What can CMR provide?
Until the last decade, the majority of textbooks mostly decried the use
of CMR for valvular pathology. Early adopters in this field however
recognized the substantial attributes attendant to CMR based on its
spatial resolution, inherent physics and mathematical capabilities and,
chiefly, on its non-reliance on a pure visual assessment to formally
quantify mitral regurgitation. CMR innately provides highly accurate and
reproducible assessment of left and right atrial and ventricular size
and function with superior endocardial definition and has become the
‘gold standard’ for evaluating cardiac chamber size. (10,15-17). It is
then a natural extension to apply all of the considerations of an ideal
chamber volumetric capability towards a valvular volumetric challenge.
(Table I)
A comprehensive CMR study is able to quantitate both atrial and
ventricular remodeling, which plays a crucial role in understanding both
the severity as well as the mechanism of regurgitation. Quantitative
parameters include regurgitant volume, regurgitant fraction, and
regurgitant orifice area. CMR offers several important advantages in the
assessment of MR. (4,7,10) This includes identifying the mechanism of
MR, quantifying MR severity, and determining its consequences on cardiac
remodeling. CMR can provide information about the mechanism of MR by
identifying morphologic abnormalities of the MV apparatus (Figure 1,
Figure 2). (18) Dedicated cine imaging on a CMR study can offer insights
into pathology of mitral valve leaflets including the presence of
prolapse or flail leaflets. (Figure 2, Figure 3a, Figure 3b). (19,20)
Two multicenter observational studies have clearly defined the role of
CMR quantification of primary MR and its use to be a better predictor
for mortality than echocardiography.(21,22) In one study, there was high
disagreement between echocardiography and MRI derived regurgitation
volumes, especially in patients with multiple or late systolic jets of
MR.(22) These studies point to a multi-modality approach in predicting
mortality, follow up and interventions in MR.
In secondary MR, CMR offers accurate assessment of LV dilation and
function in addition to identification of myocardial and papillary
muscle scar. (23,24) Additionally, late gadolinium enhancement in CMR in
patients with MR can provide additional consolidating information about
features such as myocardial infarct size as well as the significance of
scarring of papillary muscles and mitral valve fibrosis. (25-27)