To perform surgery for intracardiac malformations, the support of extracorporeal circulation alone is still not enough, although the functions of the heart and lungs are replaced with the support of extracorporeal circulation, but if the heart keeps beating, then there is no way for the surgeon to perform fine operations, especially those small babies, the heart is not much bigger than an egg, and a little deviation will lead to the failure of the operation, so the heart must be allowed in heart surgery Therefore, the heart must be stopped in order to complete the surgery successfully. So how can we stop the heart? This is one of the challenges in heart surgery, which was first done only by means of hypothermia, but this method often caused difficulties in the recovery of the heart after the surgery, and even led directly to the death of the patient. Now, after many cardiac surgeons around the world have tried and improved, myocardial arrest fluid, also known as myocardial protection fluid, is routinely used to stop the heart during cardiac surgery. Myocardial protection fluid not only relies on low temperature, but also contains high concentration of potassium ions that can relax the heart, which can keep the heart quiet during the operation. In addition, myocardial protection fluid adds some special drugs to protect the heart muscle cells, which is beneficial to promote the recovery of heart function after the operation.