Methods:Patients meeting the requirement will be randomized into 2 groups: the control group received hyperoxic reperfusion (PaO2 180-250 mmHg) throughout CPB as routine; the treatment group underwent 3 cycles of 5/5 min normal/high oxygenation (PaO2 80-150/180-250 mmHg) during cardioplegia arrest, and maintained the same hyperoxia as the control group in the rest time of CPB. The clinical data of inotropes requirement, drainage, ventilation and intensive care time will be recorded. Venous blood samples will be taken perioperatively for detecting concentration of troponin I (cTnI), tumor necrosis factor-α , interleukin-6, 10, and malondialdehyde (MDA). Atrial biopsies will be removed before cardioplegia arrest and 30min after aortic de-clamping to determine the extent of neutrophil infiltration (myeloperoxidase activity), NFkB binding DNA activity, and gene expression of inflammatory factors (TNF-α, IL-6, 10).