Proposed diagnostic criteria for arrhythmogenic cardiomyopathy: European Task Force consensus report

Arrhythmogenic cardiomyopathy (ACM) is a heart muscle disease characterized by prominent "non-ischemic" myocardial scarring predisposing to ventricular electrical instability. Diagnostic criteria for the original phenotype, arrhythmogenic right ventricular cardiomyopathy (ARVC), were first proposed in 1994 and revised in 2010 by an international Task Force (TF). A 2019 International Expert report appraised these previous criteria, finding good accuracy for diagnosis of ARVC but a lack of sensitivity for identification of the expanding phenotypic disease spectrum, which includes left-sided variants, i.e., biventricular (ABVC) and arrhythmogenic left ventricular cardiomyopathy (ALVC). The ARVC phenotype together with these left-sided variants are now more appropriately named ACM. The lack of diagnostic criteria for the left ventricular (LV) phenotype has resulted in clinical under-recognition of ACM patients over the 4 decades since the disease discovery. In 2020, the "Padua criteria" were proposed for both right- and left-sided ACM phenotypes. The presently proposed criteria represent a refinement of the 2020 Padua criteria and have been developed by an expert European TF to improve the diagnosis of ACM with upgraded and internationally recognized criteria. The growing recognition of the diagnostic role of CMR has led to the incorporation of myocardial tissue characterization findings for detection of myocardial scar using the late‑gadolinium enhancement (LGE) technique to more fully characterize right, biventricular and left disease variants, whether genetic or acquired (phenocopies), and to exclude other "non-scarring" myocardial disease. The "ring-like' pattern of myocardial LGE/scar is now a recognized diagnostic hallmark of ALVC. Additional diagnostic criteria regarding LV depolarization and repolarization ECG abnormalities and ventricular arrhythmias of LV origin are also provided. These proposed upgrading of diagnostic criteria represents a working framework to improve management of ACM patients.

A gain-of-function HCN4 mutant in the HCN domain is responsible for inappropriate sinus tachycardia in a Spanish family

In a family with inappropriate sinus tachycardia (IST), we identified a mutation (p.V240M) of the hyperpolarization-activated cyclic nucleotide-gated type 4 (HCN4) channel, which contributes to the pacemaker current (If) in human sinoatrial node cells. Here, we clinically study fifteen family members and functionally analyze the p.V240M variant. Macroscopic (IHCN4) and single-channel currents were recorded using patch-clamp in cells expressing human native (WT) and/or p.V240M HCN4 channels. All p.V240M mutation carriers exhibited IST that was accompanied by cardiomyopathy in adults. IHCN4 generated by p.V240M channels either alone or in combination with WT was significantly greater than that generated by WT channels alone. The variant, which lies in the N-terminal HCN domain, increased the single-channel conductance and opening frequency and probability of HCN4 channels. Conversely, it did not modify the channel sensitivity for cAMP and ivabradine or the level of expression at the membrane. Treatment with ivabradine based on functional data reversed the IST and the cardiomyopathy of the carriers. In computer simulations, the p.V240M gain-of-function variant increases If and beating rate and thus explains the IST of the carriers. The results demonstrate the importance of the unique HCN domain in HCN4, which stabilizes the channels in the closed state.

Risks of Ventricular Arrhythmia and Heart Failure in Carriers of RBM20 Variants

BACKGROUND

Variants in RBM20 are reported in 2% to 6% of familial cases of dilated cardiomyopathy and may be associated with fatal ventricular arrhythmia and rapid heart failure progression. We sought to determine the risk of adverse events in RBM20 variant carriers and the impact of sex on outcomes.

METHODS

Consecutive probands and relatives carrying RBM20 variants were retrospectively recruited from 12 cardiomyopathy units. The primary end point was a composite of malignant ventricular arrhythmia (MVA) and end-stage heart failure (ESHF). MVA and ESHF end points were also analyzed separately and men and women compared. Left ventricular ejection fraction (LVEF) contemporary to MVA was examined. RBM20 variant carriers with left ventricular systolic dysfunction (RBM20LVSD) were compared with variant-elusive patients with idiopathic left ventricular systolic dysfunction.

RESULTS

Longitudinal follow-up data were available for 143 RBM20 variant carriers (71 men; median age, 35.5 years); 7 of 143 had an MVA event at baseline. Thirty of 136 without baseline MVA (22.0%) reached the primary end point, and 16 of 136 (11.8%) had new MVA with no significant difference between men and women (log-rank P=0.07 and P=0.98, respectively). Twenty of 143 (14.0%) developed ESHF (17 men and 3 women; log-rank P<0.001). Four of 10 variant carriers with available LVEF contemporary to MVA had an LVEF >35%. At 5 years, 15 of 67 (22.4%) RBM20LVSD versus 7 of 197 (3.6%) patients with idiopathic left ventricular systolic dysfunction had reached the primary end point (log-rank P<0.001). RBM20 variant carriage conferred a 6.0-fold increase in risk of the primary end point.

CONCLUSIONS

RBM20 variants are associated with a high risk of MVA and ESHF compared with idiopathic left ventricular systolic dysfunction. The risk of MVA in male and female RBM20 variant carriers is similar, but male sex is strongly associated with ESHF.

A cost-effectiveness analysis of hypertrophic cardiomyopathy sudden cardiac death risk algorithms for implantable cardioverter defibrillator decision-making

AIMS

To conduct a contemporary cost-effectiveness analysis examining the use of implantable cardioverter defibrillators (ICD) for primary prevention in patients with hypertrophic cardiomyopathy (HCM).

METHODS

A discrete-time Markov model was used to determine the cost-effectiveness of different ICD decision-making rules for implantation. Several scenarios were investigated including the reference scenario of implantation rates according to observed real world practice. A 12-year time horizon with an annual cycle length was used. Transition probabilities used in the model were obtained using Bayesian analysis. The study has been reported according to the Consolidated Health Economic Evaluation Reporting Standards (CHEERS) checklist.

RESULTS

Using a 5-year SCD risk threshold of 6% was cheaper than current practice and has marginally better total quality adjusted life years (QALYs). This is the most cost-effective of the options considered, with an incremental cost effectiveness ratio of £834 per QALY. Sensitivity analyses highlighted that this decision is largely driven by what health related quality of life (HRQL) is attributed to ICD patients and time horizon.

CONCLUSION

We present a timely new perspective on HCM ICD cost-effectiveness, using methods reflecting real-world practice. While we have shown that a 6% 5-year SCD risk cut-off provides the best cohort stratification to aid ICD decision-making, this will also be influenced by the particular values of costs and HRQL for subgroups or at a local level. The process of explicitly demonstrating the main factors which drive conclusions from such an analysis will help to inform shared decision-making in this complex area for all stakeholders concerned.

iPSC-Based Modeling of Variable Clinical Presentation in Hypertrophic Cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiac disease and a frequent cause of heart failure and sudden cardiac death. Our understanding of the genetic bases and pathogenic mechanisms underlying HCM has improved significantly in the recent past, but the combined effect of various pathogenic gene variants and the influence of genetic modifiers in disease manifestation are very poorly understood. Here, we set out to investigate genotype-phenotype relationships in 2 siblings with an extensive family history of HCM, both carrying a pathogenic truncating variant in the MYBPC3 gene (p.Lys600Asnfs*2), but who exhibited highly divergent clinical manifestations.

METHODS

We used a combination of induced pluripotent stem cell (iPSC)-based disease modeling and CRISPR (clustered regularly interspersed short palindromic repeats)/Cas9 (CRISPR-associated protein 9)-mediated genome editing to generate patient-specific cardiomyocytes (iPSC-CMs) and isogenic controls lacking the pathogenic MYBPC3 variant.

RESULTS

Mutant iPSC-CMs developed impaired mitochondrial bioenergetics, which was dependent on the presence of the mutation. Moreover, we could detect altered excitation-contraction coupling in iPSC-CMs from the severely affected individual. The pathogenic MYBPC3 variant was found to be necessary, but not sufficient, to induce iPSC-CM hyperexcitability, suggesting the presence of additional genetic modifiers. Whole-exome sequencing of the mutant carriers identified a variant of unknown significance in the MYH7 gene (p.Ile1927Phe) uniquely present in the individual with severe HCM. We finally assessed the pathogenicity of this variant of unknown significance by functionally evaluating iPSC-CMs after editing the variant.

CONCLUSIONS

Our results indicate that the p.Ile1927Phe variant of unknown significance in MYH7 can be considered as a modifier of HCM expressivity when found in combination with truncating variants in MYBPC3. Overall, our studies show that iPSC-based modeling of clinically discordant subjects provides a unique platform to functionally assess the effect of genetic modifiers.

A Human Hereditary Cardiomyopathy Shares a Genetic Substrate With Bicuspid Aortic Valve

BACKGROUND

The complex genetics underlying human cardiac disease is evidenced by its heterogenous manifestation, multigenic basis, and sporadic occurrence. These features have hampered disease modeling and mechanistic understanding. Here, we show that 2 structural cardiac diseases, left ventricular noncompaction (LVNC) and bicuspid aortic valve, can be caused by a set of inherited heterozygous gene mutations affecting the NOTCH ligand regulator MIB1 (MINDBOMB1) and cosegregating genes.

METHODS

We used CRISPR-Cas9 gene editing to generate mice harboring a nonsense or a missense MIB1 mutation that are both found in LVNC families. We also generated mice separately carrying these MIB1 mutations plus 5 additional cosegregating variants in the ASXL3, APCDD1, TMX3, CEP192, and BCL7A genes identified in these LVNC families by whole exome sequencing. Histological, developmental, and functional analyses of these mouse models were carried out by echocardiography and cardiac magnetic resonance imaging, together with gene expression profiling by RNA sequencing of both selected engineered mouse models and human induced pluripotent stem cell-derived cardiomyocytes. Potential biochemical interactions were assayed in vitro by coimmunoprecipitation and Western blot.

