Genetic Cardiomyopathy Research Articles

Abstract 4121733: Comprehensive Plasma Proteomics Profiling Identifies Circulating Biomarkers to Distinguish Hypertrophic Cardiomyopathy from Other Cardiomyopathies with Left Ventricular Hypertrophy

Introduction: Hypertrophic cardiomyopathy (HCM) is the most common genetic cardiomyopathy. It is sometimes challenging to distinguish HCM from other cardiomyopathies that cause left ventricular hypertrophy (LVH) such as hypertensive LVH, transthyretin cardiac amyloidosis (ATTR-CA), and aortic stenosis (AS). We aimed to identify a set of plasma protein biomarkers that distinguishes HCM from the other cardiomyopathies with LVH. Methods: In this multi-center case-control study, we conducted plasma proteomics profiling of 4,979 proteins in cases with HCM (n=879) and controls with hypertensive LVH (n=331), ATTR-CA (n=169), and AS (n=36). We identified clinical parameters that were significantly (univariable P<0.05) different between HCM and hypertensive LVH. We then specified proteins that were significantly (multivariable P<0.001) upregulated or downregulated in HCM compared to hypertensive LVH by performing multivariable logistic regression analysis on each protein adjusting for the identified clinical parameters (comparison #1). We performed the same analysis between HCM and ATTR-CA (comparison #2) as well as between HCM and AS (comparison #3). We identified proteins that were upregulated in HCM in all 3 comparisons. We also specified proteins downregulated in HCM throughout all 3 comparisons. Finally, using these proteins, we constructed a logistic regression model to distinguish HCM from all 3 control groups combined, and calculated an area under the receiver-operating-characteristics curve (AUROC). Results: Eight clinical parameters listed in Image 1 were significantly different between HCM and the controls and adjusted for in the multivariable logistic regression analyses. In the comparison between HCM and hypertensive LVH, 444 proteins were upregulated and 267 downregulated with multivariable P<0.001 ( Image 1 ). There were 226 upregulated and 170 downregulated proteins comparing HCM with ATTR-CA, and 57 upregulated and 74 downregulated proteins when comparing HCM with AS ( Image 1 ). Among these proteins, 4 were upregulated in all 3 comparisons with multivariable P<0.001 and 5 were downregulated ( Image 2 ). The logistic regression model with these 9 proteins had AUROC of 0.86 (95% confidence interval 0.84-0.88, Image 3 ). Conclusions: This study serves as the first to apply comprehensive proteomics profiling to identify circulating biomarkers that distinguish HCM from other cardiomyopathies with LVH independently from potential confounders.

Abstract 4119187: Association of CMR derived Global Longitudinal Strain with adverse Outcomes in Arrhythmogenic Cardiomyopathy.

Background: Arrhythmogenic cardiomyopathy (ACM) is associated with high risk of ventricular arrhythmias (VA) and heart failure (HF). Different predictive models and diagnostic criteria include parameters related to myocardial structural abnormalities and right ventricular (RV) ejection fraction (EF). Nevertheless, the value of global longitudinal strain (GLS) ascertained from cardiac magnetic resonance (CMR) for risk-stratification in the context of ACM is unknown. Aim: We aim to study the association of low CMR-derived GLS with adverse outcomes in ACM patients. Methods: This was a retrospective cohort study of ACM patients seen at a single quaternary center. ACM diagnosis followed the modified 2010 ARVC modified task force criteria. Primary outcome was a composite of life-threatening VAs, heart transplant or HF hospitalization during follow up. We excluded patients who suffered events prior to diagnosis, and those with missing or inadequate CMR protocol. Imaging parameters were acquired by CMR including EF, GLS, and late gadolinium enhancement (LGE). Results: A total of 82 patients with suspected ACM were included, with a median age of 40 years, and 43 (52.4%) were females. Most common reason of initial visit was family history of genetic cardiomyopathy in 46 (56%), while 16 (20%) patients visited our clinic due to history of syncope. Out of 60 patients who had genetic testing, 21 (35%) had mutations of DSP gene. Left ventricular involvement (non-ischemic LV-LGE by CMR) was present in 42 (56.8%) out of 74 patients who had CMR with gadolinium. Median LVEF was 62% (56, 66), and RVEF of 53% (48, 59), both by CMR. Median LVGLS was -17.01% (-14.71, -18.43), while median RVGLS was -20.5% (-18.3, -24.4). A total of 15 (18%) patients suffered the composite endpoint during an average follow up period of 8 years. Patients who suffered the composite endpoint had significantly lower mean LVGLS (-15.04% vs -16.70%, p= 0.048), and lower average RVGLS (-18.45% vs -21.33%, p=0.035) compared to patients free from the adverse outcome. Meanwhile there was no significant difference in LVEF (60.13% vs 61.18%, p=0.67), nor in RVEF (49.13% vs 54.01%, p=0.065) between the two groups. Conclusion: Lower GLS was significantly associated with VAs and HF hospitalizations in our patient population. CMR derived GLS can be used as an important prognostic parameter of adverse outcomes in patients with suspected ACM. Especially in those with LV involvement and high genetic predisposition as our cohort.

