Marked variation in the cardiomyopathy associated with Friedreich's ataxia

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.

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.

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.

Friedreich ataxia in a family from Mali, West Africa/Friedreich ataxia in a Malian family

Friedreich ataxia is the most common inherited ataxia in the world, but yet to be reported in black African. We report the first genetically confirmed case in a West African family. Studying genetic diseases in populations with diverse backgrounds may give new insights into their pathophysiology for future therapeutic targets.

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.

Inducible and reversible phenotypes in a novel mouse model of Friedreich's Ataxia

Friedreich's ataxia (FRDA), the most common inherited ataxia, is caused by recessive mutations that reduce the levels of frataxin (FXN), a mitochondrial iron binding protein. We developed an inducible mouse model of Fxn deficiency that enabled us to control the onset and progression of disease phenotypes by the modulation of Fxn levels. Systemic knockdown of Fxn in adult mice led to multiple phenotypes paralleling those observed in human patients across multiple organ systems. By reversing knockdown after clinical features appear, we were able to determine to what extent observed phenotypes represent reversible cellular dysfunction. Remarkably, upon restoration of near wild-type FXN levels, we observed significant recovery of function, associated pathology and transcriptomic dysregulation even after substantial motor dysfunction and pathology were observed. This model will be of broad utility in therapeutic development and in refining our understanding of the relative contribution of reversible cellular dysfunction at different stages in disease.

The Subclinical Cardiomyopathy of Friedreich's Ataxia in a Pediatric Population

BACKGROUND

Identification of a subclinical cardiomyopathy in pediatric patients with Friedreich's ataxia (FA) has not been well-described.

METHODS

We performed echocardiography (Echo), cardiac magnetic resonance imaging (cMRI), and neurologic assessment in a cross-sectional analysis of 48 genetically confirmed FA subjects aged 9-17 years with moderate neurologic impairment but without a cardiovascular history. Echo- and cMRI-determined left ventricular mass were indexed (LVMI) to height in grams/m^2.7. LV remodeling was categorized as concentric remodeling (CR), concentric hypertrophy (CH), or eccentric hypertrophy based upon Echo- determined relative LV wall thickness.

RESULTS

Echo LVMI exceeded age-based normal values in 85% of subjects, and cMRI-determined LVMI correlated with depression of both diastolic and systolic tissue Doppler velocity (E': r = -0.65, P < .001, S': r = -0.46, P < .001) as well as increased early diastolic Doppler flow velocity/tissue velocity ratio (r= 0.55, P < .001), a marker of elevated LV filling pressure. Similar associations were found with echo-determined LV mass. Evidence of depressed LV relaxation and increased LV stiffness were observed in 88% and 71%, of subjects, respectively, despite a normal LV ejection fraction in almost all cases (mean = 60% + 7%). CR and CH were present in 40% and 44% of the study group, respectively, although significant depressions of E' and S' were observed only in subjects with CH (P < .005).

CONCLUSIONS

A subclinical hypertrophic cardiomyopathy is common in pediatric FA patients and CH is associated with both diastolic and systolic dysfunction.

Friedreich Ataxia: current status and future prospects

Friedreich ataxia (FA) represents the most frequent type of inherited ataxia. Most patients carry homozygous GAA expansions in the first intron of the frataxin gene on chromosome 9. Due to epigenetic alterations, frataxin expression is significantly reduced. Frataxin is a mitochondrial protein. Its deficiency leads to mitochondrial iron overload, defective energy supply and generation of reactive oxygen species. This review gives an overview over clinical and genetic aspects of FA and discusses current concepts of frataxin biogenesis and function as well as new therapeutic strategies.

Using human pluripotent stem cells to study Friedreich ataxia cardiomyopathy

Friedreich ataxia (FRDA) is the most common of the inherited ataxias. It is an autosomal recessive disease characterised by degeneration of peripheral sensory neurons, regions of the central nervous system and cardiomyopathy. FRDA is usually due to homozygosity for trinucleotide GAA repeat expansions found within first intron of the FRATAXIN (FXN) gene, which results in reduced levels of the mitochondrial protein FXN. Reduced FXN protein results in mitochondrial dysfunction and iron accumulation leading to increased oxidative stress and cell death in the nervous system and heart. Yet the precise functions of FXN and the underlying mechanisms leading to disease pathology remain elusive. This is particularly true of the cardiac aspect of FRDA, which remains largely uncharacterized at the cellular level. Here, we summarise current knowledge on experimental models in which to study FRDA cardiomyopathy, with a particular focus on the use of human pluripotent stem cells as a disease model.

