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Magnetic Resonance Imaging With 3-Dimensional Analysis of Left Ventricular Remodeling in Isolated Mitral Regurgitation: Implications Beyond Dimensions
Study Questions:
As assessed using three-dimensional (3D) magnetic resonance imaging (MRI), what changes in left ventricular (LV) end-systolic dimension and volume occur among patients with isolated degenerative mitral regurgitation (MR)?
Methods:
Cine MRI with tissue tagging and 3D analysis was performed among 94 patients (age 54 ± 11 years, 38% female) with degenerative isolated MR and 51 control subjects (age 44 ± 14 years, 53% female).
Results:
Among control subjects, there was a quadratic relation between LV end-systolic volume and LV end-systolic dimension, whereas this relation was cubic among 94 patients with MR, indicating a greater increase in LV end-systolic volume per end-systolic dimension among MR patients. Moreover, MRI of LV end-systolic volume from summated serial short-axis slices was significantly greater than LV end-systolic volume assessed with the Bullet formula in MR patients, a finding attributed to more spherical remodeling distal to the tips of the papillary muscles (p < 0.001). Thirty-five patients underwent mitral valve repair per current guideline recommendations. LV ejection fraction decreased from 61 ± 7% to 54 ± 8% (p < 0.0001), and maximum shortening decreased significantly below normal at 1 year postoperatively (p < 0.0001). Despite normalization of LV stroke volume and LV end-diastolic volume/mass ratio, there was a persistent significant increase in distal LV end-systolic 3D radius/wall thickness ratio and LV end-systolic volume index after surgery.
Conclusions:
Despite apparently preserved LV end-systolic dimension, patients with MR demonstrate significant spherical mid- to apical-LV end-systolic remodeling that contributes to higher LV end-systolic volume than predicted by calculations based on standard geometry. Decreased LV strain after surgery suggests that a volumetric analysis of LV remodeling and function may be preferred to evaluate disease progression in isolated MR.
Perspective:
This study uses MRI to confirm that single-dimensional and two-dimensional estimates of LV size are flawed, and that spherical remodeling of the LV associated with chronic MR results in volume that is out of proportion to diameter. In an elegant study, the authors have shown that, like the world, the LV is 3D. In an era with increased access to 3D imaging in a variety of formats, clinical decision making should evolve away from algorithms based on one-dimensional imaging.
Keywords: Mitral Valve Insufficiency, Ventricular Remodeling, Magnetic Resonance Imaging
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