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Allan Schwartz, M.D.
The guidelines for surgical correction of mitral regurgitation (MR) are based on knowledge of the natural history of MR and predictors of short term and long term outcomes after correction. Ideally, the indications would be validated by prospective data gathered from well characterized patient populations undergoing serial clinical and echocardiographic assessment. In certain patient subgroups (e.g. asymptomatic patients with normal LV function) randomized trial data would seem a reasonable goal. Similarly the ideal for evaluating corrective treatments is prospective serial clinical and echocardiographic follow up in well defined patient subgroups. Competing strategies would be evaluated by randomized comparison. The data on which current guidelines for correction of MR are based fall short of these ideals but do provide a framework for evidence based decision making. The knowledge base for ischemic and functional MR is less adequate than that for degenerative MR.
Multivariate analysis from large single institution series have demonstrated superior short and long term survival and preservation of LV function with mitral valve repair versus replacement. Long term follow has shown reoperation rates of ~10% at 10 years and ~15% at 15 years. In asymptomatic patients undergoing surgical repair rates of recurrence of MR are also relevant to decision making. In a consecutive series of 242 patients undergoing MV repair by a single surgeon serial echocardiographic follow indicated a constant rate of recurrence of MR > 2/4 of 3.7% per year. Reoperation rates at 8 years was 6% and is comparable to other published series.
Current data is strongly supportive of surgery in symptomatic patients. This applies as well to patients with transient or mild symptoms of CHF. In asymptomatic patients LV function as estimated by LVEF and end systolic dimension (LVSD) are powerful predictors of post operative survival and LV function. LVEF <60% and LVSD > 45 mm are associated with decreased survival and postoperative LV dysfunction (LVEF < 50%) in ~ 30% of patients. Conversely patients with LVEF = 60 and LVSD < 45 have post operative survival not different from the general population.
Less is known about the impart of surgery on long term prevention of atrial fibrillation but limited data suggests that patients with recent onset atrial fibrillation are likely to be in NSR 5 years post operation versus 90% of patients with chronic atrial fibrillation remaining in atrial fibrillation 5 years after valve repair. The introduction of surgical procedures for atrial fibrillation as adjuncts to valve repair will likely improve results in chronic atrial fibrillation but long term data is lacking. Although not common, the presence of significant pulmonary artery hypertension or RV dysfunction in asymptomatic patients with LVEF >60 and no symptoms is thought to carry a poor prognosis and is considered a surgical indication.
The presence of flail mitral leaflet is associated with a high progression to symptoms with 2/3 of 163 class I or II patients progressing to MV surgery over 10 years. This single retrospective study is the basis for advising MV repair in patients with flail leaflets. More recently the severity of MR by quantitative echocardiographic measurement has been shown to predict onset of CHF and death. Surgically treated patients faired better than medically treated although this study was observational with no standardized follow up or standardized indications for surgery. On the basis of these and other studies some high volume, high surgical experience centers are advising repair on patients with severe MR with preserved systolic function, NSR, normal PA pressure and no symptoms.
The guidelines for operation on asymptomatic patients with severe MR have been prospectively evaluated in 132 patients. Surgery was performed if LVSD = 45, LVEF < 60, PA pressure > 50, new onset of atrial fibrillation or onset of symptoms. Over a mean follow up of 5 years only 32 patients developed surgical indications. There was only 1 sudden death and no operative mortality. Post operation LV function and symptomatic status were excellent. These results underscore the need for caution in advising surgical repair simply, based on the presence of severe MR and the need for more prospective and randomized trials.
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