Cardiomyopathy in Friedreich ataxia

Article written and reviewed by Dr Luca Moretti

Friedreich ataxia is an autosomal recessive multisystem disease in which neurologic degeneration coexists with a primary cardiomyopathy that often remains clinically silent for many years. Cardiac involvement is not a consequence of inactivity or chest deformity, but a direct expression of frataxin deficiency in cardiomyocytes. Frataxin-deficiency cardiomyopathy is one of the main determinants of mortality and requires a pathway independent of neurologic assessment alone.

The most recognizable phenotype is predominantly non-obstructive left ventricular hypertrophy, associated with electrocardiographic abnormalities, diastolic dysfunction and subclinical myocardial injury. Ejection fraction may remain normal while energy reserve, longitudinal deformation and perfusion are already impaired. In advanced stages the wall may thin and the ventricle dilate, so an apparent reduction in hypertrophy does not necessarily mean recovery. Biphasic remodeling must be reconstructed with serial measurements.

Modern management integrates genetics, neurology, cardiology, diabetology, rehabilitation and perioperative medicine. No single parameter can summarize risk because neurologic onset, motor severity and cardiac disease may progress at different rates. The availability of omaveloxolone and the first gene-transfer studies has changed the therapeutic landscape, but does not justify considering cardiac disease resolved. Longitudinal multidisciplinary care remains the clinical foundation.

FXN genetics and GAA expansion

The FXN gene, located on chromosome 9, encodes frataxin. In the great majority of patients, both alleles contain a GAA trinucleotide expansion in the first intron; repetitive sequences promote abnormal DNA structures, heterochromatin and transcriptional repression. The result is therefore not a dominant mutant protein but an insufficient amount of normal protein. Epigenetic silencing distinguishes this disease from common sarcomeric cardiomyopathies.

Normal alleles have few repeats, whereas pathogenic expansions are generally much longer and may exceed several hundred triplets. Measurement is technically challenging because conventional PCR, repeat-primed PCR, long-range PCR and Southern blot answer different questions. The report should specify method, estimated range and limitations, avoiding numerical precision not supported by the technique. Correct GAA typing is essential before correlating genotype and prognosis.

The length of the shorter expanded allele correlates at the population level with residual frataxin, age at onset and the probability of a severe phenotype. The relationship is incomplete because of somatic instability, genetic modifiers, tissue mosaicism and non-genetic factors; two siblings may have different trajectories. A high repeat number does not replace imaging, and a relatively short expansion does not exempt the patient from cardiologic follow-up. The genotype-phenotype correlation is probabilistic, not deterministic.

A minority of people are compound heterozygotes, with a GAA expansion on one allele and a pathogenic point variant, small insertion-deletion or deletion on the other. These cases may show preserved reflexes, predominant spasticity, late onset or other atypical features, but cardiomyopathy and diabetes remain possible. If only one expansion is identified, sequencing and copy-number analysis of FXN complete the investigation. Biallelic diagnosis prevents a carrier from being incorrectly classified as affected.

Molecular diagnosis should be accompanied by genetic counseling. Pathogenicity and the in-trans phase of non-repeat variants should be demonstrated using updated criteria, segregation and functional data when available; a variant of uncertain significance does not confirm the disease. Very late-onset forms or forms with preserved reflexes also belong to the FXN spectrum, but require a careful differential diagnosis. Molecular precision guides family surveillance, reproduction and access to therapies.

Frataxin, iron-sulfur clusters and cardiac injury

Frataxin participates in the mitochondrial complex that initiates assembly of iron-sulfur clusters, cofactors required by aconitase, the respiratory chain and numerous cellular enzymes. Its reduction impairs orderly iron handling and limits ATP production precisely in tissues with high energy demand. The heart, dorsal root ganglia, spinocerebellar pathways and endocrine pancreas are particularly vulnerable. Fe-S cluster deficiency is the central biochemical node.

In the cardiomyocyte, respiratory-complex dysfunction reduces the ability to adapt oxidative phosphorylation to tachycardia, exercise, fever or pregnancy. Redox stress, calcium abnormalities, membrane injury and cell-death signaling increase, while the cell attempts to compensate with mitochondrial proliferation and hypertrophy. This adaptation initially maintains output but increases stiffness and oxygen demand. Reduced bioenergetic reserve often precedes the fall in ejection fraction.