RESULTS

Mice homozygous for the MIB1 nonsense mutation did not survive, and the mutation caused LVNC only in heteroallelic combination with a conditional allele inactivated in the myocardium. The heterozygous MIB1 missense allele leads to bicuspid aortic valve in a NOTCH-sensitized genetic background. These data suggest that development of LVNC is influenced by genetic modifiers present in affected families, whereas valve defects are highly sensitive to NOTCH haploinsufficiency. Whole exome sequencing of LVNC families revealed single-nucleotide gene variants of ASXL3, APCDD1, TMX3, CEP192, and BCL7A cosegregating with the MIB1 mutations and LVNC. In experiments with mice harboring the orthologous variants on the corresponding Mib1 backgrounds, triple heterozygous Mib1 Apcdd1 Asxl3 mice showed LVNC, whereas quadruple heterozygous Mib1 Cep192 Tmx3;Bcl7a mice developed bicuspid aortic valve and other valve-associated defects. Biochemical analysis suggested interactions between CEP192, BCL7A, and NOTCH. Gene expression profiling of mutant mouse hearts and human induced pluripotent stem cell-derived cardiomyocytes revealed increased cardiomyocyte proliferation and defective morphological and metabolic maturation.

CONCLUSIONS

These findings reveal a shared genetic substrate underlying LVNC and bicuspid aortic valve in which MIB1-NOTCH variants plays a crucial role in heterozygous combination with cosegregating genetic modifiers.

Impact of SARS-Cov-2 infection in patients with hypertrophic cardiomyopathy: results of an international multicentre registry

AIMS

To describe the natural history of SARS-CoV-2 infection in patients with hypertrophic cardiomyopathy (HCM) compared with a control group and to identify predictors of adverse events.

METHODS AND RESULTS

Three hundred and five patients [age 56.6 ± 16.9 years old, 191 (62.6%) male patients] with HCM and SARS-Cov-2 infection were enrolled. The control group consisted of 91 131 infected individuals. Endpoints were (i) SARS-CoV-2 related mortality and (ii) severe clinical course [death or intensive care unit (ICU) admission]. New onset of atrial fibrillation, ventricular arrhythmias, shock, stroke, and cardiac arrest were also recorded. Sixty-nine (22.9%) HCM patients were hospitalized for non-ICU level care, and 21 (7.0%) required ICU care. Seventeen (5.6%) died: eight (2.6%) of respiratory failure, four (1.3%) of heart failure, two (0.7%) suddenly, and three (1.0%) due to other SARS-CoV-2-related complications. Covariates associated with mortality in the multivariable were age {odds ratio (OR) per 10 year increase 2.25 [95% confidence interval (CI): 1.12-4.51], P = 0.0229}, baseline New York Heart Association class [OR per one-unit increase 4.01 (95%CI: 1.75-9.20), P = 0.0011], presence of left ventricular outflow tract obstruction [OR 5.59 (95%CI: 1.16-26.92), P = 0.0317], and left ventricular systolic impairment [OR 7.72 (95%CI: 1.20-49.79), P = 0.0316]. Controlling for age and sex and comparing HCM patients with a community-based SARS-CoV-2 cohort, the presence of HCM was associated with a borderline significant increased risk of mortality OR 1.70 (95%CI: 0.98-2.91, P = 0.0600).

CONCLUSIONS

Over one-fourth of HCM patients infected with SARS-Cov-2 required hospitalization, including 6% in an ICU setting. Age and cardiac features related to HCM, including baseline functional class, left ventricular outflow tract obstruction, and systolic impairment, conveyed increased risk of mortality.

Identification of an elusive spliceogenic MYBPC3 variant in an otherwise genotype-negative hypertrophic cardiomyopathy pedigree

The finding of a genotype-negative hypertrophic cardiomyopathy (HCM) pedigree with several affected members indicating a familial origin of the disease has driven this study to discover causative gene variants. Genetic testing of the proband and subsequent family screening revealed the presence of a rare variant in the MYBPC3 gene, c.3331−26T>G in intron 30, with evidence supporting cosegregation with the disease in the family. An analysis of potential splice-altering activity using several splicing algorithms consistently yielded low scores. Minigene expression analysis at the mRNA and protein levels revealed that c.3331−26T>G is a spliceogenic variant with major splice-altering activity leading to undetectable levels of properly spliced transcripts or the corresponding protein. Minigene and patient mRNA analyses indicated that this variant induces complete and partial retention of intron 30, which was expected to lead to haploinsufficiency in carrier patients. As most spliceogenic MYBPC3 variants, c.3331−26T>G appears to be non-recurrent, since it was identified in only two additional unrelated probands in our large HCM cohort. In fact, the frequency analysis of 46 known splice-altering MYBPC3 intronic nucleotide substitutions in our HCM cohort revealed 9 recurrent and 16 non-recurrent variants present in a few probands (≤ 4), while 21 were not detected. The identification of non-recurrent elusive MYBPC3 spliceogenic variants that escape detection by in silico algorithms represents a challenge for genetic diagnosis of HCM and contributes to solving a fraction of genotype-negative HCM cases.

Outcomes of Patients With Catecholaminergic Polymorphic Ventricular Tachycardia Treated With β-Blockers

Importance

Patients with catecholaminergic polymorphic ventricular tachycardia (CPVT) may experience life-threatening arrhythmic events (LTAEs) despite β-blocker treatment. Further complicating management, the role of implantable cardioverter defibrillator (ICD) in CPVT is debated.

Objective

To investigate the long-term outcomes of patients with RYR2 CPVT treated with β-blockers only and the cost to benefit ratio of ICD.

Design, Settings, and Participants

This prospective cohort study conducted from January 1988 to October 2020 with a mean (SD) follow-up of 9.4 (7.5) years included patients who were referred to the Molecular Cardiology Clinics of ICS Maugeri Hospital, Pavia, Italy. Participants included consecutive patients with CPVT who were carriers of a pathogenic or likely pathogenic RYR2 variant with long-term clinical follow-up.

Exposures

Treatment with selective and nonselective β-blocker only and ICD implant when indicated.

Main Outcome and Measures

The main outcome was the occurrence of the first LTAE while taking a β-blocker. LTAE was defined as a composite of 3 hard end points: sudden cardiac death, aborted cardiac arrest, and hemodynamically nontolerated ventricular tachycardia.

Results

The cohort included 216 patients with RYR2 CPVT (121 of 216 female [55%], median [IQR] age 14, [9-30] years). During a mean (SD) follow-up of 9.4 (7.5) years taking β-blockers only, 28 of 216 patients (13%) experienced an LTAE (annual rate, 1.9%; 95% CI, 1.3-2.7). In multivariable analysis, experiencing either an LTAE (hazard ratio [HR], 3.3; 95% CI, 1.2-8.9; P = .02) or syncope before diagnosis (HR, 4.5; 95% CI, 1.8-11.1; P = .001) and carrying a C-terminal domain variant (HR, 18.1; 95% CI, 4.1-80.8; P < .001) were associated with an increased LTAE risk during β-blocker therapy only. The risk of LTAE among those taking selective β-blockers vs nadolol was increased 6-fold (HR, 5.8; 95% CI, 2.1-16.3; P = .001). Conversely, no significant difference was present between propranolol and nadolol (HR, 1.8; 95% CI, 0.4-7.3; P = .44). An ICD was implanted in 79 of 216 patients (37%) who were followed up for a mean (SD) of 8.6 (6.3) years. At the occurrence of LTAE, ICD carriers were more likely to survive (18 of 18 [100%]) than non-ICD carriers (6 of 10 [60%]; P = .01).

Conclusions and Relevance

In this cohort study, selective β-blockers were associated with a higher risk of LTAE as compared with nadolol. Independently from treatment, LTAE and syncope before diagnosis and C-terminal domain variants identified patients at higher risk of β-blocker failure, and the ICD was associated with reduced mortality in high-risk patients with CPVT.

Association between common cardiovascular risk factors and clinical phenotype in patients with hypertrophic cardiomyopathy from the European Society of Cardiology (ESC) EurObservational Research Programme (EORP) Cardiomyopathy/Myocarditis registry

AIMS

The interaction between common cardiovascular risk factors (CVRF) and hypertrophic cardiomyopathy (HCM) is poorly studied. We sought to explore the relation between CVRF and the clinical characteristics of patients with HCM enrolled in the EURObservational Research Programme (EORP) Cardiomyopathy registry.

METHODS AND RESULTS

1739 patients with HCM were studied. The relation between hypertension (HT), diabetes (DM), body mass index (BMI), and clinical traits was analysed. Analyses were stratified according to the presence or absence of a pathogenic variant in a sarcomere gene. The prevalence of HT, DM, and obesity (Ob) was 37, 10, and 21%, respectively. HT, DM, and Ob were associated with older age (P<0.001), less family history of HCM (HT and DM P<0.001), higher New York Heart Association (NYHA) class (P<0.001), atrial fibrillation (HT and DM P<0.001; Ob p = 0.03) and LV (left ventricular) diastolic dysfunction (HT and Ob P<0.001; DM P = 0.003). Stroke was more frequent in HT (P<0.001) and mutation-positive patients with DM (P = 0.02). HT and Ob were associated with higher provocable LV outflow tract gradients (HT P<0.001, Ob P = 0.036). LV hypertrophy was more severe in Ob (P = 0.018). HT and Ob were independently associated with NYHA class (OR 1.419, P = 0.017 and OR 1.584, P = 0.004, respectively). Other associations, including a higher proportion of females in HT and of systolic dysfunction in HT and Ob, were observed only in mutation-positive patients.

CONCLUSION

Common CVRF are associated with a more severe HCM phenotype, suggesting a proactive management of CVRF should be promoted. An interaction between genotype and CVRF was observed for some traits.

A novel Troponin I mutation associated with severe restrictive cardiomyopathy-a case report of a 27-year-old woman with fatigue

BACKGROUND

Restrictive cardiomyopathy is rare and heterogeneous in origin, clinical manifestation, and prognosis. Familial forms have, amongst others, been associated with mutations in the TNNI3 gene. We present a case of familial restrictive cardiomyopathy associated with a novel TNNI3 mutation including longitudinal follow-up.

