Effect of semi-rigid or flexible mitral ring annuloplasty on anterior leaflet three-dimensional geometry

A saddle-shaped mitral annulus may optimize anterior leaflet shape and, in theory, reduce leaflet and chordal stress. Although annuloplasty rings alter native annular height and immobilize the posterior mitral leaflet, their effects on anterior leaflet geometry are unknown.

Four radiopaque markers were placed on the central meridian of the anterior mitral leaflet (AML), and eight on the mitral annulus, of 20 sheep. Six animals were then implanted with a Carpentier-Edwards Physio ring, and six a Medtronic Duran flexible ring. Eight animals served as controls. All animals were then studied with biplane 60 Hz videofluoroscopy at 7-10 days after surgery. The angle Theta was calculated as the angle between each AML leaflet marker and the annular septal-lateral diameter, while AML marker excursion was expressed as the difference between maximum and minimum angle Theta during the cardiac cycle. The intrinsic AML shape was described by three angles, each between three consecutive leaflet markers from the mid-septal annular marker to the leaflet edge (Phi1-3, from annulus to leaflet edge).

Hemodynamic parameters differed only in left ventricular pressure, which was higher in control animals. Anterior leaflet excursion during the cardiac cycle for all four leaflet markers did not change with ring annuloplasty. The intrinsic leaflet angles (Phi1-3) were also unaffected by annular fixation, and thus leaflet shape remained unaltered.

Neither semi-rigid nor flexible annuloplasty rings affected anterior leaflet excursion or the intrinsic geometry of the AML at end-systole or end-diastole. These data suggest that, in normal sheep hearts, annuloplasty rings do not alter anterior leaflet shape and hence do not perturb leaflet stress distribution.