Quantitative determinants of the outcome of asymptomatic mitral regurgitation

BACKGROUND: The clinical outcome of asymptomatic mitral regurgitation is poorly defined, and the treatment is uncertain. We studied the effect on the outcome of quantifying mitral regurgitation according to recent guidelines. METHODS: We prospectively enrolled 456 patients (mean [±SD] age, 63±14 years; 63 percent men; ejection fraction, 70±8 percent) with asymptomatic organic mitral regurgitation, quantified according to current recommendations (regurgitant volume, 66±40 ml per beat; effective regurgitant orifice, 40±27 mm²). RESULTS: The estimated five-year rates (±SE) of death from any cause, death from cardiac causes, and cardiac events (death from cardiac causes, heart failure, or new atrial fibrillation) with medical management were 22±3 percent, 14±3 percent, and 33±3 percent, respectively. Independent determinants of survival were increasing age, the presence of diabetes, and increasing effective regurgitant orifice (adjusted risk ratio per 10-mm² increment, 1.18; 95 percent confidence interval, 1.06 to 1.30; P<0.01), the predictive power of which superseded all other qualitative and quantitative measures of regurgitation. Patients with an effective regurgitant orifice of at least 40 mm² had a five-year survival rate that was lower than expected on the basis of U.S. Census data (58±9 percent vs. 78 percent, P=0.03). As compared with patients with a regurgitant orifice of less than 20 mm ², those with an orifice of at least 40 mm² had an increased risk of death from any cause (adjusted risk ratio, 2.90; 95 percent confidence interval, 1.33 to 6.32; P<0.01), death from cardiac causes (adjusted risk ratio, 5.21; 95 percent confidence interval, 1.98 to 14.40; P<0.01), and cardiac events (adjusted risk ratio, 5.66; 95 percent confidence interval, 3.07 to 10.56; P<0.01). Cardiac surgery was ultimately performed in 232 patients and was independently associated with improved survival (adjusted risk ratio, 0.28; 95 percent confidence interval, 0.14 to 0.55; P<0.01). CONCLUSIONS: Quantitative grading of mitral regurgitation is a powerful predictor of the clinical outcome of asymptomatic mitral regurgitation. Patients with an effective regurgitant orifice of at least 40 mm² should promptly be considered for cardiac surgery.