BACKGROUND The temporal response of the left ventricle due to the relief of volume loading after mitral valve repair, and the prognostic value of early changes in left ventricular size and function, are not fully documented. The purpose of this study was to analyze the evolution of left ventricular performance after surgery, and to evaluate how early postoperative echocardiographic parameters compare with late ventricular function. METHODS We studied 58 patients with chronic degenerative mitral regurgitation using echocardiography, before, and 9 +/- 3 days and 38 +/- 6 months after mitral valve repair. RESULTS Between the preoperative and early postoperative study, left ventricular end-diastolic and left atrial size, and ejection fraction decreased, whereas left ventricular end-systolic dimension did not change. Between the early and late postoperative study left ventricular end-systolic size decreased significantly, there was a further decrease in left ventricular end-diastolic dimension and a significant increase in ejection fraction; left atrial size did not change. Multivariate analysis showed that preoperative and early postoperative ejection fraction, and the early postoperative reduction in diastolic dimension were the best predictors of late left ventricular function. CONCLUSIONS In patients with chronic degenerative mitral regurgitation, the greatest reduction in end-diastolic dimension occurs within 2 weeks of the reversal of volume overload; a significant reduction in end-systolic dimension with an increase in ejection fraction occurs later. In our experience, early postoperative echocardiographic measurements of left ventricular size and function can provide important prognostic information.