Mitochondrial iron accumulates because it is not efficiently incorporated into clusters and because cellular homeostasis is reprogrammed. This is not systemic hemochromatosis or a simple passive deposit removable by phlebotomy; serum ferritin and transferrin saturation may be normal. Indiscriminate chelation may also remove iron from essential processes. Mitochondrial iron is a network consequence, not an automatic indication for iron-chelation therapy.

Chronic injury produces myocyte hypertrophy, fiber disorganization, focal necrosis and interstitial or replacement fibrosis. Autopsy studies have also shown iron granules and marked regional heterogeneity, helping explain discordance among biopsy, ECG and CMR. Fibrosis disrupts electrical coupling and reduces compliance before depressing global contractility. The fibrometabolic substrate links heart failure and arrhythmias.

Some mechanisms, including ferroptosis, altered mitophagy and lipid vulnerability, are convincing in experimental models but do not yet have a validated clinical biomarker or approved cardiac therapy. Translation from mouse to human is particularly difficult because excessive frataxin overexpression may be toxic and the human heart evolves over decades. Preclinical plausibility is not equivalent to benefit on heart failure, arrhythmias or survival.

Cardiac phenotype and natural history

Left ventricular hypertrophy is the most common structural finding and may be concentric, asymmetric or, more rarely, biventricular. The cavity is often small, ejection fraction preserved and dynamic left ventricular outflow tract obstruction less typical than in sarcomeric hypertrophic cardiomyopathy. Wall thickness and mass should be indexed to body surface area and interpreted in relation to sex, growth and reduced muscle mass. A non-obstructive morphology is common but not universal.

Diastolic function may be impaired by myocardial stiffness, but Doppler indices depend on heart rate, preload and image quality. Longitudinal strain and tissue velocities may reveal dysfunction when ejection fraction still appears normal; this does not mean that every minimal deviation predicts an event. Serial assessment in the same laboratory is more informative than occasional comparisons across different platforms. Subclinical dysfunction is a marker of vulnerability, not an isolated prognostic verdict.

As disease progresses, some patients show decreasing wall thickness, increasing volumes and systolic dysfunction. This transition may represent myocyte loss and fibrosis rather than favorable regression of hypertrophy; a ventricular mass that decreases together with function deserves particular attention. Not everyone follows a linear sequence and some retain a stable hypertrophic phenotype for a long time. The hypertrophy-to-dilation transition must be recognized through the individual trajectory.

Longitudinal cohorts indicate that high ventricular mass, reduced ejection fraction and development of heart failure are associated with worse prognosis. Cardiac disease may nevertheless be dissociated from the neurologic score, and a non-ambulatory patient may have preserved ventricular function while an independent young person may have severe disease. Functional assessment should not automatically attribute every episode of dyspnea or fatigue to deconditioning. Cardio-neurologic discordance requires parallel follow-up pathways.

In children, cardiomyopathy may appear early and, in rare cases, precede manifest ataxia. Infantile forms with marked hypertrophy carry a risk of supraventricular arrhythmias, heart failure and death, especially when wall thickness evolves rapidly. Growth, scoliosis and orthopedic procedures modify loading conditions and measurements, making expert pediatric cardiology necessary. The early cardiac phenotype is also a red flag for initiating genetic diagnosis.

Neurology, diabetes and systemic interactions

Ataxia results from sensory neuropathy, proprioceptive loss, spinocerebellar and corticospinal involvement, with dysarthria, oculomotor instability and progressive impairment of gait. Weakness, scoliosis, foot deformities and reduced ventilatory capacity amplify exercise limitation without necessarily being caused by the heart. A cardiology assessment should distinguish dyspnea, muscle fatigue, anxiety and low aerobic capacity. Multisystem phenotyping prevents both overdiagnosis and underestimation of heart failure.

Diabetes in Friedreich ataxia combines reduced insulin secretion, beta-cell loss and variable insulin resistance. Glucose and HbA1c should be checked at least annually and more often with symptoms, growth, steroid therapy or pregnancy; HbA1c may miss some early phases. Ketoacidosis and hyperosmolarity increase tachycardia, dehydration and myocardial energy requirements. Diabetes risk should be managed together with circulating volume and cardiac function.

