Thirty-three cases, comprizing 5 of mitral regurgitation (MR), 11 of mitral stenosis (MS), 11 of aortic regurgitation (AR) and 6 of AR and mitral steno-regurgitation (MSR), underwent both preoperative and postoperative heart catheterization in association with a muscle exercise test. Comparisons were made between preoperative and postoperative clinical symptoms, hemodynamics and cardiac functions. The following results were obtained: 1) Improvements in clinical symptoms and hemodynamics at rest were observed in all but two patients. 2) Abnormalities in hemodynamics were obtained after the muscle exercise test, even in cases exhibiting normal hemodynamics at rest. 3) An increase in pulmonary artery mean pressure was noted in MR and MS groups after the muscle exercise test. 4) The cardiac function index values in both the MR and MS groups showed lower levels than those in both the AR and AR + MSR groups. 5) The presence of atrial fibrillation and extent of myocardial fibrosis were related to improvements in postoperative cardiac functions.