We prospectively examined cardiac manifestations in 11 adult patients with MELAS syndrome harboring the MTTL1 m.3243A < G-mutation using patient records, cardiac MRI (1.5 Tesla), echocardiography, electrocardiogram (ECG), laboratory tests of cardiac markers (CK, CK-MB, Trop I, BNP), and clinical severity (NMDAS = Newcastle Mitochondrial Disease Scale). The gene discussed is MT-TL1; the disease is inborn mitochondrial metabolism disorder.