This trial is a double-blind randomized clinical trial of lisinopril versus losartan for the treatment of cardiomyopathy in Duchenne Muscular Dystrophy (DMD). Both drugs are known to be effective for the treatment of dilated cardiomyopathy. ACEi have been reported to delay the onset and progression of left ventricle dysfunction in children with DMD. Multiple studies show therapeutic efficacy of losartan in animals with cardiomyopathy related to muscular dystrophy and in patients with cardiomyopathy from diverse causes. ARBs are often reserved for patients in whom heart failure is not adequately treated or where side effects preclude the use of an ACEi. However, in DMD, losartan might be a better choice as a first line drug because of studies demonstrating a potential benefit for skeletal muscle in the mdx mouse. Considering that both skeletal and cardiac muscles are major contributors of the disability of DMD, a drug that could improve both heart and skeletal muscles simultaneously would need consideration as the drug of choice for the cardiomyopathic DMD patient.

Inclusion Criteria:

• Duchenne muscular dystrophy patients of all ages
• Null mutation of the dystrophin gene or muscle with <5% dystrophin
• Doppler echocardiogram with ejection fraction (EF) <55% within 30 days of enrollment
• Ability to cooperate for testing
• Glucocorticoid treatment acceptable including daily or weekend administration of prednisone or deflazacort

Exclusion Criteria:

• Patients with EF 55% or greater
• Patients with EF <40% after washout
• Patients taking >5 mg lisinopril, or >25 mg losartan or >5 mg enalapril
• Skeletal deformities or pulmonary anatomical variants that preclude consistent measures of Doppler echocardiography