Abstract 1803: Geometric Determinants of the Degree of Ischemic Mitral Regurgitation in Patients With Systolic Left Ventricular Dysfunction: Three-Dimensional Magnetic Resonance Imaging Study
Background: Ischemic mitral regurgitation (IMR) occurs with a structurally normal valve as a complication of systolic left ventricular dysfunction (LVD). However, the three-dimensional (3D) determinants of the degree of IMR were not precisely investigated. The purpose of this study was to clarify the 3D determinants of the degree of IMR in patients with LVD using cardiac magnetic resonance imaging (MRI).
Methods: We used the whole-heart MRI technique to evaluate the geometry of the mitral apparatus that provides 3D visualization of the entire heart using a navigator respiratory gating technique with a high spatial resolution (reconstructed voxel size = 0.6x0.9x0.7 mm3). End-systolic whole-heart MR images were acquired in 30 patients with LVD (LV ejection fraction < 50%). Three-dimensional positions of the mitral annulus and papillary muscles (tip and base) to the centroid of mitral annulus were calculated. The valvular tenting area was estimated by measuring the area enclosed by the annular plane and 2 leaflets in the central anteroposterior plane. IMR was graded as none (0), trace (0.5), mild (1), moderate (2), moderate-severe (2.5) or severe (3) using color-Doppler echocardiography. Hence, the patients were grouped by IMR grades (≥2+, n= 17 versus ≤1+, n=13).
Results: Posterior papillary muscle (PPM) tips were displaced more posteriorly in IMR(+) patients (12±5 versus 7±4mm, p < 0.01). The posterior component of the PPM tethering length (mid-septal annulus to PPM) was significantly longer in IMR(+) patients (26±6 versus 21±4mm, p= 0.01), whereas the medial and apical components did not show significant differences. The posterior component of the PPM tethering length was significantly correlated with the valvular tenting area (r = 0.61, p < 0.01). Multiple regression analysis identified the posterior component of the PPM tethering length as the strongest predictor of the IMR grade.
Conclusion: Local LV remodeling (posterior displacement of PPM) leads to excess valvular tenting and the posterior component of the PPM tethering length is the primary determinant of IMR in patients with LVD.