contribute to the evolving understanding of genetic counseling for diagnostic genomic sequencing through considering the applicability of existing genetic counseling competencies to managing emerging counseling issues and discussing genetic counseling practice implications.

Prospective comparison of the cost-effectiveness of clinical whole-exome sequencing with that of usual care overwhelmingly supports early use and reimbursement.

PURPOSE: To undertake the first prospective cost-effectiveness study of whole-exome sequencing (WES) as an early, routine clinical test for infants with suspected monogenic disorders. METHODS: Cost data for diagnosis-related investigations and assessments were collected for a prospective, sequential clinical cohort of infants (N = 40) who underwent singleton WES in parallel to usual diagnostic care. We determined costs per patient, costs per diagnosis, and incremental costs per additional diagnosis for three alternative strategies for integrating WES into the diagnostic trajectory. We performed a sensitivity analysis to examine the robustness of estimates and bootstrapping (500 replications) to examine their distributions. RESULTS: Standard care achieved an average cost per diagnosis of AU$27,050 (US$21,099) compared with AU$5,047 (US$3,937) for singleton WES. If WES had been performed after exhaustive standard investigation, then there would have been an incremental cost per additional diagnosis of AU$8,112 (US$ 6,327). Using WES to replace some investigations decreases this incremental cost to AU$2,622 (US$2,045), whereas using it to replace most investigations results in a savings per additional diagnosis of AU$2,182 (US$1,702). CONCLUSION: Use of WES early in the diagnostic pathway more than triples the diagnostic rate for one-third the cost per diagnosis, providing strong support for reimbursement as a clinical test.Genet Med advance online publication 26 January 2017.

ALPK3-deficient cardiomyocytes generated from patient-derived induced pluripotent stem cells and mutant human embryonic stem cells display abnormal calcium handling and establish that ALPK3 deficiency underlies familial cardiomyopathy.

AIMS: We identified a novel homozygous truncating mutation in the gene encoding alpha kinase 3 (ALPK3) in a family presenting with paediatric cardiomyopathy. A recent study identified biallelic truncating mutations of ALPK3 in three unrelated families; therefore, there is strong genetic evidence that ALPK3 mutation causes cardiomyopathy. This study aimed to clarify the mutation mechanism and investigate the molecular and cellular pathogenesis underlying ALPK3-mediated cardiomyopathy. METHODS AND RESULTS: We performed detailed clinical and genetic analyses of a consanguineous family, identifying a new ALPK3 mutation (c.3792G>A, p.W1264X) which undergoes nonsense-mediated decay in ex vivo and in vivo tissues. Ultra-structural analysis of cardiomyocytes derived from patient-specific and human ESC-derived stem cell lines lacking ALPK3 revealed disordered sarcomeres and intercalated discs. Multi-electrode array analysis and calcium imaging demonstrated an extended field potential duration and abnormal calcium handling in mutant contractile cultures. CONCLUSIONS: This study validates the genetic evidence, suggesting that mutations in ALPK3 can cause familial cardiomyopathy and demonstrates loss of function as the underlying genetic mechanism. We show that ALPK3-deficient cardiomyocytes derived from pluripotent stem cell models recapitulate the ultrastructural and electrophysiological defects observed in vivo. Analysis of differentiated contractile cultures identified abnormal calcium handling as a potential feature of cardiomyocytes lacking ALPK3, providing functional insights into the molecular mechanisms underlying ALPK3-mediated cardiomyopathy.

A prospective evaluation of whole-exome sequencing as a first-tier molecular test in infants with suspected monogenic disorders.

PURPOSE: To prospectively evaluate the diagnostic and clinical utility of singleton whole-exome sequencing (WES) as a first-tier test in infants with suspected monogenic disease. METHODS: Singleton WES was performed as a first-tier sequencing test in infants recruited from a single pediatric tertiary center. This occurred in parallel with standard investigations, including single- or multigene panel sequencing when clinically indicated. The diagnosis rate, clinical utility, and impact on management of singleton WES were evaluated. RESULTS: Of 80 enrolled infants, 46 received a molecular genetic diagnosis through singleton WES (57.5%) compared with 11 (13.75%) who underwent standard investigations in the same patient group. Clinical management changed following exome diagnosis in 15 of 46 diagnosed participants (32.6%). Twelve relatives received a genetic diagnosis following cascade testing, and 28 couples were identified as being at high risk of recurrence in future pregnancies. CONCLUSIONS: This prospective study provides strong evidence for increased diagnostic and clinical utility of singleton WES as a first-tier sequencing test for infants with a suspected monogenic disorder. Singleton WES outperformed standard care in terms of diagnosis rate and the benefits of a diagnosis, namely, impact on management of the child and clarification of reproductive risks for the extended family in a timely manner.Genet Med 18 11, 1090-1096.

