Effects of paracommissural septal-lateral annular cinching on acute ischemic mitral regurgitation

Background-Previous experimental studies demonstrated that central septal-lateral (SL) annular cinching (SLAC) abolishes acute ischemic mitral regurgitation (IMR), but whether localized cinching near the anterior (ACOM) or posterior (PCOM) commissure is equally effective is unknown. Methods-Six adult sheep underwent implantation of 9 radiopaque markers on the left ventricle, 8 around the mitral annulus (MA) and 1 on each papillary muscle (PM) tip. Transannular SL sutures were placed at the valve center (CENT) and near ACOM and PCOM and externalized. Acute IMR was induced by proximal circumflex coronary snare occlusion. Biplane videofluoroscopy and transesophageal echocardiography were performed before and continuously during 3 episodes of myocardial ischemia including 20 seconds of SLAC at each different location. End-systolic MA SL dimension at each suture location and distances between the anterior and posterior PM tips and mid-septal annulus ("saddle horn") were calculated from the 3-dimensional (3D) marker coordinates. Results-SLAC interventions in all 3 locations reduced the degree of IMR, but cinching at the center, SLAC_CENT, had a significantly greater effect on reducing the magnitude of IMR than SLAC_PCOM or SLAC_ACOM (mean grade of IMR reduction=1.0±0.5, 1.8±0.5, and 0.9±0.2 for SLAC _ACOM, SLAC_CENT, and SLAC_PCOM, respectively; P=0.044). Although ACOM and PCOM cinching reduced SL_CENT somewhat, only SLAC_CENT simultaneously reduced both SL_ACOM and SL_PCOM and also repositioned both PM tips closer to the annular saddle horn. Conclusions-SLAC in all 3 positions reduced acute IMR, but central SLAC cinching was most effective, reduced all mitral annular SL dimensions, and relocated both PM tips closer to the mid-septal annulus. Central SLAC is most capable of correcting the annular and subvalvular perturbations accompanying acute left ventricular ischemia that lead to IMR.