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b. Indications for Mitral Valve Operation Class I 1. MV surgery is recommended for the symptomatic patient with acute severe MR.* (Level of Evidence: B) 2. MV surgery is beneficial for patients with chronic severe MR* and NYHA functional class II, III, or IV symptoms in the absence of severe LV dysfunction (severe LV dysfunction is defined as ejection fraction less than 0.30) and/or end-systolic dimension greater than 55 mm. (Level of Evidence: B) 3. MV surgery is beneficial for asymptomatic patients with chronic severe MR* and mild to moderate LV dysfunction, ejection fraction 0.30 to 0.60, and/or end-systolic dimension greater than or equal to 40 mm. (Level of Evidence: B) 4. MV repair is recommended over MV replacement in the majority of patients with severe chronic MR* who require surgery, and patients should be referred to surgical centers experienced in MV repair. (Level of Evidence: C) Class IIa 1. MV repair is reasonable in experienced surgical centers for asymptomatic patients with chronic severe MR* with preserved LV function (ejection fraction greater than 0.60 and end-systolic dimension less than 40 mm) in whom the likelihood of successful repair without residual MR is greater than 90%. (Level of Evidence: B) 2. MV surgery is reasonable for asymptomatic patients with chronic severe MR,* preserved LV function, and new onset of atrial fibrillation. (Level of Evidence: C) 3. MV surgery is reasonable for asymptomatic patients with chronic severe MR,* preserved LV function, and pulmonary hypertension (pulmonary artery systolic pressure greater than 50 mm Hg at rest or greater than 60 mm Hg with exercise). (Level of Evidence: C) 4. MV surgery is reasonable for patients with chronic severe MR* due to a primary abnormality of the mitral apparatus and NYHA functional class III–IV symptoms and severe LV dysfunction (ejection fraction less than 0.30 and/or end-systolic dimension greater than 55 mm) in whom MV repair is highly likely. (Level of Evidence: C) Class IIb MV repair may be considered for patients with chronic severe secondary MR* due to severe LV dysfunction (ejection fraction less than 0.30) who have persistent NYHA functional class III–IV symptoms despite optimal therapy for heart failure, including biventricular pacing. (Level of Evidence: C) Class III 1. MV surgery is not indicated for asymptomatic patients with MR and preserved LV function (ejection fraction greater than 0.60 and end-systolic dimension less than 40 mm) in whom significant doubt about the feasibility of repair exists. (Level of Evidence: C) 2. Isolated MV surgery is not indicated for patients with mild or moderate MR. (Level of Evidence: C) *See Table 1 (7). The prediction of successful MV repair is important in timing surgery. This prediction is based on the skill and experience of the surgeon in performing repair, on the cause of the MR, and on MV morphology. The skill and experience of the surgeon are probably the most important determinants of the eventual success of MV repair. The number of patients undergoing MV repair for MR has increased steadily over the past decade in the United States and Canada in relation to the number undergoing MV replacement. However, among isolated MV procedures reported in the STS National Cardiac Database from 1999 to 2000 (359), the frequency of repair was only 35.7% (3027 of a total of 8486 procedures), which suggests that MV repair is underutilized. Current data indicate that the frequency of MV repair is increasing yearly (93). The STS national database also indicates an operative mortality rate of less than 2% in patients undergoing isolated MV repair in 2004, which compares favorably to the more than 6% operative mortality rate for patients undergoing isolated MV replacement (93). In light of the beneficial effect of MV repair on survival and LV function, cardiologists are strongly encouraged to refer patients who are candidates for MV repair to surgical centers experienced in performing MV repair. Symptomatic Patients With Normal Left Ventricular Function Patients with symptoms of congestive heart failure despite normal LV systolic function (ejection fraction greater than 0.60 and end-systolic dimension less than 40 mm) require surgery. Surgery should be performed in patients with even mild symptoms and severe MR (Fig. 7), especially if it appears that MV repair rather than replacement can be performed. Asymptomatic and Symptomatic Patients with Left Ventricular Dysfunction The timing of surgery for asymptomatic patients