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)