Objective: The control of myocardial temperature is very important in myocardial protection methods. We investigated the validity of myocardial protection methods at our institution using noninvasive thermography as a means of determining the effectiveness of myocardial protection, with the aim of confirming that myocardial protection solution is correctly infused. Methods: Of 52 extracorporeal circulation cases with cardiac arrest from May 2020 to June 2022, 10 cases with cardiac arrest by progressive myocardial protection with Microplegia, a blood myocardial protection, were included. Infusion was performed at an infusion temperature of 20℃, with an intracircuit pressure of less than 300 mmHg and a flow rate of 250-350 ml/min maintained in a progressive manner. Myocardial temperature in the anterior region of the heart was measured using a thermographic camera at a distance of 80 cm from the heart. Results: The cardiac surface temperature before the start of myocardial protection was 32.5±1.0℃. After the start of infusion, the cardiac surface temperature at the time cardiac arrest was obtained was 27.4±1.3℃. In all cases, the cardiac surface temperature at the time of cardiac arrest was visually heterogeneous. Further infusion was continued, and the average time to reach the lowest visually uniform surface temperature was 342±23 s. The mean cardiac surface temperature at the end of myocardial protection was 22.4±1.3℃. At the start of myocardial protection solution infusion, the myocardial surface cooled faster in muscle than in visible fat, in the order aorta>myocardium from the apex>cardiac base. The postoperative course was generally good in all cases with respect to EF, CKMB, catecholamine use, extubation time, postoperartive hospital stay, and outcomes. Conclusion: It was found that a time of about 360 s is needed to uniformly cool the myocardial temperature during infusion of myocardial protection solution. Furthermore, by confirming the cooling of the base of the heart, it is suggested that it is inferred that the whole is cooled. To avoid problems caused by inadequate myocardial protection, it is suggested that measuring myocardial temperature using a non-invasive, simple thermal imaging camera can assist in determining the effectiveness of myocardial protection, and is expected to establish the safety of further myocardial protection.