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A. Marc Gillinov, M.D.
The Cleveland Clinic Foundation
Mitral Valve Repair versus Replacement
When feasible, mitral valve repair is the preferred surgical approach to the management of mitral valve disease. Advantages of mitral valve repair over mitral valve replacement include improved long-term survival, better preservation of left ventricular function, and greater freedoms from endocarditis, thromboembolism and anticoagulant-related hemorrhage. The feasibility of mitral valve repair relates primarily to the etiology and pathophysiology of mitral valve dysfunction. Degenerative and ischemic diseases are the most common causes of mitral regurgitation; successful repair is possible in more than 90% of patients with degenerative disease, but in only 70% to 80% of patients with ischemic mitral regurgitation. Other causes of mitral valve dysfunction include rheumatic, infectious, and congenital processes. Most reparable rheumatic valves are approached with percutaneous techniques. Infectious and congenital mitral valve dysfunction are encountered relatively infrequently, but are usually amenable to repair.
Repair Techniques
Degenerative Mitral Valve Disease
Degenerative mitral valve disease is characterized by leaflet prolapse caused by chordal elongation or rupture. Posterior leaflet prolapse is the usual finding, with ruptured or elongated chordae to the middle scallop of the posterior leaflet representing the most common scenario. Anterior and bileaflet prolapse are encountered somewhat less frequently. A variety of techniques to correct prolapse have been devised by Carpentier and others, and the technique employed depends upon the site of prolapse. All repairs for degenerative disease include an annuloplasty. The annuloplasty corrects annular dilatation, prevents future annular dilatation, increases leaflet coaptation, and reduces tension on suture lines.
Posterior leaflet prolapse is usually managed by quadrangular resection and annuloplasty. With this technique, the segment of posterior leaflet subserved by pathologic chordae is resected; the annulus is plicated and the leaflet edges sewn to one another. An annuloplasty completes the repair. If there is excess leaflet tissue creating a risk of systolic anterior motion (SAM) and left ventricular outflow tract obstruction, the quadrangular resection is modified and a sliding repair performed. The sliding repair incorporates both a quadrangular resection and maneuvers to decrease the height of the remaining posterior leaflet; the latter technique moves the point of coaptation posteriorly, reducing the risk of SAM. Posterior leaflet prolapse may also be managed by triangular resection or a folding leaflet plasty, both of which are variants of quadrangular resection. Occasionally the edge-to-edge technique (Alfieri repair) is employed for posterior leaflet prolapse (see below for description).
Management of anterior leaflet prolapse is more challenging than is correction of posterior leaflet prolapse. Techniques used to treat anterior leaflet prolapse include creation of artificial chordae, chordal transfer, chordal shortening, and the edge-to-edge repair; all repairs also include an annuloplasty. Artificial chordae are usually constructed of PTFE. PTFE chordae of appropriate length are affixed to the tip of a papillary muscle and to the free edge of unsupported anterior leaflet; this is a relatively simple technique for correction of prolapse. Alternatively, normal posterior leaflet chordae or secondary anterior leaflet chordae may be detached from their native position and attached to the unsupported anterior leaflet. Because normal native chordae are used, chordal transfer does not entail measurement or estimation of chordal length. In contrast, chordal shortening requires considerable judgement to establish appropriate chordal length; this technique, which relies upon shortening of pathologic chordae, is associated with limited durability. Finally, the edge-to-edge technique was developed by Alfieri to enable simple and rapid correction of leaflet prolapse. With this approach, the free edge of unsupported anterior leaflet is sutured to the opposing free edge of normal posterior leaflet. This prevents prolapse and creates a double orifice mitral valve. As with other repair techniques, the edge-to-edge repair is completed with an annuloplasty.
Repair of degenerative valves provides excellent, durable, long-term results. Hospital mortality at experienced centers is less than 1%. Freedom from reoperation for valve dysfunction exceeds 90% at 10 and 20 years. Risk factors for reoperation include anterior leaflet prolapse, use of chordal shortening, failure to use an annuloplasty, and failure to use intraoperative echocardiography to define the mechanism(s) of valve dysfunction and to assess results. Finally, with current techniques, more than 90% of isolated mitral valve repairs can be achieved using minimally invasive approaches.
Ischemic Mitral Regurgitation
Ischemic mitral regurgitation is mitral regurgitation that is caused by coronary artery disease. In most cases, this takes the form of functional ischemic mitral regurgitation. In the patient with functional ischemic mitral regurgitation, myocardial infarction has caused changes in ventricular and annular geometry that prevent leaflet coaptation. The leaflets are distracted toward the ventricle, or tethered, creating mitral regurgitation in the absence of gross pathology of the chordae or leaflets.
Surgical repair of functional ischemic mitral regurgitation generally consists of annuloplasty alone. The annuloplasty is undersized in order to optimize leaflet coaptation. The primary mechanism for restoring valve competence with an undersized annuloplasty is reduction of the septal-lateral diameter of the mitral valve. There is some controversy concerning the best type of prosthetic annuloplasty for this entity (band vs. complete ring, flexible vs. rigid material). Annuloplasty provides long-term reduction of mitral regurgitation in 70% to 80% of patients with functional ischemic mitral regurgitation; however, within the first year of surgery, 20% to 30% of patients develop recurrent mitral regurgitation. Risk factors for recurrent mitral regurgitation include excessive leaflet tenting and important annular dilatation. In patients with these features, it is possible that additional repair techniques that address ventricular geometry will improve results.
