Indirect Annuloplasty to Treat Functional Mitral Regurgitation: Current Results and Future Perspectives

Abstract

The incidence of mitral regurgitation (MR) is approximately 1.7% in the developed world, and this increases to more than 10% in patients aged over 75 years. Functional (or secondary) mitral regurgitation (FMR) is defined as poor leaflet coaptation and tethering secondary to either ischemic or non-ischemic left ventricular (LV) dysfunction and dilatation. FMR is more common than degenerative (or primary) MR and is associated with significantly worse outcomes in patients with heart failure, post myocardial infarction and following coronary artery bypass graft surgery. Patients with severe degenerative MR have excellent outcomes with surgical repair, however the benefits of surgery in FMR are less clear. Although annuloplasty is associated with a lower operative mortality compared to replacement, the recurrence rate of mitral regurgitation is high in patients with FMR and neither surgical repair or replacement have been shown to reduce hospitalisation or death in FMR. Furthermore, nearly half of patients are deemed too high risk for surgery and therefore most patients are managed conservatively and there remains an unmet clinical need. Transcatheter mitral valve interventions are an emerging alternative for those at high surgical risk. This mini review focuses on indirect mitral annuloplasty: anatomical considerations, patient selection, current devices, implantation techniques and the associated clinical outcome data.

Keywords: annuloplasty; functional mitral regurgitation; indirect annuloplasty; mitral regurgitation; transcatheter.

Figure 1

(A) Anatomical relationships of the mitral valve, demonstrating the close proximity of the mitral annulus, coronary sinus, circumflex artery and conduction system. Adapted and reprinted from Carpentier's Reconstructive Valve Surgery with permission from Elsevier. (B) Fluoroscopic image of MitraClip implantation as a second procedure, following a previous ARTO device; fluoroscopic landmarks for this are the Atrial Septal Defect (ASD) occluder device and the T-Bar. (C) The Carillon coronary sinus implant (Cardiac Dimensions) device. Adapted and reprinted from Eurointervention, Natarajan et al, The big parade: emerging percutaneous mitral and tricuspid valve devices, 2017, with permission from Europa Digital & Publishing. (D) Graphical image of the ARTO (MVRx Inc) device following deployment, with two anchors either side of the tether. In this image projection, the T-bar anchor sits inferiorly and the atrial septal anchor (occluder device) sits superiorly. Adapted and reprinted from Eurointervention, Natarajan et al, The big parade: emerging percutaneous mitral and tricuspid valve devices, 2017, with permission from Europa Digital & Publishing. (E) Graphical image demonstrating the anatomical course of cerclage annuloplasty to reduce mitral annular dimensions. Adapted and reprinted from Mitral Loop Cerclage Annuloplasty for Secondary Mitral Regurgitation, Park et al with permission from Elsevier.

Figure 2

(A) 3-Dimensional transesophageal echocardiographic (TEE) real-time reconstruction of the mitral valve annulus and leaflets as a preliminary investigation to determine anatomical suitability for transcatheter mitral intervention. (B) CT overlay with real-time image fusion to demonstrate the optimal site for trans-septal puncture for ARTO case. Yellow line delineates inter-atrial septum, left atrium is superimposed in red. (C) CT overlay with real-time image fusion during magnet positioning during ARTO case (D) real-time image fusion demonstrating T-bar and atrial septal defect (ASD) occluder device device positioning relative to mitral annulus (orange circle) and inter-atrial septal markers (yellow circle), respectively. (E) CT overlay with real-time image fusion during transeptal puncture for transcatheter mitral valve implantation in mitral annular calcification identifying interatrial septum (orange circle), atrial anatomy (red) and mitral annular calcification (blue), aortic bioprothesis is also delineated (green). (F) CT overlay with real-time image fusion to facilitate transcatheter mitral valve in MAC positioning, atrial anatomy (red) and mitral annular calcification (blue) are visualized in addition to the superior (green) and inferior markers (orange).