Updated clinical overview on cardiac laminopathies: an electrical and mechanical disease

Missense and Non-Missense Lamin A/C Gene Mutations Are Similarly Associated with Major Arrhythmic Cardiac Events: A 20-Year Single-Centre Experience

Arrhythmic risk stratification in patients with Lamin A/C gene (LMNA)-related cardiomyopathy influences clinical decisions. An implantable cardioverter defibrillator (ICD) should be considered in patients with an estimated 5-year risk of malignant ventricular arrhythmia (MVA) of ≥10%. The risk prediction score for MVA includes non-missense LMNA mutations, despite their role as an established risk factor for sudden cardiac death (SCD) has been questioned in several studies. The purpose of this study is to investigate cardiac features and find gene-phenotype correlations that would contribute to the evidence on the prognostic implications of non-missense vs. missense mutations in a cohort of LMNA mutant patients. An observational, prospective study was conducted in which 54 patients positive for a Lamin A/C mutation were enrolled, and 20 probands (37%) were included. The median age at first clinical manifestation was 41 (IQR 19) years. The median follow-up was 8 years (IQR 8). The type of LMNA gene mutation was distributed as follows: missense in 26 patients (48%), non-frameshift insertions in 16 (30%), frameshift deletions in 5 (9%), and nonsense in 7 (13%). Among the missense mutation carriers, two (8%) died and four (15%) were admitted onto the heart transplant list or underwent transplantation, with a major adverse cardiovascular event (MACE) rate of 35%. No statistically significant differences in MACE prevalence were identified according to the missense and non-missense mutation groups (p value = 0.847). Our data shift the spotlight on this considerable topic and could suggest that some missense mutations may deserve attention regarding SCD risk stratification in real-world clinical settings.

Vascular organs-on-chip made with patient-derived endothelial cells: technologies to transform drug discovery and disease modeling

INTRODUCTION

Vascular diseases impart a tremendous burden on healthcare systems in the United States and across the world. Efforts to improve therapeutic interventions are hindered by limitations of current experimental models. The integration of patient-derived cells with organ-on-chip (OoC) technology is a promising avenue for preclinical drug screening that improves upon traditional cell culture and animal models.

AREAS COVERED

The authors review induced pluripotent stem cells (iPSC) and blood outgrowth endothelial cells (BOEC) as two sources for patient-derived endothelial cells (EC). They summarize several studies that leverage patient-derived EC and OoC for precision disease modeling of the vasculature, with a focus on applications for drug discovery. They also highlight the utility of patient-derived EC in other translational endeavors, including ex vivo organogenesis and multi-organ-chip integration.

EXPERT OPINION

Precision disease modeling continues to mature in the academic space, but end-use by pharmaceutical companies is currently limited. To fully realize their transformative potential, OoC systems must balance their complexity with their ability to integrate with the highly standardized and high-throughput experimentation required for drug discovery and development.

Ion channel dysfunction and fibrosis in atrial fibrillation: Two sides of the same coin

BACKGROUND

Atrial fibrillation (AF) is a common heart rhythm disorder that is associated with an increased risk of stroke and heart failure (HF). Initially, an association between AF and ion channel dysfunction was identified, classifying the pathology as a predominantly electrical disease. More recently it has been recognized that fibrosis and structural atrial remodeling play a driving role in the development of this arrhythmia also in these cases.

PURPOSE

Understanding the role of fibrosis in genetic determined AF could be important to better comprise the pathophysiology of this arrhythmia and to refine its management also in nongenetic forms. In this review we analyze genetic and epigenetic mechanisms responsible for AF and their link with atrial fibrosis, then we will consider analogies with the pathophysiological mechanism in nongenetic AF, and discuss consequent therapeutic options.

Electrocardiographic abnormalities in patients with cardiomyopathies

Abnormalities in impulse generation and transmission are among the first signs of cardiac remodeling in cardiomyopathies. Accordingly, 12-lead electrocardiogram (ECG) of patients with cardiomyopathies may show multiple abnormalities. Some findings are suggestive of specific disorders, such as the discrepancy between QRS voltages and left ventricular (LV) mass for cardiac amyloidosis or the inverted T waves in the right precordial leads for arrhythmogenic cardiomyopathy. Other findings are less sensitive and/or specific, but may orient toward a specific diagnosis in a patient with a specific phenotype, such as an increased LV wall thickness or a dilated LV. A "cardiomyopathy-oriented" mindset to ECG reading is important to detect the possible signs of an underlying cardiomyopathy and to interpret correctly the meaning of these alterations, which differs in patients with cardiomyopathies or other conditions.

Novel pathogenic variant in LMNA gene identified in a six-generation family causing atrial cardiomyopathy and associated right atrial conduction arrhythmias

Objective

To characterize the cardiac phenotype associated with the novel pathogenic variant (c.1526del) of LMNA gene, which we identified in a large, six-generation family.

