Life-threatening ventricular arrhythmia and left ventricular dysfunction associated with anti-mitochondrial antibody-positive myositis: a case report

Background Anti-mitochondrial antibody (AMA)-positive myositis is an atypical inflammatory myopathy characterized by chronic progression of muscle atrophy and cardiac involvement. Few detailed reports have shown the clinical course of the cardiac complications of AMA-positive myositis. Case summary A 47-year-old man presented with shortness of breath on exertion. Cardiac dilatation was visible on chest X-ray, and echocardiography demonstrated diffuse hypokinesis with a reduced left ventricular (LV) ejection fraction of 30%. He had mild muscle weakness in the bilateral iliopsoas muscles, and his creatine kinase (CK) and anti-mitochondrial M2 antibody levels were elevated. A liver biopsy showed no findings of primary biliary cholangitis. Coronary angiography revealed normal coronary arteries. An endomyocardial biopsy showed interstitial fibrosis and marked degeneration of the mitochondria. Fluorodeoxyglucose (FDG)-positron emission tomography/computed tomography showed circumferential abnormal accumulation in the LV myocardium, and he was diagnosed with cardiomyopathy associated with AMA-positive myositis. Optimal drug therapy for heart failure was started, and a cardiac resynchronization therapy-defibrillator was implanted. However, his cardiac function did not improve, and he was hospitalized due to ventricular tachycardia storm 5 years after the diagnosis. Ventricular tachycardia was terminated by radiofrequency catheter ablation on the LV-anterior papillary muscle. Steroid therapy was initiated and resulted in a decreased uptake of FDG and a normalized CK level at 3 months after his second discharge; however, LV systolic dysfunction remained 1 year later. Discussion Anti-mitochondrial antibody-positive myositis can affect the myocardium and cause severe LV dysfunction and life-threatening ventricular arrhythmia over time. Keywords Anti-mitochondrial antibody-positive myositis • Endomyocardial biopsy • Ventricular tachycardia • Left ventricular dysfunction • Case report • Magnetic resonance imaging • Near-infrared spectroscopy-intravascular ultrasound