Some patients with coronary artery stenosis can be seen by ECG, and some patients may have no ECG changes. Patients with coronary artery stenosis may show insufficient blood supply to the myocardium, and some patients may have ECG changes, such as ST depression and T-wave inversion, which can make a preliminary judgment of the patient’s condition. However, some patients have coronary artery stenosis, which may not show up on the ECG. Electrocardiogram (ECG) is a routine way to check for coronary artery disease, and patients with symptoms of cardiac discomfort should undergo ECG in a timely manner. Some patients may not have any manifestations on the ECG in normal times, but may have ST segment changes on the ECG in the event of a heart attack, which can provide a basis for the diagnosis of coronary artery disease. Electrocardiogram sometimes does not accurately reflect the lesions of coronary arteries, patients with symptoms of chest tightness should go to the hospital in a timely manner, under the guidance of the physician to carry out coronary artery angiography is the gold standard for the diagnosis of coronary heart disease.