Infiltrative Cardiomyopathies

Infiltrative cardiomyopathies can result from a wide spectrum of both inherited and acquired conditions with varying systemic manifestations. They portend an adverse prognosis, with only a few exceptions (ie, glycogen storage disease), where early diagnosis can result in potentially curative treatment. The extent of cardiac abnormalities varies based on the degree of infiltration and results in increased ventricular wall thickness, chamber dilatation, and disruption of the conduction system. These changes often lead to the development of heart failure, atrioventricular (AV) block, and ventricular arrhythmia. Because these diseases are relatively rare, a high degree of clinical suspicion is important for diagnosis. Electrocardiography and echocardiography are helpful, but advanced techniques including cardiac magnetic resonance (CMR) and nuclear imaging are increasingly preferred. Treatment is dependent on the etiology and extent of the disease and involves medications, device therapy, and, in some cases, organ transplantation. Cardiac amyloid is the archetype of the infiltrative cardiomyopathies and is discussed in great detail in this review.

A 7-year-old girl with hypertrophic cardiomyopathy and progressive scoliosis

We report a 7 year old girl who was evaluated for progressive thoracolumbar scoliosis and hypertrophic cardiomyopathy. Neurological examination was found to be abnormal and significant for absent reflexes and weakness distally in lower extremities and positive Romberg sign. Electromyogram showed length-dependent, axonal, sensorimotor polyneuropathy. Frataxin levels were low at 3ng/mL. Molecular testing for Friedreich ataxia showed significantly expanded GAA repeats at 799 (abnormal >67 GAA repeats) on one allele and a heterozygous disease causing mutation, c.317T>C (p.Leu106Ser) on the other allele, confirming the diagnosis. A review of Friedreich ataxia is provided in the case report.

[Heart involvement in Friedreich's ataxia]

Friedreich's ataxia is a rare hereditary disease and although the gene defect has already been identified as a deficiency of the mitochondrial protein frataxin, the pathophysiology is still unknown. Although a multisystem disorder organ involvement is predominantly neurological. Besides the characteristic features of spinocerebellar ataxia the heart is frequently also affected. Cardiac involvement typically manifests as hypertrophic cardiomyopathy, which can progress to heart failure and death. So far most research has focused on the neurological aspects and cardiac involvement in Friedreich's ataxia has not been systematically investigated. Thus, a better understanding of the progression of the cardiomyopathy, cardiac complications and long-term cardiac outcome is warranted. Although no specific treatment is available general cardiac therapeutic options for cardiomyopathy should be considered. The current review focuses on clinical and diagnostic features of cardiomyopathy and discusses potential therapeutic developments for Friedreich's ataxia.

Cardiomyopathy of Friedreich ataxia

Friedreich's ataxia is a rare hereditary, predominantly neurologically defined multisystem disorder of mitochondrial function. Although the gene defect has been identified, the precise pathophysiology of the deficient mitochondrial protein, frataxin, is unknown. Besides the characteristic features of spinocerebellar ataxia the heart may also be affected, and patients may experience a hypertrophic cardiomyopathy eventually progressing toward heart failure and death. So far, research focused on the neurological aspects and little attention has been paid to better characterize and understand the cardiac involvement in Friedreich's ataxia. For that, a better understanding of longitudinal progression, cardiac complications and long-term cardiac outcome is warranted. In addition, the clinician should be familiar with the therapeutic option in Friedreich cardiomyopathy. This review discusses important clinical and diagnostic features of the cardiomyopathy in Friedreich's ataxia and potential therapeutic developments.

