Introduction: Annuloplasty rings to treat functional/ischemic mitral regurgitation (FMR/IMR) include a greater downsizing of the septal-lateral (S-L) than the commissure-commissure (C-C) mitral annular dimension. This design is not only intended to maximize mitral leaflet coaptation, but also to reshape the dilated, spherical left ventricle (LV).
Hypothesis: Disease-specific FMR/IMR ring types reduce left-ventricular S-L, but not C-C dimensions during acute myocardial ischemia in the beating ovine heart.
Methods: In thirty adult sheep radiopaque markers were placed as opposing pairs on the S-L and C-C aspects of the mitral annulus (ANN) and the basal, equatorial and apical level of the LV (LV1, LV2 and LV3, respectively, Fig, A). Ten true-sized Carpentier-Edwards Physio 1 (PHY), Edwards IMR ETLogix (ETL), and GeoForm (GEO) annuloplasty rings were inserted in a releasable fashion. Under acute open chest conditions 4-D marker coordinates were obtained using biplane videofluoroscopy with ring inserted at baseline (data not reported) and after 90 seconds of left circumflex artery occlusion (RING). After ring release, another dataset was acquired before (data not reported) and after left circumflex artery occlusion (NO RING). S-L and C-C diameters were computed as the distances between the respective marker pairs at end-diastole.
Results: While all ring types significantly reduced mitral annular S-L and C-C dimensions, none of the rings altered the S-L or C-C dimensions of the LV (Fig, B).
Conclusions: Disease specific FMR/IMR annuloplasty rings do not affect LV dimensions in the acutely ischemic ovine heart. Other treatment strategies may be needed to reshape the ventricle in patients with LV dilatation.