CASE SUMMARY

A 27-year-old woman was evaluated for fatigue in the context of a family history of sudden cardiac death. Echocardiography was normal except for mild left atrial dilatation. Focused genetic screening, limited to the most common genes associated with cardiomyopathy, was unremarkable in 2006. In biopsy, mild inflammatory cardiomyopathy was diagnosed, and the patient was discharged. Thirteen years later, rapid clinical deterioration occurred in the context of new-onset atrial fibrillation (AF). Echocardiography now showed gross bi-atrial dilatation and evidence of diastolic dysfunction. Based on haemodynamic tracings during angiography, a diagnosis of restrictive cardiomyopathy was made. In 2018, next-generation sequencing revealed the hitherto undescribed Troponin I variant Lys193Glu in a functionally critical domain. Haemodynamic stabilization was achieved by pulmonary vein isolation. Until now, the patient remains symptom free under diuretic treatment.

DISCUSSION

Diagnosis of restrictive cardiomyopathy is complicated by often oligosymptomatic early presentation and a diverse clinical picture. Thorough medical and family history and early invasive haemodynamic tracing are indispensable in diagnosis. Therapy-refractory AF should raise suspicion. Reporting of longitudinal follow-up cases is essential to better understand the early symptoms, development, and prognosis of this rare disease. Broad genetic testing in unclear cases has become more available and affordable and should be considered early in the diagnostic workflow.

Subclinical Hypertrophic Cardiomyopathy in Elite Athletes: Knowledge Gaps Persist

Subclinical hypertrophic cardiomyopathy (HCM) is a phenotypic entity that has emerged from the increased use of cardiovascular magnetic resonance imaging in the evaluation and family screening of patients with HCM. We describe the case of a competitive athlete with a sarcomere gene mutation and family history of HCM who was found to exhibit the subclinical HCM phenotype on cardiovascular magnetic resonance imaging in the absence of left ventricular hypertrophy. We discuss the clinical uncertainties in her management. (Level of Difficulty: Advanced.).

Yield from family screening in a national adolescent cardiac screening program

Introduction

Cascade family screening in patients with confirmed or suspected inherited cardiac disorders is now well established. This may refute or confirm a familial clinical diagnosis and is particularly relevant in young adolescent individuals as it may be too early to manifest a distinct phenotype.

Objectives

A large cohort of 2708 adolescents aged 14–16 years gave consent to participate in a national cardiac screening program (BEAT-IT). Individuals with suspected inherited cardiac disorders were extensively evaluated. Their relatives were also invited to undergo screening. This study reports the yield of this family cardiac screening program.

Methodology

Family members of probands with suspected or confirmed inherited cardiac conditions were offered cardiac screening. A standard clinical screening protocol for all first-degree family members included a resting 12-lead ECG and echocardiogram. Those with a channelopathy suspicion also underwent postural ECGs and exercise testing. Screening second-degree relatives was also performed in a cascade fashion when clinically indicated. Relatives with a normal baseline screen were offered surveillance if younger than 25 years or a proband clinical diagnosis. Those with an abnormal ECG and/or echocardiogram were referred for further evaluation.

Results

17 probands (63% females) were suspected of harbouring inherited heart disease. Another 2 were diagnosed with a clinical phenotype. The mean age was 15.3±0.58 years. All were Caucasian.

77 family members underwent cardiac screening, with a mean age of 42.5±16.43 at first evaluation. The majority were female (n=44, 57.1%). 12 (15.6%) had an abnormal ECG. 6 (7.8%) had an abnormal echocardiogram, with 2 (2.6%) consistent with cardiomyopathy. 8 (10.4%) were diagnosed with an inherited cardiac condition (n=2 HCM, n=1 DCM, n=5 LQTS). Another 7 (9.1%) are under surveillance because of a pathological ECG in the absence of a clinical phenotype.

The highest clinical yield was in the Long QT group (n=5, 55.6%). Family members (n=25) referred because of proband lateral TWI were the second most likely to require clinical follow-up because of a pathological ECG or a clinical diagnosis (n=7, 28.0%). Relatives referred because of isolated anterior TWI on the proband's ECG had the lowest diagnostic yield (n=17, 0%). After excluding families of probands with isolated anterior TWI (n=18), the overall clinical yield increased to 13.6%. Another 11.9% are under surveillance because of a pathological ECG.

Conclusion

The yield of family screening as part of a national cardiac screening program was 10.4%. This increases to 13.6% when excluding probands with anterior TWI, with 11.9% under surveillance because of a pathological ECG. To our knowledge, this is the first such study of its kind.

Funding Acknowledgement

Type of funding sources: Public hospital(s). Main funding source(s): Beating Hearts MaltaResearch, Innovation and Development Trust (University of Malta)

Genetic variants as determinants of outcome in lamin A/C-related cardiac disease

Background

Current guidelines for the diagnosis and management of familial dilated cardiomyopathy highlight the variables “male sex” and “non-missense type variants” as risk factors for malignant ventricular arrhythmias.

Objective

Quantitative evaluation of prognostic differences between different LMNA variants associated with cardio-laminopathy.

Method

Analysis of cardiac event-free survival (sudden death, major arrhythmic events, death from heart failure and transplantation) with Kaplan-Meier approach in relation to gender & variant LMNA type. The data come from a specific database containing information on more than 1200 carriers of disease-causing LMNA variants. In the first analysis, the groups of comparison were truncating-type variants (LMNAtv) VS the global of pathogenic missense variants in the gene associated with cardiolaminopathy (LMNAm), segregated by gender. In the second analysis, it was considered missense LMNA affecting different residues (p.Arg190, p.Arg377 and p.Arg541), located in different functional domains, with enough data for comparison and with statistically different clinical behavior from that of global pathogenic variants in the gene. They were compared with the group of LMNAtv variants, as reference. The variants included were p.Arg377Cys/His, p.Arg541Cys/Ser/Gly/Pro/His and p.Arg190Trp/Gln/Pro, all of them pathogenic and associated with cardio-laminopathy.

Results

No significant differences were observed in survival between LMNAtv versus LMNAm variants (log rank=0.56) with slightly worse outcomes in males (log rank 0.03). Median survival time was 56 years for men compared to 60 years for women with LMNAtv, and 55 years compared to 66 years, respectively, among carriers of LMNAm (analysis A). In analysis B, statistically significant differences were observed between the groups considered (Log Rank p&lt;0.001). These differences were also clinically relevant (median survival time in groups p.Arg377, LMNAtv, p.Arg190 and p.Arg541 was 60, 58, 50 and 35 years, respectively). Importantly, more than 70% of the cardiac events observed were related to major ventricular arrhythmic episodes.

Conclusions

This quantitative analysis demonstrates that certain missense variants in LMNA may have a similar and even more adverse clinical course than the set of truncation-type variants. These findings highlight the relevance of the specific variant rather than the variant type in guiding actionable therapies to prevent adverse outcomes. Regarding the differences observed between genders, even though they are statistically significant, their magnitude could be clinically not relevant.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Health in Code

Alpha-protein kinase 3 (ALPK3) truncating variants cause an autosomal dominant form of hypertrophic cardiomyopathy

Background

More than half of hypertrophic cardiomyopathy (HCM) remains genetically unsolved. ALPK3 truncating variants (ALPK3tv) have been described as a cause of autosomal recessive cardiomyopathy in a small number of paediatric cases, but the pathogenicity in heterozygosity as a possible cause of autosomal dominant HCM is unknown.

Aims

To determine the frequency of heterozygous ALPK3tv in patients with HCM and to confirm their pathogenicity by means of burden testing in independent cohorts, family co-segregation studies, and functional analysis of an allelic series of ALPK3tv using human embryonic stem cell-cardiomyocytes (hESC-CM). Phenotype was compared with a cohort of 1679 genotyped HCM patients.

Methods and results

In a discovery cohort of 770 index patients with HCM, 12 (1.56%) were heterozygous for ALPK3tv, odds ratio (OR) 16.01 (95% confidence interval (95% CI): 7.89 to 29.74, p&lt;8.36e-11), compared to the Genome Aggregation Database (gnomAD) population. In a validation cohort of 2047 HCM probands, 32 (1.56%) carried heterozygous ALPK3tv, OR 16.17 (95% CI: 10.31 to 24.87; p&lt;2.2e-16, compared to gnomAD). Combined logarithm of odds score in 7 families with ALPK3tv was 2.99. In comparison with a large cohort of genotyped HCM patients, the phenotype of 51 HCM patients with ALPK3tv (probands and relatives) was characterised by a higher prevalence of apical/concentric patterns of hypertrophy (60%) compared to both sarcomere-positives or negatives (p&lt;0.001 overall), with the age at diagnosis (56±16ys) and maximum wall thickness (18±4mm) similar to sarcomere-negatives and LV systolic impairment at baseline (6%) and non-sustained ventricular tachycardia (31%) similar to sarcomere-positives. Short PR (10%, p=0.009 overall) and extensive fibrosis&gt;15% of LV segments (49%) were distinctive features. During follow-up (5.3±5.7 years), 4 (9%) patients died of heart failure or had cardiac transplantation (p=0.012 vs sarcomere-negatives and p=0.425 vs sarcomere-positives). Analysis of hESC-CM showed that ALPK3 heterozygotes had phenotypic characteristics of HCM, including increased contractile force and delayed membrane repolarization.

Conclusions

Heterozygous ALPK3tv are pathogenic and segregate with a characteristic HCM phenotype.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): MRC UK, UCLH BRC

Specific actin (ACTC1) missense variants are associated with different overlapping clinical phenotypes and outcomes

Introduction

Pathogenic variants in ACTC1 have been associated with hypertrophic (HCM), dilated (DCM), and left ventricular non-compaction (LVNC) cardiomyopathies. Phenotypes often overlap and atrial septal defects have also been reported. Prognostic data on carriers of these variants are scarce.

Methods and results

The proprietary database of a cardiovascular genetic laboratory was examined to assess penetrance and survival in the 438 carriers (191 families) of 75 missense variants in ACTC1 associated with disease. Their mean age at diagnosis was 32.4 (±18.7) years; 52% were male. The diagnosis was isolated HCM in 47%, LVNC in 17%, and DCM in 9%. LVNC with either HCM or DCM was present in an additional 8%; 13% had an atrial septal defect. Among carriers with echocardiographic information, left ventricular dilatation and dysfunction were described in 13% and 16%, respectively. Ventricular arrhythmias and conduction defects were reported in 94 and 93 carriers. Percentages have not been calculated for the latter, as we cannot ensure a denominator in whom cardiac conduction defects and arrhythmias were certainly discarded.