Clinical features of Friedreich's ataxia: classical and atypical phenotypes

One hundred and fifty years since Nikolaus Friedreich's first description of the degenerative ataxic syndrome which bears his name, his description remains at the core of the classical clinical phenotype of gait and limb ataxia, poor balance and coordination, leg weakness, sensory loss, areflexia, impaired walking, dysarthria, dysphagia, eye movement abnormalities, scoliosis, foot deformities, cardiomyopathy and diabetes. Onset is typically around puberty with slow progression and shortened life-span often related to cardiac complications. Inheritance is autosomal recessive with the vast majority of cases showing an unstable intronic GAA expansion in both alleles of the frataxin gene on chromosome 9q13. A small number of cases are caused by a compound heterozygous expansion with a point mutation or deletion. Understanding of the underlying molecular biology has enabled identification of atypical phenotypes with late onset, or atypical features such as retained reflexes. Late-onset cases tend to have slower progression and are associated with smaller GAA expansions. Early-onset cases tend to have more rapid progression and a higher frequency of non-neurological features such as diabetes, cardiomyopathy, scoliosis and pes cavus. Compound heterozygotes, including those with large deletions, often have atypical features. In this paper, we review the classical and atypical clinical phenotypes of Friedreich's ataxia.

Cardiac dysfunction exacerbated by endocrinopathies in Friedreich ataxia: a case series

Friedreich ataxia is a neurodegenerative disease characterized by gait abnormalities, cardiomyopathy, and diabetes. Congestive heart failure was recently reported as the most frequent cause of Friedreich ataxia mortality. Cardiac dysfunction is suspected to result from a frataxin deficiency that leads to oxidative damage in cardiac tissues and possible metabolic syndrome characteristics. In this report, we describe 2 patient cases whose cardiac function worsened dramatically in the presence of underlying endocrinopathies. We report on one Friedreich ataxia teenager with previously undiagnosed diabetes that resulted in diabetic ketoacidosis and rapid progression to severe left ventricular dysfunction. We also describe a Friedreich ataxia teenager whose underlying Graves disease led to rapid worsening of known cardiomyopathy. Cardiac management and treatment for the endocrinopathies returned cardiac function to baseline. We conclude that screening for and awareness of underlying endocrinopathies in Friedreich ataxia may provide novel therapeutic targets for preventing Friedreich ataxia-associated cardiac dysfunction.

Cardiac transplantation in Friedreich ataxia

In this article, we describe a 14-year-old boy with a confirmed diagnosis of Friedreich ataxia who underwent cardiac transplantation for left ventricular failure secondary to dilated cardiomyopathy with restrictive physiology. His neurological status prior to transplantation reflected early signs of neurological disease, with evidence of dysarthria, weakness, mild gait impairment, and limb ataxia. We review the ethical issues considered during the process leading to the decision to offer cardiac transplantation.

Clinical features of Friedreich ataxia

Friedreich ataxia, the most common hereditary ataxia, affects approximately 1 per 29,000 white individuals. In about 98% of these individuals, it is due to homozygosity for a GAA trinucleotide repeat expansion in intron 1 of FXN; in the other 2%, it is due to compound heterozygosity for a GAA expansion and point mutation or deletion. The condition affects multiple sites in the central and peripheral nervous system as well as a number of other organ systems, resulting in multiple signs and symptoms. Onset of this autosomal recessive condition is usually in the first 2 decades of life. Major clinical features include progressive ataxia, absent lower limb reflexes, upgoing plantar responses, and peripheral sensory neuropathy. The main nonneurological sites of morbidity are the heart, resulting in cardiomyopathy, and the pancreas, resulting in diabetes mellitus. In this review, we provide an overview of the clinical features of Friedreich ataxia and discuss differential diagnoses.

Investigation of cardiomyopathy using cardiac magnetic resonance imaging part 2: Rare phenotypes

Cardiac magnetic resonance imaging (CMRI) has emerged as a useful tertiary imaging tool in the investigation of patients suspected of many different types of cardiomyopathies. CMRI images are now of a sufficiently robust quality to enable high spatial and temporal resolution image acquisition. This has led to CMRI becoming an effective non-invasive imaging tool for many cardiomyopathies. In this two-part review we outline the typical sequences used to image cardiomyopathy and present the imaging spectrum of cardiomyopathy. Part I focused on the current classification of cardiomyopathy, the basic CMRI sequences used in evaluating cardiomyopathy and the imaging spectrum of common phenotypes. Part II illustrates the imaging spectrum of the more rare phenotypes.

