Conclusion
The data generated by CMR beyond LVEF is a potent clinical and research tool to not only assess presence or absence of disease but to define how severe the disease is and demonstrate continued change with disease progression. When looking beyond LVEF and how well the heart squeezes, myocardial strain technique will be vital in demonstration disease earlier and when used in conjunction with myocardial fibrosis by LGE will allow earlier disease detection before decline in LVEF. In populations with NMD such as DMD it is vital to have surrogate markers of cardiac disease because traditional HF signs and symptoms are not present even in late stages of disease. The use of surrogate biomarker is not only vital but the only way to detect disease and disease progression as well as response to current and future therapy. The use of CMR has shifted the paradigm from rescue therapy when LVEF is abnormal to earlier treatment when only occult cardiomyopathy is present with LGE but preserved LVEF. When testing novel cardiac therapy it is vital that CMR surrogate marker be used to detect efficacy as HF symptoms do not appear even in late stages of DMD-CM in the majority of patients. When present HF signs and symptoms are nonspecific and are often masked by skeletal and respiratory muscle weakness limiting the utility of these symptoms and disease staging by NYHA ineffective. It is clear if management of DMD patients is based on HF symptoms, many will not receive treatment until late stages when the disease can no longer be rescue. A major barrier to treatment and developing new therapy is a lack of a sensitive marker of disease. The use of CMR myocardial strain in conjunction with LGE and LVEF will allow this barrier to be traverse and newer techniques may allow earlier disease detection. NMD patients including BMD and DMD patients universally develop cardiomyopathy and without therapy, there is only one outcome. Therapy offers hope and improve detection of cardiomyopathy in conjunction with more novel therapy will offer the opportunity to alter the course of cardiomyopathy as well as prolong and improved the lives of these patients. The heart is indeed the most important and active muscle and DMD-associated cardiomyopathy is currently a leading cause of death. Treatment of DMD patients without including the impact on the heart may not ultimately alter the course of the disease and in some cases may accelerate decline in cardiac function with increased burden and stress on the cardiac muscle with increased demand due to improve ambulation. Future therapy need assess impact on the heart because without it DMD-CM will continue to be the leading cause of death despite improvement in other areas.