Long-term prognosis and genetic background of cardiomyopathy in 223 pediatric mitochondrial disease patients

•Cardiomyopathy is related to poor prognosis in pediatric mitochondrial disease patients.•However, other risk factors including genetic factors related to poor prognosis has yet to be fully elucidated.•We assessed the prognosis and genetic background of cardiomyopathy in 223 pediatric mitochondrial disease patients.•Cardiomyopathy was common (22%) and was associated with increased mortality.•Left ventricular (LV) hypertrophy, neonatal onset and chromosomal aberrations were independent predictors of mortality.•Prognosis is particularly unfavorable if LV hypertrophy is combined with neonatal onset and/or chromosomal aberrations.