The choice of antidiabetic therapy depends on residual secretion, renal function, nutrition and cardiac disease. Insulin is necessary when deficiency predominates and should not be delayed by analogy with type 2 diabetes; drugs carrying a risk of euglycemic ketoacidosis require caution during fasting, acute illness or surgery. There is no evidence that a glucose-lowering drug directly modifies frataxin-deficiency cardiomyopathy. Individual metabolic control reduces additional stress without becoming causal therapy.

Dysphagia, reduced mobility and low weight may promote malnutrition, while inactivity and perioperative steroids may increase adiposity and insulin resistance. Both extremes alter drug dosing, blood pressure and tolerance of diuretics. Nutritional assessment considers lean mass, swallowing safety and requirements, without imposing salt or fluid restriction on patients who are not congested. Body composition is clinically more useful than body mass index alone.

Hearing, vision, renal function, bone health and sleep affect adherence and the ability to recognize symptoms. Depression or chronic fatigue may reduce activity before overt dyspnea appears, whereas autonomic neuropathy may alter heart rate and blood pressure. A coordinated visit allows each change to be attributed correctly and avoids conflicting prescriptions. An inter-organ interpretation transforms a collection of checks into a coherent treatment plan.

ECG, arrhythmias and sudden risk

The ECG is abnormal in most patients, even when echocardiography does not show overt cardiomyopathy. Repolarization abnormalities, T-wave inversion, axis deviations, criteria for hypertrophy and Q waves may reflect remodeling and fibrosis, but have no pathognomonic signature. Comparison with previous tracings is essential to distinguish a chronic phenotype from ischemia, pericarditis or electrolyte imbalance. An electrocardiographic baseline prevents inappropriate acute interpretations.

Ectopy and supraventricular tachycardias become more frequent with atrial dilation and increased filling pressures. Fibrillation and flutter may precipitate heart failure in a small, stiff ventricle because loss of atrial contraction and rapid rate reduce filling. Palpitations, sudden worsening of fatigue or nocturnal dyspnea require prompt rhythm assessment. Dependence on atrial contribution explains the poor tolerance of some apparently common arrhythmias.

Ventricular tachycardia and sudden death have been described, especially in advanced cardiac disease, but incidence and specific predictors remain less well defined than in sarcomeric cardiomyopathies. Calculators developed for hypertrophic cardiomyopathy have not been validated for Friedreich ataxia and should not be applied mechanically. Fibrosis, unexplained syncope, ventricular dysfunction and documented arrhythmias contribute to assessment. Individual arrhythmic stratification acknowledges uncertainty without ignoring high-risk signals.

Holter monitoring is indicated in the presence of palpitations, syncope, ECG abnormalities, dysfunction, atrial enlargement or before major procedures. In asymptomatic people with normal tests there are insufficient data to impose the same interval on everyone; longer recordings or loop recorders are reserved for sporadic symptoms and specific questions. A negative 24-hour Holter does not exclude rare events. Rhythm surveillance should be proportionate to the phenotype.

Advanced sinus-node disease or atrioventricular block are not the dominant features seen in laminopathies or myotonic dystrophy, but they can still occur. PR, QRS and intraventricular conduction should be followed over time, especially with rate-slowing drugs. Syncope and falls should not automatically be attributed to ataxia because arrhythmia, orthostatic hypotension and hypoglycemia require different interventions. Diagnosis of syncope integrates device status, rhythm, blood pressure and neurology.

Echocardiography, CMR and biomarkers

Echocardiography measures wall thickness, mass, volumes, ejection fraction, right ventricular function, atria and valves. Assessment should document any outflow gradient, although obstruction is less characteristic, and include diastolic Doppler and strain when technically reliable. In patients with scoliosis the acoustic window may be limited and a small change may reflect acquisition. Echocardiographic standardization makes progression interpretable.

Cardiac magnetic resonance provides reproducible volumes and mass, identifies late gadolinium enhancement and allows T1 mapping and extracellular volume assessment. Recent studies describe focal, often non-ischemic fibrosis and diffuse abnormalities even with preserved function, but small samples and different protocols preclude universal prognostic thresholds. CMR is particularly useful when echocardiography is inconclusive, progression is suspected or risk and treatment decisions are being made. Myocardial tissue characterization adds information without replacing clinical assessment.