Abstract 4137543: Prevalence, Genetic Correlates and Prognostic Significance of an Apical Pseudo-Infarct Late Gadolinium Enhancement Pattern in LMNA -Mediated Cardiac Laminopathy

Background: Disease-causative variants in LMNA -encoded lamin A/C cause a genetic cardiomyopathy characterized by atrioventricular (AV) block, atrial fibrillation (AF) and ventricular arrhythmias (VA). Whether domain/variant-specific late gadolinium enhancement (LGE) patterns exist and carry prognostic significance is unclear. Objective: To determine if specific LGE patterns correlate with LMNA variant type/missense variant localization and clinical outcomes in a large cohort of cardiac laminopathy patients. Methods: Retrospectively, 621 genotype-positive arrhythmogenic/dilated cardiomyopathy patients were analyzed to identify those with a disease-causative variant in LMNA -encoded lamin A/C. After exclusion of patients without cardiac magnetic resonance data, pertinent demographic/clinical data was extracted from the electronic medical record. LGE distribution (subepicardial, midmyocardial, subendocardial, transmural) and location (septal, free wall, apical) patterns were analyzed by variant type (missense vs truncating) and missense variant localization (central rod domain vs tail domain) and correlated with advanced heart failure (AHF), MVA, AV block, AF and thromboembolic (TE) events. Results: 70 out of 116 (60%) LMNA variant-positive (mean age 39±12, 43% male and 94% Caucasian) were included. Missense variants localizing to the C-terminal tail region showed a higher prevalence of transmural and apical LGE (Table). Amongst the 5 (7%) patients with this distinct apical pseudo-infarct LGE pattern, p.Arg471His-LMNA was identified in all cases. Among the 48/70 (69%) of patients with clinically manifest disease, p.Arg471His-LMNA-positive patients (n=6) were noted to have an increased prevalence of TE events [3 (50%) vs 5 (12%), 0=0.050] despite a reduced prevalence of AF [2 (33%) vs 32 (76%), p= 0.031]. No difference in AHF or MVA were observed, but AV block was less prevalent [1 (20%) vs 29 (74%), p= 0.029]. Conclusion: p.Arg471His-LMNA causes a distinct apical pseudo-infarct LGE pattern associated with an increased risk of TE events and a decreased prevalence of AV block and AF. Future studies are needed to better refine the role of domain/variant-specific risk-stratification/anticoagulation in cardiac laminopathy.

Clinical Features and Outcomes of Pediatric MYH7-Related Dilated Cardiomyopathy.

Although genetic variants in MYH7 are the most frequent cause of pediatric genetic dilated cardiomyopathy (DCM), there are no studies available describing this entity. We sought to describe clinical features, analyze variant location, and explore predictors of bad prognosis in pediatric MYH7-related DCM. We evaluated clinical records from 44 patients (24 men; median age at diagnosis, 0.54 [interquartile range, 0.01-10.8] years) with pathogenic/likely pathogenic variants in MYH7 diagnosed with DCM at pediatric age (<18 years) followed at 13 international centers. We also explored risk factors associated with a composite end point of end-stage heart failure defined as heart transplantation or heart failure-related death. Twenty-two patients (50%) were diagnosed at age <6 months, including 7 (16%) at birth. Left ventricular (LV) hypertrabeculation features were present in 15 (38%), particularly among patients with genetic variants in the head domain. After a median follow-up of 6.1 years (interquartile range, 1.9-13.4), 15 patients (36%) required a heart transplant (n=14) or died due to end-stage heart failure (n=1), 15 patients (36%) persisted with systolic dysfunction despite treatment, 12 (29%) had a significant increase in LV ejection fraction, and 2 were lost to follow-up. Overall, end-stage heart failure event rate was 25% at 5 years. New York Heart Association class III to IV (hazard ratio [HR], 7.67 [95% CI, 2.16-27.2]; P=0.002) and LV ejection fraction ≤35% (HR, 4.00 [95% CI, 1.11-14.4]; P=0.03) were the best predictors of bad prognosis. Pediatric MYH7-related DCM is characterized by early onset, frequent LV hypertrabeculation, and poor prognosis. Advanced New York Heart Association class and low LV ejection fraction emerged as predictors of end-stage heart failure.