Overall, 50% of carriers were diagnosed by age 45, and 10% had experienced a major cardiac event. The p.Leu10Met and p.His90Tyr variants (23% of all carriers) demonstrated lower penetrance and a better prognosis than the p.Glu101Lys variant and the other missense variants.

Conclusions

Missense variants in ACTC1 are associated with a range of phenotypes that often overlap. Overall, penetrance and outcomes are age-dependent with a moderate rate of major cardiac events, which are highly dependent on the specific disease-causing variant

Funding Acknowledgement

Type of funding sources: None. Figure 1. The graph shows the percentage of carriers of pathogenic or likely pathogenic missense variants in the ACTC1 gene diagnosed at different ages. Considering all the missense variants in ACTC (in red), 50% of carriers had been diagnosed by age 45. It is worth highlighting the percentage of diagnosis (&gt;15%) in the first 15 years of life, which is higher than the figure usually observed in sarcomeric hypertrophic cardiomyopathy.Figure 2. The graph shows the survival free of major cardiovascular events (sudden, heart failure, stroke-related death, appropriate ICD therapy and heart transplant) in individuals with missense variants in ACTC1. Carriers and affected relatives without genetic study were included. Events were infrequent in two of the most informative variants (p.Leu10Met and p.His90Tyr), and significantly different compared with carriers of the other missense variants (p=0.036 for p.Leu10Met and p=0.015 for p.His90Tyr).

Narrowing of the neonatal region in the FBN1 gene

Background

Neonatal Marfan syndrome (MFS) is considered the most severe form of MFS and is characterized by early childhood death due to congestive heart failure. It has been suggested that genetic variants associated with this clinical presentation, cluster in a specific region between exons 24 and 32. It has been reported that patients carrying genetic variants in these exons have worse prognosis.

Purpose

Our purpose was to analyze cardiovascular outcome by location of the genetic variants in the “neonatal region” of the FBN1 gene.

Materials and methods

We analyzed clinical data on 1353 carriers and affected relatives with 683 missense pathogenic or likely pathogenic genetic variants of FBN1 gene (including cases identified in our laboratory and cases described in the literature) in whom age at last follow-up was available. Kaplan-Meier survival curves were generated to examine location of the genetic variant in the FBN1 gene in relation to survival free of surgical intervention or cardiovascular (CV) death (composite of deaths related to aortic dissection, heart failure/transplant, sudden, stroke or CV surgery).

Missense genetic variants were classified as located in the “neonatal region” (residues 952–1363, corresponding to exons 24–32) and in the “non-neonatal region” (residues 45–951 and 1364–2731). In the “neonatal region”, we have also analyzed a sub-region of “over-representation” of heart failure deaths in the first year of life, which we called “critical neonatal region” (amino acids 1028–1088, corresponding to exon 25 and few residues from exon 26) in comparison to the “non-critical neonatal region”.

Results

Data were examined on 1060 patients with missense variants located in the “non neonatal region” and on 293 patients with missense variants located in the “neonatal region”. Of these, 96 patients were carriers of missense variants in the “critical neonatal region”, the rest of patients carried variants in the neonatal region, outside this particular domain (“non-critical neonatal region”).

Patients carrying missense variants in the neonatal region had worse prognosis than those carrying variants outside this region. This poorer outcome was due to events occurring in patients carrying variants in the “critical neonatal region” (see Figure). These patients had the worse prognosis (p=0.000108, vs. the other groups). Furthermore, events in the non-critical neonatal region were similar to other missense variants located outside the neonatal region.

There were no differences in the “neonatal region” when analyzing by gender.

Conclusion

In our cohort, the worse prognosis seen in patients carrying missense pathogenic or likely pathogenic variants in the “neonatal region” compared to the “non-neonatal region”, was due to events in patients carrying missense variants in a small subregion which we called the “critical-neonatal region” (exons 25 and 26). These patients had the worse prognosis, irrespective of gender.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Health in Code Figure 1. Neonatal region FBN1

Molecular characterization of a cohort of individuals referred to genetic testing with suspected CPVT

Background

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is one of the most lethal inherited arrhythmogenic diseases and it mainly affects the young, in the absence of structural heart disease. This condition is difficult to diagnose and the first expression of disease can be an arrhythmic death. In the last years, genetic testing has become a useful tool in the challenging task of CPVT diagnosis.

The diagnostic yield of the genetic study is highly variable and dependent on the phenotypic characteristics of the individuals evaluated.

Purpose

This study aimed to address the clinical characteristics and genetic testing (GT) results in a cohort of individuals referred to genetic analysis with a non-definitive diagnosis of CPVT, in a real world-setting.

Methods

This is a retrospective cohort study of patients referred for GT with clinical suspicion of CPVT, but who did not strictly meet the diagnostic criteria for this disease (according to current guidelines). NGS genotyping was performed with a library of 251 genes. NGS-based genomic testing was performed with classification of identified variants according to American College of Medical Genetics and Genomics guidelines.

Results

One hundred and sixteen unrelated patients with available clinical information (patients' characteristics are summarized in TABLE1) were included in the analysis. Mean age at GT was 36 y/o (±19), 47% were women and 18% had a familial history of sudden cardiac death.

The first clinical manifestation was: exercise or stress induced syncope in 36%, exercise induced ventricular tachycardia in 30% and sudden cardiac arrest in 15.5% (78% during emotional or physical stress - 89% aborted sudden death). Mean age at sudden death was 20 y/o (±14).

GT was positive in 49.1% (n=57), negative in 37.9% (n=44) and inconclusive in 12.9% (n=15). We had identified pathogenic/likely pathogenic variants in CPVT-related genes in 40% of the referred patients: RYR2 (70.2%-n: 40), KCNJ2 (8.8%-n: 5), CASQ2 in homozygous/compound heterozygous carriers (3.5%-n: 2). In the RYR2 gene we detected 36 different genetic variants (13 were novel) in 40 different individuals. In addition, relevant variants were also identified in other genes associated with channelopathies (SCN5A, 3.5%, n: 2 and KCNQ1, 1.7%, n: 1) and in genes associated with structural heart disease: desmosomal genes (6.8%-DSP n: 1 and PKP2 n: 3) and sarcomeric genes (5.1%- MYBPC3 and MYH7) (figure 1A-B).

Conclusions

In our cohort of patients with non-definitive diagnosis of CPVT, the diagnostic yield of genetic testing was almost 50%. GT allowed confirmation of the suspicion of CPVT in 40% of the patients and, in addition, we were able to detect relevant genetic variants in other genes not associated with CPVT in 10% (differential diagnosis). The use of wide genetic panels would be useful in this context.

Funding Acknowledgement

Type of funding sources: None. Suspected CPVT. Genetic Testing.

Marfan syndrome: genetic variant determinants of cardiovascular outcomes

Background

Marfan syndrome is a systemic connective tissue disorder caused by genetic variants in the fibrillin-1 (FBN1) gene. Cardiovascular complications are the leading cause of mortality.

Purpose

To compare cardiovascular outcome by gender and by type of the genetic variant in the FBN1 gene.

Materials and methods

We analyzed clinical data on 1956 carriers and affected relatives with 1430 pathogenic or likely pathogenic genetic variants in the FBN1 gene (including cases identified in our laboratory and cases described in the literature) in whom age at last follow-up was available. We excluded patients with pathogenic or likely pathogenic genetic variants located in the so-called “neonatal region” (exon 24–32); they are recognized to have an early onset/severe phenotype.

Kaplan-Meier survival curves were generated to examine gender and type of genetic variant in relation to survival free of surgical intervention or cardiovascular (CV) death (composite of deaths related to aortic dissection, heart failure/transplant, sudden, stroke or CV surgery). Genetic variants were classified as truncating (nonsense, frameshift and splicing), “missense non-neonatal” and only those missense eliminating a Cysteine residue in the non-neonatal region (“Cys non-neonatal”).

Results

Data were examined on 896 patients with truncating variants (53% male; 47% female) and 1060 with missense variants, located outside the “neonatal region” (54% male; 46% female). Of these, 475 were missense variants substituting a cysteine residue (52% male; 48% female).

Those with truncating variants had worse prognosis versus those with missense and Cys variants (p=0.000108 and p=0.000115), with earlier onset of cardiovascular events. Overall, patients with missense variants had similar prognosis to those with missense variants eliminating a Cysteine residue. By age 65, however, almost 50% of patients with any type of variant had suffered a CV event, and with each variant type males had worse prognosis (see Figure 1). This was most evident in males aged 30 to 50 with missense variants that substituted a Cysteine residue, while female carriers of these variants had a prognosis similar to other missense variants (see Figure 2).

During the first decade carriers of missense and truncating variants mainly died of heart failure. From age 10 to 50, aortic dissection was the most common event, while later other events became more frequent, e.g. vascular intervention and sudden death.

Conclusion

In our cohort, male carriers of pathogenic or likely pathogenic variants had worse prognosis versus females. Carriers of truncating variants had the worst CV outcomes. However, it is noteworthy that by age 65, regardless of gender or mutation type, close to 50% of patients had experienced a major CV event/death.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Health in Code Figure 2. Type by gender

Alpha-protein kinase 3 (ALPK3) truncating variants are a cause of autosomal dominant hypertrophic cardiomyopathy

AIMS

The aim of this study was to determine the frequency of heterozygous truncating ALPK3 variants (ALPK3tv) in patients with hypertrophic cardiomyopathy (HCM) and confirm their pathogenicity using burden testing in independent cohorts and family co-segregation studies.

METHODS AND RESULTS

In a discovery cohort of 770 index patients with HCM, 12 (1.56%) were heterozygous for ALPK3tv [odds ratio(OR) 16.11, 95% confidence interval (CI) 7.94-30.02, P = 8.05e-11] compared to the Genome Aggregation Database (gnomAD) population. In a validation cohort of 2047 HCM probands, 32 (1.56%) carried heterozygous ALPK3tv (OR 16.17, 95% CI 10.31-24.87, P < 2.2e-16, compared to gnomAD). Combined logarithm of odds score in seven families with ALPK3tv was 2.99. In comparison with a cohort of genotyped patients with HCM (n = 1679) with and without pathogenic sarcomere gene variants (SP+ and SP-), ALPK3tv carriers had a higher prevalence of apical/concentric patterns of hypertrophy (60%, P < 0.001) and of a short PR interval (10%, P = 0.009). Age at diagnosis and maximum left ventricular wall thickness were similar to SP- and left ventricular systolic impairment (6%) and non-sustained ventricular tachycardia (31%) at baseline similar to SP+. After 5.3 ± 5.7 years, 4 (9%) patients with ALPK3tv died of heart failure or had cardiac transplantation (log-rank P = 0.012 vs. SP- and P = 0.425 vs. SP+). Imaging and histopathology showed extensive myocardial fibrosis and myocyte vacuolation.

