The heart in Friedreich ataxia: definition of cardiomyopathy, disease severity, and correlation with neurological symptoms

Early onset development of hypertrophic cardiomyopathy in less than 1 year in a patient with familial Friedrich's ataxia: Case report

Friedreich's ataxia (FRDA) is a neurodegenerative disease characterized by progressive ataxia, dysarthria, sensory loss. While neurological symptoms are prominent, cardiac manifestations significantly contribute to mortality. Cardiomyopathy in Friedreich's disease results from mitochondrial dysfunction, loss of contractile proteins and an accumulation of fibrosis in heart. To better characterize the severity of cardiac involvement, the MICONOS study group developed a classification system categorizing FRDA cardiomyopathy as "no," "mild," "intermediate," "severe." We report an uncommon case of early-onset development of hypertrophic cardiomyopathy (HCM) in a 25-year-old female diagnosed with Friedreich's ataxia (FRDA) at age 12. Through annual cardiac evaluations, no signs of cardiac disease were noted. Until presenting with dyspnea and palpitations. Clinical examination revealed truncal ataxia and dysarthria, but no signs of heart failure. However, a transthoracic echocardiography demonstrated nonobstructive hypertrophic cardiomyopathy with a maximal wall thickness of 20 mm, incomplete anterior systolic motion of the mitral valve, a significant development in less than 1 year after last normal cardiac assessment. Left ventricular systolic function was preserved (ejection fraction 50%). She was prescribed bisoprolol and dapagliflozin, with significant improvement at her latest checkup. Family screening revealed HCM in her 30 year female sibling, who also has FRDA. No cardiac abnormalities were detected in her younger brother or parents. Friedreich's hypertrophic cardiomyopathy has been reported as the most significant cause of mortality, especially among younger patients with early onset disease manifestations.

Cardiac magnetic resonance and genetics in pediatric heart failure patients with nonischemia: prognostic implications

BACKGROUND

The associations among genetic variants, cardiac magnetic resonance (CMR) features, and prognostic factors of pediatric heart failure (HF) remain unknown. This study aimed to explore the relationship between genetic differences in pediatric HF and CMR findings and their impact on prognosis of HF in children.

METHODS

This retrospective study included children with a first-time diagnosis of HF. All patients underwent echocardiogram, CMR and genetic testing. The cohort was divided into three subgroups according to late gadolinium enhancement (LGE) on CMR: the no LGE subgroup, the subendocardial LGE subgroup, and the nonsubendocardial subgroup. The endpoint was defined as a lack of improvement in HF on echocardiography after more than six months of follow-up.

RESULTS

Ninety-five children with HF were included, of whom 64 underwent genetic testing and 89 had echocardiograms at follow-up. There were 20 patients in the no LGE group, 31 in the subendocardial group, and 44 in the nonsubendocardial group. The most common genotype was MYH7 (27.0%). RBM20 and LMNA both presented a dilated phenotype, whereas GTPBP3 uniformly presented a hypertrophic phenotype. TNNI3 showed no LGE on CMR (P = 0.003) and maintained a restrictive phenotype. The subendocardial group was more likely to have septal LGE (93.5%, P < 0.001). Multivariable regression analysis indicated that a family history of cardiomyopathy, hydropericardium, and right ventricular ejection fraction (RVEF) were independent predictors of the endpoint event (P = 0.035, P = 0.005 and P = 0.032, respectively). Notably, nonsubendocardial LGE was associated with a worse prognosis than no LGE was (P = 0.030).

CONCLUSIONS

In pediatric non-ischemic HF patients, subendocardial LGE can be observed. A family history of cardiomyopathy, hydropericardium, and RVEF were predictors of HF with no improvement. The prognosis of HF is associated with the presence of LGE, particularly nonsubendocardial LGE, and less so with the genetic phenotype.

Case Report: Complex cardiac arrhythmia management in the ICU for an adolescent with Friedreich ataxia

Background

Friedreich ataxia (FRDA) is a progressive neurodegenerative disorder with specific clinical manifestations, such as scoliosis, which may impact the management of cardiac arrhythmias and heart failure.

Case description

A 17-year-old male with FRDA and hypertrophic cardiomyopathy presented with atrial flutter and resultant acute-on-chronic systolic and diastolic heart failure with reduced ejection fraction. The arrhythmias were refractory to medical management with adenosine and amiodarone. An attempted cavotricuspid isthmus ablation was unsuccessful due to abnormal cardiac positioning caused by severe scoliosis. Despite optimization with dofetilide and metoprolol, he was readmitted with recurrent atrial arrhythmias and cardiogenic shock, secondary to probable amiodarone-induced thyrotoxicosis, requiring extracorporeal membrane oxygenation. His clinical course involved multisystem complications, prolonged hospitalization, and disease progression, with no recovery in systolic function despite control of his arrhythmia burden.

Conclusion

Intensivists should be cognizant of multisystem complications that can arise when treating refractory cardiac arrhythmias, especially in those with concomitant genetic conditions.

A global perspective on research advances and future challenges in Friedreich ataxia

Friedreich ataxia (FRDA) is a rare multisystem, life-limiting disease and is the most common early-onset inherited ataxia in populations of European, Arab and Indian descent. In recent years, substantial progress has been made in dissecting the pathogenesis and natural history of FRDA, and several clinical trials have been initiated. A particularly notable recent achievement was the approval of the nuclear factor erythroid 2-related factor 2 activator omaveloxolone as the first disease-specific therapy for FRDA. In light of these developments, we review milestones in FRDA translational and clinical research over the past 10 years, as well as the various therapeutic strategies currently in the pipeline. We also consider the lessons that have been learned from failed trials and other setbacks. We conclude by presenting a global roadmap for future research, as outlined by the recently established Friedreich's Ataxia Global Clinical Consortium, which covers North and South America, Europe, India, Australia and New Zealand.

Poincaré plot analysis of electrocardiogram uncovers beneficial effects of omaveloxolone in a mouse model of Friedreich's ataxia

BACKGROUND

Friedreich's ataxia (FA) is a rare inherited neuromuscular disorder whereby most patients die of lethal cardiomyopathy and arrhythmias. Mechanisms leading to arrhythmic events in patients with FA are poorly understood.

OBJECTIVE

This study aimed to examine cardiac electrical signal propagation in a mouse model of FA with severe cardiomyopathy and to evaluate effects of omaveloxolone (OMAV), the first Food and Drug Administration-approved therapy.

METHODS

Cardiac-specific MCK-Cre frataxin knockout (FXN-cKO) mice were used to mimic FA cardiomyopathy. In vivo surface electrocardiogram (ECG) recordings, Western blotting, quantitative real-time polymerase chain reaction analysis, and histochemistry were performed.

RESULTS

Characteristics like long QT syndrome, interatrial block, and ST-segment abnormalities in patients with FA were identified in FXN-cKO mice. FXN-cKO mice exhibited sexual dimorphism in electrical signal propagation and cardiac structural integrity. Untreated FA males showed increased ventricular propagation intervals, whereas females exhibited delayed atrial propagation. OMAV showed no significant therapeutic effect on average ECG time intervals but improved chamber-specific waveforms when aggregated frequency distributions were analyzed. The J wave was absent in FXN-cKO male mice but reappeared with OMAV treatment. Poincaré plots revealed disparate idiopathic arrhythmias with multi-clustering events in individual mice with high incidence in FXN-cKO males. OMAV treatment reduced multi-clustering events to a single cluster; however, autonomic nervous system dysfunction still remained.

CONCLUSION

Our study revealed significant electrical propagation disturbances and sexual dimorphism in FXN-cKO mice with severe cardiomyopathy. Poincaré plots identified irregularities in heart rhythm and autonomic nervous system dysfunction. OMAV improved heart function by stabilizing early repolarization and reducing disparate arrhythmias. This work stresses sex-specific ECG interpretations and alternative mathematical approaches for drug testing in FA models.

Sexual dimorphism in a mouse model of Friedreich's ataxia with severe cardiomyopathy

Friedreich's ataxia (FA) is an autosomal recessive disorder caused by reduced frataxin (FXN) expression in mitochondria, where the lethal component is cardiomyopathy. Using the conditional Fxnflox/null::MCK-Cre knock-out (Fxn-cKO) mouse model, we discovered significant sex differences in the progression towards heart failure, with Fxn-cKO males exhibiting a worse cardiac phenotype, low survival rate, kidney and reproductive organ deficiencies. These differences are likely due to a decline in testosterone in Fxn-cKO males. The decrease in testosterone was related to decreased expression of proteins involved in cholesterol transfer into the mitochondria: StAR and TSPO on the outer mitochondrial membrane, and the cholesterol side-chain cleavage enzyme P450scc and ferredoxin on the inner mitochondrial membrane. Expression of excitation-contraction coupling proteins (L-type calcium channel, RyR2, SERCA2, phospholamban and CaMKIIδ) was decreased significantly more in Fxn-cKO males. This is the first study that extensively investigates the sexual dimorphism in FA mouse model with cardiac calcium signaling impairment.

