Increased plasma catecholamines in patients with Friedreich's ataxia

Cellular pathophysiology of Friedreich's ataxia cardiomyopathy

Friedreich's ataxia (FRDA) is a hereditary neuromuscular disorder. Cardiomyopathy is the leading cause of premature death in FRDA. FRDA cardiomyopathy is a complex and progressive disease with no cure or treatment to slow its progression. At the cellular level, cardiomyocyte hypertrophy, apoptosis and fibrosis contribute to the cardiac pathology. However, the heart is composed of multiple cell types and several clinical studies have reported the involvement of cardiac non-myocytes such as vascular cells, autonomic neurons, and inflammatory cells in the pathogenesis of FRDA cardiomyopathy. In fact, several of the cardiac pathologies associated with FRDA including cardiomyocyte necrosis, fibrosis, and arrhythmia, could be contributed to by a diseased vasculature and autonomic dysfunction. Here, we review available evidence regarding the current understanding of cellular mechanisms for, and the involvement of, cardiac non-myocytes in the pathogenesis of FRDA cardiomyopathy.

Parasympathetic activity in Friedrich's ataxia

We compared 19 patients with Friedreich's ataxia, a progressive hereditary neuromuscular disorder, with 19 healthy age-matched subjects. During nighttime, patients had shorter mean RR and decreased heart rate variability parameters related to parasympathetic activity than healthy subjects, whereas no difference occurred during daytime.

Friedreich's ataxia in the elderly

Friedreich's ataxia is one of the best defined and most common forms of hereditary ataxia of unknown aetiology. It is transmitted in an autosomal recessive manner, appearing sporadically, usually in childhood or adolescence. The case of an elderly patient with a possible diagnosis of late-onset Friedreich's ataxia is reported; this is thought to be the only such case in the literature. The 91-year-old Anglo female presented with ataxia that had been progressive over the last 5 years. Magnetic resonance imaging scans of the head revealed mild peripheral cerebellar atrophy and moderate cerebral atrophy. The patient's parents were unaffected but two of her six siblings had had Friedreich's ataxia starting in childhood, and four of her grandfather's siblings had had an undiagnosed illness that left them in wheelchairs early in life. Friedreich's ataxia was diagnosed in view of the strong family history and non-revealing magnetic resonance imaging of the brain.

Autonomic function in Friedreich's ataxia

Autonomic function studies were performed on 15 patients with Friedreich's ataxia, and the results compared with those of 76 healthy subjects. There was an increase in resting supine heart rate, attributed to cardiac abnormalities. Other tests of sympathetic and parasympathetic function were normal. The normal autonomic function studies are consistent with the pathological findings of degeneration predominantly of large diameter myelinated fibres with sparing of small myelinated and unmyelinated fibres.

Coronary disease, cardioneuropathy, and conduction system abnormalities in the cardiomyopathy of Friedreich's ataxia

Abnormalities of the heart are a frequent and possibly ubiquitous problem in patients with Friedreich's ataxia, but their pathogenesis is unclear. Postmortem findings are reported from the hearts of three patients with Friedreich's ataxia who died of congestive heart failure and atrial arrhythmias. Particular attention was paid to the following: the large and small coronary arteries, the nerves and ganglia, the conduction system, and the histological and cellular features of the cardiomyopathy. There were pleomorphic nuclei and focal fibrosis and degeneration throughout each heart including the conduction system. There were distinctive abnormalities of both large and small coronary arteries, and focal degeneration of nerves and ganglia. These observations suggest a mosaic concept for the pathogenesis for the cardiomyopathy of Friedreich's ataxia that involves the interplay of molecular faults, cardiomyopathy, cardioneuropathy, and coronary disease.

Cardiac involvement in Friedreich's ataxia: a clinical study of 75 patients

To establish the prevalence and to characterize the types of cardiac involvement in Friedreich's ataxia, 75 consecutive patients (39 male and 36 female), aged 10 to 66 years (mean 24) were prospectively studied. Electrocardiograms were performed in all patients, vectorcardiograms in 34 and echocardiograms in 58. Electrocardiographic and vectorcardiographic abnormalities occurred in 69 (92%) of the 75 patients. Electrocardiograms revealed ST-T wave abnormalities in 79%, right axis deviation in 40%, short PR interval in 24%, abnormal R wave in lead V1 in 20%, abnormal inferolateral Q waves in 14% and left ventricular hypertrophy (voltage and repolarization criteria) in 16%. Echocardiograms revealed concentric left ventricular hypertrophy in 11%, asymmetric septal hypertrophy in 9% and globally decreased left ventricular function in 7%. Progression from a normal echocardiogram to concentric left ventricular hypertrophy, asymmetric septal hypertrophy or globally decreased left ventricular function was identified in one patient in each category, although the study was not designed for longitudinal follow-up. Two patients died, and necropsy revealed in both a minimally dilated but flabby left ventricle. On the basis of electrocardiographic and vectorcardiographic and echocardiographic data, 95% of patients had one or more disorders. The most common abnormality was segmental myocardial "dystrophy" (electrocardiographic QRS initial force abnormalities), but global left ventricular hypokinesia occurred more often than previously recognized.(ABSTRACT TRUNCATED AT 250 WORDS)

Friedreich's ataxia with dysautonomia and labile hypertension

An Amerindian girl with Friedreich's ataxia presented at the age of 14 years with intermittent bifrontal headaches and abdominal aching, often associated with nausea and recurrent vomiting and an evanescent pink, blotchy rash on the upper trunk. In these attacks she also had hypertension up to 210/160 mm Hg. Renal function studies, including intravenous pyelogram and angiography, were normal. Plasma renin activity (2.5 ng/ml/hr) was also normal. Total body CT scan was negative for phaeochromocytoma, and repeated estimations of 24-hour excretion of urinary VMA were normal or borderline high. Levels of total catecholamines in 24-hour urine were normal twice, but two random specimens during the paroxysmal episodes contained abnormally high levels of norepinephrine and dopamine. Plasma catecholamine concentrations were increased but not as high as with phaeochromocytoma. Blood pressure monitoring demonstrated marked fluctuations with position and temperature. A clonidine suppression test showed a substantial fall of plasma catecholamine levels, consistent with dysautonomia and not with phaeochromocytoma. It is concluded that the patient has dysautonomia of central origin, probably as a manifestation of Friedreich's ataxia. These findings are discussed in relation to the recent demonstration of increased levels of plasma catecholamines in that disease.