A polymorphic miR-155 binding site in AGTR1 is associated with cardiac hypertrophy in Friedreich ataxia

Friedreich ataxia (FRDA) is an autosomal recessive neurodegenerative condition with a heterogeneous cardiac phenotype caused primarily by an expanded GAA trinucleotide repeat in the frataxin gene (FXN). FXN is important in mitochondrial iron efflux, sensitivity to oxidative stress, and cell death. The number of GAA repeats on the smaller FXN allele (GAA1) only accounts for a portion of the observed variability in cardiac phenotype. Genetic modifying factors, such as single nucleotide polymorphisms (SNPs) in genes of the Renin-Angiotensin-Aldosterone system (RAAS), may contribute to phenotype variability. This study investigated genetic variability in the angiotensin-II type-1 receptor (AGTR1), angiotensin-converting enzyme (ACE), and ACE2 genes as cardiac phenotype modifying factors in FRDA patients. Comprehensive review of the AGTR1, ACE and ACE2 genes identified twelve haplotype tagging SNPs. Correlation of these SNPs with left ventricular internal diameter in diastole (LVIDd), interventricular septal wall thickness (SWT) and left ventricular mass (LVM) was examined in a large Australian FRDA cohort (n=79) with adjustments performed for GAA repeats, age, sex, body surface area and diastolic blood pressure. A significant inverse relationship was observed between GAA1 and LVIDd (p=0.010) but not with SWT or LVM after adjustment for covariates. The AGTR1 polymorphism rs5186 was more common in FRDA patients than in a control population (p=0.002). Using a recessive model of inheritance, the C allele of rs5186 was associated with a significant increase in SWT (p=0.003) and LVM (p=0.001). This functional polymorphism increases expression of AGTR1 by altering the binding site for miR-155, a regulatory microRNA. No significant associations with left ventricular structure were observed for the remaining RAAS polymorphisms. The AGTR1 polymorphism rs5186 appears to modify the FRDA cardiac phenotype independently of GAA1. This study supports the role of RAAS polymorphisms as modifiers of cardiac phenotype in FRDA patients.

Friedreich's Ataxia: a review from a cardiology perspective

BACKGROUND

Neuromuscular disorders are not among the common causes of cardiomyopathy in the general population; however, cardiomyopathy is known to occur in several neuromuscular disorders including Friedreich's Ataxia (FA). In patients with neuromuscular disorders, concomitant cardiac involvement contributes significantly to morbidity and mortality and often leads to premature death.

METHODS

An extensive literature search of Medline and Pubmed was conducted to include all published reports on cardiac involvement in FA. Secondary articles were identified from key paper reference listings.

CONCLUSION

Hypertrophic cardiomyopathy is a cardinal feature of FA; therefore all FA patients should be screened for cardiomyopathy. A cardiac examination, ECG and ECHO are advised at diagnosis, and also on the development of any cardiac symptoms. Treatment is determined by the presence of symptoms, the presence of left ventricular outflow gradient and the sudden death risk. Institution of aggressive medical therapy early in the course of the disease may help improve quality of life and provide survival benefit.

Early changes in left ventricular long-axis function in Friedreich ataxia: relation with the FXN gene mutation and cardiac structural change

OBJECTIVE

Friedreich ataxia (FRDA) is an autosomal recessive condition due to a GAA triplet expansion in the FXN gene that causes increased left ventricular (LV) wall thickness and can progress to LV systolic dysfunction. However, the changes in myocardial function that occur before a reduction in LV ejection fraction are incompletely understood.

METHODS

LV long-axis function was assessed by measurement of tissue Doppler imaging (TDI) peak systolic (S`), early diastolic (E`), and atrial velocities (A`) at the septal and lateral borders of the mitral annulus in 60 subjects homozygous for a GAA expansion in the FXN gene who had preserved LV ejection fraction. Comparison was made with 60 sex- and age-matched controls. TDI velocities at 5 years were compared with baseline values in 17 FRDA subjects with follow-up studies who still had preserved ejection fraction.

RESULTS

S` and E` were reduced in FRDA subjects at both the septal and the lateral mitral annular borders. Lateral E` was independently and inversely related to age, blood pressure, septal wall thickness, and the number of GAA repeats in the smaller allele of the FXN gene, whereas septal E` was not correlated with GAA repeat number. At 5 years, there was a reduction in lateral S` and E` but no change in septal TDI velocities.