Methods and Results

A family tree was constructed. The clinical data of living and deceased family members were collected. DNA samples from 7 family members were analyzed for LMNA mutations using whole-exome high-throughput sequencing technology. The clinical presentation of pathogenic variant carriers was evaluated. In this six-generation family (n = 67), one member experienced sudden death at the age of 40-years-old. Three pathogenic variant carriers were identified to possess a novel heterozygous deletion mutation in LMNA gene (HGVS: NM_170707.4, c.1526del) located at exon 9 of LMNA chr1:156137145, which creates a premature translational stop signal (p.Pro509Leufs*39) in the LMNA gene and results in an mutant lamin A protein product. The main symptoms of the pathogenic variant carriers were palpitation, fatigue, and syncope, which typically occurred around 20-years-old. AV-conduction block and non-sustained ventricular tachycardia were the first signs of disease and would rapidly progress to atrial standstill around 30-years-old. Significant right atrial enlargement and bicuspid aortic valve malformation was also commonly seen in patients who carried this pathogenic variant.

Conclusion

The pathogenic variant of c.1526del p.P509Lfs*39 was a frameshift deletion located at exon 9 of LMNA chr1:156137145 and causes severe right atrial enlargement, sick sinus syndrome, atrial standstill, ventricular tachycardia, and bicuspid aortic valve malformation. Our findings expand the phenotypic spectrum of novel LMNA gene mutations.

Targeting unfolded protein response reverts ER stress and ER Ca2+ homeostasis in cardiomyocytes expressing the pathogenic variant of Lamin A/C R321X

BACKGROUND

We previously demonstrated that an Italian family affected by a severe dilated cardiomyopathy (DCM) with history of sudden deaths at young age, carried a mutation in the Lmna gene encoding for a truncated variant of the Lamin A/C protein (LMNA), R321X. When expressed in heterologous systems, such variant accumulates into the endoplasmic reticulum (ER), inducing the activation of the PERK-CHOP pathway of the unfolded protein response (UPR), ER dysfunction and increased rate of apoptosis. The aim of this work was to analyze whether targeting the UPR can be used to revert the ER dysfunction associated with LMNA R321X expression in HL-1 cardiac cells.

METHODS

HL-1 cardiomyocytes stably expressing LMNA R321X were used to assess the ability of 3 different drugs targeting the UPR, salubrinal, guanabenz and empagliflozin to rescue ER stress and dysfunction. In these cells, the state of activation of both the UPR and the pro-apoptotic pathway were analyzed monitoring the expression levels of phospho-PERK, phospho-eIF2α, ATF4, CHOP and PARP-CL. In addition, we measured ER-dependent intracellular Ca²⁺ dynamics as indicator of proper ER functionality.

RESULTS

We found that salubrinal and guanabenz increased the expression levels of phospho-eIF2α and downregulated the apoptosis markers CHOP and PARP-CL in LMNA R321X-cardiomyocytes, maintaining the so-called adaptive UPR. These drugs also restored ER ability to handle Ca²⁺ in these cardiomyocytes. Interestingly, we found that empagliflozin downregulated the apoptosis markers CHOP and PARP-CL shutting down the UPR itself through the inhibition of PERK phosphorylation in LMNA R321X-cardiomyocytes. Furthermore, upon empagliflozin treatment, ER homeostasis, in terms of ER ability to store and release intracellular Ca²⁺ was also restored in these cardiomyocytes.

CONCLUSIONS

We provided evidence that the different drugs, although interfering with different steps of the UPR, were able to counteract pro-apoptotic processes and to preserve the ER homeostasis in R321X LMNA-cardiomyocytes. Of note, two of the tested drugs, guanabenz and empagliflozin, are already used in the clinical practice, thus providing preclinical evidence for ready-to-use therapies in patients affected by the LMNA R321X associated cardiomyocytes.

Personalized Management of Sudden Death Risk in Primary Cardiomyopathies: From Clinical Evaluation and Multimodality Imaging to Ablation and Cardioverter-Defibrillator Implant

Sudden cardiac death represents the leading cause of death worldwide; although the majority of sudden deaths occur in an elderly population with coronary artery disease, some occur in young and otherwise healthy individuals, as is the case of cardiomyopathies. The aim of the present review is to provide a stepwise hierarchical approach for the global sudden death risk estimation in primary cardiomyopathies. Each individual risk factor is analyzed for its contribution to the overall risk of sudden death for each specific cardiomyopathy as well as across all primary myocardial diseases. This stepwise hierarchical and personalized approach starts from the clinical evaluation, subsequently passes through the role of electrocardiographic monitoring and multimodality imaging, and finally concludes with genetic evaluation and electro-anatomical mapping. In fact, the sudden cardiac death risk assessment in cardiomyopathies depends on a multiparametric approach. Moreover, current indications for ventricular arrhythmia ablation and defibrillator implantation are discussed.

Myocardial Inflammation as a Manifestation of Genetic Cardiomyopathies: From Bedside to the Bench

Over recent years, preclinical and clinical evidence has implicated myocardial inflammation (M-Infl) in the pathophysiology and phenotypes of traditionally genetic cardiomyopathies. M-Infl resembling myocarditis on imaging and histology occurs frequently as a clinical manifestation of classically genetic cardiac diseases, including dilated and arrhythmogenic cardiomyopathy. The emerging role of M-Infl in disease pathophysiology is leading to the identification of druggable targets for molecular treatment of the inflammatory process and a new paradigm in the field of cardiomyopathies. Cardiomyopathies constitute a leading cause of heart failure and arrhythmic sudden death in the young population. The aim of this review is to present, from bedside to bench, the current state of the art about the genetic basis of M-Infl in nonischemic cardiomyopathies of the dilated and arrhythmogenic spectrum in order to prompt future research towards the identification of novel mechanisms and treatment targets, with the ultimate goal of lowering disease morbidity and mortality.

