The primary objective of this clinical trial was to investigate the effects of insulin on myocardial blood flow reflected by CSBF which was evaluated by TEE. The second aim was to observe the effect of insulin on cardiac function and markers of myocardial damage.

Inclusion criteria included

1. age 55-80 years, ASA grade II-III, regardless of gender,
2. BMI 18.5-28.0 kg/m2,
3. scheduled for elective coronary artery bypass grafting (CABG), valve repair or replacement, or a combination of these procedures with cardiopulmonary bypass.

Exclusion criteria

1. non-first cardiac surgery;
2. emergency cardiac surgery;
3. severe heart failure with preoperative left ventricular ejection fraction <30%;
4. contraindication to TEE;
5. kidney disease requiring replacement therapy;
6. combined with multi-organ insufficiency;
7. Severe infection requiring continuous antibiotic treatment;
8. use of large doses of hormone or nonsteroidal anti-inflammatory drugs within the last 2 weeks.
9. after the patient entered the operating room, if the first blood glucose exceeded 180 mg/dl, a second test was performed 15 minutes later, and if the average of the two blood glucoses exceeded 180 mg/dl, the patient was excluded as well.

Elimination criteria included

1. unplanned secondary CPB;
2. need for intra-aortic balloon pump technical support during the study period;
3. TEE image acquired with poor quality.