Congestive heart failure due to mitochondrial cardiomyopathy in Kearns-Sayre syndrome

Stroke and Stroke-like Episodes in Muscle Disease

Background:

Though not obvious at a first glance, myopathies may be associated with ischemic stroke. Stroke-like episodes resemble ischemic stroke only to some extent but are a unique feature of certain mitochondrial disorders with a pathogenesis at variance from that of ischemic stroke. Only limited data are available about ischemic stroke in pri-mary myopathies and the management of stroke-like episodes in mitochondrial disorders. This review aims to summarize and discuss current knowledge about stroke in myopathies and to delineate stroke-like episodes from ischemic stroke.

Methods:

Literature review via PubMED using the search terms “stroke”, “cerebrovascular”, “ischemic event”, “stroke-like episode”, “stroke-mimic”, “mitochondrial disorder”.

Results:

Stroke in myopathies is most frequently cardioembolic due to atrial fibrillation or atrial flutter, dilated cardio-myopathy, or left-ventricular hypertrabeculation (noncompaction). The second most frequent cause of stroke in myopathies is angiopathy from atherosclerosis or vasculitis, which may be a feature of inflammatory myopathies. Athero-sclerosis may either result from classical risk factors, such as diabetes, arterial hypertension, hyperlpidemia, or smoking, associated with muscle disease, or may be an inherent feature of a mitochondrial disorder. In case of severe heart failure from cardiomyopathy as a manifestation of muscle disease low flow infarcts may occur. Thrombophilic stroke has been described in polymyositis and dermatomyositis in association with anti-phospholipid syndrome. Stroke-like episodes occur particularly in mitochondrial encephalopathy, lactacidosis and stroke-likeepisode syndrome but rarely also in Leigh-syndrome and other mitochondrial disorders. Stroke-like episodes are at variance from ischemic stroke, pathogenically, clinically and on imaging. They may be the manifestation of a vascular, metabolic or epileptic process and present with predominantly vasogenic but also cytotoxic edema on MRI. Differentiation between ischemic stroke and stroke-like episodes is essential in terms of management and prognosis. Management of ischemic stroke in patients with myopathy is not at variance from the treatment of ischemic stroke in non-myopathic patients. There is no standardized treatment of stroke-like episodes but there is increasing evidence that these patients profit from the administration of L-arginine and conse-quent antiepileptic treatment if associated with seizure activity.

Conclusions:

Ischemic stroke may be a complication of myopathy and needs to be delineated from stroke-like episodes, which are unique to mitochondrial disorders, particularly mitochondrial encephalopathy, lactacidosis and stroke-likeepisode syndrome. Ischemic stroke in myopathies is most frequently cardioembolic and treatment is not at variance from non-myopathic ischemic stroke. Treatment of stroke-like episodes is not standardized but seems to respond to L-arginine and adequate antiepileptic treatment.

Cardiac dysfunction in patients with chronic progressive external ophthalmoplegia

BACKGROUND

Chronic progressive external ophthalmoplegia (CPEO), which includes Kearns-Sayre syndrome, is a mitochondrial disorder with large deletions of mitochondrial DNA. Recently, mtDNA deletions in cardiac muscle cells were thought to be a cause of dilated cardiomyopathy. However, the cardiac involvement in patients with CPEO is generally considered to be limited to the cardiac conduction system.

HYPOTHESIS

The purpose of this study was to evaluate left ventricular function in patients with CPEO.

METHODS

We evaluated the cardiac function of five patients with CPEO by means of carotid pulse recording and Doppler echocardiography.

RESULTS

The ratio of the pre-ejection period to ejection time was increased to 0.67 in one patient and to 0.50 in another. Echocardiography showed left ventricular dilatation and diffuse hypokinetic wall motion in both cases. Left ventricular fractional shortening was decreased to 5 and 19%, respectively, and the mean rate of circumferential shortening was decreased to 0.12 and 0.63 circ/s, respectively. One of the two patient died of congestive heart failure 2 months after the study. The Doppler pattern of left ventricular filling in the three remaining patients showed a decrease in the ratio of peak flow velocity in early diastole to that in late diastole, with an increase in deceleration time.

CONCLUSION

Although cardiac involvement in patients with CPEO is generally considered to be limited to the cardiac conduction system, left ventricular dysfunction may be present and should receive more attention in the management of patients with CPEO.

Cardiomyopathy in respiratory chain disorders

Disorders of mitochondrial oxidative phosphorylation may disturb cardiac energy metabolism and cause cardiomyopathy. Twenty one cases from the literature and one further patient with cardiomyopathy due to biochemically defined respiratory chain defects were reviewed for clinical course, morphology, and pathophysiological mechanisms of the cardiomyopathy. All cases showed concentric hypertrophy of the myocardium without an outflow tract obstruction. In most patients the cardiomyopathy was diagnosed early in infancy and showed rapid deterioration with death before the age of 2 years. Hypertrophy of the myocardium appears to result from swelling of the cardiomyocytes caused by accumulation of mitochondria and by morphologically abnormal megamitochondria.

Sinus dysrhythmia in Kearns-Sayre syndrome

Kearns-Sayre syndrome is the triad of progressive external ophthalmoplegia, pigmentary retinopathy, and complete AV block. The etiology is unknown, but is thought to be due to a mitochondrial DNA deletion. Reported electrocardiographic abnormalities include first-degree AV block, fascicular blocks, and complete heart block, as well as non-specific S-T segment changes and T wave abnormalities, but has not included sinus node dysfunction. We report a case with episodes of sinus arrest in an asymptomatic patient with Kearns-Sayre syndrome resulting in pauses lasting up to 6 seconds.

Different copy numbers of apparently identically deleted mitochondrial DNA in tissues from a patient with Kearns-Sayre syndrome detected by PCR

An apparently identical deletion of 4.977 bp in length (position 8,483-13,459) was detectable in the mitochondrial DNA from skeletal muscle, heart muscle, kidney, and liver of a patient with Kearns-Sayre syndrome. The proportion of deleted genome varied from 60% for the skeletal muscle to 15% for heart muscle and kidney, and was below 5% in the liver. The mtDNA heteroplasmy of the liver was only detectable after amplification by PCR. In skeletal and heart muscle histochemical and immunocytochemical findings concerning cytochrome c oxidase were in good correlation with the proportion of deleted mitochondrial DNA.

Fatal mitochondrial cardiomyopathy in Kearns-Sayre syndrome

The clinical and postmortem findings in a 26 year old man with Kearns-Sayre syndrome are described. In the last years of his life he suffered from cardiac arrhythmias and a congestive cardiomyopathy, dying of cardiac pump failure. The heart was enlarged, especially the left ventricle which was fibrotic and excessively dilated. Histological and fine structural investigation revealed an excessive loss of myofibrils and an increase of enlarged mitochondria with lamellar and atypically tubular cristae in widespread heart muscle cells. Mitochondrial anomalies were also observed in some cells of the conductive system. This patient thus suffered not only from a mitochondrial myopathy with ragged red fibers but also from a fatal mitochondrial cardiomyopathy. The anomalies observed in the mitochondria of the conductive system cells suggest that the well-known conductive abnormalities in patients with Kearns-Sayre syndrome might be at least partly caused by disturbed function of these mitochondria.