Approaches to Genetic Screening in Cardiomyopathies: Practical Guidance for Clinicians

Patients and families benefit when the genetic etiology of cardiomyopathy is elucidated through a multidisciplinary approach including genetic counseling and judicious use of genetic testing. The yield of genetic testing is optimized when performed on a proband with a clear phenotype, and interrogates genes that are validated in association with that specific form of cardiomyopathy. Variants of uncertain significance are frequently uncovered and should not be overinterpreted. Identifying an impactful genetic variant as the cause of a patient's cardiomyopathy can have important prognostic impact, and enable streamlined cascade testing to highlight at risk relatives. Certain genotypes are associated with unique potential cardiac and noncardiac risk factors and may dictate personalized approaches to treatment.

Cardiovascular manifestations of hypermobile Ehlers-Danlos syndrome and hypermobility spectrum disorders

Introduction: Mitral valve prolapse and aortic root dilatation are reported in association with hypermobile Ehlers-Danlos syndrome (hEDS), but the full phenotypic spectrum of cardiovascular complications in this condition has not been studied in the aftermath of updated nosology and diagnostic criteria. Methods: We performed a retrospective review of 258 patients (> 94% adults) referred to a multidisciplinary clinic for evaluation of joint hypermobility between January 2017 and December 2020 and diagnosed with hEDS or a hypermobility spectrum disorder (HSD) to determine the incidence and spectrum of cardiovascular involvement. Results: Mitral valve prolapse was present in 7.5% and thoracic aortic dilatation in 15.2%. Aortic dilatation was more frequent in individuals with hEDS (20.7%) than with HSD (7.7%) and similarly prevalent between males and females, although was mild in > 90% of females and moderate-to-severe in 50% of males. Five individuals (1.9%) with hEDS/HSD had extra-aortic arterial involvement, including cervical artery dissection (CeAD, n = 2), spontaneous coronary artery dissection (SCAD, n = 2), and SCAD plus celiac artery pseudoaneurysm (n = 1). This is the first series to report the prevalence of CeAD and SCAD in hEDS/HSD. Conclusions: Cardiovascular manifestations in adults with hEDS/HSD, especially females, are typically mild and readily assessed by echocardiography. Since the risk of progression has not yet been defined, adults with hEDS/HSD who are found to have aortic dilatation at baseline should continue ongoing surveillance to monitor for progressive dilatation. Cardiovascular medicine specialists, neurologists, and neurosurgeons should consider hEDS/HSD on the differential for patients with CeAD or SCAD who also have joint hypermobility.

Dysautonomia in hypermobile Ehlers-Danlos syndrome and hypermobility spectrum disorders is associated with exercise intolerance and cardiac atrophy

Dysautonomia is a recognized manifestation in patients with joint hypermobility (JH) disorders. Symptoms can be highly debilitating and commonly include physical deconditioning and poor aerobic fitness. In this study, the prevalence of dysautonomia, range of associated symptoms, patient-reported physical activity levels, and echocardiographic features were assessed retrospectively in a cohort of 144 patients (94% female) with hypermobile Ehlers-Danlos syndrome (hEDS) or hypermobility spectrum disorder (HSD). Echocardiographic parameters of left ventricular size and function were compared between patients with and without dysautonomia as well as to reported values from healthy controls. Dysautonomia was identified in 65% of female and 44% of male subjects and was associated with a high burden of symptomatology, most commonly exercise intolerance (78%). Exercise capacity was limited by dysautonomia, often postural symptoms, in half of all patients. We observed a reduction in physical activity following the onset or significant flare of hEDS/HSD, most strikingly noting the proportion of dysautonomic patients with sedentary lifestyle, which increased from 44% to 85%. JH-related dysautonomia was associated with smaller cardiac chamber sizes, consistent with the previous reports in positional orthostatic tachycardia syndrome. Dysautonomia is prevalent in patients with hEDS/HSD, and exercise intolerance is a key feature and leads to drastic decline in physical activity. Unfavorable cardiac geometry may underlie dysautonomia symptoms and may be due to cardiac atrophy in the setting of aerobic deconditioning.

Burden of Cardiomyopathic Genetic Variation in Lethal Pediatric Myocarditis

BACKGROUND

Acute myocarditis (AM) is a well-known cause of sudden death and heart failure, often caused by prevalent viruses. We previously showed that some pediatric AM correlates with putatively damaging variants in genes related to cardiomyocyte structure and function. We sought to evaluate whether deleterious cardiomyopathic variants were enriched among fatal pediatric AM cases in New York City compared with ancestry-matched controls.

