【Abstract】 Objective: To investigate the effective plasma concentration of propofol that impacts the myocardial contractility of patients aged 60~69 by echocardiography and target-controlled infusion (TCI) technique. Methods: 50 ASA physical status I~II patients aged 60 to 69 that had been scheduled for elective surgery undergoing general anesthesia were chosen. Those patients having cardiovascular diseases were excluded. The patients were randomly allocated into five groups based on the initial plasma concentration of propofol administered by TCI(n=10 each): 3.5, 4.0, 4.5, 5.0 and 5.5μg/ml. Systolic blood pressure (SP), diastolic blood pressure (DP), and heart rate (HR) were recorded by a non-invasive monitoring before injection (T0), and 1 minute (T1), 3 minutes (T2), 5 minutes (T3), 8 minutes (T4), and 10 minutes (T5) after injection. Meanwhile, the left ventricular motions were continuously monitored by echocardiography, and the left ventricular diastolic diameter (Dd), the end systolic diameter (Ds), the left ventricular ejection fraction (EF), the left ventricular fractional shortening (FS), and the heart cardiac output (CO) were recorded at the time points as well. Probit regression analysis was used to calculate the EC50 of which the EF and FS decrease over 10% and 20%. Results: Compared to T0, the SP, DP, and CO at T2, T3, T4, and T5 decreased (P<0.05) in all groups; while EF and FS at T3, T4, T5 decreased (P<0.05) in groups II~V. Compared to T2, the SP, EF, and FS at T3, T4, T5 decreased in groups II~V while the DP decreased (P<0.05) in group V, the CO showed no significant difference (P>0.05) in all groups. Compared to group I, the EF and FS at T3, T4, and T5 decreased (P<0.05) in groups II~V. Compared to group IV, the EF and FS at T3 and T4 decreased (P<0.05) in group V. The EC50 was respectively 4.40μg/ml and 5.20μg/ml when the EF decreased over 10% and 20% in all groups at T3, while the EC50 was respectively 4.01μg/ml and 5.20μg/ml when the FS decreased over 10% and 20%. Conclusion: Propofol target plasma concentration of 4.0~5.5μg/ml in patients aged 60~69 could inhibit the myocardial contractility at a dose-dependent manner; within this range, the EC50 is respectively 4.40μg/ml and 5.20μg/ml when EF decreases over 10% and 20%.