Reduced perfusion reserve has been observed even in the absence of coronary stenosis and may reflect microvascular dysfunction, high demand and altered bioenergetics. This finding does not justify diagnosing coronary artery disease or prescribing revascularization without appropriate anatomic assessment. Chest pain and dynamic troponin still require the usual work-up because a person with a rare disease can develop common conditions. Microvascular dysfunction is a plausible mechanism, not an exclusion of epicardial ischemia.

High-sensitivity troponin may remain stably above the upper reference limit in a relevant proportion of adults and correlates with septal thickness or myocyte injury. Obtaining a baseline value under stable conditions is useful so that an acute rise can be interpreted against the person's trajectory. Chronic values should neither be dismissed nor automatically labeled myocardial infarction. Individual troponin integrates symptoms, temporal change, ECG and imaging.

BNP or NT-proBNP reflects wall stress and filling pressures, but depends on age, renal function, rhythm and body composition. It may remain low during compensated hypertrophy and rise with dysfunction, atrial fibrillation or congestion; a single normal value does not exclude reduced reserve. Serial measurements are more useful when accompanied by weight, volume signs and imaging. A biomarker-imaging profile is superior to an isolated threshold.

Diagnosis and cardiology surveillance

Suspicion arises in a young person with progressive ataxia, loss of vibration sense, areflexia, scoliosis, pes cavus, diabetes or cardiomyopathy. Non-obstructive hypertrophic cardiomyopathy associated with neurologic signs should prompt consideration of FXN alongside Pompe disease, Danon disease, mitochondrial defects and other storage disorders. In cardiac-onset cases, diagnosis may precede the typical neurologic syndrome. Neuromuscular red flags guide targeted but complete genetic testing.

Confirmation requires two pathogenic FXN alleles. The laboratory should search for expansions on both alleles and, if only one is detected, proceed with sequencing and deletion analysis; standard exome sequencing may not correctly measure large repeats. Frataxin measurement in blood or cells may support interpretation in expert centers but does not replace adequate genetic testing. The combined diagnostic strategy prevents technical false negatives.

At diagnosis, cardiac history, examination, blood pressure, ECG and echocardiography are recommended even in the absence of symptoms. Disease-specific guidelines indicate ECG and echocardiography at least annually; greater frequency is appropriate in children, rapid progression, marked hypertrophy, fibrosis, dysfunction or arrhythmias. CMR, Holter and cardiopulmonary exercise testing answer additional questions and do not have the same schedule for everyone. Minimum annual surveillance is intensified according to actual risk.

Each follow-up should reconstruct syncope, palpitations, pain, orthopnea, edema and changes in functional capacity relative to neurologic limitations. Weight, heart rate, blood pressure, saturation, auscultation and signs of congestion complement imaging and biomarkers. New symptoms do not wait for the annual visit, while infection, ketoacidosis and surgery may expose limited reserve. Early reassessment is part of the program, not an organizational exception.

Assessment before major orthopedic surgery should include a recent ECG, ventricular function, arrhythmias, respiratory capacity, swallowing and glycemic control. In severe phenotypes, facilities with monitoring and cardiac intensive care are appropriate because bleeding, fluids, pain and tachycardia may rapidly destabilize filling. The plan is shared before admission and not improvised on the day of surgery. Perioperative risk stratification reduces predictable risk.

Cardiac therapy, devices and transplantation

No conventional cardiac therapy has been proven to prevent hypertrophy caused by frataxin deficiency. With thick walls but preserved function, empirical use of drugs for sarcomeric cardiomyopathy should not be automatic, especially with low blood pressure and reduced stroke volume. Tachycardia, hypertension or documented obstruction may provide specific indications. Phenotype-guided therapy avoids treating an image without a clinical objective.

When systolic dysfunction develops, heart-failure therapy follows general principles with neurohormonal inhibition, beta-blockade, mineralocorticoid antagonism and other appropriate drugs, titrated to blood pressure, renal function, potassium and heart rate. Evidence is derived largely from common heart failure rather than Friedreich-specific studies. Diuretics treat congestion, but a small, stiff ventricle may poorly tolerate hypovolemia and reduced preload. Cautious titration matters more than applying a standard regimen in full.

