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.