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Newsletter
Mitral Valve Regurgitation: Replace?, Repair?, Revascularize?Mark A. Chaney, MD
Recent data suggest that mitral regurgitation has substantial negative outcome implications that are dependent on the degree of regurgitation, both for mitral regurgitation due to organic disease of the mitral valve and mitral regurgitation due to ischemic heart disease. Surgical correction of mitral valve regurgitation has become a very sophisticated procedure that truly affects outcome. Traditionally, information obtained from intraoperative transesophageal echocardiography has guided the surgeon toward appropriate management (repair or replace). It is now very clear that mitral valve repair is superior to mitral valve replacement in terms of survival, preservation of left ventricular function, avoidance of long-term anticoagulation, and greater freedom from reoperation. Thus, our role in the operating room (providing echocardiographic information regarding viability of mitral valve repair) is an important one. With the recent emergence of ischemic mitral regurgitation, our skills regarding intraoperative transesophageal echo become even more important because of the expanded possibilities regarding surgical correction of mitral valve regurgitation. Only a few years ago, the choices were repair or replacement. Now, the choices include valve replacement, valve repair, revascularization alone (for ischemic mitral regurgitation), or a combination of therapies. The mitral valve apparatus is a complex structure consisting of the anterior and posterior leaflets, chordae tendinae, anterolateral and posteromedial papillary muscles, the annulus, and the left ventricular wall. All of these structures are essential for proper function of the mitral valve and play an important role in left ventricular performance. Normal function of the mitral valve depends on the integrated function of all its components. Failure of any component may initiate mitral regurgitation. Thus, there are many causes (and classifications) of mitral regurgitation. Mitral regurgitation may be observed with normal leaflet motion, excessive leaflet motion, or restricted leaflet motion. Potential causes of mitral regurgitation include myxomatous degeneration (a biochemical defect involving connective tissue), mitral valve prolapse, rheumatic heart disease, chordae tendinae rupture, and papillary muscle dysfunction, among others. Ischemic mitral regurgitation is a complex phenomenon that is likely caused by ischemic alterations in the annulus and left ventricle. Structural pathology is oftentimes not present. Ischemic mitral regurgitation is certainly important because it is commonly observed and appears to affect clinical outcome. However, at the present time, there is no consensus regarding treatment (revascularization?, valve repair?, ventricular reconstruction?) because underlying mechanisms remain poorly understood. When encountered with mitral regurgitation, the goals of the echocardiographer are to identify structural abnormalities, propose a mechanism of mitral regurgitation, and assess mitral regurgitation severity. Mitral regurgitation severity may be assessed via spatial area mapping, evaluation of the pulmonary venous velocity profile, calculation of regurgitant volume/fraction/orifice area, and/or measurement of the proximal jet diameter. It is impossible to formulate rigid guidelines regarding surgical intervention for mitral regurgitation. A thorough appraisal of the advantages and disadvantages of surgical versus medical treatment of mitral regurgitation must be assessed in each individual patient. However, most feel that surgical intervention is indicated when severe mitral regurgitation is present and mitral valve repair is preferable to mitral valve replacement. Also, treatment of moderate mitral regurgitation with revascularization alone appears to be associated with decreased early mortality (yet improvement of mitral regurgitation is infrequent) and treatment of moderate mitral regurgitation with revascularization and mitral valve repair appears to be associated with better long-term survival. Causes of mitral regurgitation most amenable to repair include posterior leaflet dysfunction, pure annular dilatation, bileaflet prolapse, and ruptured chordae tendinae. The highest rates of successful repair appear to be associated with myxomatous disease of the posterior leaflet (flail or prolapsing segment). Causes of mitral regurgitation least amenable to repair include severe/diffuse chordal elongation, severe leaflet billowing, severe calcification, and active infection. While therapeutic approaches for both medical and surgical treatment of mitral regurgitation have not been evaluated by randomized clinical trials, certain conclusions from the currently available literature exist. If possible, mitral valve repair is always preferable to mitral valve replacement. Whenever possible, the native mitral valve should be preserved. Ischemic mitral regurgitation remains a work in progress (much remains a mystery surrounding this phenomenon) and appropriate correction technique (repair?, revascularize?, ventricular reconstruction?, combination of therapies?) must be determined on an individual basis. It is imperative that we, as echocardiographers, present cardiac surgeons with enough quality information in order to embark on the proper course that benefits the individual patient the most. Thourani VH, Weintraub WS, Guyton RA, et al. Outcomes and long-term survival for patients undergoing mitral valve repair versus replacement; Effect of age and concomitant coronary artery bypass grafting. Circulation 108:298-304, 2003. Enriquez-Sarano M, Schaff HV, Frye RL. Mitral regurgitation: What causes the leakage is fundamental to the outcome of valve repair (Editorial). Circulation 108:253-256, 2003. Mickleborough LL. Is mitral valvuloplasty always indicated in patients with poor left ventricular function and ischemic cardiomyopathy? (Editorial). J Thorac Cardiovasc Surg 125:S57, 2003. Miller DC. Ischemic mitral regurgitation redux - To repair or to replace? (Editorial). J Thorac Cardiovasc Surg 125:S58-S61, 2003. Gillinov AM, Faber C, Houghtaling PL, et al. Repair versus replacement for degenerative mitral valve disease with coexisting ischemic heart disease. J Thorac Cardiovasc Surg 125:1350-1362, 2003. Adams DH, Filsoufi F. Another chapter in an enlarging book: Repair degenerative mitral valves (Editorial). J Thorac Cardiovasc Surg 125:1197-1199, 2003. Table of Contents:
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