Phase I gene therapy clinical trial design of RP-A601 in adult patients with PKP2-arrhythmogenic cardiomyopathy (PKP2-ACM)

Abstract Background Arrhythmogenic cardiomyopathy (ACM) is a rare, progressive, autosomal dominant disorder characterized by increased risk of ventricular arrhythmias and sudden cardiac death. Up to 45% of all ACM cases are caused by pathogenic variants in the PKP2 gene, which encodes for the desmosomal protein Plakophilin-2. This genetic cardiomyopathy is referred to as PKP2-ACM. AAVrh.74-PKP2a is a recombinant adeno-associated viral (AAV) vector containing the coding sequence of human PKP2 isoform A (PKP2a) and delivers the functional PKP2 gene to cardiomyocytes. Preclinical testing conducted in a clinically relevant mouse model of PKP2-ACM (with survival ≤50 days post disease onset) demonstrated that administration of a single AAVrh.74-PKP2a dose after disease onset extended survival through 5 months with improved right ventricular (RV) function, and decreased cardiac dilation, myocardial fibrosis, and arrhythmias. Additional studies in rodents and nonhuman primates demonstrated AAVrh.74-PKP2a safety. These preclinical findings support clinical initiation. Purpose We describe the design of a phase I trial to assess safety and preliminary efficacy of AAVrh.74-PKP2a (RP-A601) in high-risk adult patients with PKP2-ACM. Methods This study (NCT05885412) is a multi-center, open-label, dose escalation trial evaluating the safety and preliminary efficacy of a single intravenous infusion of RP-A601 in adult patients (age ≥18 yrs) with clinical and genetic PKP2-ACM diagnosis and an implanted ICD. Patients with severe right ventricular dysfunction, LV ejection fraction ≤50% (echocardiogram or cardiac MRI) and/or NYHA Class IV heart failure are excluded. Preliminary efficacy will be assessed at 12 months after RP-A601 infusion and includes evaluation of change in PKP2 myocardial tissue expression and clinical markers of arrhythmia burden. Conclusions PKP2-ACM is a devastating disease associated with high morbidity and mortality. This Phase I trial will evaluate the safety and preliminary efficacy of RP-A601 and was initiated based on robust preclinical efficacy and safety data.

Impact of high intensity and long duration exercise in genetic arrhythmogenic left ventricular cardiomyopathy

Abstract Background Arrhythmogenic left ventricular (LV) cardiomyopathy (ALVC) is a genetic disease associating extensive LV myocardial fibrosis with or without dysfunction and no or mild right ventricle (RV) involvement, at risk of life-threatening ventricular arrhythmias (VA). While high intensity (HI) and long duration (LD) exercise has been identified as a precipitating factor of RV dysfunction and VA in arrhythmogenic RV cardiomyopathy including in asymptomatic genetic variant carriers, the impact of exercise on disease phenotype and risk is not known in ALVC. Objective To study the relationship between practicing HI and LD exercise and the risk of developing an ALVC phenotype and its severity. Methods In a monocentric retrospective observational study, patients with a pathogenic variant in common ALVC genes (DSP, FLNC, DES, PLN, RBM20, TMEM43), including asymptomatic carriers without ALVC phenotype, were interviewed about their physical practice from age 7 to the time of genetic or disease diagnosis. Intensity and weekly duration of each activity were reported. HI and LD exercise were defined as having practiced at least 1 sport with an intensity ≥ 6 METs and ≥ 2.5 hours/week respectively. We studied the association of HI and LD exercise practice with the risk of ALVC phenotype occurrence and its severity, derived from clinical, ECG and imaging data. Results 114 out of 128 eligible patients answered the questionnaire and were included (85 (74.6%) with a DSP variant, 22 FLNC (19.3%), 6 DES (5.3%), 1 RBM20 (0.9%)). 35 were probands (31%) and 79 relatives (69%) among 46 families. 31 (27%) had no ALVC phenotype at the time of genetic diagnosis. Mean age at diagnosis was 41±18. 62 (54%) patients were women. 97 (85%) had practiced at least one sport, among which 81 (83.5%) at HI and 79 (81.4%) of LD. Median lifetime exercise dose was 18.5 MET.h/week. There were no differences in HI and LD exercise practice between probands and relatives (74.3% vs 69.6%, p=0.6 and 74.3% vs 67.1%, p=0.4 respectively), as well as between patients with and patients without ALVC phenotype at the time of diagnosis (74.7% vs 61.3%, p=0.2 and 72.3% vs 61.3%, p=0.3 respectively). Phenotypic features at diagnosis did not differ between patients with and without HI and LD practice (Table 1). Multivariate analysis adjusted on age and gender showed that HI and LD exercise were not significantly associated with an increased risk of developing an ALVC phenotype (Odds Ratio [95% confidence interval] for age, gender, HI and LD exercise were 1.03 [1.01-1.06] (p=0.013), 1.41 [0.58 ; 3.47] (p=0.45), 2.15 [0.63 ; 7.27] (p=0.22) and 1.17 [0.35 ; 3.87] (p=0.79) respectively). Phenotypic features at diagnosis did not differ across observed quartiles of lifetime exercise dose (Table 2). Conclusion Practicing HI and LD exercise was not associated with an increased risk of developing an ALVC phenotype and its severity at the time of diagnosis in genetic ALVC variant carriers.