Accelerated Aging in LMNA Mutations Detected by Artificial Intelligence ECG-Derived Age

OBJECTIVE

To demonstrate early aging in patients with lamin A/C (LMNA) gene mutations after hypothesizing that they have a biological age older than chronological age, as such a finding impacts care.

PATIENT AND METHODS

We applied a previously trained convolutional neural network model to predict biological age by electrocardiogram (ECG) [Artificial Intelligence (AI)-ECG age] to LMNA patients evaluated by multiple ECGs from January 1, 2003, to December 31, 2019. The age gap was the difference between chronological age and AI-ECG age. Findings were compared with age-/sex-matched controls.

RESULTS

Thirty-one LMNA patients who had a total of 271 ECGs were studied. The median age at symptom onset was 22 years (range, <1-53 years; n=23 patients); eight patients were asymptomatic family members carrying the LMNA mutation. Cardiac involvement was detected by ECG and echocardiogram in 16 patients and consisted of ventricular arrhythmias (13), atrial fibrillation (12), and cardiomyopathy (6). Four patients required cardiac transplantation. Fourteen patients had neurological manifestations, mainly muscular dystrophy. LMNA mutation carriers, including asymptomatic carriers, were 16 years older by AI-ECG than non-LMNA carriers, suggesting accelerated biological age. Most LMNA patients had an age gap of more than 10 years, compared with controls (P<.001). Consecutive AI-ECG analysis showed accelerated aging in the LMNA group compared with controls (P<.0001). There were no significant differences in age-gap among LMNA patients based on phenotype.

CONCLUSION

AI-ECG predicted that LMNA patients have a biological age older than chronological age and accelerated aging even in the absence of cardiac abnormalities by traditional methods. Such a finding could translate into early medical intervention and serve as a disease biomarker.

Genomic analysis of a novel pathogenic variant in the gene LMNA associated with cardiac laminopathies found in Ecuadorian siblings: A case report

Introduction

Cardiac laminopathies are caused by mutations in the LMNA gene and include a wide range of clinical manifestations involving electrical and mechanical changes in cardiomyocytes. In Ecuador, cardiovascular diseases were the primary cause of death in 2019, accounting for 26.5% of total deaths. Cardiac laminopathy-associated mutations involve genes coding for structural proteins with functions related to heart development and physiology.

Family description

Two Ecuadorian siblings, self-identified as mestizos, were diagnosed with cardiac laminopathies and suffered embolic strokes. Moreover, by performing Next-Generation Sequencing, a pathogenic variant (NM_170707.3:c.1526del) was found in the gene LMNA.

Discussion and conclusion

Currently, genetic tests are an essential step for disease genetic counseling, including cardiovascular disease diagnosis. Identification of a genetic cause that may explain the risk of cardiac laminopathies in a family can help the post-test counseling and recommendations from the cardiologist. In the present report, a pathogenic variant ((NM_170707.3:c.1526del) has been identified in two Ecuadorian siblings with cardiac laminopathies. The LMNA gene codes for A-type laminar proteins that are associated with gene transcription regulation. Mutations in the LMNA gene cause laminopathies, disorders with diverse phenotypic manifestations. Moreover, understanding the molecular biology of the disease-causing mutations is essential in deciding the correct type of treatment.

The Aging Heart: A Molecular and Clinical Challenge

Aging is associated with an increasing burden of morbidity, especially for cardiovascular diseases (CVDs). General cardiovascular risk factors, ischemic heart diseases, heart failure, arrhythmias, and cardiomyopathies present a significant prevalence in older people, and are characterized by peculiar clinical manifestations that have distinct features compared with the same conditions in a younger population. Remarkably, the aging heart phenotype in both healthy individuals and patients with CVD reflects modifications at the cellular level. An improvement in the knowledge of the physiological and pathological molecular mechanisms underlying cardiac aging could improve clinical management of older patients and offer new therapeutic targets.

Inflammation on Endomyocardial Biopsy Predicts Risk of MACE in Undefined Left Ventricular Arrhythmogenic Cardiomyopathy

BACKGROUND

Predictors of major adverse cardiovascular events (MACE) in patients with undefined left ventricular arrhythmogenic cardiomyopathy (ULVACM) have not been described.

OBJECTIVES

The purpose of this study was to investigate the prognostic value of genetic testing and histology in a cohort of ULVACM patients.

METHODS

We identified 313 patients with ULVACM defined by new-onset ventricular arrhythmia (VA), nonischemic pattern of late gadolinium enhancement limited to the left ventricle (LV), and no severe dilated cardiomyopathy (LV ejection fraction ≥40%) from a retrospective multicenter registry. Patients undergoing next generation sequencing (NGS) for cardiomyopathy genes and endomyocardial biopsy (EMB) were compared with subjects without these studies. The primary endpoint was the occurrence of MACE, defined as the composite of cardiac death, heart transplantation, and malignant VA (ventricular tachycardia, ventricular fibrillation, appropriate implantable cardioverter-defibrillator treatment), at 60 months after clinical presentation.