CONCLUSION

Subjects with FRDA have impairment of septal and lateral long-axis LV function, but there also seem to be regional differences in the effects of this condition that are at least partly related to the degree of genetic abnormality.

Combined therapy with idebenone and deferiprone in patients with Friedreich's ataxia

Iron chelators are a new therapeutical approach for patients with Friedreich's ataxia, on the basis that oxidative cell damage that occurs in these patients is due to the increasing deposits of mitochondrial iron pools. The objective of the study was to evaluate the effects of the combined therapy of idebenone and low oral doses of deferiprone on the neurological signs and cardiac function parameters. This study was designed as a prospective open-label single-arm study. Twenty Friedreich's ataxia patients were treated with idebenone (20 mg/kg/day) and deferiprone (20 mg/kg/day) for 11 months. Patients were evaluated before the start and throughout the study with the International Cooperative Ataxia Rating Scale (ICARS) scores, echocardiographic measurements and MRI (magnetic resonance imaging) techniques to asses brain iron deposits in the dentate nucleus. No significant differences were observed in total ICARS scores when comparing baseline status and the end of the study in the whole group of patients. Posture and gait scores increased significantly after 11 months of therapy (Wilcoxon's test, p = 0.04) and kinetic function improved significantly (Wilcoxon's test, p = 0.015). Echocardiography data showed a significant reduction of the interventricular septum thickness (Wilcoxon's test, p = 0.04) and in the left ventricular mass index (Wilcoxon's test, p = 0.038) after the start of the therapy. The MRI values in the dentate nucleus showed a statistically significant reduction (Wilcoxon's test p = 0.007) between baseline conditions and after 11 months of the therapy. Combined therapy with idebenone and deferiprone in patients with FDRA indicates a stabilizing effect in neurologic dysfunctions due to an improvement in the kinetic functions, with a worsening of gait and posture scores. Heart hypertrophy parameters and iron deposits in dentate nucleus improved significantly. Combined therapy was well tolerated with mild side effects, apart from the risk of neutropenia and progressive reduction of plasma iron parameters.

Friedreich's ataxia: pathology, pathogenesis, and molecular genetics

The pathogenic mutation in Friedreich's ataxia (FRDA) is a homozygous guanine-adenine-adenine (GAA) trinucleotide repeat expansion on chromosome 9q13 that causes a transcriptional defect of the frataxin gene. Deficiency of frataxin, a small mitochondrial protein, is responsible for all clinical and morphological manifestations of FRDA. This autosomal recessive disease affects central and peripheral nervous systems, heart, skeleton, and endocrine pancreas. Long expansions lead to early onset, severe clinical illness, and death in young adult life. Patients with short expansions have a later onset and a more benign course. Some are not diagnosed during life. The neurological phenotype reflects lesions in dorsal root ganglia (DRG), sensory peripheral nerves, corticospinal tracts, and dentate nuclei (DN). Most patients succumb to cardiomyopathy, and many become diabetic during the course of their disease. This review seeks to reconcile the diverse clinical features with pathological and molecular data. In the pathogenesis of the lesion in DRG, dorsal spinal roots, and sensory peripheral nerves, developmental defects and atrophy occur in combination. The progressive lesion of the DN lacks a known developmental component. Destruction of the DN, optic atrophy, and degeneration of the corticospinal tracts are intrinsic central nervous system lesions. Fiber loss in dorsal columns and spinocerebellar tracts, and atrophy of the neurons in the dorsal nuclei of Clarke are secondary to the lesion in DRG. The role of frataxin deficiency in the pathogenesis of FRDA is still unclear because the protein has multiple functions in the normal state, including biogenesis of iron-sulfur clusters; iron chaperoning; iron storage; and control of iron-mediated oxidative tissue damage.