A systematic review and meta-analysis to determine the biological sex ratio in monogenic genetic and non-genetic dilated cardiomyopathy

Abstract Background Dilated cardiomyopathy (DCM) is characterised by left ventricular or biventricular systolic dysfunction and dilatation, in the absence of abnormal loading conditions or coronary artery disease (1). Up to 30% of cases have an identified monogenic cause, usually with autosomal dominant (AD) inheritance (2). The disease appears to be twice as common in males, suggesting either a sex specific penetrance or a potential difference in expressivity. This sex ratio has not been systematically evaluated for genetic forms of DCM. Purpose To assess the sex ratio in patients with all-cause DCM compared to genetic (monogenic) and gene-elusive subtypes, defined by the presence or absence of a pathogenic variant in DCM-associated genes. Methods A literature search was conducted to identify cohorts of DCM patients with identifiable sex ratios. Exclusion criteria were patients with syndromic, X-linked, mitochondrial, or autosomal recessive (AR) DCM. Studies with a small cohort size (n&amp;lt;100), a paediatric population, unidentifiable sex ratio, or ischaemic and peripartum DCM were excluded. 98 studies with a total of 36,662 participants were included in this study. A random-effects meta-analysis generated a pooled proportion of female participants with a 95% confidence interval (95% CI) for an overall DCM cohort as well as for the subtypes – all genetic DCM, individual gene level for 10 key DCM genes (including titin, TTN, and lamin, LMNA), and gene elusive DCM. Results The overall DCM cohort had a 0.30 female proportion (95% CI: 0.28-0.32; Figure 1). This corresponds to a male:female (M:F) ratio of 2.38:1. This ratio did not significantly change in patients with an identified causative DCM variant (0.31 [95% CI 0.26-0.36]; M:F ratio of 2.22:1; p=0.563). There was also no significant difference when compared to patients who had been genetically tested with no identified variant (0.30 [95% CI 0.24-0.37]; M:F ratio of 2.29:1; p=0.814). Furthermore, the ratio within participants with AD gene variants was not significantly different for the specific genes of TTN (0.28 [95% CI 0.22-0.36]; M:F ratio of 2.51:1) and LMNA (0.35 [95% CI 0.27-0.44]; M:F ratio of 1.84:1). Overall, the sex ratio amongst patients with these AD gene variants was similar to the all-cause group (0.34 [95% CI 0.28-0.40]; M:F ratio of 1.98:1; p=0.18); Figure 2. Conclusions This meta-analysis suggests that DCM is twice as prevalent in males than females, even in pooled monogenic genetic subtypes with an equally prevalent genetic risk factor, indicating a difference in penetrance between the sexes. Further studies are required to determine the drivers of this sex specific penetrance.Forest plots: overall DCM cohortForest plots: gene-specific DCM cohort

Novel &lt;i&gt;FLNC&lt;/i&gt; Gene Variant Associated with Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiomyopathy, affecting approximately 1 in 500 people. It is the most common genetic cardiomyopathy inherited as a Mendelian trait in approximately 50% of patients, mainly due to pathogenic variants in genes encoding sarcomeric proteins. Mutations in the sarcomeric protein filamin C (&lt;em&gt;FLNC&lt;/em&gt;) gene, with a cytogenetic localization on 7q32.1, have been linked to hypertrophic cardiomyopathy, as they have been determined to increase the risk of ventricular arrhythmia and sudden death. We present the case of a patient with HCM recognized by magnetic resonance imaging and echocardiography with a family history of cardiopathies. The molecular study in this patient was performed by next-generation sequencing on the Illumina MiniSeq instrument, comparing the results with international databases. In genetic studies, a novel mutation in the protein &lt;em&gt;FLNC&lt;/em&gt; was detected. It is heterozygous, missence type. It is a variant where Cytosine is changed by timina at position 6305 of the &lt;em&gt;FLNC&lt;/em&gt; gene. This produces the change of the amino acid proline by leucine at position 2102 of the Filamin C protein. The rare variant is located in Ig-like domain 19 within the ROD2 domain. This variant report suggests that there may indeed be a direct relationship between &lt;em&gt;FLNC&lt;/em&gt; variants, mainly the ROD2 domain, and HCM. We think this new result should be considered for future genetic counseling of families affected by this type of cardiomyopathy.

Exercise training improves cardiovascular fitness in dilated cardiomyopathy caused by truncating titin variants

BackgroundParticipation in regular exercise activities is recommended for patients with chronic heart failure. However, less is known about the effect of exercise in patients with genetic dilated cardiomyopathy (DCM). We...