Skeletal Muscle Involvement in Friedreich Ataxia

Friedreich Ataxia (FRDA) is an inherited neuromuscular disorder triggered by a deficit of the mitochondrial protein frataxin. At a cellular level, frataxin deficiency results in insufficient iron-sulfur cluster biosynthesis and impaired mitochondrial function and adenosine triphosphate production. The main clinical manifestation is a progressive balance and coordination disorder which depends on the involvement of peripheral and central sensory pathways as well as of the cerebellum. Besides the neurological involvement, FRDA affects also the striated muscles. The most prominent manifestation is a hypertrophic cardiomyopathy, which also represents the major determinant of premature mortality. Moreover, FRDA displays skeletal muscle involvement, which contributes to the weakness and marked fatigue evident throughout the course of the disease. Herein, we review skeletal muscle findings in FRDA generated by functional imaging, histology, as well as multiomics techniques in both disease models and in patients. Altogether, these findings corroborate a disease phenotype in skeletal muscle and support the notion of progressive mitochondrial damage as a driver of disease progression in FRDA. Furthermore, we highlight the relevance of skeletal muscle investigations in the development of biomarkers for early-phase trials and future therapeutic strategies in FRDA.

Insights into the effects of Friedreich ataxia on the left ventricle using T1 mapping and late gadolinium enhancement

BACKGROUND

The left ventricular (LV) changes which occur in Friedreich ataxia (FRDA) are incompletely understood.

METHODS

Cardiac magnetic resonance (CMR) imaging was performed using a 1.5T scanner in subjects with FRDA who are homozygous for an expansion of an intron 1 GAA repeat in the FXN gene. Standard measurements were performed of LV mass (LVM), LV end-diastolic volume (LVEDV) and LV ejection fraction (LVEF). Native T1 relaxation time and the extracellular volume fraction (ECV) were utilised as markers of left ventricular (LV) diffuse myocardial fibrosis and late gadolinium enhancement (LGE) was utilised as a marker of LV replacement fibrosis. FRDA genetic severity was assessed using the shorter FXN GAA repeat length (GAA1).

RESULTS

There were 93 subjects with FRDA (63 adults, 30 children, 54% males), 9 of whom had a reduced LVEF (<55%). A LVEDV below the normal range was present in 39%, a LVM above the normal range in 22%, and an increased LVM/LVEDV ratio in 89% subjects. In adults with a normal LVEF, there was an independent positive correlation of LVM with GAA1, and a negative correlation with age, but no similar relationships were seen in children. GAA1 was positively correlated with native T1 time in both adults and children, and with ECV in adults, all these associations independent of LVM and LVEDV. LGE was present in 21% of subjects, including both adults and children, and subjects with and without a reduced LVEF. None of GAA1, LVM or LVEDV were predictors of LGE.

CONCLUSION

An association between diffuse interstitial LV myocardial fibrosis and genetic severity in FRDA was present independently of FRDA-related LV structural changes. Localised replacement fibrosis was found in a minority of subjects with FRDA and was not associated with LV structural change or FRDA genetic severity in subjects with a normal LVEF.

Phenotypic variation of FXN compound heterozygotes in a Friedreich ataxia cohort

OBJECTIVE

Most individuals with Friedreich ataxia (FRDA) have homozygous GAA triplet repeat expansions in the FXN gene, correlating with a typical phenotype of ataxia and cardiomyopathy. A minority are compound heterozygotes carrying a GAA expansion on one allele and a mutation on the other. The study aim was to examine phenotypic variation among compound heterozygotes.

METHODS

Data on FXN mutations were obtained from the Friedreich Ataxia Clinical Outcome Measures Study (FA-COMS). We compared clinical features in a single-site FA-COMS cohort of 51 compound heterozygous and 358 homozygous patients, including quantitative measures of cardiac, neurologic, and visual disease progression.

RESULTS

Non-GAA repeat mutations were associated with reduced cardiac disease, and patients with minimal/no function mutations otherwise had a typical FRDA phenotype but with significantly more severe progression. The partial function mutation group was characterized by relative sparing of bulbar and upper limb function, as well as particularly low cardiac involvement. Other clinical features in this group, including optic atrophy and diabetes mellitus, varied widely depending on the specific type of partial function mutation.

INTERPRETATION

These data support that the typical FRDA phenotype is driven by frataxin deficiency, especially severe in compound heterozygotes with minimal/no function mutations, whereas the heterogeneous presentations of those with partial function mutations may indicate other contributing factors to FRDA pathogenesis.

Cardiopulmonary exercise testing on adaptive equipment in children and adults with Friedreich ataxia

INTRODUCTION/AIMS

Traditional exercise is often difficult for individuals with Friedreich ataxia (FRDA), and evidence is limited regarding how to measure exercise performance in this population. We evaluated the feasibility, reliability, and natural history of adaptive cardiopulmonary exercise test (CPET) performance in children and adults with FRDA.

METHODS

Participants underwent CPET on either an arm cycle ergometer (ACE) or recumbent leg cycle ergometer (RLCE) at up to four visits (baseline, 2 weeks, 4 weeks, and 1 year). Maximum work, oxygen consumption (peak VO2), oxygen (O2) pulse, and anaerobic threshold (AT) were measured in those who reached maximal volition. Test-retest reliability was assessed with intraclass coefficients, and longitudinal change was assessed using regression analysis.

RESULTS

In our cohort (N = 23), median age was 18 years (interquartile range [IQR], 14-23), median age of FRDA onset was 8 years (IQR 6-13), median Friedreich Ataxia Rating Scale score was 58 (IQR 54-62), and GAA repeat length on the shorter FXN allele (GAA1) was 766 (IQR, 650-900). Twenty-one (91%) completed a maximal CPET (n = 8, ACE and n = 13, RLCE). Age, sex, and GAA1 repeat length were each associated with peak VO2. Preliminary estimates demonstrated reasonable agreement between visits 2 and 3 for peak work by both ACE and RLCE, and for peak VO2, O2 pulse, and AT by RLCE. We did not detect significant performance changes over 1 year.

DISCUSSION

Adaptive CPET is feasible in FRDA, a relevant clinical trial outcome for interventions that impact exercise performance and will increase access to participation as well as generalizability of findings.

Predictors of Survival in Friedreich's Ataxia: A Prospective Cohort Study

BACKGROUND

Friedreich's ataxia (FA) is a rare multisystemic disorder which can cause premature death.

OBJECTIVES

To investigate predictors of survival in FA.

METHODS

Within a prospective registry established by the European Friedreich's Ataxia Consortium for Translational Studies (EFACTS; ClinicalTrials.gov identifier NCT02069509) we enrolled genetically confirmed FA patients at 11 tertiary centers and followed them in yearly intervals. We investigated overall survival applying the Kaplan-Meier method, life tables, and log-rank test. We explored prognostic factors applying Cox proportional hazards regression and subsequently built a risk score which was assessed for discrimination and calibration performance.

RESULTS

Between September 2010 and March 2017, we enrolled 631 FA patients. Median age at inclusion was 31 (range, 6-76) years. Until December 2022, 44 patients died and 119 terminated the study for other reasons. The 10-year cumulative survival rate was 87%. In a multivariable analysis, the disability stage (hazard ratio [HR] 1.51, 95% CI 1.08-2.12, P = 0.02), history of arrhythmic disorder (HR 2.93, 95% CI 1.34-6.39, P = 0.007), and diabetes mellitus (HR 2.31, 95% CI 1.05-5.10, P = 0.04) were independent predictors of survival. GAA repeat lengths did not improve the survival model. A risk score built on the previously described factors plus the presence of left ventricular systolic dysfunction at echocardiography enabled identification of four trajectories to prognosticate up to 10-year survival (log-rank test P < 0.001).

CONCLUSIONS

Arrhythmias, progressive neurological disability, and diabetes mellitus influence the overall survival in FA. We built a survival prognostic score which identifies patients meriting closer surveillance and who may benefit from early invasive cardiac monitoring and therapy. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Genome-wide enhancer-associated tandem repeats are expanded in cardiomyopathy

BACKGROUND

Cardiomyopathy is a clinically and genetically heterogeneous heart condition that can lead to heart failure and sudden cardiac death in childhood. While it has a strong genetic basis, the genetic aetiology for over 50% of cardiomyopathy cases remains unknown.

