Surgical treatment of functional ischemic mitral regurgitation.

In many ways we are at a crossroad in terms of what constitutes optimal FIMR treatment: is CABG combined with mitral valve ring annuloplasty better than CABG alone in moderate FIMR? Is mitral valve repair really better than replacement? And does adding a valvular repair or subvalvular reverse remodeling procedure shift that balance? In the present thesis I aim to shed further light on these questions by addressing the current status and future perspectives of the surgical treatment of FIMR. CURRENT SURGICAL TREATMENT FOR FIMR. CABG alone: The overall impression from the literature is that patients are left with a high grade of persistent/recurrent FIMR from isolated CABG. CABG is most effective to treat FIMR in patients with viable myocardium (at least five viable segments) and absence of dyssynchrony between papillary muscles (< 60 ms). Mitral valve ring annuloplasty. A vast number of different designs are available to perform mitral valve ring annuloplasty with variations over the theme of complete/partial and rigid/semi-rigid/flexible. Also, the three-dimensional shape of the rigid and semi-rigid rings is the subject of great variation. A rigid or semi-rigid down-sized mitral valve ring annuloplasty is the most advocated treatment in chronic FIMR grade 2+ or higher. Combined CABG and mitral valve ring annuloplasty: CABG combined with mitral valve ring annuloplasty leads to reverse LV remodeling and reduced volumes. Despite this, the recurrence rate after combined CABG and mitral valve ring annuloplasty is 20-30% at 2-4 years follow-up. This is also true for studies strictly using down-sized mitral valve ring annuloplasty by two sizes. A number of preoperative risk factors to develop recurrent FIMR were identified, e.g. LVEDD > 65-70 mm, coaptation depth > 10 mm, anterior leaflet angle > 27-39.5°, posterior leaflet angle > 45° and interpapillary muscle distance > 20 mm. CABG alone vs. combined CABG and mitral valve ring annuloplasty: The current available literature, including three randomized studies and a meta analysis, indicate that combined CABG and mitral valve ring annuloplasty has no late survival difference compared with CABG alone, and early mortality might even be higher. Meanwhile, adding a mitral valve ring annuloplasty results in a lower NYHA functional class, most likely as a consequence of a lower incidence of persistent or recurrent FIMR. More randomized studies are being conducted to further address this topic. Mitral valve ring annuloplasty vs. mitral valve replacement. The early survival may be higher after repair compared with replacement, meanwhile, the literature is more ambiguous in terms of late survival advantages, and recent reports find no late survival advantage from repair over replacement. The recurrence rates after ring annuloplasty addressed above were also present in this subset of patients, whereas the incidence of recurrent FIMR after valve replacement is scarcely reported. There was an overall tendency of slightly higher incidence of reoperations after ring annuloplasty. The mitral valve annulus: Innovations in mitral valve ring annuloplasty: The latest innovation in mitral valve ring annuloplasty design includes adjustable rings, allowing adjustment of septo-lateral dimensions intra- or postoperatively. Minimally invasive ring annuloplasty using indirect coronary sinus devices, has been introduced, but so far have produced suboptimal results in terms of safety and efficacy. Also, first in man testing of direct percutaneous catheter based mitral annuloplasty techniques have been conducted. Leaflets and chordae: Direct repair techniques: Surgical methods have been developed to directly address the mitral valve leaflets and chordae tendineae to correct leaflet tethering in FIMR. Both the Alfieri stich and the minimally invasive MitraClip attaches the anterior and posterior leaflets, typically the A2-P2 region, to correct incomplete leaflet coaptation. Patch augmentation of the posterior leaflet in the P2-P3 region increases coaptation in the area most prone to cause FIMR. Chordal cutting of the secondary "strut" chordae releases the anterior leaflet from the tethering due to papillary muscle displacement and improves mitral valve geometry. The mitral subvalvular apparatus: Numerous subvalvular approaches to improve outcome in patients with FIMR have been introduced. They include very invasive techniques such as surgical ventricular restoration procedure, surgical techniques directly addressing the papillary muscle dis-placement, and beating heart procedures using transventricular and epicardial devices applied in a few minutes. The role of the transventricular and epicardial devices still remains to be defined and many of these devices seem to have a hard time ganing their footing in the clinical practise and until now only constitute a footnote in the surgical literature. Meanwhile, the current results with adjunct techniques to CABG and ring annuloplasty, such as the papillary muscle approximation technique introduced by Hvass et al and the papillary muscle relocation technique introduced by Kron et al and further developed by Langer et al are gaining continuing support in the surgical community since these techniques can be used with only little added time consumption but with very good clinical outcome.