CONCLUSIONS

Heterozygous ALPK3tv are pathogenic and segregate with a characteristic HCM phenotype.

Protein haploinsufficiency drivers identify MYBPC3 variants that cause hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiac disease. Variants in MYBPC3, the gene encoding cardiac myosin-binding protein C (cMyBP-C), are the leading cause of HCM. However, the pathogenicity status of hundreds of MYBPC3 variants found in patients remains unknown, as a consequence of our incomplete understanding of the pathomechanisms triggered by HCM-causing variants. Here, we examined 44 nontruncating MYBPC3 variants that we classified as HCM-linked or nonpathogenic according to cosegregation and population genetics criteria. We found that around half of the HCM-linked variants showed alterations in RNA splicing or protein stability, both of which can lead to cMyBP-C haploinsufficiency. These protein haploinsufficiency drivers associated with HCM pathogenicity with 100% and 94% specificity, respectively. Furthermore, we uncovered that 11% of nontruncating MYBPC3 variants currently classified as of uncertain significance in ClinVar induced one of these molecular phenotypes. Our strategy, which can be applied to other conditions induced by protein loss of function, supports the idea that cMyBP-C haploinsufficiency is a fundamental pathomechanism in HCM.

Nanomechanical Phenotypes in Cardiac Myosin-Binding Protein C Mutants That Cause Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a disease of the myocardium caused by mutations in sarcomeric proteins with mechanical roles, such as the molecular motor myosin. Around half of the HCM-causing genetic variants target contraction modulator cardiac myosin-binding protein C (cMyBP-C), although the underlying pathogenic mechanisms remain unclear since many of these mutations cause no alterations in protein structure and stability. As an alternative pathomechanism, here we have examined whether pathogenic mutations perturb the nanomechanics of cMyBP-C, which would compromise its modulatory mechanical tethers across sliding actomyosin filaments. Using single-molecule atomic force spectroscopy, we have quantified mechanical folding and unfolding transitions in cMyBP-C domains targeted by HCM mutations that do not induce RNA splicing alterations or protein thermodynamic destabilization. Our results show that domains containing mutation R495W are mechanically weaker than wild-type at forces below 40 pN and that R502Q mutant domains fold faster than wild-type. None of these alterations are found in control, nonpathogenic variants, suggesting that nanomechanical phenotypes induced by pathogenic cMyBP-C mutations contribute to HCM development. We propose that mutation-induced nanomechanical alterations may be common in mechanical proteins involved in human pathologies.

Prognostic implications of troponin T variations in inherited cardiomyopathies using systems biology

The cardiac troponin T variations have often been used as an example of the application of clinical genotyping for prognostication and risk stratification measures for the management of patients with a family history of sudden cardiac death or familial cardiomyopathy. Given the disparity in patient outcomes and therapy options, we investigated the impact of variations on the intermolecular interactions across the thin filament complex as an example of an unbiased systems biology method to better define clinical prognosis to aid future management options. We present a novel unbiased dynamic model to define and analyse the functional, structural and physico-chemical consequences of genetic variations among the troponins. This was subsequently integrated with clinical data from accessible global multi-centre systematic reviews of familial cardiomyopathy cases from 106 articles of the literature: 136 disease-causing variations pertaining to 981 global clinical cases. Troponin T variations showed distinct pathogenic hotspots for dilated and hypertrophic cardiomyopathies; considering the causes of cardiovascular death separately, there was a worse survival in terms of sudden cardiac death for patients with a variation at regions 90–129 and 130–179 when compared to amino acids 1–89 and 200–288. Our data support variations among 90–130 as being a hotspot for sudden cardiac death and the region 131–179 for heart failure death/transplantation outcomes wherein the most common phenotype was dilated cardiomyopathy. Survival analysis into regions of high risk (regions 90–129 and 130–180) and low risk (regions 1–89 and 200–288) was significant for sudden cardiac death (p = 0.011) and for heart failure death/transplant (p = 0.028). Our integrative genomic, structural, model from genotype to clinical data integration has implications for enhancing clinical genomics methodologies to improve risk stratification.

Mortality Among Referral Patients With Hypertrophic Cardiomyopathy vs the General European Population

Importance

It is unclear whether hypertrophic cardiomyopathy (HCM) conveys excess mortality when compared with the general population.

Objective

To compare the survival of patients with HCM with that of the general European population.

Design, Setting, and Participants

Retrospective cohort study of 4893 consecutive adult patients with HCM presenting at 7 European referral centers between 1980 and 2013. The data were analyzed between April 2018 and August 2019.

Main Outcomes and Measures

Survival was compared using standardized mortality ratios (SMRs) calculated with data from Eurostat, stratified by study period, country, sex, and age, and using a composite end point in the HCM cohort of all-cause mortality, aborted sudden cardiac death, and heart transplant.

Results

Of 4893 patients with HCM, 3126 (63.9%) were male, and the mean (SD) age at presentation was 49.2 (16.4) years. During a median follow-up of 6.2 years (interquartile range, 3.1-9.8 years), 721 patients (14.7%) reached the composite end point. Compared with the general population, patients with HCM had excess mortality throughout the age spectrum (SMR, 2.0, 95% CI, 1.48-2.63). Excess mortality was highest among patients presenting prior to the year 2000 but persisted in the cohort presenting between 2006 and 2013 (SMR, 1.84; 95% CI, 1.55-2.18). Women had higher excess mortality than men (SMR, 2.66; 95% CI, 2.38-2.97; vs SMR, 1.68; 95% CI, 1.52-1.85; P < .001).

Conclusions and Relevance

Among patients referred to European specialty centers, HCM was associated with significant excess mortality through the life course. Although there have been improvements in survival with time, potentially reflecting improved treatments for HCM, these findings highlight the need for more research into the causes of excess mortality among patients with HCM and for better risk stratification.

Value of a comprehensive exercise echocardiography assessment for patients with hypertrophic cardiomyopathy

BACKGROUND

Exercise echocardiography (ExE) may assess left ventricular (LV) systolic and diastolic function, LV outflow tract (LVOT) obstruction, and mitral regurgitation (MR). We aimed to evaluate the prognostic value of these assessments during exercise in patients with hypertrophic cardiomyopathy (HCM).

METHODS

LV systolic function, LV-derived filling pressures, LVOT gradients, and MR were prospectively evaluated during treadmill ExE in 285 patients with HCM and preserved LV ejection fraction (EF) (≥50%). Recordings were obtained at rest and peak exercise for LV systolic function and at rest and post-exercise for LVOT gradients, MR, and ratio of early LV inflow velocity to early tissue Doppler annulus velocity (E/e´).

RESULTS

Thirty-seven patients (13%) had LVOT obstruction at rest, and 76 (27%) developed exercise-induced LVOT obstruction. New wall motion abnormalities were detected in 38 patients (13%). E/e´>14 was observed in 129 patients at rest (45%) and in 134 at post-exercise (47%). Corresponding figures for significant MR (moderate or severe) were 21 (7%) and 17 (6%). During follow-up (3.9 ± 2.5 years), 27 patients had a hard event, 39 a combined event (hard plus new atrial fibrillation or syncope), and 58 a combined event or intervention. Exercise electrocardiographic testing, exercise LVEF, and the combination of positive ExE and increased E/e´ with exercise predicted outcome. The worst event rate corresponded to patients with raised E/e' values at post-exercise and positive ExE (annualized hard event-rate of 5.9%).

CONCLUSIONS

A comprehensive assessment during ExE is feasible for patients with HCM and preserved LV systolic function, and provides significant incremental prognostic information.

Clinical Profile of Cardiac Involvement in Danon Disease: A Multicenter European Registry

BACKGROUND

The X-linked Danon disease manifests by severe cardiomyopathy, myopathy, and neuropsychiatric problems. We designed this registry to generate a comprehensive picture of clinical presentations and outcome of patients with Danon disease in cardiomyopathy centers throughout Europe.

METHODS

Clinical and genetic data were collected in 16 cardiology centers from 8 European countries.

RESULTS

The cohort comprised 30 male and 27 female patients. The age at diagnosis was birth to 42 years in men and 2 to 65 in women. Cardiac involvement was observed in 96%. Extracardiac manifestations were prominent in men but not in women. Left ventricular (LV) hypertrophy was reported in 73% of male and 74% of female patients. LV systolic dysfunction was reported in 40% of men (who had LV ejection fraction, 34±11%) and 59% of women (LV ejection fraction, 28±13%). The risk of arrhythmia and heart failure was comparable among sexes. The age of first heart failure hospitalization was lower in men (18±6 versus 28±17 years; P<0.003). Heart failure was the leading cause of death (10 of 17; 59%), and LV systolic dysfunction predicted an adverse outcome. Eight men and 8 women (28%) underwent heart transplantation or received an LV assist device. Our cohort suggests better prognosis of female compared with male heart transplant recipients.

CONCLUSIONS

Danon disease presents earlier in men than in women and runs a malignant course in both sexes, due to cardiac complications. Cardiomyopathy features, heart failure and arrhythmia, are similar among the sexes. Clinical diagnosis and management is extremely challenging in women due to phenotypic diversity and the absence of extracardiac manifestations.

Prognostic value of reduced heart rate reserve during exercise stress-echocardiography in hypertrophic cardiomyopathy

Background

Heart rate reserve (HRR) during exercise evaluates chronotropic incompetence and is a prognostically important marker of cardiac autonomic dysfunction, additive to regional wall motion abnormalities (RWMA) in patients with coronary artery disease.

Objectives

To assess determinants and prognostic value of HRR in patients with hypertrophic cardiomyopathy (HCM).

