Three-dimensional geometric comparison of partial and complete flexible mitral annuloplasty rings

Background: It has previously been shown in sheep that mitral annular physiologic dynamics during the cardiac cycle are abolished by complete ring annuloplasty, but recent clinical studies suggest that flexible partial ring annuloplasty preserves normal mitral annular dynamics. Methods: Eight radiopaque markers were sutured equidistantly around the mitral anulus in 3 groups of sheep: no-ring control animals (n = 16); animals with a flexible Tailor partial ring annuloplasty (n = 6; St Jude Medical, Inc, St Paul, Minn); and animals with a flexible Duran ring annuloplasty (n = 7; Medtronic, Inc, Minneapolis, Minn). After 7 to 10 days&' recovery, 3-dimensional marker coordinates were measured by biplane cinefluoroscopy. Mitral annular area and folding (defined as displacement of the mitral anulus from a least-squares plane) and mitral annular septal-lateral and commissure-commissure dimensions were calculated from the 3-dimensional marker coordinates throughout the cardiac cycle every 17 ms. Results: In the no-ring control group mitral annular area varied from 8.0 ± 0.2 to 7.2 ± 0.2 cm2 (10% ± 2%), and the septal-lateral and commissure-commissure dimensions varied from 27.7 ± 0.4 to 25.9 ± 0.4 mm (7% ± 1%) and from 38.2 ± 0.8 to 36.4 ± 0.8 mm (5% ± 1%), respectively (mean ± standard error of the mean, P