Surgical Decisions in Mitral Regurgitation
ABSTRACT & COMMENTARY
Synopsis: Patients with severe mitral regurgitation and class III/IV symptoms have higher mortality independent of other baseline characteristics.
Source: Tribouilloy CM, et al. Circulation 1999; 99:400-405.
Despite compelling evidence that surgery should be considered in asymptomatic patients with severe mitral regurgitation who meet certain clinical criteria (i.e., left ventricular ejection fraction < 60%), clinicians find this a tough sell. Thus, Tribouilloy and associates from the Mayo Clinic evaluated 478 consecutive patients who underwent operations for severe mitral regurgitation between 1984 and 1991. Patients with associated mitral stenosis and those with mitral regurgitation due to ischemic or cardiomyopathic disease were excluded. Patients with concomitant coronary disease were not excluded. Of the 478 patients, 379 had mitral valve prolapse, 39 had rheumatic disease, 39 had endocarditis, and 21 had miscellaneous symptoms. The New York Heart Association functional class was I/II in 199 and III/IV in 279 prior to surgery. Valve replacement was performed in 155 patients, repair in 323, and concomitant coronary bypass in 130 (27%). Post-operative long-term survival was higher at 10 years in class I/II vs. the III/IV patients (76% vs 48%; P < 0.001); part of this difference was due to a lower perioperative mortality (0.5% vs 5.4%; P < 0.003). Compared to age- and sex-matched actuarial data, class I/II patients had a survival rate equal to expected, whereas class III/IV had a survival rate only 74% of expected. Other predictors of survival in the multivariate model were age, atrial fibrillation, valve repair, ejection fraction, and coronary artery disease. However, the survival difference between functional classes persisted in all these subgroups. Tribouilloy et al conclude that patients with severe mitral regurgitation and class III/IV symptoms have excess mortality independent of other baseline characteristics. Thus, surgery should be considered before this level of symptoms develops.
Comment by Michael H. Crawford, MD
Since a randomized clinical trial of class I/II patients with severe mitral regurgitation (randomized to surgery or medical follow-up) will never be done, this type of observational study will be our best effort to answer the question of who to send to surgery. Also, since there is no known effective medical therapy, surgery is our only option; but surgery includes repair, which, in the appropriate candidates, can be done with little or no excess mortality. Unfortunately, only about 80% of patients referred for repair actually get it; the others get prosthetic valves, which, in the mitral position, usually require anticoagulation. Previous studies have shown that preoperative ejection fraction, coronary artery disease, atrial fibrillation, large left atrium, pulmonary hypertension, and left ventricular end-systolic volume are predictive of postoperative outcome. Thus, the clinical decisions in this study were done with this knowledge. However, previous trials have not carefully evaluated the role of symptoms in decision-making, which makes this study valuable.
The message of this study is that in the current milieu, symptom status is the strongest independent predictor of postoperative survival. To say that it is stronger than other characteristics of the patients assumes that all factors were distributed equally and did not affect the clinician’s decisions. We know this is not the case since knowledge of previous trial results was present and there were baseline differences between the two symptom class groups in age, atrial fibrillation, and the number repaired vs. replaced. Also, it is assumed that symptom history was not a major factor in the decision for surgery. This is more tenable since there are few prior data to support its role; yet, it is hard to ignore symptom status and, consequently, it may have influenced decision-making. Despite these limitations, it appears that surgery should be considered in severe mitral regurgitation in class I/II patients.
The recently published ACC/AHA guidelines (J Am Coll Cardiol 1998;32:1486-1588) address this issue and consider all symptomatic patients (NYHA Class II-IV) with severe mitral regurgitation Class I surgical candidates. Asymptomatic patients (NYHA Class I) are only considered Class II surgical candidates (data less firm) if they have atrial fibrillation, pulmonary hypertension, left ventricular dysfunction (EF < 60%), or in whom repair is highly likely. It is not possible for these guidelines to have influenced decisions in this trial, but the data they were based upon could have. The only real difference is the more firm recommendation for surgery in the asymptomatic (Class I) patient based upon the Mayo experience. When they separated the Class I and II patients, Class I patients had a slightly higher survival than Class II patients, but the difference did not reach statistical significance. Part of this may be the difficulty in distinguishing Class I from II status in patients with a chronic illness.
One factor that helps propel the notion of operating in Class I/II patients is the low operative mortality in this study—0.6% for repair, 0% if younger than age 75, and 0% if no bypass surgery. If the patient was older than age 75 or had class III/IV symptoms increased their operative mortality to 2.5-3.6%. Also, repair, which was accomplished in 84% of those operated since 1988, is associated with a 25% increase in 10-year survival vs. replacement. Thus, many patients have benefited from improved surgical techniques.
Tribouilloy et al suggest that surgery should be strongly recommended in symptom class I/II patients with mitral regurgitation if: 1) severe mitral regurgitation is well documented; 2) the mitral regurgitation is not due to ischemia or cardiomyopathy; 3) the likelihood of valve repair is high; and 4) the operative risk is low. If these criteria are not met, other factors, such as left ventricular function, pulmonary pressure, etc., should be taken into consideration per the ACC/AHA guidelines.
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