Mitochondrial disease and the heart

### Learning objectives Mitochondrial diseases (MDs) include a wide range of clinical entities involving tissues that have high energy requirements such as heart, muscle, kidney and the endocrine system1 (figure 1). Defects in mitochondrial DNA (mtDNA) mutations are the most common cause of MDs in adults.2 ,3 However, the nuclear gene defects are increasingly recognised as a cause of disease.4 Although the true prevalence of cardiac involvement in MD is unknown, cardiovascular involvement presents specific clinical issues that require systematic evaluation. In addition, in some MD-related mutations (eg, m.3243A.G) cardiac disease is the most common cause of early death.5 Hence, cardiologists are likely to become increasingly involved in the multidisciplinary care of patients with MD. Figure 1 Clinical features of mitochondrial disease. A detailed description of the genetics of the mitochondria is beyond the scope of this review, but the general principles are summarised in box 1.Box 1 ### Biology and genetics of mitochondria Structure and function Inheritance mtDNA is maternally inherited