RESULTS

Of the whole cohort (age 46 ± 14 years, 63% men, LV ejection fraction 55% ± 7%), 160 (51%) and 198 patients (63%), respectively, underwent NGS and EMB. NGS identified pathogenic or likely-pathogenic cardiomyopathy variants (pathogenic variants/likely pathogenic variants) in 25 of 160 cases (16%). EMB showed active myocardial inflammation (AM) in 102 of 198 patients (52%), 47 of whom (46%) received immunosuppressive therapy. After 58-month median follow-up, 93 of 313 patients (30%) experienced MACE. On multivariable analysis, presentation with malignant VA and EMB-proven AM were positively associated with the primary endpoint (HR: 2.8; 95% CI: 1.4-5.5; P = 0.003; and HR: 3.9; 95% CI: 1.9-7.5; P < 0.001, respectively), whereas immunosuppressive therapy showed a reverse association with MACE at 60 months (HR: 0.10; 95% CI: 0.05-0.40; P < 0.001).

CONCLUSIONS

Presentation with malignant VA or AM associates with MACE in ULVACM patients.

Laminopathies: should Wenckebach be a cause for concern? A case report

Background

LMNA cardiomyopathy is a cause of dilated cardiomyopathy (DCM) characterized by aggressive heart failure, high risk of arrhythmias, and sudden cardiac death. We present a case of a male presenting with an LMNA mutation with an aggressive DCM leading to sudden cardiac death (SCD).

Case summary

A 42-year-old male presented with the feeling of lethargy and intermittent dizziness. Electrocardiogram demonstrated atrioventricular block in keeping with Mobitz type 1, at a rate of 40 b.p.m. and cardiac monitoring showed non-sustained ventricular tachycardia. Cardiac magnetic resonance imaging showed preserved left ventricular (LV) ejection function (59%) but features suggesting DCM. These included mild LV dilatation with an end diastolic volume (EDV) of 213 mL and late enhancement showing a single mid myocardial focus of high signal over the distal right ventricular insertion point inferiorly and a linear area of high signal over the basal septum. After discussion at the cardiology multi-disciplinary meeting, a pacemaker was implanted so that beta-blockers could be initiated to suppress the ventricular arrhythmias. A laminopathy was suspected and if this was confirmed from genetic testing the plan was to upgrade to an implantable defibrillator. Due to stability, this was decided to be done in an outpatient setting. He unfortunately had an out-of-hospital VF arrest and died. Post-mortem showed subtle cardiomyopathy in keeping with a DCM. Genetic tests results were returned a few months later which confirmed a pathogenic variant in LMNA.

Discussion

Because of the complexity of LMNA-related cardiac disease, they should be managed and followed up in centres with special expertise in inherited cardiomyopathy.

Clinical Features of LMNA-Related Cardiomyopathy in 18 Patients and Characterization of Two Novel Variants

Dilated cardiomyopathy (DCM) refers to a spectrum of heterogeneous myocardial disorders characterized by ventricular dilation and depressed myocardial performance in the absence of hypertension, valvular, congenital, or ischemic heart disease. Mutations in LMNA gene, encoding for lamin A/C, account for 10% of familial DCM. LMNA-related cardiomyopathies are characterized by heterogeneous clinical manifestations that vary from a predominantly structural heart disease, mainly mild-to-moderate left ventricular (LV) dilatation associated or not with conduction system abnormalities, to highly pro-arrhythmic profiles where sudden cardiac death (SCD) occurs as the first manifestation of disease in an apparently normal heart. In the present study, we select, among 77 DCM families referred to our center for genetic counselling and molecular screening, 15 patient heterozygotes for LMNA variants. Segregation analysis in the relatives evidences other eight heterozygous patients. A genotype-phenotype correlation has been performed for symptomatic subjects. Lastly, we perform in vitro functional characterization of two novel LMNA variants using dermal fibroblasts obtained from three heterozygous patients, evidencing significant differences in terms of lamin expression and nuclear morphology. Due to the high risk of SCD that characterizes patients with lamin A/C cardiomyopathy, genetic testing for LMNA gene variants is highly recommended when there is suspicion of laminopathy.

Importance of clinical suspicion and multidisciplinary management for early diagnosis of a cardiac laminopathy patient: A case report

BACKGROUND

Laminopathies are rare diseases, whose cardiac manifestations are heterogeneous and, especially in their initial stage, similar to those of more common conditions, such as ischemic heart disease. Early diagnosis is essential, as these conditions can first manifest themselves with sudden cardiac death. Electrical complications usually appear before structural complications; therefore, it is important to take into consideration these rare genetic disorders for the differential diagnosis of brady and tachyarrhythmias, even when left ventricle systolic function is still preserved.