METHODS

In this study, we analyse the characteristics of tandem repeats from genome sequence data of unrelated individuals diagnosed with cardiomyopathy from Canada and the United Kingdom (n = 1216) and compare them to those found in the general population. We perform burden analysis to identify genomic and epigenomic features that are impacted by rare tandem repeat expansions (TREs), and enrichment analysis to identify functional pathways that are involved in the TRE-associated genes in cardiomyopathy. We use Oxford Nanopore targeted long-read sequencing to validate repeat size and methylation status of one of the most recurrent TREs. We also compare the TRE-associated genes to those that are dysregulated in the heart tissues of individuals with cardiomyopathy.

FINDINGS

We demonstrate that tandem repeats that are rarely expanded in the general population are predominantly expanded in cardiomyopathy. We find that rare TREs are disproportionately present in constrained genes near transcriptional start sites, have high GC content, and frequently overlap active enhancer H3K27ac marks, where expansion-related DNA methylation may reduce gene expression. We demonstrate the gene silencing effect of expanded CGG tandem repeats in DIP2B through promoter hypermethylation. We show that the enhancer-associated loci are found in genes that are highly expressed in human cardiomyocytes and are differentially expressed in the left ventricle of the heart in individuals with cardiomyopathy.

INTERPRETATION

Our findings highlight the underrecognized contribution of rare tandem repeat expansions to the risk of cardiomyopathy and suggest that rare TREs contribute to ∼4% of cardiomyopathy risk.

FUNDING

Government of Ontario (RKCY), The Canadian Institutes of Health Research PJT 175329 (RKCY), The Azrieli Foundation (RKCY), SickKids Catalyst Scholar in Genetics (RKCY), The University of Toronto McLaughlin Centre (RKCY, SM), Ted Rogers Centre for Heart Research (SM), Data Sciences Institute at the University of Toronto (SM), The Canadian Institutes of Health Research PJT 175034 (SM), The Canadian Institutes of Health Research ENP 161429 under the frame of ERA PerMed (SM, RL), Heart and Stroke Foundation of Ontario & Robert M Freedom Chair in Cardiovascular Science (SM), Bitove Family Professorship of Adult Congenital Heart Disease (EO), Canada Foundation for Innovation (SWS, JR), Canada Research Chair (PS), Genome Canada (PS, JR), The Canadian Institutes of Health Research (PS).

Targeted genetic therapies for inherited disorders that affect both cardiac and skeletal muscle

Skeletal myopathies and ataxias with secondary cardiac involvement are complex, progressive and debilitating conditions. As life expectancy increases across these conditions, cardiac involvement often becomes more prominent. This highlights the need for targeted therapies that address these evolving cardiac pathologies. Musculopathies by and large lack cures that directly target the genetic basis of the diseases; however, as our understanding of the genetic causes of these conditions has evolved, it has become tractable to develop targeted therapies using biologics, to design precision approaches to target the primary genetic causes of these varied diseases. Using the examples of Duchenne muscular dystrophy, Friedreich ataxia and Pompe disease, we discuss how the genetic causes of such diseases derail diverse homeostatic, energetic and signalling pathways, which span multiple cellular systems in varied tissues across the body. We outline existing therapeutics and treatments in the context of emerging novel genetic approaches. We discuss the hurdles that the field must overcome to deliver targeted therapies across the many tissue types affected in primary myopathies.

Management of Friedreich Ataxia-Associated Cardiomyopathy in Pregnancy: A Review of the Literature

A major manifestation of Friedreich ataxia (FRDA) is cardiomyopathy, caused by mitochondrial proliferation in myocytes. Because the lifespan for patients with FRDA improves with better treatment modalities, more patients are becoming pregnant, meaning that more medical providers must know how to care for this population. This report provides a review of the literature on multidisciplinary management of pregnant patients with FRDA and cardiomyopathy from preconception through lactation. A cardio-obstetrics team, including cardiology, anesthesiology, and obstetrics, should be involved for this entire period. All patients should be counseled on pregnancy risk using elements of existing stratification systems, and contraception should be discussed, highlighting the safety of intrauterine devices. Electrocardiogram should be obtained at baseline and each trimester, looking for atrial arrhythmias and ST-segment changes, as should transthoracic echocardiogram, with a focus on left ventricular ejection fraction-which is typically normal in FRDA cardiomyopathy-and relative wall thickness and global longitudinal strain-which tend to decrease as cardiomyopathy progresses. Brain natriuretic peptide is also a helpful marker to detect adverse events. If heart failure develops, it should be treated like any other etiology of heart failure during pregnancy. Atrial arrhythmias should be treated with β blockers or electrical cardioversion and anticoagulation, as necessary. Most patients with FRDA can deliver vaginally, and neuraxial analgesia is recommended during labor because of the risks associated with general anesthesia. Breastfeeding is encouraged, even for those taking cardiac medications.

The Cardiac Calcium Handling Machinery is Remodeled in Friedreich's Ataxia

Background

Friedreich's ataxia (FA) is an inherited neurodegenerative disorder that causes progressive nervous system damage resulting in impaired muscle coordination. FA is the most common autosomal recessive form of ataxia and is caused by an expansion of the DNA triplet guanine-adenine-adenine (GAA) in the first intron of the Frataxin gene (FXN), located on chromosome 9q13. In the unaffected population, the number of GAA repeats ranges from 6 to 27 repetitions. In FA patients, GAA repeat expansions range from 44 to 1,700 repeats which decreases frataxin protein expression. Frataxin is a mitochondrial protein essential for various cellular functions, including iron metabolism. Reduced frataxin expression is thought to negatively affect mitochondrial iron metabolism, leading to increased oxidative damage. Although FA is considered a neurodegenerative disorder, FA patients display heart disease that includes hypertrophy, heart failure, arrhythmias, conduction abnormalities, and cardiac fibrosis.

Objective

In this work, we investigated whether abnormal Ca 2+ handling machinery is the molecular mechanism that perpetuates cardiac dysfunction in FA.

Methods

We used the frataxin knock-out (FXN-KO) mouse model of FA as well as human heart samples from donors with FA and from unaffected donors. ECG and echocardiography were used to assess cardiac function in the mice. Expression of calcium handling machinery proteins was assessed with proteomics and western blot. In left ventricular myocytes from FXN-KO and FXN-WT mice, the IonOptix system was used for calcium imaging, the seahorse assay was utilized to measure oxygen consumption rate (OCR), and confocal imaging was used to quantify the mitochondrial membrane potential (Δψm) and reactive oxygen species (ROS).

Results

We found that major contractile proteins, including SERCA2a and Ryr2, were downregulated in human left ventricular samples from deceased donors with FA compared to unaffected donors, similar to the downregulation of these proteins in the left ventricular tissue from FXN-KO compared to FXN-WT. On the ECG, the RR, PR, QRS, and QTc were significantly longer in the FXN-KO mice compared to FXN-WT. The ejection fraction and fractional shortening were significantly decreased and left ventricular wall thickness and diameter were significantly increased in the FXN-KO mice versus FXN-WT. The mitochondrial membrane potential Δψm was depolarized, ROS levels were elevated, and OCR was decreased in ventricular myocytes from FXN-KO versus FXN-WT.

Conclusion

The development of left ventricular contractile dysfunction in FA is associated with reduced expression of calcium handling proteins and mitochondrial dysfunction.

Cardiac Involvement in Mitochondrial Disorders

PURPOSE OF REVIEW

We review pathophysiology and clinical features of mitochondrial disorders manifesting with cardiomyopathy.

RECENT FINDINGS

Mechanistic studies have shed light into the underpinnings of mitochondrial disorders, providing novel insights into mitochondrial physiology and identifying new therapeutic targets. Mitochondrial disorders are a group of rare genetic diseases that are caused by mutations in mitochondrial DNA (mtDNA) or in nuclear genes that are essential to mitochondrial function. The clinical picture is extremely heterogeneous, the onset can occur at any age, and virtually, any organ or tissue can be involved. Since the heart relies primarily on mitochondrial oxidative metabolism to fuel contraction and relaxation, cardiac involvement is common in mitochondrial disorders and often represents a major determinant of their prognosis.

