Since the 1970s, with the development of economy and improvement of people’s lifestyle, the incidence of coronary heart disease in China has increased sharply, and in recent years, the trend is younger, which has become one of the main diseases that seriously threaten people’s health. Therefore, early diagnosis and treatment become especially important. So, how can we know if we are suffering from coronary heart disease? Besides having typical symptoms (such as anterior heart area, throat obstruction, pain in the anterior heart area, radiating to the back and upper limbs, whether the symptoms last three to five minutes or even more), related risk factors (such as smoking, obesity, family history, unreasonable diet structure, overexertion, etc.), abnormal electrocardiogram and myocardial enzyme test, coronary CT and angiography are the more accurate methods to diagnose coronary heart disease in clinical practice. Coronary CT, using a specially shaped cardiac catheter sent to the root of the aorta via the femoral artery, radial artery or brachial artery, is inserted into the left and right coronary artery orifices respectively, and a small amount of iodine contrast is injected, so that the coronary arteries are clearly visualized. Clinically, some patients often talk about “iodine” and believe that it has large side effects on the human body, so they refuse diagnostic tests such as coronary CT and coronary angiography, thus delaying the disease and affecting the therapeutic effect. We would like to introduce the adverse reactions, risk factors and precautions for the use of iodine contrast agents. Adverse reactions – is iodine contrast agent really that terrible? 1. Contrast nephropathy It refers to an increase in serum creatinine of at least 44umol/L or more than 25% of the basal value within 2-3 days after intravascular injection of iodine contrast agent, excluding other causes of elevated serum creatinine. In fact, the elevation of blood creatinine caused by iodine contrast agent is mostly transient, with blood creatinine peaking 3 days after administration and mostly returning to baseline in about 10 days; however, for people with severe renal insufficiency, iodine contrast agent can cause irreversible kidney damage. 2, systemic adverse reactions Iodine allergy agent systemic adverse reactions can be divided into three kinds: 1) acute adverse reactions: within 1 hour after the injection of contrast agent, the most common. Mild can be manifested as rash, skin flushing, nausea and vomiting, nasal congestion, etc. Severe can cause fatal cardiac arrhythmia, laryngeal edema, convulsions, seizures, loss of consciousness and even respiratory and cardiac arrest. 2) Late onset adverse reactions: Occurs 1 hour-1 week after injection of contrast agent. It can be manifested as nausea, vomiting, headache, skeletal muscle pain, fever, etc. 3) Late onset of adverse reactions: usually occurs 1 week after contrast injection and may cause hyperthyroidism. Risk factors – Who is not suitable for iodography? 1. History of iodine contrast allergy 2. Allergies such as eczema, urticaria, neurodermatitis, asthma, food and pollen allergy 3. Hyperthyroidism, goiter 4. Severe kidney disease 5. Severe liver disease 6. Severe diabetes 7. Severe lung disease (respiratory insufficiency, pulmonary hypertension, pulmonary embolism, etc.) 8. Brain injury (recent cerebrovascular injury, convulsions, cranial trauma) 9. 10.Recent use of contrast 11.Long-term use of beta-blockers: prone to bronchospasm and possible untreatable bradycardia 12.Use of biguanide hypoglycemic agents (prone to renal insufficiency, lactic acidemia) 13.Pregnancy and lactation. Precautions – reasonable use, not so terrible! 1.Preparation of patients before coronary CT examination: 1)Fasting for more than 4 hours to reduce stomach contents and avoid patients’ nausea and vomiting due to the use of iodine contrast agent which may lead to accidental aspiration. 2) Take dexamethasone about half an hour in advance to prevent allergic reactions. 3)The examination needs to be accompanied by family members. 2. Patients need to pay attention to drink a lot of water after the examination (1000-2000ml of water within 6-8 hours after the procedure) to promote the excretion of contrast agent. 3. For diabetic patients, there are several precautions: 1) Metformin must be stopped for 48 hours before the use of iodine contrast agent. 2) Metformin should not be used again until at least 48 hours after the use of iodine contrast agent and renal function has returned to normal.