CASE SUMMARY

A 60-year-old man, without history of previous disorders, presented in September 2019 to the emergency department because of the onset of syncope associated with hypotension. The patient was diagnosed with a high-grade atrioventricular block. A dual chamber pacemaker was implanted, but after the onset of a sustained ventricular tachycardia during physical exertion, a drug eluting stent was implanted on an intermediate stenosis on the left anterior descending artery, which had previously been considered non-haemodynamically significant. During the follow-up, the treating cardiologist, suspicious of the overall clinical picture, recommended a genetic test for the diagnosis of cardiomyopathies, which tested positive for a pathogenetic mutation of the lamin A/C gene. While awaiting the result of the genetic test and, later, the pacemaker to be upgraded to a biventricular defibrillator, a remote monitoring device was given to the patient in order to minimize in-person clinical evaluations during the coronavirus disease 2019-related lockdown.

CONCLUSION

This case aims to raise awareness of the cardiological manifestations of laminopathies, which can be dangerously misdiagnosed as other, more common conditions.

Timing of pacemaker and ICD implantation in LMNA mutation carriers

AIMS

LMNA-cardiomyopathy is often associated with pathology in the cardiac conduction system necessitating device implantations. The aim was to study the timing and types of device implantations and need for re-implantations in LMNA mutation carriers.

METHODS

We studied the hospital records of 60 LMNA mutation carriers concerning device implantations and re-implantations and their indications. Data were collected until April 2019.

RESULTS

The median follow-up time from the first ECG recording to the last clinical follow-up, transplantation, or death was 7.7 (IQR=9.1) years. Altogether 61.7% (n=37) of the LMNA mutation carriers received a pacemaker or an implantable cardioverter defibrillator (ICD), and of them 27.0% (n=10) needed a device upgrade. Notably, in some patients the upgrade took place very soon after the first implantation. The first device was implanted at an average age of 47.9 years (SD=9.5), whereas the upgrade took place at an average age of 50.3 years (SD=8.1). Most upgrades were ICD implantations. Male patients underwent device upgrade more often and at a younger age than women. By the end of follow-up, 35.0% (n=21) of the patients fulfilled echocardiographic criteria for dilated cardiomyopathy, and 90.5% of them (n=19) needed pacemaker implantation.

CONCLUSION

Most LMNA mutation carriers underwent pacemaker implantation in this study. Due to the progressive nature of LMNA-cardiomyopathy, device upgrades are quite common. An ICD should be considered when the initial device implantation is planned in an LMNA mutation carrier.

Persistent atrial fibrillation ablation in cardiac laminopathy: Electrophysiological findings and clinical outcomes

BACKGROUND

Little is known about persistent atrial fibrillation (AF) ablation in patients with cardiac laminopathy (CLMNA).

OBJECTIVES

We aimed to characterize atrial electrophysiological properties and to assess the long-term outcomes of persistent AF ablation in patients with CLMNA.

METHODS

All patients with CLMNA referred in our center for persistent AF ablation were retrospectively included. Left atrial (LA) volume, left atrial appendage (LAA) cycle length, interatrial conduction delay, and LA voltage amplitude were analyzed during the ablation procedure. Sinus rhythm maintenance and LA contractile function were assessed during long-term follow-up.

RESULTS

From 2011 to 2020, 8 patients were included. The mean age was 47 ± 14 years, and 3 patients (38%) were women. The LA volume was 205.8 ± 43.7 mL; the LAA AF cycle length was 250.7 ± 85.6 ms; and the interatrial conduction delay was 296.5 ± 110.1 ms. Large low-voltage areas (>50% of the LA surface; <0.5 mV electrogram) were recorded in all 8 patients. Two patients had inadvertent LAA disconnection during ablation. All A waves recorded by pulsed Doppler in sinus rhythm were <30 cm/s before and after AF ablation. Early arrhythmia recurrence was recorded in 7 patients (87%) (time to recurrence 4 ± 4 months; 1.5 procedures per patient). After a mean follow-up of 4.4 ± 3.2 years, 4 patients underwent implantable cardioverter-defibrillator therapy for life-threatening ventricular arrhythmia and 3 patients finally underwent heart transplantation.

CONCLUSION

Patients with persistent AF afflicted by CLMNA exhibit severe LA impairment because of large low-voltage areas, prolonged conduction velocity, and reduced contractile function. Ablation procedures have a limited effect with a high recurrence rate.

Late gadolinium enhancement role in arrhythmic risk stratification of patients with LMNA cardiomyopathy: results from a long-term follow-up multicentre study

Aims

We aimed at addressing the role of late gadolinium enhancement (LGE) in arrhythmic risk stratification of LMNA-associated cardiomyopathy (CMP).

Methods and results

We present data from a multicentre national cohort of patients with LMNA mutations. Of 164 screened cases, we finally enrolled patients with baseline cardiac magnetic resonance (CMR) including LGE sequences [n = 41, age 35 ± 17 years, 51% males, mean left ventricular ejection fraction (LVEF) by echocardiogram 56%]. The primary endpoint of the study was follow-up (FU) occurrence of malignant ventricular arrhythmias [MVA, including sustained ventricular tachycardia (VT), ventricular fibrillation, and appropriate implantable cardioverter-defibrillator (ICD) therapy]. At baseline CMR, 25 subjects (61%) had LGE, with non-ischaemic pattern in all of the cases. Overall, 23 patients (56%) underwent ICD implant. By 10 ± 3 years FU, eight patients (20%) experienced MVA, consisting of appropriate ICD shocks in all of the cases. In particular, the occurrence of MVA in LGE+ vs. LGE− groups was 8/25 vs. 0/16 (P = 0.014). Of note, no significant differences between LGE+ and LGE− patients were found in currently recognized risk factors for sudden cardiac death (male gender, non-missense mutations, baseline LVEF &lt;45% and non-sustained VT), all P-value &gt;0.05.