Catheter ablation vs advanced therapy for patients with severe heart failure and ventricular electrical storm

BackgroundCurrent data on outcomes of an initial strategy of catheter ablation vs advanced therapy in patients with severe heart failure (HF) and electric storm (ES) are limited. ObjectiveThe purpose of this study was to evaluate the outcomes of ventricular tachycardia (VT) ablation vs left ventricular assist device (LVAD) or heart transplantation (HT) in patients with severe HF and ventricular ES. MethodsPatients with severe HF and ES who underwent VT ablation, LVAD, or HT between 2012 and 2022 at our medical center were reviewed. Severe HF was defined as ejection fraction ≤ 35% or presence of severe restrictive, valvular, or genetic cardiomyopathy. We assessed in-hospital adverse events and 1-year outcomes between the 2 groups. ResultsOf the 73 patients, 43 underwent VT ablation and 30 received advanced therapy (21 HT and 9 LVAD). One-year survival was similar (76.7% vs 86.7%; log-rank, P = .308). However, 10 patients (23.3%) in the ablation group underwent HT during follow-up. After multivariable analysis, United Network for Organ Sharing status 1 or 2 by VT criteria (hazard ratio 5.52; 95% confidence interval 1.27–24.12; P = .023) and early VT recurrence (hazard ratio 5.67; 95% confidence interval 1.68–19.09; P = .005) were associated with HT or mortality in patients who underwent VT ablation. ConclusionPatients with severe HF and ES who underwent VT ablation had similar overall survival to patients who directly proceeded with advanced therapy, although rates of HT were high during follow-up. Predictors of HT or mortality after catheter ablation include United Network for Organ Sharing status 1 or 2 by VT criteria and early VT recurrence.

Paracentral Acute Middle Maculopathy and Risk of Cardiovascular Disease, Stroke, and Death: A Longitudinal Study

To evaluate the risk of acute cardiovascular events (CVE), including cardiovascular diseases, cerebrovascular diseases, and all-cause mortality in patients with paracentral acute middle maculopathy (PAMM). Retrospective cohort study METHODS: We studied 43 individuals with optical coherence tomography -documented PAMM attending Moorfields Eye Hospital between January 2014 and June 2021. We excluded patients with preceding (< 2 years) major adverse cardiac events. We stratified patients by age (<50 years & ≥50 years) and whether associated with retinal vascular diseases (RVD) or isolated (iPAMM). We assessed risk factors, clinical characteristics, and visual prognosis of the patients. CVE risk was estimated using Kaplan-Meier curves, the log-rank test, and Cox proportional hazards regression. In young patients with iPAMM patients (n=12), underlying predisposing factors included six (50%) sickle cell disease and five (41.6%) others, including breakthrough bleeding in pregnancy, migraine, genetic cardiomyopathy, amphetamine use; among those with PAMM+RVD (n=12) one (9%) had a vascular disorder, and four (44.4%) oral contraceptive use. In the older group of 20 patients, 15 (75%) had at least one coronary risk factor. During a median follow-up of 14 months (range 12-54), older subjects with iPAMM had a higher risk of developing CVE than those with PAMM+RVD (p<0.001). Notably, iPAMM displayed a significantly earlier peak in peri-PAMM CVE risk compared to PAMM+RVD (median: 1 month, range 1-40 months vs. 36 months, range 12-54 months). Relative to those with PAMM+RVD, risk of CVE was significantly higher in patients with iPAMM, adjusted for age and sex (hazard ratio: 6.37, 95% Confidence Interval 1.68-24.14, p=0.017). No young patients experienced adverse CVE. At baseline, older iPAMM patients mean best corrected visual acuity of 0.7 (0-1.8) LogMAR, which improved significantly to 0.2 (0-1.30) LogMAR at the latest visit (p=0.033). Young individuals with iPAMM have a higher prevalence of predisposing factors compared to those presenting with combined PAMM+RVD. Older patients with iPAMM had a higher risk of CVE than those with PAMM+RVD, especially in the peri-onset timeframe. This suggests the need for a prompt cardiovascular assessment to rule out systemic etiologies and optimize cardiovascular risk factors, in addition to ongoing ophthalmology input.

Phenotypic Spectrum of Subclinical Sarcomere-Related Hypertrophic Cardiomyopathy and Transition to Overt Disease.

