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.