Diffuse Ventricular Fibrosis on Cardiac Magnetic Resonance Imaging Associates With Ventricular Tachycardia in Patients With Hypertrophic Cardiomyopathy.

INTRODUCTION: Non-sustained ventricular tachycardia (NSVT) is a risk factor for sudden cardiac death (SCD) in patients with hypertrophic cardiomyopathy (HCM). We aimed to assess whether diffuse ventricular fibrosis on cardiac magnetic resonance (CMR) imaging could be a surrogate marker for ventricular arrhythmias in patients with HCM. METHODS: A total of 100 patients with HCM (mean age 51 ± 13 years, septal wall thickness 20 ± 5 mm) underwent CMR with a 1.5 T scanner to determine the presence of ventricular late gadolinium enhancement (LGE) for focal fibrosis, and post-contrast T1 mapping for diffuse ventricular fibrosis. The presence of NSVT was determined by Holter monitoring and a subset of high risk patients received an implantable cardioverter-defibrillator (ICD). RESULTS: NSVT was detected in 23 of 100 patients with HCM. Focal ventricular fibrosis (by LGE) was observed in 87%, with no significant difference between patients with (96%) or without NSVT (86%, P = 0.19). However, LGE mass was greater in patients with (16.5 ± 19.1 g) versus without NSVT (7.6 ± 10.2 g, P < 0.01). NSVT was associated with a significant reduction in ventricular T1 relaxation time (422 ± 54 milliseconds) versus patients without NSVT (512 ± 115 milliseconds; P < 0.001). There was significant reduction in ventricular T1 relaxation time in patients with (430 ± 48 milliseconds) versus without aborted SCD (495 ± 113 milliseconds; P = 0.01) over a mean follow-up of 40 ± 10 months. On multivariate analysis post-contrast ventricular T1 relaxation time and septal wall thickness were the only predictors of NSVT. CONCLUSION: Post-contrast T1 relaxation time on CMR is associated with ventricular arrhythmias in patients with HCM. Diffuse ventricular fibrosis may be an important marker of arrhythmic risk in patients with HCM.

The Cardiac Genetics Clinic: a model for multidisciplinary genomic medicine.

OBJECTIVES: To describe patient characteristics, standard operating procedure, and uptake of genetic testing at the multidisciplinary Cardiac Genetics Clinic (CGC) at the Royal Melbourne Hospital during its first 6 years. DESIGN: Database exploration of referral diagnoses, sex, number of clinic visits and incidence of genetic testing in a population of individuals attending the CGC. SETTING: Tertiary referral hospital (Royal Melbourne Hospital) providing cardiac genetics services to the state of Victoria. PARTICIPANTS: All individuals initially attending the clinic between July 2007 and July 2013, either as the proband or as an at-risk family member. MAIN OUTCOME MEASURES: Classification of patients into diagnostic categories, number of probands and at-risk relatives assessed, incidence and outcomes of genetic testing. RESULTS: 1170 individuals were seen for the first time over the 6-year period; 57.5% made only one visit. The median age was 39 years. Most were encompassed within four broad diagnostic categories: cardiomyopathy (315 patients), aortopathy (303 patients), arrhythmia disorders (203 patients) and resuscitated cardiac arrest and/or family history of sudden cardiac death (341 patients); eight patients had "other" diagnoses. Genetic testing (mutation detection or predictive testing) was undertaken in 381 individuals (32.6%), and a pathogenic mutation was identified in 47.6% of tests, representing 15.3% of the total population. CONCLUSION: The CGC fulfils an important role in assisting clinicians and patients by reviewing genetic cardiac diagnoses. Clinical practice during the study period moved from a selected candidate gene approach to broader gene panel-based testing. This move to next-generation sequencing may increase the detection of mutations and variants of unknown significance. A major contribution by the clinic to the care of these individuals and their families is the provision (or negating) of a diagnosis, and of a plan for managing risks of predictable cardiac disease.

Genetic Counseling for Indigenous Australians: an Exploratory Study from the Perspective of Genetic Health Professionals.

Indigenous populations are thought to have particularly low levels of access to genetic health services, and cultural issues may be a contributing factor. This article presents the findings of the first study of genetic health service provision to Indigenous Australians. This qualitative study aimed to identify elements of culturally-competent genetic health service provision in Indigenous Australian contexts. Twelve semi-structured interviews were conducted with genetic counselors and clinical geneticists from around Australia who had delivered services to Indigenous Australians. Participants were asked to describe their experiences and identify any collective cultural needs of Indigenous clients, as well as comment on specific training and resources they had received or used. Interviews were audio-recorded and transcribed with thematic analysis conducted on the data. The findings show that participants were reluctant to generalize the needs of Indigenous peoples. Some participants asserted that Indigenous peoples have needs that differ from the general population, while others felt that there were no collective cultural needs, instead advocating an individualized approach. Being flexible and practical, taking time to build rapport, recognizing different family structures and decision-making processes, as well as socio-economic disadvantage were all identified as important factors in participants' interactions with Indigenous clients. Indigenous support workers and hospital liaison officers were seen as valuable resources for effective service provision. The implications of this study for training and practice are discussed.