Feasibility of implantable cardioverter defibrillator treatment in five patients with familial Friedreich's ataxia--a case series

Friedreich's ataxia (FRA) is an autosomal recessive disease of the central nervous system that is associated with familial cardiomyopathy. Cardiac involvement is seen in more than 90% of the patients and is the most common cause of death in these patients. We present a case series and discuss the indications for implantable cardioverter defibrillator (ICD) implantation in FRA with review of the literature. Five pediatric patients who suffer from FRA (four female and one male, mean age 17.4 years) underwent ICD implantation between 2007 and 2008 in the University Hospital of Goettingen. The diagnosis of FRA was established by standard clinical criteria and proven in each case by genotyping at the frataxin locus. The time from diagnosis to ICD implantation was 10.4±1.73 years (range 8-15 years). All patients received transvenous lead systems. There were no intraoperative and postoperative complications. At the latest follow-up, the neuromuscular symptoms exhibited no further progress and no ICD activations were noticed. Only minor repolarization changes were seen on electrocardiogram. All patients had normal echocardiographic findings and no angina has been reported. Coronary angiographies were normal. It is evident that many FRA patients develop ventricular dysfunction. In the absence of a definitive surgical cure an ICD is generally indicated in young patients with hemodynamically significant sustained ventricular tachyarrhythmias for prevention of sudden cardiac death. Our experience implies the safe use of ICD in children with FRA.

Idebenone in Friedreich ataxia cardiomyopathy-results from a 6-month phase III study (IONIA)

BACKGROUND

Friedreich ataxia (FRDA) is commonly associated with hypertrophic cardiomyopathy, but little is known about its frequency, severity, or treatment. In this 6-month randomized, double-blind, controlled study, we sought to determine whether idebenone improves cardiac measures in FRDA.

METHODS

Seventy pediatric subjects were treated either with idebenone (450/900 mg/d or 1,350/2,250 mg/d) or with placebo. Electrocardiograms (ECGs) were assessed at each visit, and echocardiograms, at baseline and week 24.

RESULTS

We found ECG abnormalities in 90% of the subjects. On echocardiogram, 81.4% of the total cohort had left ventricular (LV) hypertrophy, as measured by increased LV mass index-Dubois, and the mean ejection fraction (EF) was 56.9%. In linear regression models, longer PR intervals at baseline were marginally associated with longer GAA repeat length (P = .011). Similarly, GAA repeat length did not clearly predict baseline EF (P = .086) and LV mass by M-mode (P = .045). Left ventricular mass index, posterior wall thickness, EF, and ECG parameters were not significantly improved by treatment with idebenone. Some changes in echocardiographic parameters during the treatment phase correlated with baseline status but not with treatment group.

CONCLUSIONS

Idebenone did not decrease LV hypertrophy or improve cardiac function in subjects with FRDA. The present study does not provide evidence of benefit in this cohort over a 6-month treatment period.

Hypertrophic cardiomyopathy in childhood

Hypertrophic cardiomyopathy has important differences in children compared with adults, particularly with regard to the range of causes and the outcomes in infants. Survival is highly dependent on etiology, particularly in the youngest patients, and pursuit of the specific cause is therefore necessary. The clinical utility of defining the genotype in children with familial hypertrophic cardiomyopathy exceeds that at other ages and has a highly favorable cost/benefit ratio. Although most of the available information concerning treatment and prevention of sudden death is derived in adults, management of children requires consideration of the differences in age-specific risk/benefit ratios.

Uncharted waters: rare and unclassified cardiomyopathies characterized on cardiac magnetic resonance imaging

Cardiac magnetic resonance imaging (CMR) has undergone considerable technology advances in recent years, so that it is now entering into mainstream cardiac imaging practice. In particular, CMR is proving to be a valuable imaging tool in the detection, morphological assessment and functional assessment of cardiomyopathies. Although our understanding of this broad group of heart disorders continues to expand, it is an evolving group of entities, with the rarer cardiomyopathies remaining poorly understood or even unclassified. In this review, we describe the clinical and pathophysiological aspects of several of the rare/unclassified cardiomyopathies and their appearance on CMR.