METHODS

Twenty-four children (aged 3 weeks to 20 years) with death due to AM were identified through autopsy records; histologies were reviewed to confirm that all cases met Dallas criteria for AM and targeted panel sequencing of 57 cardiomyopathic genes was performed. Controls without cardiovascular disease were identified from a pediatric database and matched by genetic ancestry to cases using principal components from exome sequencing. Rates of putative deleterious variations (DV) were compared between cases and controls. Where available, AM tissues underwent viral analysis by polymerase chain reaction.

RESULTS

DV were identified in 4 of 24 AM cases (16.7%), compared with 2 of 96 age and ancestry-matched controls (2.1%, P=0.014). Viral causes were proven for 6 of 8 AM cases (75%), including the one DV+ case where tissue was available for testing. DV+ cases were more likely to be female, have no evidence of chronic inflammation, and associate with sudden cardiac death than DV- cases.

CONCLUSIONS

Deleterious variants in genes related to cardiomyocyte integrity are more common in children with fatal AM than controls, likely conferring susceptibility. Additionally, genetically mediated AM may progress more rapidly and be more severe.

Myopathic Cardiac Genotypes Increase Risk for Myocarditis

Impairments in certain cardiac genes confer risk for myocarditis in children. To determine the extent of this association, we performed genomic sequencing in predominantly adult patients with acute myocarditis and matched control subjects. Putatively deleterious variants in a broad set of cardiac genes were found in 19 of 117 acute myocarditis cases vs 34 of 468 control subjects (P = 0.003). Thirteen genes classically associated with cardiomyopathy or neuromuscular disorders with cardiac involvement were implicated, including >1 associated damaging variant in DYSF, DSP, and TTN. Phenotypes of subjects who have acute myocarditis with or without deleterious variants were similar, indicating that genetic testing is necessary to differentiate them.

Genomic Screening Identifies Individuals at High Risk for Hereditary Transthyretin Amyloidosis

The TTR V142I variant associated with hereditary transthyretin amyloidosis (hATTR) is present in up to 4% of African American (AA) and 1% of Hispanic/Latinx (HL) individuals and increases risk for heart failure. Delayed and missed diagnoses could potentiate health disparities in these populations. We evaluated whether population-based genomic screening could effectively identify individuals at risk for hATTR and prompt initiation of risk management. We identified participants of the BioMe Biobank in New York City who received TTR V142I results through a pilot genomic screening program. We performed a retrospective medical record review to evaluate for the presence hATTR-related systemic features, uptake of recommended follow-up, and short-term outcomes. Thirty-two AA (N = 17) and HL (N = 15) individuals received a TTR V142I result (median age 57, 81% female). None had a previous diagnosis of hATTR. Eighteen (56%) had hATTR-related systemic features, including 4 (13%) with heart failure, 10 (31%) with carpal tunnel syndrome, and 10 (31%) with spinal stenosis. Eighteen (56%) pursued follow-up with a cardiologist within 8 months. One person received a diagnosis of hATTR. Thus, we found that the majority of V142I-positive individuals had hATTR-related systemic features at the time of result disclosure, including well-described red flags. Genomic screening can help identify hATTR risk and guide management early on, avoiding potential delays in diagnosis and treatment.

A genotype-first approach to exploring Mendelian cardiovascular traits with clear external manifestations

Purpose:

The purpose of this study is to use a genotype-first approach to explore highly penetrant, autosomal dominant cardiovascular diseases with external features, the RASopathies and Marfan syndrome (MFS), using biobank data.

Methods:

This study uses exome sequencing and corresponding phenotypic data from Mount Sinai’s BioMe (n = 32,344) and the United Kingdom Biobank (UKBB; n = 49,960). Variant curation identified pathogenic/likely pathogenic (P/LP) variants in RASopathy genes and FBN1.

Results:

Twenty-one subjects harbored P/LP RASopathy variants; three (14%) were diagnosed, and another 46% had ≥1 classic Noonan syndrome (NS) feature. Major NS features (short stature (9.5% p = 7e-5) and heart anomalies (19%, p < 1e-5)) were less frequent than expected. Prevalence of hypothyroidism/autoimmune disorders was enriched compared to biobank populations (p = 0.007). For subjects with FBN1 P/LP variants, 14/41 (34%) had a MFS diagnosis or highly suggestive features. 5/15 participants (33%) with echocardiographic data had aortic dilation, fewer than expected (p=8e-6). Ectopia lentis affected only 15% (p < 1e-5).

Conclusions:

Substantial fractions of individuals harboring P/LP variants with partial or full phenotypic matches to a RASopathy or MFS remain undiagnosed, some not meeting diagnostic criteria. Routine population genotyping would enable multi-disciplinary care and avoid life-threatening events.