Remember Friedreich ataxia even in a toddler with apparently isolated dilated (not hypertrophic!) cardiomyopathy. Revisited

Friedreich ataxia (FRDA) is the most common form of ataxia in late childhood. Neurological manifestations often precede cardiac involvement, presenting mainly as hypertrophic cardiomyopathy. We describe a toddler with apparently isolated severe heart failure, successfully managed with heart transplant (HT). Although well described in adolescents and adults, onset of FRDA is very uncommon in toddlers and neurological ataxic features are predominant. The presenting symptom of cardiomyopathy is very rare. Similar history is rarely reported in literature, that we described, including an aggressive cardiomyopathy in children younger than 5 years-old. RESULTS: Our patient was diagnosed with FRDA at a postoperative stage due to minimal neurological manifestations. Moreover, the novelty of this study lies in demonstrating a major DNA triplet repeat expansion in skeletal muscle compared to DNA from peripheral blood leukocytes. These results support the concept that triplet repeat expansion is variable among different tissues in FRDA, and in our case it was more expanded in the post mitotic muscular tissue than in blood cells. We believe on the importance of taking in consideration this rare condition even in a toddler with apparently isolated cardiomyopathy and especially when conventional investigations give negative results. We discuss potential trigger effect of HT as a precipitating factor in manifesting neurological symptoms. This observation corresponds to our experience and relates to three patients described so far (the third patient died suddenly). Early onset cardiomyopathy with FRDA should increase awareness of this rare condition and we highlight HT successful outcome. Further reports are needed to delineate this rare condition in youngsters.

Beyond Sarcomeric Hypertrophic Cardiomyopathy: How to Diagnose and Manage Phenocopies

PURPOSE OF REVIEW

We describe the most common phenocopies of hypertrophic cardiomyopathy, their pathogenesis, and clinical presentation highlighting similarities and differences. We also suggest a step-by-step diagnostic work-up that can guide in differential diagnosis and management.

RECENT FINDINGS

In the last years, a wider application of genetic testing and the advances in cardiac imaging have significantly changed the diagnostic approach to HCM phenocopies. Different prognosis and management, with an increasing availability of disease-specific therapies, make differential diagnosis mandatory. The HCM phenotype can be the cardiac manifestation of different inherited and acquired disorders presenting different etiology, prognosis, and treatment. Differential diagnosis requires a cardiomyopathic mindset allowing to recognize red flags throughout the diagnostic work-up starting from clinical and family history and ending with advanced imaging and genetic testing. Different prognosis and management, with an increasing availability of disease-specific therapies make differential diagnosis mandatory.

Neuromuscular diseases and their cardiac manifestations under the spectrum of cardiovascular imaging

Neuromuscular diseases (NMDs) include a broad spectrum of disorders that affect motor unit in every possible site, extending from the cell body of peripheral nerves to the muscle. The different lesion sites make this group of inherited disorders difficult to diagnose. Many NMDs, especially those involving skeletal muscles, can present significant cardiovascular complications, ranging from rhythm disturbances to the development of dilated or hypertrophic cardiomyopathy. Heart disease represents a major cause of morbidity and mortality among NMD patients, underlining the vital need for further familiarization with the pathogenesis and assessment of cardiac involvement. Cardiovascular imaging is the cornerstone for the evaluation of heart disorders in NMDs, with conventional echocardiography still offering a portable, affordable, and easily accessible solution. Meanwhile, newer echocardiographic techniques such as speckle tracking imaging in combination with cardiac magnetic resonance add new insights into further substrate characterization. The purpose of this review is to offer a brief presentation of the main NMDs and their cardiovascular complications, as well as the presentation of data that highlight the importance of cardiovascular imaging in early diagnosis, monitoring, and prognosis of these patients. Lastly, the authors provide a simple guide about which clinical features, imaging findings, and follow-up plan to adopt in each myopathic disorder.

Cardiovascular Research in Friedreich Ataxia: Unmet Needs and Opportunities

Friedreich Ataxia (FRDA) is an autosomal recessive disease in which a mitochondrial protein, frataxin, is severely decreased in its expression. In addition to progressive ataxia, patients with FRDA often develop a cardiomyopathy that can be hypertrophic. This cardiomyopathy is unlike the sarcomeric hypertrophic cardiomyopathies in that the hypertrophy is associated with massive mitochondrial proliferation within the cardiomyocyte rather than contractile protein overexpression. This is associated with atrial arrhythmias, apoptosis, and fibrosis over time, and patients often develop heart failure leading to premature death. The differences between this mitochondrial cardiomyopathy and the more common contractile protein hypertrophic cardiomyopathies can be a source of misunderstanding in the management of these patients. Although imaging studies have revealed much about the structure and function of the heart in this disease, we still lack an understanding of many important clinical and fundamental molecular events that determine outcome of the heart in FRDA. This review will describe the current basic and clinical understanding of the FRDA heart, and most importantly, identify major gaps in our knowledge that represent new directions and opportunities for research.

Friedreich's ataxia-associated childhood hypertrophic cardiomyopathy: a national cohort study

OBJECTIVE

Hypertrophic cardiomyopathy (HCM) is an important predictor of long-term outcomes in Friedreich's ataxia (FA), but the clinical spectrum and survival in childhood is poorly described. This study aimed to describe the clinical characteristics of children with FA-HCM.

DESIGN AND SETTING

Retrospective, longitudinal cohort study of children with FA-HCM from the UK.

PATIENTS

78 children (<18 years) with FA-HCM diagnosed over four decades.

INTERVENTION

Anonymised retrospective demographic and clinical data were collected from baseline evaluation and follow-up.

MAIN OUTCOME MEASURES

The primary study end-point was all-cause mortality (sudden cardiac death, atrial arrhythmia-related death, heart failure-related death, non-cardiac death) or cardiac transplantation.

RESULTS

The mean age at diagnosis of FA-HCM was 10.9 (±3.1) years. Diagnosis was within 1 year of cardiac referral in 34 (65.0%) patients, but preceded the diagnosis of FA in 4 (5.3%). At baseline, 65 (90.3%) had concentric left ventricular hypertrophy and 6 (12.5%) had systolic impairment. Over a median follow-up of 5.1 years (IQR 2.4-7.3), 8 (10.5%) had documented supraventricular arrhythmias and 8 (10.5%) died (atrial arrhythmia-related n=2; heart failure-related n=1; non-cardiac n=2; or unknown cause n=3), but there were no sudden cardiac deaths. Freedom from death or transplantation at 10 years was 80.8% (95% CI 62.5 to 90.8).

CONCLUSIONS

This is the largest cohort of childhood FA-HCM reported to date and describes a high prevalence of atrial arrhythmias and impaired systolic function in childhood, suggesting early progression to end-stage disease. Overall mortality is similar to that reported in non-syndromic childhood HCM, but no patients died suddenly.

Cur@SF NPs alleviate Friedreich's ataxia in a mouse model through synergistic iron chelation and antioxidation

Abnormal iron metabolism, mitochondrial dysfunction and the derived oxidative damage are the main pathogeneses of Friedrich's ataxia (FRDA), a single-gene inherited recessive neurodegenerative disease characterized by progressive cerebellar and sensory ataxia. This disease is caused by frataxin (FXN) mutation, which reduces FXN expression and impairs iron sulfur cluster biogenesis. To date, there is no effective therapy to treat this condition. Curcumin is proposed harboring excellent ability to resist oxidative stress through Nrf2 activation and its newly found ability to chelate iron. However, its limitation is its poor water solubility and permeability. Here, we synthesized slow-release nanoparticles (NPs) by loading curcumin (Cur) into silk fibroin (SF) to form NPs with an average size of 150 nm (Cur@SF NPs), which exhibited satisfactory therapeutic effects on the improvement of FRDA manifestation in lymphoblasts (1 μM) derived from FRDA patients and in YG8R mice (150 mg/kg/5 days). Cur@SF NPs not only removed iron from the heart and diminished oxidative stress in general but also potentiate iron-sulfur cluster biogenesis, which compensates FXN deficiency to improve the morphology and function of mitochondria. Cur@SF NPs showed a significant advantage in neuron and myocardial function, thereby improving FRDA mouse behavior scores. These data encourage us to propose that Cur@SF NPs are a promising therapeutic compound in the application of FRDA disease.

Diagnostic and Prognostic Value of Cardiovascular Magnetic Resonance in Neuromuscular Cardiomyopathies

Neuromuscular diseases (NMD) encompass a broad spectrum of diseases with variable type of cardiac involvement and there is lack of clinical data on Cardiovascular Magnetic Resonance (CMR) phenotypes or even prognostic value of CMR in NMD. We explored the diagnostic and prognostic value of CMR in NMD-related cardiomyopathies. The study included retrospective analysis of a cohort of 111 patients with various forms of NMD; mitochondrial: n = 14, Friedreich's ataxia (FA): n = 27, myotonic dystrophy: n = 27, Becker/Duchenne's muscular dystrophy (BMD/DMD): n = 15, Duchenne's carriers: n = 6, other: n = 22. Biventricular volumes and function and myocardial late gadolinium enhancement (LGE) pattern and extent were assessed by CMR. Patients were followed-up for the composite clinical endpoint of death, heart failure development or need for permanent pacemaker/intracardiac defibrillator. The major NMD subtypes, i.e. FA, mitochondrial, BMD/DMD, and myotonic dystrophy had significant differences in the incidence of LGE (56%, 21%, 62% & 30% respectively, chi² = 9.86, p = 0.042) and type of cardiomyopathy phenotype (chi² = 13.8, p = 0.008), extent/pattern (p = 0.006) and progression rate of LGE (p = 0.006). In survival analysis the composite clinical endpoint differed significantly between NMD subtypes (p = 0.031), while the subgroup with LGE + and LVEF < 50% had the worst prognosis (Log-rank p = 0.0034). We present data from a unique cohort of NMD patients and provide evidence on the incidence, patterns, and the prognostic value of LGE in NMD-related cardiomyopathy. LGE is variably present in NMD subtypes and correlates with LV remodelling, dysfunction, and clinical outcomes in patients with NMD.

