Different Mechanisms of Ischemic Mitral Regurgitation in Patients With Inferior and Anterior Myocardial Infarction

Abstract

Background. Basic mechanism of ischemic mitral regurgitation (MR) is displacement of papillary muscles (PMs) due to left ventricular (LV) remodeling. Variability in LV remodeling can potentially cause heterogeneous PM displacements. The aim of this study is to compare the mitral valve complex geometry in patients with ischemic MR due to inferior and anterior myocardial infarction (MI).
Methods. In 33 patients with prior inferior MI, 61 with anterior MI, and 22 controls, LV volume, mitral annular area, PM tethering distance, and MR were quantified by echocardiography.
Results. Significant MR (MR fraction > 20%) was observed in 12 of the 33 with inferior MI and 7 of the 61 with anterior MI. In patients with MR due to inferior MI, tethering distance was significantly longer in medial compared to lateral PM (42.6 ± 4.9 vs. 36.1 ± 1.7 mm, p < 0.001), demonstrating asymmetric medial PM displacement. Patients with MR due to anterior MI had comparable increases in both PM tethering distances (41.0 ± 2.4 vs. 41.4 ± 1.8 mm, n.s.), demonstrating symmetric bilateral PM displacement.
Conclusions. Although patients with ischemic MR due to inferior MI have asymmetrically predominant medial PM displacement, those with ischemic MR due to anterior MI have symmetric bilateral PM displacements.