Headaches in hypermobility syndromes: A pain in the neck?

Headache and neck pain (cervicalgia) are frequently reported among patients with joint hypermobility but the prevalence and scope of these symptoms has not been studied in the era of contemporary Ehlers-Danlos and hypermobility disorder nosology. We performed a single-center retrospective study on the incidence of head and neck symptoms in 140 patients with hypermobility disorders over a 2-year period. Overall, 93 patients (66%) reported either headache or neck pain with 49 of those (53%) reporting both. Migraine (83%) was the most common headache type among those with headache disorders and cervical spondylosis (61%) the most common pathology among those with neck symptoms. Fifty-nine percent of spondylosis patients who underwent cervical facet procedures reported significant improvement in neck and head symptoms. Of patients with both head and neck complaints, 82% had both migraine and spondylosis, which, when combined with the high response rate to injections raises the possibility of cervicogenic headache. In this large multidisciplinary retrospective study of patients with hypermobility disorders, head and neck symptoms were highly prevalent, with migraine and cervical spondylosis common, often coexisting, and frequently responsive to targeted therapy for the cervical spine suggesting that degenerative spinal pathology may cause or contribute to headache symptoms in some patients with hypermobility disorders.

Viral myocarditis--diagnosis, treatment options, and current controversies

Myocarditis--a frequent cause of dilated cardiomyopathy and sudden cardiac death--typically results from cardiotropic viral infection followed by active inflammatory destruction of the myocardium. Characterization of this disease has been hampered by its heterogeneous clinical presentations and diverse aetiologies. Advances in cardiac MRI and molecular detection of viruses by endomyocardial biopsy have improved our ability to diagnose and understand the pathophysiological mechanisms of this elusive disease. However, therapeutic options are currently limited for both the acute and chronic phases of myocarditis. Several randomized, controlled trials have demonstrated potential benefit with immunosuppressive and immunomodulatory therapies, but further investigations are warranted. In this Review, we explore the pathophysiology, natural history, and modes of diagnosis of myocarditis, as well as evidence-based treatment strategies. As novel imaging techniques and human in vitro models of the disease emerge, the landscape of therapies for myocarditis is poised to improve.

Abstract 256: mRNA-based Nanoparticles Are Highly Effective Agents For Cardiac Gene Therapy

Gene therapy holds promise for repair and regeneration of damaged myocardium after infarction. Viral vectors used in most studies, while highly effective, carry concerns of safety and immunogenicity. Nanoparticle (NP)-enabled transfection using polymeric and lipidoid reagents mitigates some of the concerns related to the use of viral vectors. However, these agents have been less effective in transfecting cardiac myocytes, which are primarily post-mitotic and only weakly facilitate DNA entry to the nucleus. Because translation occurs in the cytosol, transfection with RNA obviates the need for nuclear entry. Recent work has shown that synthetic alterations to messenger RNA (mRNA) can prolong its half-life in the cytosol and diminish the host’s immune response. We hypothesized that transfection of cardiac myocytes with lipidoid NPs formed using modified mRNA would lead to high levels of protein expression. Neonatal rat (NRCM), adult rat (ARCM) and human embryonic stem cell-derived (hES-CM) cardiac myocytes were transfected with modified GFP-mRNA NPs using a lipidoid vehicle (Stemfect TM , Stemgent, Cambridge, MA) or Lipofectamine2000 (LF, Invitrogen) and GFP expression was assessed after 24 hours. Average transfection efficiency in NRCM was significantly higher using Stemfect versus LF as measured by flow cytometry (48.5% vs. 6.6% at 20ng mRNA; 47.4% vs. 11.8% at 40ng mRNA, 48.1% vs. 18.6% at 80ng mRNA; 48.1% vs. 28% at 160ng mRNA; n=3, p<0.01 for each pair). In hES-CM transfection was also more robust with Stemfect NPs versus LF (91.6% vs. 62.2%, p<0.05 at 40ng mRNA; 96.1 vs. 87.8%, p<0.01 at 160ng mRNA; n=3). GFP expression was noted by fluorescence microscopy to be higher in ARCMs transfected with Stemfect NPs versus LF. In conclusion, we have shown that difficult-to-transfect cardiac myocytes are readily transfected with mRNA-based NPs in vitro and with significantly higher efficiency when using Stemfect rather than Lipofectamine. Gene therapy with mRNA represents a novel approach to cardiac repair and may be preferable to DNA because of the transient window of protein expression and lower side effect profile.