The role of imaging in characterizing the cardiac natural history of Duchenne muscular dystrophy

Duchene muscular dystrophy (DMD) is a rare but devastating disease resulting in progressive loss of ambulation, respiratory failure, DMD-associated cardiomyopathy (DMD-CM), and premature death. The use of corticosteroids and supportive respiratory care has improved outcomes, such that DMD-CM is now the leading cause of death. Historically, most programs have focused on skeletal myopathy with less attention to the cardiac phenotype. This omission is rather astonishing since patients with DMD possess an absolute genetic risk of developing cardiomyopathy. Unfortunately, heart failure signs and symptoms are vague due to skeletal muscle myopathy leading to limited ambulation. Traditional assessment of cardiac symptoms by the New York Heart Association American College of Cardiology/American Heart Association Staging (ACC/AHA) classification is of limited utility, even in advanced stages. Echocardiographic assessment can detect cardiac dysfunction late in the disease course, but this has proven to be a poor surrogate marker of early cardiovascular disease and an inadequate predictor of DMD-CM. Indeed, one explanation for the paucity of cardiac therapeutic trials for DMD-CM has been the lack of a suitable end-point. Improved outcomes require a better proactive treatment strategy; however, the barrier to treatment is the lack of a sensitive and specific tool to assess the efficacy of treatment. The use of cardiac imaging has evolved from echocardiography to cardiac magnetic resonance imaging to assess cardiac performance. The purpose of this article is to review the role of cardiac imaging in characterizing the cardiac natural history of DMD-CM, highlighting the prognostic implications and an outlook on how this field might evolve in the future.