title: Myocardial ultrastructure and the development of atrioventricular block in Kearns-Sayre syndrome.
abstract: A right ventricular endomyocardial biopsy specimen from a 30-year-old male with chromic progressive external ophthalmoplegia, retinal pigmentation and complete atrioventricular block (Kearns-Sayre syndrome) was examined in the electron microscope. There was a proliferation of mitochondria between the myofibrils and beneath the sarcolemma. Many of the mitochondria showed morphologic abnormalities not previously described in this condition. There were associated accumulations of glycogen. A similarly affected female with left anterior hemiblock developed complete atrioventricular block at age 26 years, Despite the ultrastructural changes, clinically detectable myocardial disease is not a feature of Kearns-Sayre syndrome. However, intraventricular conduction defects show an unusually rapid progression to potentially fatal complete atrioventricular block and are an indication for prophylactic cardiac pacing.
mesh_terms: D000328:Adult; D005260:Female; D006327:Heart Block / Q000150:complications*; D006801:Humans; D008297:Male; D008929:Mitochondria, Heart / Q000648:ultrastructure; D009206:Myocardium / Q000648:ultrastructure*; D009210:Myofibrils / Q000648:ultrastructure; D009886:Ophthalmoplegia / Q000150:complications*; D010857:Pigment Epithelium of Eye / Q000473:pathology; D010859:Pigmentation Disorders / Q000150:complications; D013577:Syndrome