| The incidence and mortality of ischaemic heart disease have been increasing with the improvement of living standard. It is important to select anesthetics having less effects upon heart functions to the patients with ischaemic heart disease who need surgical operations. Propofol and midazolam are two common intravenous anesthetics used in clinical anesthesia. Their cardiovascular inhibitory effects had been thorougly investigated, but the study about their influences in ischaemic heart disease are few.We used acute myocardial infarction model induced by ligation of left coronary artery in rats to investigate the effect of propofol and midazolam upon haemodynamics,heart function, myocardial infarction size,ultrastructure of myocardial tissue following infusion with propofol and midazolam. After 30 minutes infusion, plasma concentrations ofpropofol were measured with fluorometric assay.Results: 1． Propofol caused a greater decrease in the mean arterial pressure(MAP),the heart rate (HR),the left ventricular systolic pressure(LVSP),the maxium rates of left ventricular pressure rise and drop(±dp/dtmax),the velocity of the contractile element shortening (Vce-5kPa) ,the maximal velocity (Vmax) and oxygen myocardial consumpution index(Omcci) than equivalent midazolam when the average plasma concentration of propofol was at the range of (3～13) μg·ml-1(P<0.05). In addition , isovolumetric time (IT) was more prolonged by propofol than by equivalent midazolam and left ventricular end-diastolic pressure(LVEDP) had no significant changes in all rats(P>0.05). 2. Myocardial infarction sizes in propofol group and midazolam group were 23.7%～29.2% and 24.3%～28.9% respectively. There are no significant changes in myocardial infarction size compared with controled group(23.3%～26.9%).3. There are no significant changes in ultrastructure of myocardial tissue in propofol group ,midazolam group and controled group (P>0.05). conclusions:1. Midazolam may be less depressant to cardiovascular system than propofol in the rat with acute myocardial infarction. 2. There are no significant changes in myocardial infarction size and ultrastructure of myocardial tissue in all groups.
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