Atrial arrhythmias require rate or rhythm control, correction of precipitating factors and thromboembolic assessment. Cardioversion and ablation may be considered according to anatomy, duration and anesthetic risk; recurrence is promoted by fibrosis and atrial dilation. Anticoagulation is decided according to guidelines and the cardiomyopathy context, balancing falls and bleeding without withholding it solely because of disability. Early atrial management protects filling and reduces embolic events.

Pacemakers, defibrillators and resynchronization follow documented clinical indications. An ICD is appropriate after cardiac arrest or sustained ventricular tachycardia and may be considered for primary prevention with severe dysfunction or major markers, but there is no specific threshold based solely on a Friedreich diagnosis. CRT may be useful with dyssynchrony and heart failure according to standard criteria. The device decision considers extracardiac prognosis, independence and the person's goals.

In advanced heart failure, mechanical support and transplantation are not excluded a priori. Selection must establish whether the heart is the main prognostic limitation and whether respiratory function, diabetes, dysphagia, rehabilitation potential and neurologic progression allow sustainable benefit. Selected cases have achieved favorable outcomes, but experience remains limited and requires a center with expertise in cardiomyopathies and neuromuscular disease. Personalized candidacy avoids both diagnostic exclusion and technically possible overtreatment.

Omaveloxolone and disease-modifying therapies

Omaveloxolone activates the Nrf2 pathway and modulates antioxidant and metabolic responses that are reduced in Friedreich ataxia. In the European Union it is authorized for adults and adolescents aged 16 years and older, based on improvement in the mFARS neurologic scale versus placebo in the MOXIe study. The registrational benefit concerns neurologic impairment and motor function, not a cardiac endpoint. The approved neurologic indication must be distinguished from a hypothetical myocardial effect.

MOXIe was neither designed nor powered to demonstrate reductions in ventricular mass, fibrosis, arrhythmias, hospitalizations or mortality. Patients with more severe heart disease were poorly represented and the controlled follow-up does not resolve long-term outcomes. It is therefore incorrect to promise regression of cardiomyopathy or reduce surveillance after treatment begins. The limitation of cardiac endpoints should be explicit during consent.

Before and during omaveloxolone, aminotransferases, bilirubin, lipid profile and parameters specified in the product information are monitored; BNP and signs of volume overload deserve attention in patients with heart disease. Enzyme elevations are common and require management according to regulatory thresholds, whereas edema, rapid weight gain or dyspnea require clinical assessment. Metabolic interactions and contraception should be reviewed. Drug safety cannot be delegated to neurologic monitoring alone.

Idebenone and other antioxidant strategies have produced conflicting results. Small studies had suggested reductions in wall thickness, but the phase III IONIA cardiac study did not demonstrate a significant decrease in hypertrophy or functional improvement; therefore there is no standard cardiac therapy with idebenone. Iron chelators, erythropoietin, resveratrol and supplements have not demonstrated prevention of cardiac events. Negative or uncertain evidence protects against inappropriate replacement of heart-failure therapy.

Cardiotropic FXN gene transfer has reached clinical investigation. In 2026, a nonrandomized analysis of 17 adults treated with AAVrh.10hFXN showed increased frataxin in biopsies and exploratory signals of reduced ventricular mass and troponin; the small sample, lack of control and limited follow-up do not demonstrate clinical efficacy. One case of possibly related myocarditis highlights immunologic complexity. Experimental gene therapy requires controlled studies and prolonged surveillance.

Other programs aim to replace frataxin, reactivate FXN, modify the epigenome, stabilize mRNA or correct mitochondrial stress. The amount of frataxin must reach the correct tissue and remain within a safe range, while neutralizing anti-AAV antibodies and immunosuppression limit some platforms. Endpoints such as mass or troponin must ultimately translate into function, events and survival. Complete clinical validation comes before any curative claim.

Exercise, anesthesia and surgery

Inactivity accelerates deconditioning, loss of mass and reduction in aerobic capacity, but a program cannot ignore cardiomyopathy, balance and fall risk. Moderate-intensity aerobic exercise, adapted strengthening and activity in safe positions are prescribed after clinical assessment; symptoms, rhythm and blood pressure guide progression. The goal is to improve function without prolonged exhaustion. Exercise prescription replaces both absolute prohibition and indiscriminate training.