The dynamin-related protein 1 is decreased and the mitochondrial network is altered in Friedreich's ataxia cardiomyopathy

Friedreich ataxia is an autosomal recessive congenital neurodegenerative disease caused by a deficiency in the frataxin protein and is often diagnosed in young adulthood. An expansion of guanine-adenine-adenine repeats in the first intron of the FXN gene leads to decreased frataxin expression. Frataxin plays an essential role in mitochondrial metabolism. Most Friedreich ataxia patients are diagnosed with left ventricular hypertrophic cardiomyopathy, and 60% of patients die with hypertrophic cardiomyopathy. However, the mitochondrial anatomy in Friedreich ataxia hypertrophic cardiomyopathy is still poorly understood. We investigated mitochondrial fission, fusion, and function using biochemical, microscopy, and computational stochastic analysis in human induced pluripotent stem cell derived cardiomyocytes from a patient with Friedreich ataxia hypertrophic cardiomyopathy and a healthy individual. We found a significantly higher mitochondrial footprint, decreased mitochondrial fission protein dynamin-related protein, and mitochondrial fission rate over fusion with more giant mitochondrial clusters in human induced pluripotent stem cell derived cardiomyocytes from a patient with Friedreich ataxia hypertrophic cardiomyopathy, compared to an unaffected individual. We also found significantly depolarized mitochondrial membrane potential and higher reactive oxygen species levels in Friedreich ataxia human induced pluripotent stem cell cardiomyocytes. Our results show that frataxin's depletion may dampen the mitochondrial fission machinery by reducing dynamin-related protein1. The loss of mitochondrial fission might lead to elevated reactive oxygen species and depolarized mitochondrial membrane potential, which may cause oxidative damage in Friedreich ataxia hypertrophic cardiomyopathy. Further investigations are needed to identify the mechanism of downregulating dynamin-related protein1 due to the frataxin deficiency in Friedreich ataxia hypertrophic cardiomyopathy.

Characterizing cardiac phenotype in Friedreich's ataxia: The CARFA study

BACKGROUND

Friedreich's ataxia is an autosomal recessive mitochondrial disease caused by a triplet repeat expansion in the frataxin gene (FXN), exhibiting cerebellar sensory ataxia, diabetes and cardiomyopathy. Cardiac complications are the major cause of early death.

AIMS

To characterize the cardiac phenotype associated with Friedreich's ataxia, and to assess the evolution of the associated cardiopathy over 1 year.

METHODS

This observational single-centre open label study consisted of two groups: 20 subjects with Friedreich's ataxia and 20 healthy controls studied over two visits over 1 year. All subjects had transthoracic echocardiography, cardiac magnetic resonance imaging, cardiopulmonary exercise testing, quantification of serum cardiac biomarkers and neurological assessment.

RESULTS

Patients with Friedreich's ataxia had left ventricular hypertrophy, with significantly smaller left ventricular diastolic diameters and volumes and increased wall thicknesses. Cardiac magnetic resonance imaging demonstrated significant concentric left ventricular remodelling, according to the mass/volume ratio, and focal myocardial fibrosis in 50% of patients with Friedreich's ataxia. Cardiopulmonary exercise testing showed alteration of left ventricular diastolic filling in patients with Friedreich's ataxia, with an elevated VE/VCO₂ slope (ventilatory flow/exhaled volume of carbon dioxide). High-sensitivity troponin T plasma concentrations were higher in subjects with Friedreich's ataxia. None of the previous variables changed at 1 year. Neurological assessments remained stable for both groups, except for the nine-hole pegboard test, which was altered over 1 year.

CONCLUSIONS

The multivariable characterization of the cardiac phenotype of patients with Friedreich's ataxia was significantly different from controls at baseline. Over 1 year there were no clinically significant changes in patients with Friedreich's ataxia compared with healthy controls, whereas the neurological severity score increased modestly.

Diagnosis and Management of Cardiovascular Involvement in Friedreich Ataxia

Friedreich ataxia (FRDA) is an autosomal recessive neurodegenerative disorder caused by a homozygous GAA triplet repeat expansion in the frataxin gene. Cardiac involvement, usually manifesting as hypertrophic cardiomyopathy, can range from asymptomatic cases to severe cardiomyopathy with progressive deterioration of the left ventricular ejection fraction and chronic heart failure. The management of cardiac involvement is directed to prevent disease progression and cardiovascular complications. However, direct-disease therapies are not currently available for FRDA. The present review aims to describe the current state of knowledge regarding cardiovascular involvement of FRDA, focusing on clinical-instrumental features and management of cardiac manifestation.

Left atrial appendage thrombosis in a patient with Friedreich Ataxia-related cardiomyopathy, left ventricular systolic dysfunction, and atrial fibrillation

Friedreich ataxia is the most common form of hereditary ataxia. Heart involvement in Friedreich ataxia is common and can include increased left ventricular wall thickness, atrial fibrillation, and in the later stages, a reduction of left ventricular ejection fraction. We present the case of a 45-year-old man with a history of paroxysmal atrial fibrillation and a congestive heart failure, hypertension, age ⩾ 75 years, diabetes mellitus, stroke, vascular disease, age 65–74 years, and female sex (CHA2DS2-VASc) score of only 1 (because of reduced left ventricular ejection fraction) who presented with pneumonia and was also found to have atrial fibrillation with a rapid ventricular response. Despite already being on long-term therapy with a non-vitamin K-antagonist oral anticoagulant, a transesophageal echocardiogram showed a mobile floating thrombus in the left atrial appendage. In accordance with previous necropsy evidence of thrombosis and thromboembolism in Friedreich ataxia subjects who likely have had only non-sex-related CHA2DS2-VASc score ⩽1, this case suggests that the risk of thromboembolism in Friedreich ataxia subjects with atrial fibrillation may not be adequately predicted by the sole CHA2DS2-VASc score.

Quality Assurance of Segmental Strain Values Provided by Commercial 2-D Speckle Tracking Echocardiography Using in Silico Models: A Report from the EACVI-ASE Strain Standardization Task Force

The aim of this study was to determine the accuracy and reproducibility of vendor-specific regional strain values by echocardiography using in silico data. Synthetic 2-D ultrasound gray-scale images of the left ventricle (LV) were generated with knowledge of the longitudinal segmental strain values from the underlying electromechanical LV model. Four of five models mimicked transmural infarctions with systolic segmental stretching in different vascular areas. Cine loops in the three apical views were synthetically generated at four noise levels. All in silico images were repeatedly analyzed by a single investigator and some by another investigator. The absolute errors varied significantly between vendors from 3.3 ± 3.1% to 11.2 ± 5.9%. The area under the curve for the identification of segmental stretching ranged from 0.80 (confidence interval: 0.77-0.83) to 0.96 (0.95-0.98). The levels of agreement for intra-investigator variability varied between -3.0% to 2.9% and -5.2% to 4.8%, and for inter-investigator variability, between -3.6% to 3.5% and -14.5% to 8.5%. Segmental strain analysis allows the identification of areas with segmental stretching with good accuracy. However, single segmental peak-strain values are not accurate and should be interpreted with caution. Nevertheless, our results indicate the usefulness of semiquantitative strain assessment for the detection of regional dysfunction.

Genetics of Cardiomyopathy: Clinical and Mechanistic Implications for Heart Failure

Genetic cardiomyopathies are an important cause of sudden cardiac death across all age groups. Genetic testing in heart failure clinics is useful for family screening and providing individual prognostic insight. Obtaining a family history of at least three generations, including the creation of a pedigree, is recommended for all patients with primary cardiomyopathy. Additionally, when appropriate, consultation with a genetic counsellor can aid in the success of a genetic evaluation. Clinical screening should be performed on all first-degree relatives of patients with genetic cardiomyopathy.

