Impact of late gadolinium enhancement in assessment of MR:
Late gadolinium enhancement (LGE) can detect myocardial scar and/or
fibrosis, which has a significant impact in understanding the
pathophysiology of mitral regurgitation.
LGE has been reported on CMR images in patients with primary MR,
especially in those with mitral valve prolapse.(20,43) Left ventricular
remodeling seems to be associated with the presence of delayed
enhancement on CMR in primary MR.(43) In addition, in patients with
primary MR, LGE of papillary muscles is associated with complex
ventricular arrhythmias.(44) Persistent volume overload from MR results
in impaired LV function and the presence of diffuse myocardial
fibrosis.(45) Mitral annulus disjunction is an abnormal atrial
displacement of the hinge point of the mitral valve away from the
ventricular myocardium as noted above; it has been associated with
mitral valve prolapse and sudden cardiac death owing to ventricular
arrhythmias. (46,47)
In severe secondary MR in the setting of ischemic cardiomyopathy, the
presence of severe scarring in the region of the posterior papillary
muscle, as detected by preoperative CMR, can render these patients
unsuitable for mitral annuloplasty.(48) Moreover, the extent of
myocardial scarring is also informative about the progression of
ischemic MR.(27) In one large prospective trial, presence of both
significant ischemic MR (mitral regurgitation fraction ≥35%) and large
myocardial infarct size as determined by LGE (≥30% of LV mass) carries
a very high risk for all-cause mortality and/or heart transplant,
despite surgical mitral valve intervention. On the other hand, patients
with significant ischemic MR (mitral regurgitant fraction ≥35%) and low
myocardial infarct size (<15% of LV mass) had survival
benefit after surgical intervention. Taken together, these results show
that CMR is an important noninvasive imaging modality, not only for risk
stratification but also for the individualization of treatment decisions
for these complex patients.(26) Mitral valve enhancement is present in a
large number of post myocardial infarction (MI) patients but rarely in
non-post-MI patients in one observational study. Post-MI patients with
mitral valve enhancement are far more likely to have MR. (25)