Methods

From 1998 to 2019, we enrolled 774 HCM patients (age = 48.8±15.9 years, 410 men) with exercise stress echocardiography (ESE) in 10 certified centres of the international stress echo network. During ESE we assessed: left ventricular outflow tract obstruction (LVOTO, significant when &gt;50 mmHg); RWMA; HRR (peak/ rest heart rate), 344 in beta-blockers therapy (44.4%). Patients were followed for a median 49 months (IQ range, 25–78 months). The study end-point was all-cause mortality.

Results

During ESE, we observed stress-induced RWMA in 42 (5.4%) and LVOTO in 248 (33%); HRR was 1.92.±0.41. There were no difference in patients with normal and abnormal HRR with and without beta-blockers therapy (147, 41.1% vs 211, 58.9%, p=0.079). During follow-up, 43 deaths occurred. Beta blockers therapy in univariate analysis did not have prognostic role (HR 1.105, 95% CI 0.602–2.028, p=0.768). The lowest HRR quartile (≤1.62) had a 10-fold higher 6-year death rate (10.9%) than the highest quartile (&gt;2.16, 1.04%): see figure. At multivariable analysis, lowest HRR quartile (HR 2.074, 95% CI 1.082–6.773, p=0.034), age (HR 1.045, 95% CI 1.014–1.077, p=0.004), maximal wall thickness (HR 1.137, 95% CI 1.054–1.226, p=0.001), stress-induced RWMA s(HR 4.289, 95% CI 1.733–10.615, p=0.002) and ≥ moderate mitral regurgitation at rest (HR 3.127, 95% CI 1.507–6.488, p=0.002) predicted death.

Conclusions

A blunted HRR during ESE predicts adverse outcome independent of inducible RWMA in HCM patients. Autonomic dysfunction deserves consideration as a potential therapeutic target in this disease.

Figure 1

Funding Acknowledgement

Type of funding source: None

Gender variability in the clinical phenotype of hypertrophic cardiomyopathy

Introduction

Hypertrophic cardiomyopathy (HCM) is a structural heart disease defined by an increase in left-ventricular (LV) wall thickness, that may be complicated with a clinical syndrome of heart failure, arrhythmia and death.

Purpose

To characterize the clinically significant factors for female HCM patients and bring forward the awareness to gender-based differences in HCM.

Methods

We reviewed the patient records of 1297 patients age ≥18 years, diagnosed with HCM, from two tertiary medical centers in Spain and Israel, and analyzed 748 male and female patients matched for age ≥60 years at admission, BMI, hypertension, diabetes and obstructive HCM.

Results

Female patients were older at original diagnosis [median 54 years (38–66) vs. 50 years (35–60), p=0.007], and had higher rates of family history of both HCM (46% vs. 37%, p=0.01) and sudden cardiac death (23% vs. 15%, p=0.02). Female patients had lower rates of active smoking (11% vs. 25%, p&lt;0.001) and coronary disease (3% vs. 8%, p=0.007). In echocardiographic studies, females had a smaller LV cavity both during diastole [median 42mm (39–46) vs. 46 (42–50), p&lt;0.001] and during systole [median 24 (21–29) vs. 27 (23–31), p&lt;0.001]. Female patients had higher rates of significant mitral insufficiency (37% vs. 19%, p&lt;0.001), and despite no significant differences in the rates of obstructive HCM, diastolic dysfunction, left-atrial enlargement, atrial fibrillation, ventricular tachyarrhythmia or pulmonary disease, they also had more significant pulmonary hypertension (≥45mmHg, 29% vs. 14%, p&lt;0.001). Women had a lower functional capacity (p&lt;0.001 for differences in NYHA, see fig.), and lower exercise capacity [median 7.0 METs (5–10) vs. 10.0 (7–12), p&lt;0.001) and more abnormal blood pressure response to exercise (35% vs. 26%, p=0.03). Electrocardiographic features were similar across genders, except for a non-clinically significant shorter QRS duration in females. No significant differences were seen in 5-year mortality follow-up, which was ∼3% in the entire cohort.

Conclusions

Female patients suffering from HCM have a clinical phenotype defined by slightly later presentation (and shorter time until admission to a tertiary-center cardiomyopathy clinic), smaller LV cavity size, higher severity of mitral insufficiency and pulmonary hypertension and worse functional and exercise capacities. Genders did not differ in 5-year mortality, which was relatively low.

Functional and exercise capacity

Funding Acknowledgement

Type of funding source: None

Genotype/Phenotype correlation and prognosis for undescribed ACTC1 missense variants

Purpose

Establish the genotype/phenotype correlation for missense undescribed variants in ACTC1, and evaluate their prognostic implications.

Methods

A systematic screening for the ACTC1 gene was performed using NGS in 17,683 individuals with inherited cardiovascular disease, 6,984 of them with hypertrophic cardiomyopathy, 3,507 with dilated cardiomyopathy, and 760 left ventricular non-compaction. These phenotypes were clinically diagnosed by each center prior to the genetic study. Frequency of the variants was compared with gene gnomAD and ClinVar databases. A systematic review of the literature was performed to search for previously reported variants.

We evaluated available follow up data and constructed Kaplan-Meier survival curves free from cardiovascular death (sudden death, Heart transplant, heart failure death, appropriate ICD discharge and stroke related death). Log-rank test was used to compare event-free survival time between males and females.

Results

39 missense variants were identified in 283 carriers (125 index cases; 158 first-degree relatives). Twenty-two have not been previously described or identified in public databases. 17 have been reported in gnomAD or Clinvar. Carriers phenotypes were: 120 HCM; 43 LVNC; 16 DCM; three had cardiac septal defect and two had sudden death. Some of the carriers had overlapped or combined phenotypes: 7 HCM and LVNC, 7 septal defects and LVNC, 3 HCM and septal defects, 4 MCD and LVNC. 24 were healthy carriers, and we have no phenotypic data of the remaining individuals. Family studies were performed in 12 families out of the 22 undescribed variants, showing cosegregation in 8 variants. One case was “de novo”.

Interestingly, a rare variant, previously identified as VUS in ClinVar, showed a clearly cosegregation with HCM. The Leu10Met variant with a frequency of 9/282084 alleles in gnomAD (1/15671 individuals) was identified in 20 index cases, which represents 1/884 of all the genotyped (0.11%), and 1/387 patients with HCM (0.35%). We found it in 2/9289 patients with other phenotypes (p&lt;0.001).

51 patients (18%) presented an event during follow up. In several cases, carriers developed early atrial fibrillation.

The survival curve shows adverse events from the first decade of life, with a 10% cumulative rate of events at age 40, 80% survival at age 60, and a 60% survival at age 70. No significant differences in the incidence of cardiovascular death between men and women were observed.

Conclusion

HCM is the most frequent phenotype in carriers of ACTC1 variants, followed by LVNC, and DCM. Septal defects are not rare, and they are usually described in combination with cardiomyopathies.

Disease course seems to have a good prognosis. Sudden death is an exception at early ages and appears to be associated with severe morphological expression.

Given the presence of cosegregation with disease in rare variants, many of the ACTC1 variants may have an incomplete penetrance, and late disease expression.

ACTC1

Funding Acknowledgement

Type of funding source: Private company. Main funding source(s): Health in Code

Novel Filamin C missense mutation associated with severe restrictive cardiomyopathy overlapping with left ventricular non-compaction

Introduction

Filamin C gene (FLNC) missense mutations have been previously reported in association with restrictive cardiomyopathy (RCM). The association of FLNC missense variants with non-compaction cardiomyopathy has been reported only in a single proband, but familiar or functional evidence on its causative effect is limited. Overlapping traits among cardiomyopathies related to the same genetic substrate is an emerging and a challenging scenario nowadays.

Purpose

To report a new pathogenic FLNC missense variant in association with a particular form of restrictive/non-compaction overlapping cardiomyopathy.

Methods

The probands fulfill the diagnostic criteria for RCM based on current guidelines. Genetic testing in the probands was performed by NGS, using a broad gene panel (containing over 240 genes). Clinical and genetic cascade screening were expanded to first-degree relatives when it was possible. All mutation carriers underwent clinical assessment including physical examination, 12-lead ECG, echocardiography, cardiac magnetic resonance (MRI), 24h Holter monitoring, and ergometry. None of them had major systemic illnesses nor clinical symptoms of muscular involvement.

Results

The p.Gly2011Arg variant in the FLNC gene was the only relevant variant in the three probands. This variant is virtually absent in the general population (gnomAD). The variant showed a de novo presentation in the first family and segregated with the phenotype in the four studied relatives from the second family (three affected carriers and one unaffected non-carrier). In the third case no familial information was available. This variant affects an ultraconserved residue and is located in a relevant sub-region of Filamin-C, which is necessary for its interaction with other Z-disc proteins. Detailed clinical information is available on all carriers (n=5, 1 male). The average age at diagnosis is 17 years [1–36]. An abnormal ECG was the earliest clinical manifestation (left ventricular hypertrophy by voltage criteria and extensive repolarization abnormalities). Significant hypertrabeculations, mainly at the anterolateral wall and basal anteroseptal segments, was present in all affected carriers. Interestingly, none of them showed an abnormal late-gadolinium enhancement pattern on MRI. The four carriers who were older than 35 years were found to have severe restrictive pattern on echocardiography (functional parameters and secondary features such as bi-atrial dilation), all four suffered from limiting dyspnea, and two are under pre-transplant workup (A-II-1 and B-III-1). One of them had a cardioembolic event (femoral acute ischemia, A-II-1). One relative has recently died from advanced heart failure (B-II-2).

Conclusion

This is the first description on this overlapping (restrictive/non-compaction cardiomyopathy) and aggressive phenotype associated with a missense FLNC variant. This description widens the clinical spectrum related to FLNC missense mutations.

Pedigrees and clinical characterization

Funding Acknowledgement

Type of funding source: Private company. Main funding source(s): Health in Code

Value of a comprehensive exercise echocardiography assessment for patients with hypertrophic cardiomyopathy

Background

Exercise echocardiography (ExE) may assess left ventricular (LV) systolic and diastolic function, LV outflow tract (LVOT) obstruction and mitral regurgitation (MR). We aimed to assess the feasibility and prognostic value of the assessment of all these issues during exercise in patients with hypertrophic cardiomyopathy (HCM).