Genetics has played an important role in the understanding of different cardiomyopathies, and the field of heart failure (HF) genetics is progressing rapidly. Much research has also focused on distinguishing markers of risk in patients with cardiomyopathy using genetic testing. While these efforts currently remain incomplete, new genomic technologies and analytical strategies provide promising opportunities to further explore the genetic architecture of cardiomyopathies, afford insight into the early manifestations of cardiomyopathy, and help define the molecular pathophysiological basis for cardiac remodeling. Cardiovascular physicians should be fully aware of the utility and potential pitfalls of incorporating genetic test results into pre-emptive treatment strategies for patients in the preliminary stages of HF. Future work will need to be directed towards elucidating the biological mechanisms of both rare and common gene variants and environmental determinants of plasticity in the genotype-phenotype relationship. This future research should aim to further our ability to identify, diagnose, and treat disorders that cause HF and sudden cardiac death in young patients, as well as prioritize improving our ability to stratify the risk for these patients prior to the onset of the more severe consequences of their disease.

Clinical Insights Into Heritable Cardiomyopathies

Cardiomyopathies (CMs) encompass a heterogeneous group of structural and functional abnormalities of the myocardium. The phenotypic characteristics of these myocardial diseases range from silent to symptomatic heart failure, to sudden cardiac death due to malignant tachycardias. These diseases represent a leading cause of cardiovascular morbidity, cardiac transplantation, and death. Since the discovery of the first locus associated with hypertrophic cardiomyopathy 30 years ago, multiple loci and molecular mechanisms have been associated with these cardiomyopathy phenotypes. Conversely, the disparity between the ever-growing landscape of cardiovascular genetics and the lack of awareness in this field noticeably demonstrates the necessity to update training curricula and educational pathways. This review summarizes the current understanding of heritable CMs, including the most common pathogenic gene variants associated with the morpho-functional types of cardiomyopathies: dilated, hypertrophic, arrhythmogenic, non-compaction, and restrictive. Increased understanding of the genetic/phenotypic associations of these heritable diseases would facilitate risk stratification to leveraging appropriate surveillance and management, and it would additionally provide identification of family members at risk of avoidable cardiovascular morbidity and mortality.

Cardiac Involvement in Movement Disorders

Background

Several conditions represented mainly by movement disorders are associated with cardiac disease, which can be overlooked in clinical practice in the context of a prominent primary neurological disorder.

Objectives

To review neurological conditions that combine movement disorders and primary cardiac involvement.

Methods

A comprehensive and structured literature search following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses criteria was conducted to identify disorders combining movement disorders and cardiac disease.

Results

Some movement disorders are commonly or prominently associated with cardiac disease. Neurological and cardiac symptoms may share underlying physiopathological mechanisms in diseases, such as Friedreich's ataxia and Wilson's disease, and in certain metabolic disorders, including Refsum disease, Gaucher disease, a congenital disorder of glycosylation, or cerebrotendinous xanthomatosis. In certain conditions, such as Sydenham's chorea or dilated cardiomyopathy with ataxia syndrome (ATX-DNAJC19), heart involvement can present early in the course of disease, whereas in others such as Friedreich's ataxia or Refsum disease, cardiac symptoms tend to present in later stages. In another 68 acquired or inherited conditions, cardiac involvement or movement disorders are seldom reported.

Conclusions

As cardiac disease is part of the phenotypic spectrum of several movement disorders, heart involvement should be carefully investigated and increased awareness of this association encouraged as it may represent a leading cause of morbidity and mortality.

Pre-clinical left ventricular myocardial remodeling in patients with Friedreich's ataxia: A cardiac MRI study

BACKGROUND

Heart Failure (HF) is the most common cause of death in Friedreich's ataxia (FRDA), an inherited mitochondrial disease. Myocardial fibrosis and myocardial hypertrophy are well-documented autopsy features among FRDA patients with HF.

OBJECTIVES

To leverage the unique tissue characterization features of cardiac magnetic resonance (CMR) for characterizing myocardial remodeling in patients with genetically confirmed FRDA without HF and preserved left ventricular ejection fraction (LVEF > 55%).

METHODS

Twenty-seven FRDA's patients (age 27.6 ± 9.7 years, 15 women) and 10 healthy controls (32.6±7.3 years, 5 women) underwent a CMR for assessment of LV function, myocardial T1, late gadolinium enhancement (LGE), extracellular volume fraction (ECV), and intracellular water-lifetime (τic), a marker of cardiomyocyte size.

RESULTS

As compared to controls, FRDA patients had a preserved LVEF (LVEF: 70.5±7.4% vs. 63.9±9.0%, P<0.058), larger LV mass index (LVMASSi: 61±21.7 vs. 45±4.2g/m2, P<0.02), and decreased LV end-diastolic volume index (LVEDVi 53.1±12.0 vs. 75.7±16.1ml/m2, P<0.001), compared with controls. Additionally, ECV and cardiomyocyte size (τic,) were larger in FRDA patients (ECV: 0.36 ±0.05 vs. 0.25±0.02, P<0.001; τic: 0.15±0.08 vs. 0.06±0.03 s, P = 0.02). ECV and τic were positively associated with LV mass-to-volume ratio (ECV: r = 0.57, P = 0.003; τic: r = 0.39; P = 0.05). LVMASSi and cardiomyocyte mass-index [(1-ECV)·LVMASSi] declined with age at the CMR exam, independent of the age at initial diagnosis.

CONCLUSIONS

LV hypertrophy and concentric LV remodeling in FRDA are associated at the tissue level with an expansion of the ECV and an increase in cardiomyocyte size. The adverse tissue remodeling assessed by ECV and τic is associated with more severe cardiomyopathy classification, suggesting a role for these markers in tracking disease progression.

Cardiomyopathy of Friedreich's Disease. Modern Methods of Diagnostic

Friedreich's disease is a hereditary neurodegenerative multiple organ disease, primarily affecting the most energy-dependent tissues (cells of the nervous system, myocardium, pancreas), the lesion of which is characterized by progressive ataxia, dysarthria, dysphagia, oculomotor disorders, loss of deep tendon reflexes, pyramid signs, diabetes mellitus, visual impairment. Friedreich's ataxia is the most common of all hereditary ataxias; nevertheless, this disease is considered orphan. By its pathogenesis, Friedreich's disease is mitochondrial ataxia, caused by a deficiency in the transcription of the FXN gene, leading to a decrease in the synthesis of the frataxin protein. Frataxin is a protein associated with the inner mitochondrial membrane, which in turn is involved in the formation of iron-sulfur clusters, the lack of which leads to a decrease in the production of mitochondrial ATP, an increase in the level of mitochondrial iron and oxidative stress. The basis of the clinical picture of Friedreich's disease is ataxia of a mixed (sensitive and cerebellar) nature. The steady and gradual progression of neurological symptoms significantly affects the quality of life of patients and is most often the leading reason for seeking medical attention. However, the prognosis is primarily due to the involvement of cardiac tissue in the pathological process. The main causes of death in patients with Friedreich's ataxia are severe heart failure and sudden cardiac death due to cardiomyopathy. The overwhelming majority of foreign and domestic publications on Friedreich's ataxia are devoted to the neurological manifestations of this disease, and little attention is paid to this problem in the cardiological scientific and practical society. The purpose of this review is to provide up-to-date information on modern methods of diagnosing myocardial damage at various stages of Friedreich's disease.

Mitochondrial iron and calcium homeostasis in Friedreich ataxia

Friedreich Ataxia is a neuro-cardiodegenerative disease caused by the deficiency of frataxin, a mitochondrial protein. Many evidences indicate that frataxin deficiency causes an unbalance of iron homeostasis. Nevertheless, in the last decade many results also highlighted the importance of calcium unbalance in the deleterious downstream effects caused by frataxin deficiency. In this review, the role of these two metals has been gathered to give a whole view of how iron and calcium dyshomeostasys impacts on cellular functions and, as a result, which strategies can be followed to find an effective therapy for the disease.

Prognostic value of longitudinal strain and ejection fraction in Friedreich's ataxia

BACKGROUND

Friedreich's ataxia (FA) is a rare autosomal recessive mitochondrial disease most commonly due to a triplet repeat expansion guanine-adenine-adenine (GAA) in the FXN gene. Cardiac disease is the major cause of death, patients with reduced left ventricular ejection fraction (LVEF) having the worse prognosis. Longitudinal strain (LS) appeared to be a better predictor of outcome than LVEF in different diseases. We compared the prognostic value of LS measured from the 4 chambers view to LVEF.

METHODS

From 2003 to 2017 consecutive patients with FA were included and LS analysis was retrospectively performed.

