[Cardiac involvement in mitochondrial disease: a clinical study of 38 patients]

Several reports showed that abnormality of mitochondrial DNA (mt DNA) can be an etiology of cardiomyopathy in recent years. Cardiac involvement in mitochondrial disease other than Kearns-Sayre syndrome (KSS), however, has not been documented clearly. Therefore, cardiac involvement, abnormality of mt DNA and defects of the respiratory chain in mitochondrial disease were studied. Thirty-eight patients with mitochondrial disease were studied. The patients were consisted of 2 patients with KSS, 1 patient with probable KSS, 15 patients with ocular myopathy, 1 patient with myoclonus epilepsy with ragged-red fibers (MERRF), 6 patients with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS), 5 patients with undefined mitochondrial encephalomyopathy and 8 patients with mitochondrial myopathy. Cardiac involvement was evaluated by electrocardiogram (ECG), chest roentgenogram and echocardiogram. Abnormality of mt DNA was examined using Southern blotting and polymerase chain reaction method in 25 patients. Defects of the respiratory chain were examined in 27 patients. All of the KSS and probable KSS showed heart block, and 2 of the 3 patients showed abnormalities on echocardiogram. Five of the 15 patients with ocular myopathy showed abnormalities on EGG. Four of the 6 patients with MELAS showed abnormalities on ECG, 1 showed cardiomegaly, and 3 showed left ventricular hypertrophy on echocardiogram. Three of the 5 patients with undefined mitochondrial encephalomyopathy showed abnormalities on ECG, 2 showed cardiomegaly and 2 showed asymmetric septal hypertrophy and wall motion abnormalities on echocardiogram. Large-scale deletions of mt DNA were detected in all of the KSS and probable KSS, and 7 patients with ocular myopathy. Deletions of mt DNA in the skeletal and cardiac muscles were proved to be identical in a case of KSS. A point mutation in mt DNA was detected in 5 patients with MELAS. Defects of the respiratory chain were detected in 22 patients. In conclusion, cardiac involvement is frequently seen in mitochondrial disease. Abnormality of ECG, especially heart block, is characteristic of KSS. Left ventricular hypertrophy is characteristic of mitochondrial encephalomyopathy.