Septal-lateral annular cinching ('SLAC') reduces mitral annular size without perturbing normal annular dynamics

Background and aim of the study: Septal-lateral (S-L) mitral annular diameter reduction is thought to be central to the efficacy of ring annuloplasty in correcting functional mitral regurgitation (MR), but rings perturb mitral annulus (MA) dynamic motion and limit posterior leaflet excursion. The effects of S-L annular cinching ('SLAC'), a novel method for mitral annular reduction, were investigated. Methods: Eight adult sheep had multiple radio-opaque markers placed on the left ventricle, leaflet edges, and around the MA. The S-L trans-annular suture was anchored to the mid-septal MA and externalized through the mid-lateral MA and left ventricular wall. Animals were studied immediately postoperatively with biplane videofluoroscopy before and after suture cinching to reduce annular size. MA area (MAA) and S-L dimension were calculated throughout the cardiac cycle from the annular marker coordinates. MAA contraction (ΔMAA) was expressed as percentage decrease from maximum to minimum MAA. Anterior (AML) and posterior (PML) leaflet angular excursion were calculated as the change in angle between each leaflet edge marker and the S-L annular dimension during the cardiac cycle. MA folding was calculated as the change in distance during systole of the mid-septal annular marker from a plane fitted to the lateral MA markers. Results: SLAC reduced end-diastolic (ED) S-L diameter (21.6 ± 2.8 versus 17.1 ± 2.6 mm; p = 0.0005) and ED MAA (618 ± 126 versus 525 ± 114 mm²; p = 0.0004), but did not perturb normal ΔMAA (15.8 ± 4.1 versus 15.1 ± 4.8%; p = 0.4), annular flexion (2.0 ± 0.7 versus 1.8 ± 0.7 mm, p = 0.3) or AML excursion (55 ± 7 versus 53 ± 7°; p = 0.1). PML excursion was decreased only slightly (52 ± 11 versus 44 ± 12°; p = 0.002). Conclusion: SLAC substantially reduced S-L annular size, but without perturbing normal MA contraction dynamics, MA flexion, or anterior leaflet excursion. This novel surgical method might represent an alternative to mitral annuloplasty for patients with certain types of mitral pathology.