Conclusions

In LMNA-CMP patients, LGE at baseline CMR is significantly associated with MVA. In particular, as suggested by this preliminary experience, the absence of LGE allowed to rule-out MVA at 10 years mean FU.

Identification of Target Genes and Transcription Factors in Mice with LMNA-Related Dilated Cardiomyopathy by Integrated Bioinformatic Analyses

BACKGROUND Dilated cardiomyopathy (DCM), which is characterized by enlarged ventricular dimensions and systolic dysfunction, is the most common type of cardiomyopathy. Mutations in the LMNA gene are reported in approximately 10% of familial DCM cases. However, the mechanism of LMNA mutations in human DCM remains unclear. MATERIAL AND METHODS We used the GSE36502 and GSE123916 datasets to obtain gene expression profiles from LMNA-related DCM mice and to identify differentially expressed genes (DEGs). Crucial function and pathway enrichment analyses of DEGs were performed. Protein-protein interaction (PPI) network analysis was carried out to identify the top 10 hub genes, which were validated using reverse transcription-polymerase chain reaction (RT-PCR) to find target genes. Weighted gene co-expression network analysis (WGCNA) was used to explore the module relevant to external traits of LMNA-related DCM mice. Transcription factors (TFs) for the selected genes were analyzed using NetworkAnalyst. RESULTS A total of 156 common DEGs (co-DEGs) were identified, including 80 up-regulated and 76 down-regulated genes. The enriched biological functions and pathways were oxidative stress, regulation of apoptosis, regulation of fibrosis, and MAPK pathways. Five target genes (Timp1, Hmox1, Spp1, Atf3, and Adipoq) were verified after RT-PCR. Most co-DEGs were discovered to be related to the development of external traits. Three TFs (ELF1, ETS1, and NRF1) showed close interactions with the hub genes. CONCLUSIONS Our study used integrated bioinformatic analyses and revealed some important genes in mice with LMNA-related DCM, which could provide novel insights into the mechanism underlying human LMNA-related DCM.

Emerging concepts in arrhythmogenic dilated cardiomyopathy

Dilated cardiomyopathy (DCM) represents one of the primary cardiomyopathies and may lead to heart failure and sudden death. Until recently, ventricular arrhythmias were considered to be a direct consequence of the systolic dysfunction of the left ventricle (LV) and guidelines for implantable cardioverter defibrillator implantation were established on this basis. However, the identification of heritable dilated cardiomyopathy phenotypes that presented with mildly impaired or moderate LV dysfunction, with or without chamber dilatation, and ventricular arrhythmias exceeding the degree of the underlying morphological abnormalities lead to the identification of the arrhythmogenic phenotypes and genotypes of DCM. This subset of DCM patients presents phenotypic and in many cases genotypic overlaps with left dominant arrhythmogenic cardiomyopathy (LDAC). LMNA, SCN5A, FLNC, TTN, and RBM20 are the main genes responsible for arrhythmogenic DCM. Moreover, desmosomal genes such as DSP and other non-desmosomal such as DES and PLN have been associated with both LDAC and arrhythmogenic DCM. The aim of this review is to highlight the importance of genetic profiling among DCM patients with disproportionate arrhythmic burden and the significance of the electrocardiogram, cardiac magnetic resonance, Holter monitoring, detailed family history, and other assays in order to identify red flags for arrhythmogenic DCM and proceed to an early preventive approach for sudden cardiac death. A special consideration was given to the phenotypic and genotypic overlap with LDAC. The role of myocarditis as a common disease expression of LDAC and arrhythmogenic DCM is also analyzed supporting the premise of their phenotypic overlap.

Septal Late Gadolinium Enhancement and Arrhythmic Risk in Genetic and Acquired Non-Ischaemic Cardiomyopathies

BACKGROUND

In many genetic and acquired non-ischaemic cardiomyopathies (NICM) there have been frequent reports of involvement of the interventricular septum (IVS) by late gadolinium enhancement (LGE) at cardiac magnetic resonance (CMR). However, no studies have investigated the relationship between septal LGE and arrhythmias in different NICM subtypes.

METHODS

This study enrolled 103 patients with septal LGE at baseline CMR and different NICM: hypertrophic (n=29) or lamin A/C gene (LMNA)-associated (n=23) cardiomyopathy, and acute (n=30) or previous (n=21) myocarditis. During follow-up, the occurrences of malignant ventricular arrhythmias (MVA) and major bradyarrhythmias (BA) were evaluated.