Methods

LV systolic and diastolic function, LVOT gradients, and MR were evaluated during ExE in 285 patients with HCM (age 60±14 years, 168 men) and preserved LVEF (≥50%). Recordings were obtained at rest and peak exercise for regional/global LV systolic function and at rest and within 1.5 min after exercise for the rest of assessments: LVOT gradients, MR and ratio of early LV inflow velocity to early tissue Doppler septal annulus velocity (E/e').

Results

Feasibility was 100%, 97%, 98% and 98% for LV systolic function, E/e', LVOT gradients, and MR assessments at exercise, respectively. Thirty-seven patients (13%) had LVOT obstruction at rest, and 76 (27%) developed exercise-induced LVOT obstruction. Mean resting LVEF was 63±3%. New wall motion abnormalities (WMAs) were detected in 38 patients (13%). E/e'&gt;15 was observed in 108 patients at rest (38%) and in 119 at exercise (42%). Corresponding figures for significant MR (moderate or severe) were 20 (7%) and 17 (6%). During follow-up of 3.9±2.5 years, 21 patients had a hard event (cardiac death or transplantation, appropriate discharge of a defibrillator, stroke, myocardial infarction, hospitalization for heart failure), 33 a combined event (hard plus new atrial fibrillation or syncope), and 53 a combined event plus any interventionism.

After adjustment, LV wall thickness, resting LVEF, maximal workload in Metabolic Equivalents (METs), and E/e' post-exercise resulted independent predictors of hard events (HR=1.45, 95% CI: 1.21–1.74, p&lt;0.001; HR=0.80, CI: 0.71–0.89, p&lt;0.001; HR=0.73, 95% CI: 0.62–0.86, p&lt;0.001; HR=1.08, 95% CI: 1.02–1.14, p&lt;0.009, respectively). Independent predictors of combined events included also LV wall thickness, resting LVEF, and METs, along with therapy with beta-blockers at the time of ExE (HR=1.29, 95% CI: 1.12–1.50, p=0.001; HR=0.89, CI: 0.81–0.97, p=0.012; HR=0.83, 95% CI: 0.74–0.93, p=0.001; HR=2.51, 95% CI: 1.20–5.25, p=0.015), whereas the model for combined events+any interventionism consisted of beta-blockers, LV wall thickness, LA dimension, METs and new WMAs. (HR=2.15, 95% CI: 1.20–3.86, p=0.01; HR=1.17, 95% CI: 1.03–1.32, p=0.02; HR=1.07, CI: 1.02–1.11, p=0.005; HR=0.90, 95% CI: 0.82–0.98, p=0.01; HR=2.33, 95% CI: 1.17–4.63, p=0.016)

Conclusions

A comprehensive assessment during ExE is feasible for patients with HCM and provides significant incremental prognostic information

Funding Acknowledgement

Type of funding source: None

Effect of hypokintic transformation on the clinical phenotype and functional capacity in hypertrophic cardiomyopathy

Background

Advanced hypertrophic cardiomyopathy (HCM) may be complicated by a dilated hypokinetic transformation. Reduced left ventricular ejection fraction (HFrEF) has been described in terms of specific risks of morbidity and mortality, and specifically in terms of increased risk for fatal arrhythmias. Nevertheless, recent publications have casted doubt regarding the role of arrhythmia in non-ischemic HFrEF and questioned the role of primary prevention strategies in these cases.

Methods

We've reviewed clinical characteristics of 883 patients age ≥40, diagnosed with HCM who were evaluated in the cardiomyopathy clinic in two tertiary medical centers in Israel and Spain.

Results

Forty-five patients (5%) suffered from hypokinetic transformation. They were younger at diagnosis (median 32 [IQR 24–55] vs. 49 [35–60], p&lt;0.001), had a lower body-mass index (28.4 [±4.7] vs. 26.0 [±3.9], p&lt;0.001), and suffered more from strokes (19% vs 6%, p&lt;0.001). They had lower had a lower NYHA class (p=0.001) and lower exercise capacity (7.3 [4.5–10.8] vs. 9.6 [6.7–12.0] METS, p&lt;0.001). Patients with hypokinetic HCM had higher rates of pacemaker and implanted defibrillator (ICD) implantations (41% vs 11%, p&lt;0.001) and (43% vs 13%, p&lt;0.001) respectively. These patients had a higher incidence of sustained ventricular tachyarrhythmias (14% vs 2%, p&lt;0.001). Among patients who had an ICD, patients suffering from hypokinetic transformation had received more appropriate ICD therapy (27% vs 12%, p&lt;0.001). These patients received more heart transplantations (13% vs 1%, p&lt;0.001), and had a trend for higher incidence rate of Sudden cardiac death (6% vs 2% p=0.06) and a higher 5-year mortality rates (21% vs. 5%, p&lt;0.001).

Conclusions

HCM patients suffering from hypokinetic transformation have lower functional and exercise capacities, are more likely to suffer from ventricular tachyarrhythmias and experience appropriate ICD therapy, and undergo heart transplantation. They also have a significantly lower 5-year survival.

Five-year survival

Funding Acknowledgement

Type of funding source: None

Prognostic implications of pathogenic truncating variants in the TTN gene

INTRODUCTION AND OBJECTIVES

TTN gene truncating variants (TTNtv) are a frequent cause of dilated cardiomyopathy (DCM). However, there are discrepant data on the associated prognosis. Our objectives were to describe the prevalence of TTNtv in our cohort and to compare the clinical course with that described in the literature.

METHODS

We included patients with DCM and genetic testing performed using next-generation sequencing. Through a systematic literature research, we collected information about carriers and affected relatives with TTNtv. We compared the cumulative percentage of affected carriers and the survival free of cardiovascular death.

RESULTS

One hundred and ten DCM patients were evaluated. A total of 13 TTNtv distributed in 14 probands were identified (12.7%). We found a 21.4% prevalence in familial cases. No significant differences in the relation between age and clinical disease expression were identified. Survival free of cardiovascular death curves constructed from data in the literature seems not to overestimate the risk in our population.

CONCLUSIONS

The identification of TTNtv in patients with DCM is frequent and provides relevant information about the disease prognosis. The risk of cardiovascular death should not be underestimated. Age related penetrance need to be considered in the familial evaluation.

Clinical Phenotypes and Prognosis of Dilated Cardiomyopathy Caused by Truncating Variants in the TTN Gene

BACKGROUND

Truncating variants in the TTN gene (TTNtv) are the commonest cause of heritable dilated cardiomyopathy. This study aimed to study the phenotypes and outcomes of TTNtv carriers.

METHODS

Five hundred thirty-seven individuals (61% men; 317 probands) with TTNtv were recruited in 14 centers (372 [69%] with baseline left ventricular systolic dysfunction [LVSD]). Baseline and longitudinal clinical data were obtained. The primary end point was a composite of malignant ventricular arrhythmia and end-stage heart failure. The secondary end point was left ventricular reverse remodeling (left ventricular ejection fraction increase by ≥10% or normalization to ≥50%).

RESULTS

Median follow-up was 49 (18-105) months. Men developed LVSD more frequently and earlier than women (45±14 versus 49±16 years, respectively; P=0.04). By final evaluation, 31%, 45%, and 56% had atrial fibrillation, frequent ventricular ectopy, and nonsustained ventricular tachycardia, respectively. Seventy-six (14.2%) individuals reached the primary end point (52 [68%] end-stage heart failure events, 24 [32%] malignant ventricular arrhythmia events). Malignant ventricular arrhythmia end points most commonly occurred in patients with severe LVSD. Male sex (hazard ratio, 1.89 [95% CI, 1.04-3.44]; P=0.04) and left ventricular ejection fraction (per 10% decrement from left ventricular ejection fraction, 50%; hazard ratio, 1.63 [95% CI, 1.30-2.04]; P<0.001) were independent predictors of the primary end point. Two hundred seven of 300 (69%) patients with LVSD had evidence of left ventricular reverse remodeling. In a subgroup of 29 of 74 (39%) patients with initial left ventricular reverse remodeling, there was a subsequent left ventricular ejection fraction decrement. TTNtv location was not associated with statistically significant differences in baseline clinical characteristics, left ventricular reverse remodeling, or outcomes on multivariable analysis (P=0.07).

CONCLUSIONS

TTNtv is characterized by frequent arrhythmia, but malignant ventricular arrhythmias are most commonly associated with severe LVSD. Male sex and LVSD are independent predictors of outcomes. Mutation location does not impact clinical phenotype or outcomes.

Clinical utility of genetic testing in patients with dilated cardiomyopathy

INTRODUCTION AND OBJECTIVES

Dilated cardiomyopathy (DCM) is the most frequent cause of heart transplantation. The prevalence of familial disease can reach 50%. Our objective was to describe the genetic basis of DCM in a cohort with a high proportion of transplanted patients.

METHODS

We included patients with DCM and genetic testing performed using next-generation sequencing (NGS) that included at least 80 genes. Clinical data, family history and genetic results were retrospectively analysed. When possible, assessment of first-degree relatives was carried out.

RESULTS

Eighty-seven DCM patients and 308 relatives from 70 families were evaluated. Clinical prevalence of familial disease was 37% (32 patients). Forty-four percent of patients (38 patients) had required heart transplantation. A relevant variant was found in 43 patients (49%), 25 patients (29%) carried variants of unknown significance and in 19 patients (22%) the study was negative. Most genetic variants were found in sarcomeric genes and the yield of genetic testing was higher in patients with familial DCM.

CONCLUSIONS

The yield of genetic testing in our DCM cohort was high, reaching 69% in familial cases. Mutational spectrum was heterogeneous and the identification of the specific aetiology of the disease often provided prognostic information.

Risk predictors in a Spanish cohort with cardiac laminopathies. The REDLAMINA registry

INTRODUCTION AND OBJECTIVES

According to sudden cardiac death guidelines, an implantable cardioverter-defibrillator (ICD) should be considered in patients with LMNA-related dilated cardiomyopathy (DCM) and ≥ 2 risk factors: male sex, left ventricular ejection fraction (LVEF) <45%, nonsustained ventricular tachycardia (NSVT), and nonmissense genetic variants. In this study we aimed to describe the clinical characteristics of carriers of LMNA genetic variants among individuals from a Spanish cardiac-laminopathies cohort (REDLAMINA registry) and to assess previously reported risk criteria.

