3-DIMENSIONAL DYNAMIC GEOMETRY OF THE NORMAL CANINE MITRAL ANNULUS AND PAPILLARY-MUSCLES

Background Despite an incomplete knowledge of the geometry and dynamic s of the mitral annulus (MA), papillary muscle (PM), and the chordae t endineae, chordal-sparing MVR is popular. Methods and Results The syst olic reduction in three-dimensional distance between each PM tip and e ight MA sites (D-T-A) was measured in nine normal closed-chest dogs by use of surgically implanted radiopaque markers. Three loci (tip, junc tion, and base) on each PM were also projected onto the MA plane at en d diastole and end systole to assess PM dynamics. The anterior PM tip showed significant shortening of D-T-A toward the opposite side of the MA or the midanterior MA region (P<.005 or P<.05, respectively, versu s same MA side [MANOVA]); conversely, the posterior PM tip D-T-A short ened toward the opposite side of the MA near the anterior commissure o r the area between the anterior commissure and midposterior MA (P<.005 versus same MA side). Annular projection revealed three-dimensional m otion (relative to the MA) of the anterior PM tip, junction, and base toward the right trigone, while posterior PM motion was oriented towar d the opposite side of the MA. Conclusions Both PMs in normal canine h earts demonstrated systolic relative motion in a direction compatible with the ''oblique'' chordal configuration, ie, from the anterior PM t o the anterior MA near the right trigone and from the posterior PM to the opposite side of the posterior MA. These observations warrant furt her investigation of three-dimensional PM-MA dynamics with various met hods of chordal preservation during MVR to assess their impact on left ventricular systolic and diastolic function.