[A case of mitochondrial cardiomyopathy with heart failure, sick sinus syndrome and diabetes mellitus: mitochondrial DNA adenine-to-guanine transition at 3243 of mitochondrial tRNA(LEU)(UUR) gene].

A 42-year-old woman with diabetes mellitus lost consciousness and was transferred to the Yokohama City University Hospital. Blood chemistry findings indicated low blood sugar levels and chest X-ray examination revealed cardiomegaly and bilateral pleural effusions. These clinical abnormalities were corrected by treatment with glucose, diuretics, angiotensin converting enzyme inhibitor and digitalis. Cardiological laboratory examinations were performed after admission. Electrocardiography revealed first degree atrioventricular block and incomplete right bundle branch block. Ultrasonography showed lower grade of ejection fraction and diffuse hypokinesis of the cardiac wall. After admission, sinus arrest suddenly occurred. The diagnosis was sick sinus syndrome. Scintigraphy using iodine-123 betamethyl-p-iodophenyl-pentadecanoic acid showed abnormal mottled defects. Coronary angiography found no significant stenosis of the coronary artery. Electron microscopy showed abnormally shaped mitochondrial accumulations in an endomyocardial biopsy specimen. Mitochondrial DNA amplification by polymerase chain reaction followed by restriction enzyme Apa I digestion revealed adenine-to-guanine transition at 3243 of the mitochondrial tRNA(LEU)(UUR) gene.