Heart attack is caused by the formation of blood clots on the basis of coronary artery stenosis. Stressful situations can lead to plaque instability or even rupture in the coronary arteries and the formation of blood clots, thus causing myocardial infarction. The precursor symptoms of myocardial infarction are as follows: Chest pain at night or at rest: when there is dull pain or crushing-like pain or burning pain in the precordial area without any reason at rest or at night when sleeping, or a sore and swollen feeling in the jaw, or with sore and swollen pain in the left upper limb, be on high alert for a heart attack. Continuous nocturnal attacks need to be seen in the cardiology department of the hospital as soon as possible. Aggravation of angina symptoms: Patients with pre-existing angina present with aggravation of angina symptoms, manifested as chest pain with light physical activity, increased frequency of chest pain, and prolonged duration of chest pain, medically known as exertional worsening angina, should be on high alert for an attack of heart attack. New onset of angina symptoms: people who have never had chest pain symptoms and have recently experienced activity-related dullness or pressure-like pain or burning pain in the precordial region, or jaw soreness and swelling, or with soreness and swelling of the left upper limb, and still experience chest pain episodes when the intensity of activity gradually decreases, especially people who have the habit of morning exercise and experience the above-mentioned chest pain symptoms during morning exercise, should be on high alert for a heart attack. Pain in other parts related to angina: If there is pain in other parts related to activities, such as epigastric pain, toothache, jaw pain, left upper limb pain, shoulder and back pain, all need to be alert. In summary, if the degree, duration, and triggering factors of chest pain are different from previous episodes, you should be highly alert to the occurrence of heart attack.