RESULTS

At 4.9±0.7 years of follow-up, the occurrence of MVA and major BA in genetic vs acquired NICM were 10 of 52 vs 12 of 51, and 10 of 52 vs 4 of 51, respectively (both p=n.s.). However, MVA occurred more frequently in LMNA-NICM (eight of 23 vs two of 29 hypertrophic, p=0.015) and in previous myocarditis (nine of 21 vs three of 30 acute, p=0.016), while major BAs were particularly common in LMNA-NICM patients only (nine of 23 vs one of 29 hypertrophic, p=0.003). Different patterns of septal LGE were consistently retrospectively identified at baseline CMR: junctional and limited to the base in 79.3% of uneventful hypertrophic NICM; extended and focally transmural in LMNA-NICM with follow-up arrhythmias (both p<0.05); transitory in patients with acute myocarditis, who, differently from the post-myocarditis ones, showed follow-up arrhythmias only in the presence of unmodified LGE at follow-up CMR (five of 13, p=0.009).

CONCLUSION

Septal LGE was significantly associated with MVA at the 5-year follow-up in LMNA-NICM or previous myocarditis, and with major BA in LMNA-NICM only. These differences correlated with heterogeneous patterns of IVS LGE in different NICM.

Cardiac and Neuromuscular Features of Patients With LMNA-Related Cardiomyopathy

BACKGROUND

Mutations in the LMNA (lamin A/C) gene have been associated with neuromuscular and cardiac manifestations, but the clinical implications of these signs are not well understood.

OBJECTIVE

To learn more about the natural history of LMNA-related disease.

DESIGN

Observational study.

SETTING

13 clinical centers in Italy from 2000 through 2018.

PATIENTS

164 carriers of an LMNA mutation.

MEASUREMENTS

Detailed cardiologic and neurologic evaluation at study enrollment and for a median of 10 years of follow-up.

RESULTS

The median age at enrollment was 38 years, and 51% of participants were female. Neuromuscular manifestations preceded cardiac signs by a median of 11 years, but by the end of follow-up, 90% of the patients had electrical heart disease followed by structural heart disease. Overall, 10 patients (6%) died, 14 (9%) received a heart transplant, and 32 (20%) had malignant ventricular arrhythmias. Fifteen patients had gait loss, and 6 had respiratory failure. Atrial fibrillation and second- and third-degree atrioventricular block were observed, respectively, in 56% and 51% of patients with combined cardiac and neuromuscular manifestations and 37% and 33% of those with heart disease only.

LIMITATIONS

Some of the data were collected retrospectively. Neuromuscular manifestations were more frequent in this analysis than in previous studies.

CONCLUSION

Many patients with an LMNA mutation have neurologic symptoms by their 30s and develop progressive cardiac manifestations during the next decade. A substantial proportion of these patients will have life-threatening neurologic or cardiologic conditions.

PRIMARY FUNDING SOURCE

None.

Current understanding of fibrosis in genetic cardiomyopathies

Myocardial fibrosis is the excessive deposition of extracellular matrix proteins, including collagens, in the heart. In cardiomyopathies, the formation of interstitial fibrosis and/or replacement fibrosis is almost always part of the pathological cardiac remodeling process. Different forms of cardiomyopathies show particular patterns of myocardial fibrosis that can be considered as distinctive hallmarks. Although formation of fibrosis is initially aimed to be a reparative mechanism, in the long term, on-going and excessive myocardial fibrosis may lead to arrhythmias and stiffening of the heart wall and subsequently to diastolic dysfunction. Ultimately, adverse remodeling with progressive myocardial fibrosis can lead to heart failure. Not surprisingly, the presence of fibrosis in cardiomyopathies, even when subtle, has consistently been associated with complications and adverse outcomes. In the last decade, non-invasive in vivo techniques for visualization of myocardial fibrosis have emerged, and have been increasingly used in research and in the clinic. In this review, we will describe the epidemiology, distribution, and role of myocardial fibrosis in genetic cardiomyopathies, including hypertrophic, dilated, arrhythmogenic, and non-compaction cardiomyopathy, and a few specific forms of genetic cardiomyopathies.

Importance of Genetic Testing in Dilated Cardiomyopathy: Applications and Challenges in Clinical Practice

Dilated cardiomyopathy (DCM) is a clinical syndrome characterized by left ventricular dilatation and contractile dysfunction. It is the most common cause of heart failure in young adults. The advent of next-generation sequencing has contributed to the discovery of a large amount of genomic data related to DCM. Mutations involving genes that encode cytoskeletal proteins, the sarcomere, and ion channels account for approximately 40% of cases previously classified as idiopathic DCM. In this scenario, geneticists and cardiovascular genetics specialists have begun to work together, building knowledge and establishing more accurate diagnoses. However, proper interpretation of genetic results is essential and multidisciplinary teams dedicated to the management and analysis of the obtained information should be considered. In this review, we approach genetic factors associated with DCM and their prognostic relevance and discuss how the use of genetic testing, when well recommended, can help cardiologists in the decision-making process.

Familial cardiomyopathy caused by a novel heterozygous mutation in the gene LMNA (c.1434dupG): a cardiac MRI-augmented segregation study

In a five-generation family carrying a novel frameshift LMNA variant (c.1434dupG, p.Leu479AlafsX72), imaging-augmented segregation analysis supports its association with lamin heart disease. Affected members exhibit conduction abnormalities, supraventricular and ventricular arrythmias, dilated cardiomyopathy with non-infarct pattern midwall septal fibrosis, heart failure and thromboembolic complications.