Analysis of the factors influencing the cardiac phenotype in Friedreich's ataxia

Friedreich's ataxia (FRDA) has been associated with both cardiac hypertrophy and to a lesser degree dilated cardiomyopathy. We have conducted a cross sectional magnetic resonance imaging (MRI) study of 25 patients with clinically and genetically confirmed FRDA and 24 healthy controls to analyse how disease parameters influence cardiac features in FRDA. MR cine imaging in the long and short axis planes was performed alongside clinical assessments. LV mass was most pronounced in FRDA patients with a larger genetic mutation (GAA1 repeats >600), earlier age of onset (<16years) and a shorter disease duration (<15 years). LV mass decreased with longer disease duration (>15 years), and independent of GAA1 repeat size and age of onset, suggesting cardiac thinning occurred with prolonged disease. Heart function was lower in patients with larger GAA1 repeat number and longer disease duration. Consequently, cardiac hypertrophy was more marked in FRDA patients with a larger GAA1 repeat number and younger age of onset, while prolonged disease duration was associated with lower LV mass and decreased heart function. It is important not only to understand the biochemical basis for these cardiac changes but also allow for these changes when assessing the effect of treatment of FRDA patients.

Friedreich ataxia presenting as sudden cardiac death in childhood: clinical, genetic and pathological correlation, with implications for genetic testing and counselling

Friedreich ataxia (FRDA) is the most common cause of childhood onset ataxia. We report on a 4 year old boy who suffered sudden cardiac death and was found to have a dilated cardiomyopathy with left ventricular hypertrophy on post-mortem studies. Molecular genetic testing subsequently confirmed the diagnosis of Friedreich ataxia. To our knowledge, this is the first report of Friedreich ataxia presenting as sudden cardiac death in early childhood.

Prevalence of interatrial block in patients with Friedreich's ataxia

Interatrial block is a predictor of atrial arrhythmias. Aim of the present study was to estimate the prevalence of interatrial block (IAB) in Friedreich's Ataxia (FA) compared to controls and correlate it with echocardiographic and genetic features.

METHODS

IAB, defined as an electrocardiographic (ECG) derived P-wave duration >120 ms, echocardiographic variables and genetic markers were evaluated in 23 FA patients with no manifestation of cardiac involvement and were compared to 23 sex- and age-matched controls.

RESULTS

IAB was significantly more frequent among FA patients compared to controls (11/23 vs 1/23, p<0.005 respectively). However, no correlations with echocardiographic parameters or Guanine-Adenine-Adenine (GAA) trinucleotide repeat lengths could be established.

CONCLUSION

Early recognition of IAB could allow the identification of asymptomatic FA patients who are prone to develop potentially life-threatening arrhythmias.

The longitudinal course of cardiomyopathy in Friedreich's ataxia during childhood

BACKGROUND

Clinical heart disease was recognized in the first descriptions of Friedreich's ataxia (FA). Cardiac manifestations reported for this progressive neurologic disease include hypertrophic cardiomyopathy, dilated cardiomyopathy, and electrophysiologic disturbances. Longitudinal data for childhood cases are limited. This study aimed to define the longitudinal course of the cardiac abnormalities with FA diagnosed during childhood and to correlate the presence of cardiomyopathy with clinical and genetic factors.

METHODS

A retrospective chart review was conducted, with prospective, blinded interpretation of echocardiograms and electrocardiograms. All the patients with a diagnosis of FA referred to the cardiology department of a single institution from 1974 to 2004 were included in the study.

RESULTS

This study investigated a total of 113 echocardiograms for 28 patients. Overall, the group had left ventricular hypertrophy and normal systolic function, with a median mass z-score of 2.48 (range, -3.8 to 35.6) and a median ejection fraction (EF) of 61% (range, 23-81%). Of the 28 patients, 23 (82%) had two or more echocardiograms. The median follow-up time to the most recent echocardiogram was 5.1 years (range, 0.4-16.5 years). Many in this longitudinal follow-up cohort (57%) showed hypertrophic cardiomyopathy on at least one echocardiogram, with the last follow-up assessment showing systolic dysfunction for 38% of these patients. There was a slow nonlinear decline in systolic function over time, with the mean EF decreasing more rapidly as age increased (p = 0.02) and maintenance of EF in the normal range until the age of 22 years. Of the 12 patients with systolic dysfunction and follow-up echocardiograms, 10 showed improvement to the normal EF range on at least one echocardiogram, and 5 remained normal through the last study. None of the trends in cardiac function and morphology correlated with frataxin GAA repeat length (the primary genetic defect in FA) or ambulatory status. One patient required an implantable defibrillator. There were no deaths or heart transplantations.