Genetic hypertrophic cardiomyopathy (HCM) is classically caused by pathogenic/likely pathogenic variants in sarcomere genes (G+). Currently, HCM is diagnosed if there is unexplained left ventricular (LV) hypertrophy with LV wall thickness ≥15 mm in probands or ≥13 mm in at-risk relatives. Although LV hypertrophy is a key feature, this binary metric does not encompass the full constellation of phenotypic features, particularly in the subclinical stage of the disease. Subtle phenotypic manifestations can be identified in sarcomere variant carriers with normal LV wall thickness, before diagnosis with HCM (G+/LV hypertrophy-; subclinical HCM). We conducted a systematic review to summarize current knowledge about the phenotypic spectrum of subclinical HCM and factors influencing penetrance and expressivity. Although the mechanisms driving the development of LV hypertrophy are yet to be elucidated, activation of profibrotic pathways, impaired relaxation, abnormal Ca2+ signaling, altered myocardial energetics, and microvascular dysfunction have all been identified in subclinical HCM. Progression from subclinical to clinically overt HCM may be more likely if early phenotypic manifestations are present, including ECG abnormalities, longer mitral valve leaflets, lower global E' velocities on Doppler echocardiography, and higher serum N-terminal propeptide of B-type natriuretic peptide. Longitudinal studies of variant carriers are critically needed to improve our understanding of penetrance, characterize the transition to disease, identify risk predictors of phenotypic evolution, and guide the development of novel treatment strategies aimed at influencing disease trajectory.

Genetic cardiomyopathy and significant systolic heart failure treated with cardiac contractility modulation therapy

Genetic cardiomyopathy and significant systolic heart failure treated with cardiac contractility modulation therapy

Distribution of myocardial fibrosis in patients with nonischemic cardiomyopathy and ventricular tachycardia based on genetic variant

BackgroundMany genetic nonischemic dilated cardiomyopathies (NICMs) cause ventricular tachycardias (VTs) originating from scar substrate identified as areas of low electrogram voltage. Substrate locations vary, and the causes of scar are not well defined. ObjectiveThis study evaluated VT substrate locations in genetic NICM patients undergoing VT ablation to evaluate spatial relationships between specific variants and substrate locations. MethodsIn this retrospective case series analysis, 32 patients (aged 55 ± 16 years; 94% male; left ventricular ejection fraction, 34% ± 13%) with genetic NICM referred for VT ablation between October 2018 and November 2022 at a single medical center were evaluated. Scar locations were defined as areas of low unipolar or bipolar voltage. ResultsOf the 32 patients evaluated, mutations in TTN (n = 11), LMNA (n = 6), PKP2 (n = 5), MYBPC3 (n = 3), DSP (n = 2), TTR (n = 1), FLNC (n = 1), AGL (n = 1), DES (n = 1), and DSG2 (n = 1) were observed. Substrates associated with mutations in TTN were observed only in basal subregions, predominantly anterior (100%) and septal (50%) regions. LMNA mutations were associated with fibrosis in mid inferolateral (60%) and apical inferolateral (60%) regions. Substrate location for individuals with PKP2 mutations was solely observed in the right ventricle, predominantly basal inferolateral regions. ConclusionUnderstanding spatial relationships between genetic variants causing NICM and VT substrate locations can help lead to generalizable regions in patients with genetically related NICM presenting in VT, which can be investigated during ablation procedures.

Viral myocarditis in combination with genetic cardiomyopathy as a cause of sudden death. An autopsy series

Sudden cardiac death (SCD) is a major public health issue worldwide. In the young (< 40 years of age), genetic cardiomyopathies and viral myocarditis, sometimes in combination, are the most frequent, but underestimated, causes of SCD. Molecular autopsy is essential for prevention. Several studies have shown an association between genetic cardiomyopathies and viral myocarditis, which is probably underestimated due to insufficient post-mortem investigations. We report on four autopsy cases illustrating the pathogenesis of these combined pathologies. In two cases, a genetic hypertrophic cardiomyopathy was diagnosed in combination with Herpes Virus Type 6 (HHV6) and/or Parvovirus-B19 (PVB19) in the heart. In the third case, autopsy revealed a dilated cardiomyopathy and virological analyses revealed acute myocarditis caused by three viruses: PVB19, HHV6 and Epstein-Barr virus. Genetic analyses revealed a mutation in the gene coding for desmin. The fourth case illustrated a channelopathy and a PVB19/HHV6 coinfection. Our four cases illustrate the highly probable deleterious role of cardiotropic viruses in the occurrence of SCD in subjects with genetic cardiomyopathies. We discuss the pathogenetic link between viral myocarditis and genetic cardiomyopathy. Molecular autopsy is essential in prevention of these SCD, and a close collaboration between cardiologists, pathologists, microbiologists and geneticians is mandatory.