is controversial, but most would now agree that MV surgery is indicated with the appearance of echocardiographic indicators of LV dysfunction. These include LV ejection fraction less than or equal to 0.60 and/or LV end-systolic dimension greater than or equal to 40 mm (Fig. 7). MV surgery should also be recommended for symptomatic patients with evidence of LV systolic dysfunction (ejection fraction less than or equal to 0.60 and/or end-systolic dimension greater than or equal to 40 mm). Determining the surgical candidacy of the symptomatic patient with MR and far-advanced LV dysfunction is a common clinical dilemma. The question that often arises is whether the patient with MR with advanced LV dysfunction is no longer a candidate for surgery. Although it is difficult, one must distinguish primary cardiomyopathy with secondary “functional” MR from primary MR with secondary myocardial dysfunction. In the latter case, surgery should still be contemplated if MV repair appears likely (Fig. 7). In patients with severe LV dysfunction and significant functional MR, the modification of MV geometry by an “undersized” annular ring may be beneficial (360–365), although the impact on outcomes compared with aggressive medical therapy, including beta blockers and cardiac resynchronization therapy (338–341), has not been studied in a prospective randomized trial. Asymptomatic Patients With Normal Left Ventricular Function As noted previously, repair of a severely regurgitant valve may be contemplated in an asymptomatic patient with severe MR and normal LV function to preserve LV size and function and prevent the sequelae of chronic severe MR (324). Although there are no randomized data with which to recommend this approach to all patients, the committee recognizes that some experienced centers are moving in this direction for patients for whom the likelihood of successful repair is high. Natural history studies indicate uniformly that asymptomatic patients with severe MR and normal LV function have a high likelihood of developing symptoms and/or LV dysfunction that warrants surgery over the course of 6 to 10 years (313,317,324,325). Two recent studies have also addressed the risk of sudden death in asymptomatic patients with severe MR and normal LV function (324,325). In a long-term retrospective study in which severity ofMRwas quantified by Doppler echocardiography (324), 198 patients with an effective orifice area greater than 40 mm2 had a 4% per year risk of cardiac death during a mean follow-up period of 2.7 years. However, in the second study of 132 patients followed up prospectively for 5 years, during which the indications for surgery were symptoms, development of LV dysfunction (ejection fraction less than 0.60), LV dilatation (LV end-systolic dimension greater than 45 mm), atrial fibrillation, or pulmonary hypertension, there was only 1 cardiac death in an asymptomatic patient, but this patient had refused surgery which was indicated by development of LV dilatation (325). MV repair is often recommended in hemodynamically stable patients with newly acquired severe MR, such as might occur with ruptured chordae. Surgery is also recommended in asymptomatic patients with chronic MR with recent onset of atrial fibrillation in whom there is a high likelihood of successful valve repair (see below). Surgery for asymptomatic patients with severe MR and normal LV function should only be considered if there is a greater than 90% likelihood of successful valve repair in a center experienced in this procedure. As noted above, cardiologists are strongly encouraged to refer patients who are candidates for MV repair to surgical centers experienced in performing MV repair. Atrial Fibrillation The development of atrial fibrillation is independently associated with a high risk of cardiac death or heart failure (366), and preoperative atrial fibrillation is an independent predictor of reduced long-term survival after MV surgery for chronic MR (333,366–368). Hence, many clinicians consider the recent onset of atrial fibrillation to be an indication in and of itself for surgery, if there is a high likelihood of valve repair (Fig. 7) (356,369). In patients presenting for MV operation with chronic atrial fibrillation, a concomitant Maze procedure may prevent future thromboembolic events by restoring normal sinus rhythm (370–376). The decision to proceed with a Maze procedure should be based on the age and health of the patient, as well as the surgical expertise, because this procedure may add to the morbidity of the operation.