Ethical dilemmas associated with genetic testing: which are most commonly seen and how are they managed?

PURPOSE: The aim of this study was to document the range and frequency of ethical dilemmas associated with genetic testing encountered by genetic health professionals and to determine the strategies used to manage them. METHODS: An online survey was used to document how often the 11 key ethical dilemmas have been encountered; whether any additional dilemmas have been encountered; and how these dilemmas have been managed. Members of the Australasian Association of Clinical Geneticists, Australasian Society of Genetic Counsellors, and genetic social workers practicing in Australia and New Zealand were invited to participate. RESULTS: A total of 102 responses were received (31% response rate). Respondents had encountered all of the 11 ethical dilemmas included in the survey, and 18 respondents had encountered 14 additional dilemmas. Respondents encountered an average of 2.2 dilemmas per year of practice. Peer and clinical supervision were the most common strategies used to manage dilemmas, and seeking advice from clinical ethics committees was rare. Occasionally, respondents facilitated practices they deemed unethical as a consequence of client deception. CONCLUSION: Ethical dilemmas of genetic testing are encountered regularly in clinical genetics practice. Evidence provided by our study can assist in targeting training, support, and guidance to help genetic health professionals navigate such dilemmas in the future.

Clinical predictors of genetic testing outcomes in hypertrophic cardiomyopathy.

PURPOSE: Genetic testing for hypertrophic cardiomyopathy has been commercially available for almost a decade; however, low mutation detection rate and cost have hindered uptake. This study sought to identify clinical variables that can predict probands with hypertrophic cardiomyopathy in whom a pathogenic mutation will be identified. METHODS: Probands attending specialized cardiac genetic clinics across Australia over a 10-year period (2002-2011), who met clinical diagnostic criteria for hypertrophic cardiomyopathy and who underwent genetic testing for hypertrophic cardiomyopathy were included. Clinical, family history, and genotype information were collected. RESULTS: A total of 265 unrelated individuals with hypertrophic cardiomyopathy were included, with 138 (52%) having at least one mutation identified. The mutation detection rate was significantly higher in the probands with hypertrophic cardiomyopathy with an established family history of disease (72 vs. 29%, P < 0.0001), and a positive family history of sudden cardiac death further increased the detection rate (89 vs. 59%, P < 0.0001). Multivariate analysis identified female gender, increased left-ventricular wall thickness, family history of hypertrophic cardiomyopathy, and family history of sudden cardiac death as being associated with greatest chance of identifying a gene mutation. Multiple mutation carriers (n = 16, 6%) were more likely to have suffered an out-of-hospital cardiac arrest or sudden cardiac death (31 vs. 7%, P = 0.012). CONCLUSION: Family history is a key clinical predictor of a positive genetic diagnosis and has direct clinical relevance, particularly in the pretest genetic counseling setting.

The burden of splice-disrupting variants in inherited heart disease and unexplained sudden cardiac death.

There is an incomplete understanding of the burden of splice-disrupting variants in definitively associated inherited heart disease genes and whether these genes can amplify from blood RNA to support functional confirmation of splicing outcomes. We performed burden testing of rare splice-disrupting variants in people with inherited heart disease and sudden unexplained death compared to 125,748 population controls. ClinGen definitively disease-associated inherited heart disease genes were amplified using RNA extracted from fresh blood, derived cardiomyocytes, and myectomy tissue. Variants were functionally assessed and classified for pathogenicity. We found 88 in silico-predicted splice-disrupting variants in 128 out of 1242 (10.3%) unrelated participants. There was an excess burden of splice-disrupting variants in PKP2 (5.9%), FLNC (2.7%), TTN (2.8%), MYBPC3 (8.2%) and MYH7 (1.3%), in distinct cardiomyopathy subtypes, and KCNQ1 (3.6%) in long QT syndrome. Blood RNA supported the amplification of 21 out of 31 definitive disease-associated inherited heart disease genes. Our functional studies confirmed altered splicing in six variants. Eleven variants of uncertain significance were reclassified as likely pathogenic based on functional studies and six were used for cascade genetic testing in 12 family members. Our study highlights that splice-disrupting variants are a significant cause of inherited heart disease, and that analysis of blood RNA confirms splicing outcomes and supports variant pathogenicity classification.