RESULTS

We studied 140 patients, with a median age of 34 (26-41) years (Q1-Q3) with age at onset of 14 (11-19) years and GAA repeats on the shorter allele of 600 (467-783) pb. Mean LS was 19.9 ± 5.0% and LVEF 64 ± 8%. After a mean follow-up of 7.4 ± 3.9 years, 14 patients died. In univariate Cox analysis, all-cause mortality was associated with: LS (HR 0.83; 95%CI, 0.75-0.91, p = 0.0002), LVEF (HR 0.30; 95%CI, 0.19-0.49, p < 0.0001), GAA repeats on the shorter allele (HR 1.29; 95%CI, 1.10-1.51, p = 0.002), age at onset (HR 0.87; 95%CI, 0.77-0.98, p = 0.018), LVSystolic Diameter (HR 1.17; 95%CI, 1.09-1.26, p < 0.0001), LVMass index (HR 1.02; 95%CI, 1.00-1.04, p = 0.027), and LVDiastolic Diameter (HR1.12; 95%CI, 1.01-1.23, p = 0.028). In multivariate analysis, LVEF was the only independent predictor of mortality (HR 0.41; 95%CI, 0.23-0.74, p = 0.0029).

CONCLUSION

In FA, LS was not an independent predictor of mortality, LVEF remained the only independent predictor in the present study.

Efficacy of echocardiography for differential diagnosis of left ventricular hypertrophy: special focus on speckle-tracking longitudinal strain

Left ventricular (LV) hypertrophy (LVH) is a frequent imaging finding in daily clinical practice, and its presence is associated with poor outcomes and ventricular arrhythmias. It is commonly detected in athletes, arterial hypertension, aortic stenosis, hypertrophic cardiomyopathy, cardiac amyloidosis, Fabry disease, or Friedreich’s ataxia. Echocardiography plays an important role in detecting LVH and underlying causes in current clinical practice. While echocardiography is essential for the quantification and early detection of LV structural findings for various cardiovascular diseases, it has been reported that speckle-tracking echocardiographic parameters are also useful for the detection of early LV structural abnormalities. In particular, global longitudinal strain (GLS) assessed by two-dimensional speckle-tracking echocardiography is reportedly a sensitive marker for early subtle abnormalities of LV myocardial performance, helpful for the prediction of outcomes for various cardiac diseases, and superior to conventional echocardiographic indices. GLS is determined as the averaged peak longitudinal strain of 18 LV segments from standard apical views and can be assessed as a polar plot. This polar plot longitudinal strain mapping offers an intuitive visual overview of the global and regional LV longitudinal myocardial function status of various cardiomyopathies with LVH. This mapping is clinically practicable and the plot patterns obtainable as the result of further development of this technique for clinical practice provide clues to the etiology of cardiomyopathies. This article reviews the efficacy of echocardiography for differential diagnosis of LVH, with a special focus on the utility of speckle-tracking longitudinal strain.

Friedreich's Ataxia: Case series and the Additive Value of Cardiovascular Magnetic Resonance

BackgroundFriedreich's ataxia (FA) is an autosomal-recessive neurodegenerative disease characterised by neurologic, cardiac and endocrine abnormalities. Currently, Friedreich cardiomyopathy (FA-CM) staging is based on early ECG findings, high sensitivity troponin (hsTNT) ≥14 ng/ml and echocardiographic left ventricular (LV) morphologic and functional evaluation. However, further parameters, accessible only by cardiovascular magnetic resonance (CMR), such as myocardial oedema, perfusion defects, replacement and/or diffuse myocardial fibrosis, may have a place in the staging of FA-CA. Our aim was to elucidate the additive value of CMR in FA-CM.MethodsThree FA cases were assessed using ECG, 24 h Holter recording, hsTNT, routine ECHO including wall dimension, valvular and ventricular function evaluation and CMR using 1.5T Ingenia system. Ventricular volumes-function, wall dimensions and fibrosis imaging using late gadolinium enhancement (LGE) was performed.ResultsAll FA patients had non-specific ECG changes, almost normal 24 h Holter recording, mild hypertrophy with normal function assessed by echocardiography and increased hsTNT. However, the CMR evaluation revealed the presence of LGE >5% of LV mass, indicative of severe fibrosis. Therefore, the FA patients were re-categorized as having severe FA-CA, although their LVEF remained normal.ConclusionThe combination of classical diagnostic indices and CMR may reveal early asymptomatic FA-CM and motivate the early initiation of cardiac treatment. Furthermore, these indices can be also used to validate specific treatment targets in FA, potentially useful in the prevention of FA-CM.

A Drosophila model of Friedreich ataxia with CRISPR/Cas9 insertion of GAA repeats in the frataxin gene reveals in vivo protection by N-acetyl cysteine

Friedreich ataxia (FA) is caused by GAA repeat expansions in the first intron of FXN, the gene encoding frataxin, which results in decreased gene expression. Thanks to the high degree of frataxin conservation, the Drosophila melanogaster fruitfly appears as an adequate animal model to study this disease and to evaluate therapeutic interventions. Here, we generated a Drosophila model of FA with CRISPR/Cas9 insertion of approximately 200 GAA in the intron of the fly frataxin gene fh. These flies exhibit a developmental delay and lethality associated with decreased frataxin expression. We were able to bypass preadult lethality using genetic tools to overexpress frataxin only during the developmental period. These frataxin-deficient adults are short-lived and present strong locomotor defects. RNA-Seq analysis identified deregulation of genes involved in amino-acid metabolism and transcriptomic signatures of oxidative stress. In particular, we observed a progressive increase of Tspo expression, fully rescued by adult frataxin expression. Thus, Tspo expression constitutes a molecular marker of the disease progression in our fly model and might be of interest in other animal models or in patients. Finally, in a candidate drug screening, we observed that N-acetyl cysteine improved the survival, locomotor function, resistance to oxidative stress and aconitase activity of frataxin-deficient flies. Therefore, our model provides the opportunity to elucidate in vivo, the protective mechanisms of this molecule of therapeutic potential. This study also highlights the strength of the CRISPR/Cas9 technology to introduce human mutations in endogenous orthologous genes, leading to Drosophila models of human diseases with improved physiological relevance.

Treatment of dilated cardiomyopathy in a mouse model of Friedreich's ataxia using N-acetylcysteine and identification of alterations in microRNA expression that could be involved in its pathogenesis

Deficient expression of the mitochondrial protein, frataxin, leads to a deadly cardiomyopathy. Our laboratory reported the master regulator of oxidative stress, nuclear factor erythroid 2-related factor-2 (Nrf2), demonstrates marked down-regulation after frataxin deletion in the heart. This was due, in part, to a pronounced increase in Keap1. To assess if this can be therapeutically targeted, cells were incubated with N-acetylcysteine (NAC), or buthionine sulfoximine (BSO), which increases or decreases glutathione (GSH), respectively, or the NRF2-inducer, sulforaphane (SFN). While SFN significantly (p < 0.05) induced NRF2, KEAP1 and BACH1, NAC attenuated SFN-induced NRF2, KEAP1 and BACH1. The down-regulation of KEAP1 by NAC was of interest, as Keap1 is markedly increased in the MCK conditional frataxin knockout (MCK KO) mouse model and this could lead to the decreased Nrf2 levels. Considering this, MCK KO mice were treated with i.p. NAC (500- or 1500-mg/kg, 5 days/week for 5-weeks) and demonstrated slightly less (p > 0.05) body weight loss versus the vehicle-treated KO. However, NAC did not rescue the cardiomyopathy. To additionally examine the dys-regulation of Nrf2 upon frataxin deletion, studies assessed the role of microRNA (miRNA) in this process. In MCK KO mice, miR-144 was up-regulated, which down-regulates Nrf2. Furthermore, miRNA screening in MCK KO mice demonstrated 23 miRNAs from 756 screened were significantly (p < 0.05) altered in KOs versus WT littermates. Of these, miR-21*, miR-34c*, and miR-200c, demonstrated marked alterations, with functional clustering analysis showing they regulate genes linked to cardiac hypertrophy, cardiomyopathy, and oxidative stress, respectively.

