The precautions to be taken before cardiography are: perfecting the preoperative examination, adjusting the diet, and making good psychological preparation. 1. Improve the preoperative examination: Improve the routine examination of blood, biochemistry (liver function, kidney function), urine, etc. to ensure that the physical condition can tolerate the cardiography surgery; conduct the iodine allergy experiment before the surgery to rule out the contraindications to the surgery as the contrast agent is iodine. 2. Adjustment of diet. A low-fat, low-salt diet is needed for a period of time before the operation, and the bowels should be emptied before the operation. 3. Make good psychological preparation. Before the operation, you should fully communicate with the doctor, understand the procedure and risks of the operation, make good psychological preparation, maintain a calm state of mind, and avoid excessive tension and anxiety. Specific precautions are recommended according to the patient’s condition, consult the clinician’s opinion.