Contemporary Cardiac Issues in Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is an X-linked genetic disorder diagnosed in childhood. It affects ≈1 in every 5000 live male births (≈20 000 new cases worldwide each year).1,2 This results in a US prevalence of 1.3 to 1.8 per 10 000 males 5 to 24 years of age. DMD is caused by mutations in the gene encoding the dystrophin protein. The loss of dystrophin results in a cascade of events leading to progressive loss of muscle function. Without supportive care, young men with DMD typically die in their late teens and early 20s. Historically, the most common cause of death has been respiratory failure. However, with improved respiratory support, an increasingly important source of morbidity and mortality is cardiomyopathy leading to heart failure and arrhythmias.3,4 There are important differences in DMD cardiomyopathy compared with other types of pediatric dilated cardiomyopathy.5 DMD cardiomyopathy is similar to the cardiomyopathy seen in some forms of limb girdle muscular dystrophy and congenital muscular dystrophy. In particular, a shared cardiomyopathic process is seen in those disorders in which the primary mutation alters components that directly or indirectly interact with dystrophin. There is less left ventricular (LV) enlargement at diagnosis in DMD. Only 30% of boys with DMD have cardiac symptoms at diagnosis (far fewer than other dilated cardiomyopathy). DMD cardiomyopathy is less often treated at the time of diagnosis. However, treatment rates have increased over time. Finally, there is a higher mortality for DMD cardiomyopathy than for other dilated cardiomyopathies. The DMD Care Considerations published in 2010 addressed cardiac care recommendations based on minimal surveillance standards with echocardiography.6,7 However, echocardiography has known limitations in DMD patients.8 Since the 2010 publication of the DMD Care Considerations,6,7 there have been significant advances in the understanding …