Modelling of a RYR2-associated left ventricular non-compaction and sudden cardiac death overlap syndrome in hiPSC-EHTs

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): ESC training grant; DZHK Background Genetic cardiomyopathies contribute to a significant proportion of morbidity and mortality among young people. Over the past decades, a wide range of underlying molecular mechanisms has been discovered. The current project arose from the clinical observation of a left ventricular non-compaction and sudden cardiac death overlap syndrome in a large family in northern Italy. Whole exome sequencing performed on family members of different generations revealed a single nucleotide polymorphism in the RYR2 gene (RYR2 c.5654G&amp;gt;A homozygous – RyR2 p.G1885E - exon37:missense) with an autosomal-recessive inheritance pattern. The mutation is localized in the DR3 region of the RyR2 protein, adjacent to the FKBP12.6 binding site, a protein that is known to stabilize RyR2, preventing aberrant activation of the channel. Methods and Results Patient-derived, human induced pluripotent stem cells (hiPSCs), carrying the variant homo- and heterozygously, were generated by reprogramming patient-derived peripheral blood mononuclear cells using a non-integrative Sendai virus protocol. The lines were fully characterized and expressed high levels of pluripotency markers at the RNA and protein level. Patient lines were all able to efficiently differentiate into cardiomyocytes. Subsequently, 3D strip-format, force-generating Engineered Heart Tissues (EHTs) were cast and structurally and functionally characterized. Contraction analysis over 60 days showed differences in force development of the patient-derived lines. In particular, the EHTs carrying the homozygous pathogenic variant showed progressive reduction in both beating rate and force over time, increased spontaneous arrhythmogenicity and reduced inotropic response after exposure to isoprenaline, compared to the heterozygous line and unrelated healthy controls. Starting from day 30 after casting, patient-derived EHTs developed morphological changes with areas of marked cellular overgrowth and reduced troponin expression. Transcriptomic and proteomic analysis at 30 and 60 days after EHTs generation, as well as in 2D cardiomyocytes, complement the phenotyping and provide molecular insights into the underlying pathophysiology. To directly evaluate pathogenicity of the genetic variant identified, we generated isogenic homo- and heterozygously corrected hiPSCs, using CRISPR/ Cas9 technology, starting from the homozygous patient-line. The characterization of these corrected clones is currently ongoing. The genetically corrected 3D tissue models will be critical not only in defining the role of the novel RyR2 variant in the familial phenotype described, but also to unveil mechanistic roles of ryanodine receptor in cardiac disease. Conclusion We describe a novel recessive RYR2 variant associated with a left ventricular non- compaction and sudden cardiac death overlap syndrome. 3D cardiac tissue modelling based on patient-derived hiPSCs uncovered a proarrhythmic and structural phenotype of the mutated lines.

Coexistence of cardiac sarcoidosis and genetic cardiomyopathies: a conundrum

Abstract Introduction Cardiac sarcoidosis (CS) is a chronic inflammatory disease characterized histologically by the formation of non-caseating granuloma in the myocardium, however, causes remain largely unknown. Genetic arrhythmogenic cardiomyopathy (ACM) is an important differential diagnosis of CS. Until now, few data are available about the coexistence of CS in a patient with genetic ACM harboring a desmoglein-2 (DSG2) variant. Purpose We report a case series of patients who demonstrate coexistence of histologically proven CS and genetic ACM. Methods This is a multicentric study, which included patients from four high-volume cardiology referral centres for heart failure and ACM in Switzerland, Italy, and Austria. Patients with both a biopsy-proven diagnosis of sarcoidosis with cardiac involvement (according to the 2014 HRS criteria) also harboring a pathogenic/likely pathogenic (P/LP) variant for cardiomyopathy-associated genes were 1:1 matched for age, gender and genetic variant with patients with genetic ACM without CS (Gen-only). Clinical and imaging data (echocardiography (TTE), cardiac magnetic resonance (CMR) and positron-emission tomography (18FFDG-PET/CT) were collected. Results Each group included 5 patients (Gen+CS: age 48 ± 11 years, Gen only: age 52 ± 13.7 years, n=3 (60%) female in both groups). For each group, the following genes with P/LP variants were found: PKP2: n=2 (40%), DSG2: n=1 (20%), DSP: n=1 (20%), TTN: n=1 (20%). In patients with Gen+CS, atrio-ventricular block (AVB) I° (80% vs 20%, p=0.05) and paroxysmal atrial fibrillation (80% vs 0%, p=0.004) were more frequent, and median NT-proBNP levels (1346ng/l, IQR:103-4276 vs. 214ng/l, IQR:131-326, p=0.046), as well as high-sensitive C-reactive protein levels were higher (3.1g/dl, IQR:1.1-24.2 vs. 0.7g/dl, IQR:0.3-0.95, p=0.016). On imaging, Gen+CS patients were more likely to have septal involvement (60% vs 0%, p=0.021), as highlighted by positive late-gadolinium enhancement on CMR, metabolic activity on PET, or focal wall motion anomalies on TTE. Conclusions CS and genetic ACM can coexist. Hence, detection of a P/LP genetic variant associated with ACM should not lead to exclusion of CS, which more frequently presents with AVB, septal involvement, heart failure, and metabolic activity on imaging. On the contrary, CS can be associated with genetic variants in cardiomyopathy-associated genes.FDG-PET/CT

