Regional and Global Patterns of Annular Remodeling in Ischemic Mitral Regurgitation

Background The mammalian mitral annulus is saddle shaped. Experimental studies have shown that loss of saddle shape occurs in ischemic mitral regurgitation. However, neither the temporal pattern of global annular remodeling nor the geometric pattern of regional annular remodeling has been described. We sought to characterize these changes using real-time three-dimensional echocardiography in an ovine model. Methods Ten sheep underwent real-time three-dimensional echocardiography at baseline and 1 hour and 8 weeks after posterobasal myocardial infarction. Multiple mitral annular geometric indexes were measured at each time point to assess regional and global annular remodeling. Results One hour after infarction, global annular height decreased from 5.8 ± 0.5 mm to 4.0 ± 0.4 mm (p < 0.001) while intercommissural width increased from 29.0 ± 1.3 mm to 35.7 ± 1.7 mm (p = 0.023), resulting in a decrease in the global annular height to commissural width ratio from 20.0% ± 1.6% to 11.2% ± 0.9% (p < 0.001). Eight weeks after infarction, global annular height decreased to 3.9 ± 0.2 mm (p < 0.05) while intercommissural width increased to 40.7 ± 1.5 mm (p < 0.001), resulting in an additional decrease in the global annular height to commissural width ratio to 9.4% ± 0.4% (p < 0.001). Although annular remodeling involved the entire mitral annulus, there was regional heterogeneity in its extent. Conclusions Significant global annular flattening and dilatation occur during the development of ischemic mitral regurgitation in an ovine model. Regional annular remodeling is heterogeneous and is not limited the posterior commissure or the posterior annulus.