Mitochondrial Cardiomyopathies

Primary mitochondrial diseases (PMD) are caused by mitochondrial dysfunction due to mutations in nuclear or mitochondrial DNA. Cardiac involvement is present in the majority of patients with cardiomyopathy, arrhythmias, and conduction defects being the most prevalent. Hypertrophic cardiomyopathy is the most frequently encountered cardiomyopathy in PMD but also dilated cardiomyopathy and left ventricular non-compaction can occur. Cardiac symptoms may be the presenting sign of PMD or can be found when screening patients with suspected PMD. Early-onset PMD (0–3 years) is generally more severe with multi-organ involvement than late-onset PMD (adolescence/early adulthood). Where PMD like Barth syndrome, Sengers syndrome, and MELAS used to be clinical diagnoses, DNA analysis plays an increasingly important role early in the diagnostic process and should be performed as soon as PMD or a mitochondrial cardiomyopathy is suspected. Since mitochondria, and thus mutant mitochondrial DNA, are randomly distributed during the cell cycle, disease phenotype may vary greatly. Treatment for mitochondrial cardiomyopathies is mainly supportive and comprises a combination of diuretics, beta-blockers, and angiotensin-converting enzyme inhibitors in case of reduced left ventricular systolic function and cardiac device therapy. Furthermore, an increasing number of supplements are being used to improve mitochondrial function and to ameliorate the effects of mitochondrial dysfunction. Despite supportive therapy mortality in mitochondrial cardiomyopathy remains high (up to 84%) and is inversely related to age at presentation