Stress-Induced Mouse Model of the Cardiac Manifestations of Friedreich's Ataxia Corrected by AAV-mediated Gene Therapy

Friedreich's ataxia (FA), an autosomal recessive disorder caused by a deficiency in the expression of frataxin (FXN), is characterized by progressive ataxia and hypertrophic cardiomyopathy. Although cardiac dysfunction is the most common cause of mortality in FA, the cardiac disease remains subclinical for most of the clinical course because the neurologic disease limits muscle oxygen demands. Previous FXN knockout mouse models exhibit fatal cardiomyopathy similar to human FA, but in contrast to the human condition, untreated mice become moribund by 2 months of age, unlike humans where the cardiac disease often does not manifest until the third decade. The study was designed to create a mouse model for early FA disease relevant to the time for which a gene therapy would likely be most effective. To generate a cardiac-specific mouse model of FA cardiomyopathy similar to the human disease, we used a cardiac promoter (αMyhc) driving CRE recombinase cardiac-specific excision of FXN exon 4 to generate a mild, cardiac-specific FA model that is normal at rest, but exhibits the cardiac phenotype with stress. The hearts of αMyhc mice had decreased levels of FXN and activity of the mitochondrial complex II/complex IV respiratory chain. At rest, αMyhc mice exhibited normal cardiac function as assessed by echocardiographic assessment of ejection fraction and fractional shortening, but when the heart was stressed chemically with dobutamine, αMyhc mice compared with littermate control mice had a 62% reduction in the stress ejection fraction (p < 2 × 10-4) and 71% reduction in stress-related fractional shortening (p < 10-5). When assessing functional cardiac performance using running on an inclined treadmill, αMyhc mice stayed above the midline threefold less than littermate controls (p < 0.02). A one-time intravenous administration of 1011 genome copies of AAVrh.10hFXN, an adeno-associated virus (AAV) serotype rh10 gene transfer vector expressing human FXN, corrected the stress-induced ejection fraction and fractional shortening phenotypes. Treated αMyhc mice exhibited exercise performance on a treadmill indistinguishable from littermate controls (p > 0.07). These αMyhc mice provide an ideal model to study long-term cardiac complications due to FA and AAV-mediated gene therapy correction of stress-induced cardiac phenotypes typical of human FA.

Antioxidant Therapies and Oxidative Stress in Friedreich´s Ataxia: The Right Path or Just a Diversion?

Friedreich´s ataxia is the commonest autosomal recessive ataxia among population of European descent. Despite the huge advances performed in the last decades, a cure still remains elusive. One of the most studied hallmarks of the disease is the increased production of oxidative stress markers in patients and models. This feature has been the motivation to develop treatments that aim to counteract such boost of free radicals and to enhance the production of antioxidant defenses. In this work, we present and critically review those "antioxidant" drugs that went beyond the disease´s models and were approved for its application in clinical trials. The evaluation of these trials highlights some crucial aspects of the FRDA research. On the one hand, the analysis contributes to elucidate whether oxidative stress plays a central role or whether it is only an epiphenomenon. On the other hand, it comments on some limitations in the current trials that complicate the analysis and interpretation of their outcome. We also include some suggestions that will be interesting to implement in future studies and clinical trials.

Predictors of Left Ventricular Dysfunction in Friedreich's Ataxia in a 16-Year Observational Study

BACKGROUND

Friedreich's ataxia (FRDA) is a cerebellar ataxia due to GAA repeat expansions in the FXN gene, and in affected patients, lower left ventricular ejection fraction (LVEF) leads to poorer prognosis. We aimed to identify patients likely to develop worsening LVEF at an early stage.

METHODS

We included 115 FRDA patients aged 30 ± 10 years with 620 ± 238 GAA repeats on the shorter allele and disease onset of 15 ± 7 years.

RESULTS

At baseline, left ventricular (LV) hypertrophy was present in 53%, with LVEF 65 ± 7%, LV end diastolic diameter (LVEDD) 43 ± 5 mm, septal wall thickness (SWT) 11.8 ± 2.7 mm, and posterior wall thickness 11.1 ± 2.5 mm. After a mean follow-up of 13 ± 6 years, LVEF ≤ 50% was observed in 12 patients. The main determinants of LVEF ≤ 50% were GAA repeat number on the shorter allele (odds ratio [OR] 1.007, 95% confidence interval [CI] 1.003-1.012, p = 0.002), LVEDD (OR 1.217, 95% CI 1.058-1.399, p = 0.006), and SWT (OR 1.352, 95% CI 1.016-1.799, p = 0.04). High-risk patients were predicted 5 years before LVEF ≤ 50% occurred: area under the curve of 0.91, 95% CI 0.85-0.97. Patients with GAA repeats > 800 were categorized as high risk, patients with 500 < GAA < 800 were high risk if LVEDD was ≥ 52.6 mm and SWT was ≥ 13.3 mm, and patients with GAA < 500 were low risk if LVEDD was < 52.6 mm and SWT was < 13.3 mm.

CONCLUSIONS

Echocardiographic follow-up combined with size assessment of GAA repeat expansions is a powerful tool to identify patients at high risk of developing LV systolic dysfunction up to 5 years before clinical symptoms. Further studies are mandatory to investigate if these patients would benefit from cardiac interventions.

Myocardial tissue characterisation using echocardiographic deformation imaging

Myocardial pathology results in significant morbidity and mortality, whether due to primary cardiomyopathic processes or secondary to other conditions such as ischemic heart disease. Cardiac imaging techniques characterise the underlying tissue directly, by assessing a signal from the tissue itself, or indirectly, by inferring tissue characteristics from global or regional function. Cardiac magnetic resonance imaging is currently the most investigated imaging modality for tissue characterisation, but, due to its accessibility, advanced echocardiography represents an attractive alternative. Speckle tracking echocardiography (STE) is a reproducible technique used to assess myocardial deformation at both segmental and global levels. Since distinct myocardial pathologies affect deformation differently, information about the underlying tissue can be inferred by STE. In this review, the current available studies correlating STE deformation parameters with underlying tissue characteristics in humans are examined, with separate emphasis on global and segmental analysis. The current knowledge is placed in the context of integrated backscatter and the future of echocardiographic based tissue characterisation is discussed. The use of these imaging techniques to more precisely phenotype myocardial pathology more precisely will allow the design of translational cardiac research studies and, potentially, tailored management strategies.

Left ventricular structural and functional changes in Friedreich ataxia - Relationship with body size, sex, age and genetic severity

Introduction

Although a concentric pattern of left ventricular (LV) geometry appears to be common in Friedreich ataxia (FRDA), there is no accepted method for diagnosing LV abnormalities in FRDA, sex and body size have often not been taken into consideration, and it has not been clear whether children and adults should be classified using the same criteria. The aim of this study was to better define the LV geometric changes in FRDA with respect to sex, body size and subject age, and to investigate the relationship of LV changes with genetic severity, as assessed by GAA repeat length within the shorter allele of the FXN gene (GAA1).

Methods

Echocardiography was performed in 216 subjects (68 children, 148 adults), measurements were made at end-diastole of LV internal diameter (LVEDID), septal wall thickness (SWT), LV length (LVEDL) and LV volume (LVEDV), and calculations were made of relative wall thickness (RWT), LV mass and LV ejection fraction (LVEF).

Results

The most common LV abnormalities in both adults and children with FRDA were increases in RWT and age-normalized RWT. In adults with a normal LVEF, all LV variables other than RWT were larger in males independent of body surface area (BSA), and all LV variables other than SWT and RWT were positively correlated with BSA. After adjustment for sex and BSA, GAA1 was a positive correlate of SWT and RWT (but not of LV mass), and was an inverse correlate of LVEDID, LVEDL and LVEDV. In children with a normal LVEF, SWT, LV mass and LVEDL were larger in males than females after adjusting for BSA, and in combination with sex, BSA was a positive correlate of all the LV variables except SWT and RWT. In children there were no correlations of GAA1 with any of the LV variables.

Conclusion

In FRDA, increases in RWT and age-normalized RWT are the most frequent LV structural abnormalities, sex and body size are important determinants of most other LV structural variables in both children and adults, and increased genetic severity is associated with a smaller left ventricle and increased LV wall thickness in adults, but not associated with LV size or wall thickness in children.

Cardiac Phenotypes in Hereditary Muscle Disorders: JACC State-of-the-Art Review

Hereditary muscular diseases commonly involve the heart. Cardiac manifestations encompass a spectrum of phenotypes, including both cardiomyopathies and rhythm disorders. Common biomarkers suggesting cardiomuscular diseases include increased circulating creatine kinase and/or lactic acid levels or disease-specific metabolic indicators. Cardiac and extra-cardiac traits, imaging tests, family studies, and genetic testing provide precise diagnoses. Cardiac phenotypes are mainly dilated and hypokinetic in dystrophinopathies, Emery-Dreifuss muscular dystrophies, and limb girdle muscular dystrophies; hypertrophic in Friedreich ataxia, mitochondrial diseases, glycogen storage diseases, and fatty acid oxidation disorders; and restrictive in myofibrillar myopathies. Left ventricular noncompaction is variably associated with the different myopathies. Conduction defects and arrhythmias constitute a major phenotype in myotonic dystrophies and skeletal muscle channelopathies. Although the actual cardiac management is rarely based on the cause, the cardiac phenotypes need precise characterization because they are often the only or the predominant manifestations and the prognostic determinants of many hereditary muscle disorders.