A novel homozygous mutation in the TRDN gene causes a severe form of pediatric malignant ventricular arrhythmia

BACKGROUND

Triadin is a protein expressed in cardiac and skeletal muscle that has an essential role in the structure and functional regulation of calcium release units and excitation-contraction coupling. Mutations in the triadin gene (TRDN) have been described in different forms of human arrhythmia syndromes with early onset and severe arrhythmogenic phenotype, including triadin knockout syndrome.

OBJECTIVE

The purpose of this study was to characterize the pathogenetic mechanism underlying a case of severe pediatric malignant arrhythmia associated with a defect in the TRDN gene.

METHODS

We used a trio whole exome sequencing approach to identify the genetic defect in a 2-year-old boy who had been resuscitated from sudden cardiac arrest and had frequent episodes of ventricular fibrillation and a family history positive for sudden death. We then performed in vitro functional analysis to investigate possible pathogenic mechanisms underlying this severe phenotype.

RESULTS

We identified a novel homozygous missense variant (p.L56P) in the TRDN gene in the proband that was inherited from the heterozygous unaffected parents. Expression of a green fluorescent protein (GFP)-tagged mutant human cardiac triadin isoform (TRISK32-L56P-GFP) in heterologous systems revealed that the mutation alters protein dynamics. Furthermore, when co-expressed with the type 2 ryanodine receptor, caffeine-induced calcium release from TRISK32-L56P-GFP was relatively lower compared to that observed with the wild-type construct.

CONCLUSION

The results of this study allowed us to hypothesize a pathogenic mechanism underlying this rare arrhythmogenic recessive form, suggesting that the mutant protein potentially can trigger arrhythmias by altering calcium homeostasis.

Updates on the Genetic Paradigm in Heart Failure

PURPOSE OF REVIEW

The rapidly evolving field of cardiovascular genetics has already improved the care of patients with heart failure and families. The purpose of the current review is to describe the most and provide the most pertinent updates in the field of heart failure genetics.

RECENT FINDINGS

Recent advanced in heart failure genetics have begun to not only increase the yield of testing through improving technology and use of whole exome or whole genome screening, but also enabled the improving technology and increasing use of whole exome or whole genome screening, but also enabled an enhanced understanding of the implications of results of genetic testing. For instance, new data have described differential responses to heart failure therapies based on genetic testing. Additionally, variant analysis by locus in genetic cardiomyopathies has facilitated a much-improved prognostic understanding of phenotype. Recent years have seen advancements in the understanding of the genetics of rare disorders, including pediatric-onset cardiomyopathies, previously under-investigated; restrictive cardiomyopathies; and non-compaction cardiomyopathy. The last few years have heralded not only a broader understanding of the scope of the genetics of heart failure, but have also provided notable leaps in mechanistic and prognostic understanding, which will serve as the foundation for clinical investigation and future genetic variant assessment.

Cardiac diseases as a predictor warning of hereditary muscle diseases. The case of laminopathies

Mutations in the LMNA gene are associated with a wide spectrum of disease phenotypes, ranging from neuromuscular, cardiac and metabolic disorders to premature aging syndromes. Skeletal muscle involvement may present with different phenotypes: limb-girdle muscular dystrophy type 1B or LMNA-related dystrophy; autosomal dominant Emery-Dreifuss muscular dystrophy; and a congenital form of muscular dystrophy, frequently associated with early onset of arrhythmias. Heart involvement may occur as part of the muscle involvement or independently, regardless of the presence of the myopathy. Notably conduction defects and dilated cardiomyopathy may exist without a muscle disease. This paper will focus on cardiac diseases presenting as the first manifestation of skeletal muscle hereditary disorders such as laminopathies, inspired by two large families with cardiovascular problems long followed by conventional cardiologists who did not suspect a genetic muscle disorder underlying these events. Furthermore it underlines the need for a multidisciplinary approach in these disorders and how the figure of the cardio-myo-geneticist may play a key role in facilitating the diagnostic process, and addressing the adoption of appropriate prevention measures.

Role of Lamin A/C Gene Mutations in the Signaling Defects Leading to Cardiomyopathies

Nuclear lamin A/C are crucial components of the intricate protein mesh that underlies the inner nuclear membrane and confers mainly nuclear and cytosolic rigidity. However, throughout the years a number of other key physiological processes have been associated with lamins such as modulation of both genes expression and the activity of signaling mediators. To further solidify its importance in cell physiology, mutations in the lamin A/C gene (LMNA) have been associated to diverse pathological phenotypes with skeletal muscles and the heart being the most affected systems. When affected, the heart develops a wide array of phenotypes spanning from dilated cardiomyopathy with conduction defects to arrhythmogenic right ventricular cardiomyopathy. The surprising large number of cardiac phenotypes reflects the equally large number of specific mutations identified in the LMNA gene. In this review, we underlie how mutations in LMNA can impact the activity and the spatial/temporal organization of signaling mediators and transcription factors. We analyzed the ever-increasing amount of findings collected in Lmna^H222P/H222P mice whose cardiomyopathy resemble the most important features of the disease in humans and a number of key evidences from other experimental models. With this mini review, we attempt to combine the newest insights regarding both the pathogenic effects of LMNA mutations in terms of signaling abnormalities and cardiac laminopathies.