Energy States in Mitochondrial Cardiomyopathy

itochondrial cardiomyopathy is one of the main features in patients with mitochondrial diseases caused by mitochondrial DNA (mtDNA) mutations, and it determines the prognosis, as well as encephalopathy.1–3 In particular, an A-to-G transition mutation at nucleotide position 3243 (A3243G) in mtDNA, which was originally discovered in patients with mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS),1 is the most common cause of mitochondrial cardiomyopathy.2,3 Accumulated abnormal mitochondria and increased mutant mtDNA in the myocardium of patients with mitochondrial cardiomyopathy have been demonstrated in pathological studies.3,4 Although in vitro biological studies using cultured cells have demonstrated that increased mutant mtDNA provokes respiratory chain failure, which leads to decreased ATP production and enhanced oxidative stress,5 the pathogenesis of mitochondrial cardiomyopathy in living patients remains obscure. Recent in vivo functional imaging studies demonstrated the energy states in the myocardium of living patients.