METHODS

The relationship between risk factors and cardiovascular events was evaluated in a cohort of 140 carriers (age ≥ 16 years) of pathogenic LMNA variants (54 probands, 86 relatives). We considered: a) major arrhythmic events (MAE) if there was appropriate ICD discharge or sudden cardiac death; b) heart failure death if there was heart transplant or death due to heart failure.

RESULTS

We identified 11 novel and 21 previously reported LMNA-related DCM variants. LVEF <45% (P=.001) and NSVT (P <.001) were related to MAE, but not sex or type of genetic variant. The only factor independently related to heart failure death was LVEF <45% (P <.001).

CONCLUSIONS

In the REDLAMINA registry cohort, the only predictors independently associated with MAE were NSVT and LVEF <45%. Therefore, female carriers of missense variants with either NSVT or LVEF <45% should not be considered a low-risk group. It is important to individualize risk stratification in carriers of LMNA missense variants, because not all have the same prognosis.

Mutations in TRIM63 cause an autosomal-recessive form of hypertrophic cardiomyopathy

OBJECTIVE

Up to 50% of patients with hypertrophic cardiomyopathy (HCM) show no disease-causing variants in genetic studies. TRIM63 has been suggested as a candidate gene for the development of cardiomyopathies, although evidence for a causative role in HCM is limited. We sought to investigate the relationship between rare variants in TRIM63 and the development of HCM.

METHODS

TRIM63 was sequenced by next generation sequencing in 4867 index cases with a clinical diagnosis of HCM and in 3628 probands with other cardiomyopathies. Additionally, 3136 index cases with familial cardiovascular diseases other than cardiomyopathy (mainly channelopathies and aortic diseases) were used as controls.

RESULTS

Sixteen index cases with rare homozygous or compound heterozygous variants in TRIM63 (15 HCM and one restrictive cardiomyopathy) were included. No homozygous or compound heterozygous were identified in the control population. Familial evaluation showed that only homozygous and compound heterozygous had signs of disease, whereas all heterozygous family members were healthy. The mean age at diagnosis was 35 years (range 15-69). Fifty per cent of patients had concentric left ventricular hypertrophy (LVH) and 45% were asymptomatic at the moment of the first examination. Significant degrees of late gadolinium enhancement were detected in 80% of affected individuals, and 20% of patients had left ventricular (LV) systolic dysfunction. Fifty per cent had non-sustained ventricular tachycardia. Twenty per cent of patients suffered an adverse cerebrovascular event (20%).

CONCLUSION

TRIM63 appears to be an uncommon cause of HCM inherited in an autosomal-recessive manner and associated with concentric LVH and a high rate of LV dysfunction.

Familial Recurrent Myocarditis Triggered by Exercise in Patients With a Truncating Variant of the Desmoplakin Gene

Background

Variants of the desmosomal protein desmoplakin are associated with arrhythmogenic cardiomyopathy, an important cause of ventricular arrhythmias in children and young adults. Disease penetrance of desmoplakin variants is incomplete and variant carriers may display noncardiac, dermatologic phenotypes. We describe a novel cardiac phenotype associated with a truncating desmoplakin variant, likely causing mechanical instability of myocardial desmosomes.

Methods and Results

In 2 young brothers with recurrent myocarditis triggered by physical exercise, screening of 218 cardiomyopathy‐related genes identified the heterozygous truncating variant p.Arg1458Ter in desmoplakin. Screening for infections yielded no evidence of viral or nonviral infections. Myosin and troponin I autoantibodies were detected at high titers. Immunohistology failed to detect any residual DSP protein in endomyocardial biopsies, and none of the histologic criteria of arrhythmogenic cardiomyopathy were fulfilled. Cardiac magnetic resonance imaging revealed no features associated with right ventricular arrhythmogenic cardiomyopathy, but multifocal subepicardial late gadolinium enhancement was present in the left ventricles of both brothers. Screening of adult cardiomyopathy cohorts for truncating variants identified the rare genetic variants p.Gln307Ter, p.Tyr1391Ter, and p.Tyr1512Ter, suggesting that over subsequent decades critical genetic/exogenous modifiers drive pathogenesis from desmoplakin truncations toward different end points.

Conclusions

The described novel phenotype of familial recurrent myocarditis associated with a desmoplakin truncation in adolescents likely represents a serendipitously revealed subtype of arrhythmogenic cardiomyopathy. It may be caused by a distinctive adverse effect of the variant desmoplakin upon the mechanical stability of myocardial desmosomes. Variant screening is advisable to allow early detection of patients with similar phenotypes.

Verification of Underlying Genetic Cause in a Cohort of Russian Patients with Familial Hypercholesterolemia Using Targeted Next Generation Sequencing

Russian patients with familial hypercholesterolemia (FH) were screened for pathogenic mutations using targeted next generation sequencing. Genetic testing was performed in 52 probands with definite or probable FH based on the Dutch lipid clinic network criteria (DLCN score ≥6). Blood samples were studied by massive parallel sequencing (Illumina HiSeq 1500 platform) using a custom capture library related to dyslipidemia and premature atherosclerosis. Mutations considered to be responsible for monogenic FH were identified in 48% of the probands: 24 with mutations in the LDLR gene and two with a mutation in the APOB gene. There were 22 pathogenic/likely pathogenic mutations in LDLR, eight of which have not been previously described in the literature. Four patients with a clinical picture of homozygous FH had two heterozygous LDLR mutations. Although mutation-negative patients had highly elevated total cholesterol and low-density lipoprotein cholesterol levels, only half of them had a family history of hypercholesterolemia. With respect to heterozygous FH, mutation-positive patients had higher maximum total cholesterol levels (p = 0.01), more severe carotid atherosclerotic lesions, and a higher percentage of premature peripheral artery disease (p = 0.03) than mutation-negative ones. However, the number of patients who suffered from myocardial infarction was similar between the two groups.

Deletions of specific exons of FHOD3 detected by next-generation sequencing are associated with hypertrophic cardiomyopathy

Despite new strategies, such as evaluating deep intronic variants and new genes in whole-genome-sequencing studies, the diagnostic yield of genetic testing in hypertrophic cardiomyopathy (HCM) is still around 50%. FHOD3 has emerged as a novel disease-causing gene for this phenotype, but the relevance and clinical implication of copy-number variations (CNVs) have not been determined. In this study, CNVs were evaluated using a comparative depth-of-coverage strategy by next-generation sequencing (NGS) in 5493 HCM probands and 2973 disease-controls. We detected three symmetrical deletions in FHOD3 that involved exons 15 and 16 in three HCM families (no CNVs were detected in the control group). These exons are part of the diaphanous inhibitory domain of FHOD3 protein, considered a cluster of mutations for HCM. The clinical characteristics of the affected carriers were consistent with those reported in FHOD3 in previous studies. This study highlights the importance of performing CNV analysis systematically in NGS genetic testing panels for HCM, and reinforces the relevance of the FHOD3 gene in the disease.

Whole Exome Sequencing Provides the Correct Diagnosis in a Case of Osteopathia Striata with Cranial Sclerosis: Case Report of a Novel Frameshift Mutation in AMER1

The diagnosis of rare diseases with multisystem manifestations can constitute a difficult process that delays the determination of the underlying cause. Whole exome sequencing (WES) provides a suitable option to examine multiple target genes associated with several disorders that display common features. In this study, we report the case of a female patient suspected of having Sotos syndrome. Screening for the initially selected genes, considering Sotos syndrome and Sotos-like disorders, did not identify any pathogenic variants that could explain the phenotype. The extended analysis, which considered all genes in the exome associated with features consistent with those shown by the studied patient, revealed a novel frameshift variant in the AMER1 gene, responsible for osteopathia striata with cranial sclerosis. WES analysis and an updated revision of previously reported disease-causing mutations, proved useful to reach an accurate diagnosis and guide further examination to identify critical abnormalities.

A Pathogenic Galactosidase A Mutation Coexisting With an MYBPC3 Mutation in a Female Patient With Hypertrophic Cardiomyopathy

The coexistence of GLA (Pro259Ser, c.775C>T) and MYBPC3 (c.1351+2T>C) mutations was found in a female patient with hypertrophic cardiomyopathy. Histology documented abundant vacuolisation with osmiophilic lamellar bodies and positive Gb3 immunohistochemistry. In the presence of a hypertrophic cardiomyopathy phenotype, the systematic search for unusual findings is mandatory to rule out a phenocopy.

Identification, clinical manifestation and structural mechanisms of mutations in AMPK associated cardiac glycogen storage disease

Background

Although 21 causative mutations have been associated with PRKAG2 syndrome, our understanding of the syndrome remains incomplete. The aim of this project is to further investigate its unique genetic background, clinical manifestations, and underlying structural changes.

Methods

We recruited 885 hypertrophic cardiomyopathy (HCM) probands and their families internationally. Targeted next-generation sequencing of sudden cardiac death (SCD) genes was performed. The role of the identified variants was assessed using histological techniques and computational modeling.

Findings

Twelve PRKAG2 syndrome kindreds harboring 5 distinct variants were identified. The clinical penetrance of 25 carriers was 100.0%. Twenty-two family members died of SCD or heart failure (HF). All probands developed bradycardia (HRmin, 36.3 ± 9.8 bpm) and cardiac conduction defects, and 33% had evidence of atrial fibrillation/paroxysmal supraventricular tachycardia (PSVT) and 67% had ventricular preexcitation, respectively. Some carriers presented with apical hypertrophy, hypertension, hyperlipidemia, and renal insufficiency. Histological study revealed reduced AMPK activity and major cardiac channels in the heart tissue with K485E mutation. Computational modelling suggests that K485E disrupts the salt bridge connecting the β and γ subunits of AMPK, R302Q/P decreases the binding affinity for ATP, T400N and H401D alter the orientation of H383 and R531 residues, thus altering nucleotide binding, and N488I and L341S lead to structural instability in the Bateman domain, which disrupts the intramolecular regulation.

Interpretation

Including 4 families with 3 new mutations, we describe a cohort of 12 kindreds with PRKAG2 syndrome with novel pathogenic mechanisms by computational modelling. Severe clinical cardiac phenotypes may be developed, including HF, requiring close follow-up.