NPPB and inborn mitochondrial metabolism disorder: 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).