Impact of Perioperative Treatment With Intravenous Glutamine on Myocardial Protection in Cardiac Surgery Patients With Aortic Stenosis

The purpose of this study is to confirm if myocardial protection effect can be obtained by intravenous administration of glutamine in patients undergoing aortic valve replacement with severe aortic stenosis (who are at high risk for ischemia-reperfusion injury). As a prospective double blinded randomized placebo-controlled trial, the investigators detect and compare the degree of myocardial damage(with CK-MB and Troponin T) and myocardial protection (through hsp 70 expression in atrial tissue), cardiovascular index, inflammatory reaction, and clinical manifestation.