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In the Western World, most surgery on the mitral valve nowadays is performed for insufficiency secondary to degenerative disease, rather than for the rheumatic lesions seen so widely in the past.
The advantages of mitral valve repair over prosthetic replacement for degenerative mitral insufficiency are well established, including lower early and late mortality rates, superior preservation of left ventricular function, and greater freedom from thromboembolism, anticoagulant-related complications, and endocarditis.
It has been acknowledged that, in dedicated centers, mitral valve repair for these lesions is feasible in about 95% of cases.1 In the United States, a recent survey performed by the Society of Thoracic Surgeons shows that the rate of valve repair versus replacement has gradually increased over decades, and now approximates 70%.2
Two technical advances—in surgery and in echocardiography—have enabled marked improvement in the conservative treatment of the more complex degenerative lesions of the mitral valve.
Surgical. Although the implantation of an annuloplasty ring has remained an integral part of the reconstructive procedures of the mitral valve, the most important surgical innovation has been the introduction of expanded polytetrafluoroethylene (PTFE) sutures (GORE-TEX® sutures, W.L. Gore & Associates, Inc.; Flagstaff, Ariz) for replacement of the native chordae tendineae,3 which has supplanted earlier techniques, such as chordal shortening, chordal transposition, and extensive leaflet resections.
Echocardiographic. On the cardiologic side, echocardiographic examination has gained fundamental importance. Advances in echocardiographic techniques have allowed us to better understand the tridimensional geometry and functional mechanism of the mitral valve complex, and they have enabled us to recognize 4 landmark characteristics: the coaptation point, the coaptation length, the coaptation depth, and the triangle of coaptation (Fig. 1). Further, they have enabled us to identify specific abnormalities in these characteristics that are caused by such pathologic conditions as elongated chordae, mitral prolapse (Fig. 2), marginal prolapse (Fig. 3), and Barlow syndrome.
Putting the Two Together. On the basis of this echocardiographic information, we endeavor to achieve a competent and durable single-orifice native valve by restoring the geometric and functional characteristics of the mitral valve complex: that is, we reconstruct the triangle of coaptation in such a manner as to attain appropriate coaptation length (at least 6 mm) and coaptation depth and to position the coaptation point well within the left ventricle.
How We Do It. Surgically, the correction is performed by anchoring a series of double-ended 4/5-0 pericardium-pledgeted PTFE mattress sutures to the tip of the papillary muscle and by suturing them onto the unsupported portions of the valvular leaflets. The leaflets are maintained at the correct level of the left ventricular cavity by artificial chordae—the lengths of which have been determined by echocardiographic measurement. This precision ensures a symmetrical closure line.
At the end of the procedure, after discontinuation of cardiopulmonary bypass, we perform a transesophageal echocardiographic examination on the beating heart in order to check for residual mitral regurgitation and to evaluate the reconstruction of the triangle of coaptation, the positioning of the coaptation point within the left ventricular cavity, and the coaptation length and depth. Failure to accomplish success in each of these aspects is an indication of potential late failure, so we revise the repair in such cases.
Traditionally, posterior mitral leaflet insufficiency hasbeen corrected by quadrangular resection, with or without a sliding plasty. Because quadrangular posterior mitral leaflet resection alters the anatomy and reduces leaflet mobility and coaptation surface area, during the last 2 years we have regularly performed posterior leaflet repair with artificial chordae only, and we have avoided quadrangular resection.4 We have dealt with excessive residual tissue by means of limited triangular resection. These particular techniques, overall, have resulted in improved physiologic valvular function, satisfactory posterior leaflet mobility, and excellent leaflet coaptation.
Conclusion. On the basis of our 12 years' operative experience in 1,167 patients whose mitral insufficiency was corrected in 98% of the cases (with a hospital mortality rate of 0.9% and a recurrence rate of 1.8% at a mean follow-up of 5.6 years [range, 4 mo–12 yr]), we believe that mitral valve repair for degenerative disease can achieve a competent and durable single-orifice native valve in over 95% of cases, with low mortality and morbidity rates and stable late results. Avoiding quadrangular resection of the posterior leaflet and then correcting with PTFE chordae (with appropriate adjustments) increases the mobility of the posterior leaflet and improves coaptation. The “edge-to-edge” stitch might be indicated as a 2nd-choice technique in a minority of compromised patients who require time-consuming concomitant procedures. Prosthetic valve replacement is seldom necessary and should be reserved for patients who present with extreme alterations of the entire mitral apparatus.
Address for reprints: Ugo F. Tesler, MD, Clinica San Gaudenzio, Via Bottini 3, 28100 Novara, Italy E-mail: firstname.lastname@example.org
Presented at the 16th International Symposium of the Denton A. Cooley Cardiovascular Surgical Society, Galveston, Texas, 4–7 June 2009.