Propofol Effects on Mitral Valve Annular Velocity

The purpose of this study is to evaluate the effects of different concentration of propofol on patients who are undergoing cardiac surgery. The patients will receive infusion remifentanil 0.5mcg/kg/min with different target-site propofol concentration namely 1.0ng/ml, 2.0ng/ml and 3.0ng/ml. Tissue Doppler Imaging by transesophageal echocardiography will be done to assess the changes in cardiac function.