Effects of different annuloplasty rings on anterior mitral leaflet dimensions

Abstract

To assess the effects of annuloplasty rings on anterior mitral leaflet dimensions. Sixteen radiopaque markers were sutured evenly spaced over the surface of the anterior mitral leaflet in 57 sheep. The following rings were implanted in a releasable fashion: size 28-mm Cosgrove-Edwards band (Edwards Lifesciences, Irvine, Calif) (n = 11), rigid saddle-shaped annuloplasty ring (St Jude Medical Inc, St Paul, Minn) (n = 12), Carpentier-Edwards Physio (Edwards Lifesciences) (n = 12), IMR-ETlogix (Edwards Lifesciences) (n = 10), and GeoForm (Edwards Lifesciences) (n = 12). Under acute open chest conditions, 4-dimensional marker coordinates were measured using biplane videofluoroscopy with the annuloplasty ring inserted and after annuloplasty ring release. Septal-lateral and commissure-commissure dimensions were calculated from opposing marker pairs on the septal-lateral and commissure-commissure aspect of the anterior mitral leaflet at end diastole and end systole. To assess changes in anterior mitral leaflet shape, a "planarity index" was assessed by calculating the root mean square values as distances of the 16 anterior mitral leaflet markers to a best fit anterior mitral leaflet plane at end systole. At end diastole, anterior mitral leaflet septal-lateral and commissure-commissure dimensions did not change with the Cosgrove ring compared with control, whereas the rigid saddle-shaped annuloplasty ring and Physio, IMR-ETlogix, and GeoForm rings reduced anterior mitral leaflet commissure-commissure but not septal-lateral anterior mitral leaflet dimensions. At end systole, the septal-lateral anterior mitral leaflet dimension was smaller with the IMR-ETlogix and GeoForm rings, but did not change with the Cosgrove ring, rigid saddle-shaped annuloplasty ring, and Physio ring. Anterior mitral leaflet shape was unchanged in all 5 groups. With no changes in anterior mitral leaflet planarity, the 4 complete, rigid rings (rigid saddle-shaped annuloplasty ring, Physio, IMR-ETlogix, and GeoForm) reduced the anterior mitral leaflet commissure-commissure dimension at end diastole. The IMR-ETlogix and GeoForm rings decreased the septal-lateral anterior mitral leaflet dimension at end systole, probably as the result of inherent disproportionate downsizing. These changes in anterior mitral leaflet geometry could perturb the stress patterns, which in theory may affect repair durability.