Background: More precise understanding of annular remodeling in the evolution of chronic ischemic mitral regurgitation is needed to provide a more rational basis for optimal annuloplasty ring sizing and selection as well as the design of new reparative techniques. Three-dimensional in vivo data describing these geometric perturbations however are lacking. Using an ovine model of chronic myocardial infarction we determined the three-dimensional distortions of the mitral annulus associated with the development of chronic ischemic mitral regurgitation.
Methods: Ten sheep underwent placement of radiopaque markers on the left ventricle and mitral annulus as well as placement of snares around the second and third obtuse marginal coronary arteries. After 8 days biplane cinefluoroscopy provided three-dimensional marker data and snare occlusion created an inferior infarction. After 7 more weeks the animals were studied again.
Results: Severity of mitral regurgitation increased (0.6 +/- 0.5 to 2.5 +/- 0.7). Septal-lateral (2.99 +/- 0.20 cm to 3.64 +/- 0.35 cm, maximum dimension) and commissure-commissure (3.71 +/- 0.32 cm to 4.40 +/- 0.30 cm) mitral annular diameters and the lengths of the muscular (7.77 +/- 0.39 cm to 9.51 +/- 0.72 cm) and fibrous annular perimeters (3.36 +/- 0.37 cm to 3.85 +/- 0.39 cm, p < 0.0001 for all) increased while the height of the annular "saddle horn" above a best-fit plane fell (0.73 +/- 0.52 cm to 0.57 +/- 0.42 cm, minimum dimension, p = 0.01).
Conclusions: These three-dimensional in vivo data reflect annular remodeling in chronic ischemic mitral regurgitation and suggest that mitral repair in this context should be aimed at preventing further lengthening of the intertrigonal distance, reducing the septal-lateral annular diameter to reestablish adequate leaflet coaptation, and restoring the saddle shape of the annulus.