Cardiovascular manifestations in duchenne/becker muscular dystrophy and other primary myopathies

Patients with muscular dystrophy face a lifetime of physical challenges due to their neuromuscular disease. Physical challenges are faced on a daily basis, and as such this is the initial focus from a clinical perspective. Over the past decades, improvements in physical and respiratory therapy, coupled with advances in technology, have substantially improved quality of life for this patient group. Improvements in computer technology such as voice recognition have increased access to education and allowed greater independence for muscular dystrophy patients. Use of assisted cough techniques and ventilatory support, particularly non-invasive support, has significantly prolonged the lifespan of patients with neuromuscular disease, particularly Duchenne muscular dystrophy. As a result, cardiac disease is now thought to be the leading cause of death among those with Duchenne muscular dystrophy, and represents a new medical challenge for the current generation of patients. Because skeletal and cardiac muscle share a common embryologic origin, the underlying genetic mutations generally impact both skeletal and cardiac muscle. Cardiac disease is common among patients with neuromuscular disease. Essentially all men with Duchenne muscular dystrophy will develop cardiomyopathy by age 18. In contrast, cardiac involvement in other muscular dystrophy patients depends on the specific subtype. For example, LGMD1B patients commonly have arrhythmias and cardiomyopathy while LGMD1C patients have isolated cases of hypertrophic cardiomyopathy. Patients with Becker muscular dystrophy exhibit a broad range of cardiac phenotype-from patients with no cardiac involvement to those with severe cardiomyopathy requiring heart transplant. Yet while cardiac disease is common, its scope and impact in neuromuscular patients is under recognized. Neurology clinics dedicated to muscular dystrophy are common, while only a handful of dedicated neuromuscular cardiomyopathy clinics exist (primarily at academic centers). Fewer still receive active treatment for cardiac disease. In this chapter, we begin with a concise review of the basic assessment and workup of congestive heart failure in the general adult population. With this as a backdrop, the cardiac management of three common neuromuscular diseases- the dystrophinopathies, Limb-Girdle muscular dystrophy, and congenital muscular dystrophy.