For the evaluation of efficacy of cardiopulmonary exercise testing, we compared New York Heart Association functional class with peak oxygen consumption rate (VO(2)peak) in 31 patients with severe mitral regurgitation who underwent mitral valve repair surgery. One year later, the VO(2)peak values did not show significant improvement; however, the patients who had more than a mild degree of residual mitral regurgitation (n = 14) after 1 year of surgery had a VO(2)peak value that was significantly decreased (from 22.7 +/- 6.4 to 21.0 +/- 6.3 ml/kg/min, p = 0.04). Patients with a higher preoperative VO(2)peak value (>/=18.5 ml/kg/min) had a significantly better New York Heart Association functional class 1 year after surgery than patients with a lower VO(2)peak value (<18.5 ml/kg/min, p = 0.03).