CONCLUSIONS

Overall, patients with FA have preserved cardiac function with increased mass throughout childhood. Because many patients who experience depressed systolic function show improvement in subsequent studies, evaluation for potentially reversible causes of heart failure should be conducted. Relative clinical stability during childhood and maintenance of normal systolic function into the second decade may be helpful for parent and patient education.

Friedreich's ataxia and scoliosis: the experience at two institutions

PURPOSE

Friedreich's ataxia is a genetically transmitted, progressive spinocerebellar degenerative disease characterized by ataxia. The purpose of this study is to evaluate the demographics, progression, nonoperative, and operative treatment of spinal deformities in patients with Friedreich's ataxia at 2 tertiary pediatric orthopaedic hospitals.

METHODS

After institutional review board approval, chart review of Friedreich's ataxia patients identified those having scoliosis. Demographic data, length of follow-up, brace treatment, operative treatment, and complications were determined. Radiographic review was also performed.

RESULTS

Seventy-seven patients were identified as having Friedreich's ataxia, of which 49 (63%) were diagnosed with scoliosis. Twenty-seven were male; 22 were female. Mean age at diagnosis of scoliosis was 12.8 years (4.9-20 years). Mean follow-up was 3.7 years (0-13 years). There were 16 (33%) double major curves, with 8 (22%) of the thoracic curves being left sided. Hyperkyphosis was present in 12 (24.5%).Twenty-four (49%) of patients progressed > or =6 degrees. Using a chi-square analysis, there was no association, with a curve magnitude of 10 degrees before the age of 10 years and progression of the curve (P = 0.4386). Ten (20%) patients were treated in braces, with average progression in brace of 15 (0-44) degrees. Sixteen (33%) patients were treated with spinal fusion (15 posterior spinal fusion and 1 anterior spinal fusion). Thirteen (81%) of 16 patients who underwent operative intervention were wheelchair dependent. Somatosensory evoked potentials monitoring was attempted in 11 patients but was effective in only 1. Immediate postoperative correction averaged 49% in the thoracic spine (24%-87%) and 51% in the lumbar spine (26%-82%). This correction decreased to 39% in the thoracic (-22% to 85 %) and 30% in the lumbar spine (-35% to 82%) at final follow-up. The average postoperative follow-up was 3.6 years (2-6.5). One patient (6.2%) developed an infection and was the only patient who underwent reoperation.

CONCLUSIONS

Scoliosis in Friedreich's ataxia is common (63%). Curve patterns are variable and do not necessarily resemble idiopathic curves. Although few patients were braced, results were poor. Fusion using modern segmental constructs was effective in creating substantial intraoperative correction and maintaining correction postoperatively. SSEP monitoring was usually ineffective, so preparation for a wake-up test is recommended.

SIGNIFICANCE

Patients with Friedreich's ataxia need to be carefully screened for scoliosis and counseled about the high rate of surgical fusion. Using modern implants, correction can be achieved and maintained.

Cardiomyopathy in Friedreich's ataxia-assessment by cardiac MRI

Cardiomyopathy is an important and frequently life limiting manifestation of Friedreich's ataxia (FA), the most prevalent form of autosomal recessive ataxia. Left ventricular mass is used as primary outcome measure in recent intervention studies but systematic analyses of FA cardiomyopathy are sparse. To assess cardiac hypertrophy by cardiac magnetic resonance imaging (MRI) in vivo, we assessed 41 adult patients with genetically confirmed FA and 33 age- and sex-matched healthy controls by cardiac MRI and echocardiogarphy. Septal hypertrophy and left ventricular mass index were determined by two independent raters. MRI revealed hypertrophy of the interventricular septum in 40% and increased left ventricular mass index in 29% of patients. Interobserver variability was less than 5% for both measures. GAA repeat length had only minor influence on interventricular septum thickness. Left ventricular mass index decreased with age. Severity of ataxia did not correlate with cardiac disease. In echocardiography wall diameter was assessable only in 31 of 41 FA patients with 32% of patients presenting septal hypertrophy and 6% increased left ventricular mass index. We conclude that cardiac hypertrophy is present only in a minority of adult FA patients. If despite this limitation intervention studies use left ventricular mass as outcome measure, MRI is recommended as the most accurate assessment of cardiac anatomy in vivo.