A randomized trial published in 2026 showed that 12 weeks of individualized exercise, with or without nicotinamide riboside, was feasible in selected participants with ejection fraction of at least 45% and the ability to train. Improved fitness does not demonstrate prevention of fibrosis, arrhythmias or heart failure and does not automatically extend to advanced cardiac disease. Longer programs must clarify durability and safety. Participant selection defines what the result allows one to conclude.

Cardiopulmonary exercise testing can separate central limitation, muscular limitation and deconditioning, but requires protocols adapted to coordination and assistive devices. A non-ambulatory person may exercise with an upper-limb ergometer or assisted devices provided the technique does not create an unmeasured load. Exertional syncope, pain, sustained tachycardia or a fall in blood pressure require stopping and investigation. Cardiometabolic rehabilitation should be accessible even beyond ambulation.

Anesthesia requires a shared assessment of ventricular function, rhythm, airway, scoliosis, ventilation, dysphagia and diabetes. No anesthetic is universally contraindicated solely because of the diagnosis, but hypotension, tachycardia, hypoxia, shivering and acid-base imbalance increase energy cost. Neuromuscular drugs are monitored and fasting is not prolonged unnecessarily. Perioperative hemodynamic stability is more important than rigid context-free lists.

Scoliosis surgery may involve blood loss, large fluid shifts and prolonged neurophysiologic monitoring. In severe cardiomyopathy, proportionate access and monitoring, intensive-care availability and a postoperative plan for analgesia, ventilation and nutritional resumption are needed. Volume overload may cause edema, whereas excessive restriction compromises a small, stiff cavity. Fluid balance is guided by hemodynamics rather than generic protocols.

Pregnancy, family and prognosis

Pregnancy increases plasma volume, heart rate and cardiac output and may reveal reduced cardiac reserve. Before conception, ECG, echocardiography, rhythm, functional class, diabetes, respiratory function and medications are reassessed; reduced ejection fraction or previous heart failure indicates higher maternal and fetal risk. Cardiology and high-risk obstetrics plan surveillance, delivery and the postpartum period. Preconception counseling enables informed decisions before therapeutic changes.

The postpartum period deserves particular attention because uterine autotransfusion and fluid mobilization may precipitate congestion after an apparently stable delivery. Neuraxial analgesia may limit the adrenergic response when appropriate, but technique and anticoagulation must be coordinated. Heart-failure medications are adapted to pregnancy and breastfeeding, avoiding fetotoxic agents. Peripartum surveillance continues beyond obstetric discharge.

Autosomal recessive inheritance means that, for siblings of an affected person whose parents are carriers, each pregnancy carries a 25% probability of disease, 50% probability of carrier status and 25% probability of being a non-carrier. Risk to the patient's children depends on the partner's status; partner testing, prenatal diagnosis and preimplantation genetic testing are discussed without presupposing a choice. Heterozygous carriers are not considered at risk of the typical cardiomyopathy. Reproductive counseling translates the family genotype into understandable probabilities.

At-risk siblings deserve timely access to counseling and testing because early diagnosis, cardiac and metabolic surveillance and therapeutic availability have medical consequences. Management of minors considers maturity, health interests and psychological support, avoiding both secrecy and unaccompanied testing. Once the familial variant is identified, relatives are tested in a targeted manner. The family cascade reduces diagnostic delays and ambiguous results.

Cardiac disease remains one of the leading causes of death, but historical survival averages should not be presented as an individual's destiny. Age at onset, shorter GAA allele, ventricular mass, ejection fraction, arrhythmias, diabetes and respiratory status contribute to prognosis with variable weight. Supportive therapies and earlier diagnosis modify contemporary cohorts. Dynamic prognosis is updated with events and trajectories, not derived from a single genetic datum.

Transition from pediatric to adult care should transfer not only a report, but also wall-thickness curves, ECGs, CMR, biomarkers, arrhythmic history and drug response. An emergency plan describes cardiomyopathy, diabetes, dysphagia, assistive devices and specialist contacts. In advanced stages, early palliative care may accompany devices and active therapy, supporting symptoms and decisions. Continuity of care protects the patient during transitions when the risk of loss to follow-up is greatest.