LGE and DMD-associated Cardiac Disease
After, injection of a gadolinium based contrast agent, the normal
myocardial is able to transport the contrast out and the myocardium
remains dark post contrast imaging (Fig 6a-b). The myocardial fibrosis
pattern in myocardial infarction patients is sub-endocardial and
restricted to affected coronary artery distributions (Fig 6c-e). In
comparison, the LGE in DMD-CM is sub-epicardial and spares the
sub-endocardium even in advance disease (Fig 6f-h). Earlier studies
reported extensive LGE which was associated with age and abnormal
ejection fraction (Fig 7g-h)50,
51. The study by Puchalski et al,
described presence of LGE in some young patients in the setting of
normal LVEF (Fig 7c-f) and suggested that LGE may be a precursor to
DMD-CM before LVEF decline is evident56,
80. These findings changed clinical
practice including LGE assessment in all DMD patients and altered timing
of treatment.
A larger follow-up study confirmed that LGE was a precursor to
development of abnormal global function and described age of onset as
well as prevalence of disease in different age group37. LGE was noted in
patients as young as 7.5 years of age. LGE occurred in 17% of patients
under 10 years of age, increased to 34% for those between age 10-15
years and for those patients who are older than 15 years of age more
than 59% have LGE. LGE was presence in 30% of patients with normal
LVEF and the prevalence increased to greater than 84% when LVEF was
abnormal. A distinct LGE pattern was also noted in this same study and
confirmed by other investigators56. LGE first occur in
the subepicardial region of the lateral wall progress to other segments
in myocardium but always sparing the subendocardial (Fig 6c-h). When LGE
is seen in the ventricular septum it is usually associated with older
age and lower ejection fraction(Fig 6g-h, green arrows)37,
56. A study by Tandon et al. including
serial CMR findings demonstrated that LGE burden can predict severity of
DMD-CM. The study confirmed that patients with LGE have lower LVEF than
patients without LGE. Furthermore, increased number of segments with LGE
resulted in lower LVEF and for each ventricular segment that is LGE
positive, LVEF declined by nearly 1%. Serial CMR data demonstrated that
DMD patients without LGE did not have significant decline in LVEF but
those with LGE declined by approximately 2.2% per year79. These studies
concluded that LGE can occur early and is a precursor to development of
abnormal LVEF. In addition, LGE in DMD-CM has a distinct pattern and the
extent of LGE impacts on LVEF and rate of progression of DMD-CM. The
findings of LGE has impacted on clinical as well. The most recent
Cardiac Care Considerations recommends the initiation of cardiac therapy
when LGE is first noted even in the setting of normal LVEF. At our
institution CMR has changed our practice and presence and extent of LGE
has results in change in medication regimen and occurs in real time and
has altered follow-up plans.