In vivo rescue of genetic dilated cardiomyopathy by systemic delivery of nexilin

BackgroundDilated cardiomyopathy (DCM) is one of the most common causes of heart failure. Multiple identified mutations in nexilin (NEXN) have been suggested to be linked with severe DCM. However, the exact association between multiple mutations of Nexn and DCM remains unclear. Moreover, it is critical for the development of precise and effective therapeutics in treatments of DCM.ResultsIn our study, Nexn global knockout mice and mice carrying human equivalent G645del mutation are studied using functional gene rescue assays. AAV-mediated gene delivery is conducted through systemic intravenous injections at the neonatal stage. Heart tissues are analyzed by immunoblots, and functions are assessed by echocardiography. Here, we identify functional components of Nexilin and demonstrate that exogenous introduction could rescue the cardiac function and extend the lifespan of Nexn knockout mouse models. Similar therapeutic effects are also obtained in G645del mice, providing a promising intervention for future clinical therapeutics.ConclusionsIn summary, we demonstrated that a single injection of AAV-Nexn was capable to restore the functions of cardiomyocytes and extended the lifespan of Nexn knockout and G645del mice. Our study represented a long-term gene replacement therapy for DCM that potentially covers all forms of loss-of-function mutations in NEXN.

Allele-Specific Suppression of Variant MHC With High-Precision RNA Nuclease CRISPR-Cas13d Prevents Hypertrophic Cardiomyopathy.

Familial hypertrophic cardiomyopathy has severe clinical complications of heart failure, arrhythmia, and sudden cardiac death. Heterozygous single nucleotide variants (SNVs) of sarcomere genes such as MYH7 are the leading cause of this type of disease. CRISPR-Cas13 (clustered regularly interspaced short palindromic repeats and their associated protein 13) is an emerging gene therapy approach for treating genetic disorders, but its therapeutic potential in genetic cardiomyopathy remains unexplored. We developed a sensitive allelic point mutation reporter system to screen the mutagenic variants of Cas13d. On the basis of Cas13d homology structure, we rationally designed a series of Cas13d variants and obtained a high-precision Cas13d variant (hpCas13d) that specifically cleaves the MYH7 variant RNAs containing 1 allelic SNV. We validated the high precision and low collateral cleavage activity of hpCas13d through various in vitro assays. We generated 2 HCM mouse models bearing distinct MYH7 SNVs and used adenovirus-associated virus serotype 9 to deliver hpCas13d specifically to the cardiomyocytes. We performed a large-scale library screening to assess the potency of hpCas13d in resolving 45 human MYH7 allelic pathogenic SNVs. Wild-type Cas13d cannot distinguish and specifically cleave the heterozygous MYH7 allele with SNV. hpCas13d, with 3 amino acid substitutions, had minimized collateral RNase activity and was able to resolve various human MYH7 pathological sequence variations that cause hypertrophic cardiomyopathy. In vivo application of hpCas13d to 2 hypertrophic cardiomyopathy models caused by distinct human MYH7 analogous sequence variations specifically suppressed the altered allele and prevented cardiac hypertrophy. Our study unveils the great potential of CRISPR-Cas nucleases with high precision in treating inheritable cardiomyopathy and opens a new avenue for therapeutic management of inherited cardiac diseases.

Genetic Testing Resources and Practice Patterns Among Pediatric Cardiomyopathy Programs.

The use of genetic testing has enhanced the diagnostic accuracy of heritable genetic cardiomyopathies. However, it remains unclear how genetic information is interpreted and incorporated into clinical practice for children with cardiomyopathy. The primary aim of this study was to understand how clinical practice differs regarding sequence variant classifications amongst pediatric cardiologists who treat children with cardiomyopathy. A secondary aim was to understand the availability of genetic testing and counseling resources across participating pediatric cardiomyopathy programs. An electronic survey was distributed to pediatric heart failure, cardiomyopathy, or heart transplantation physicians between August and September 2022. A total of 106 individual providers from 68 unique centers responded to the survey. Resources for genetic testing and genetic counseling vary among large pediatric cardiomyopathy programs. A minority of centers reported having a geneticist (N = 16, 23.5%) or a genetic counselor (N = 21, 31%) on faculty within the division of pediatric cardiology. A total of 9 centers reported having both (13%). Few centers (N = 13, 19%) have a formal process in place to re-engage patients who were previously discharged from cardiology follow-up if variant reclassification would alter clinical management. Clinical practice patterns were uniform in response to pathogenic or likely pathogenic variants but were more variable for variants of uncertain significance. Efforts to better incorporate genetic expertise and resources into the clinical practice of pediatric cardiomyopathy may help to standardize the interpretation of genetic information and better inform clinical decision-making surrounding heritable cardiomyopathies.