Coronary artery disease cannot be fully detected by an electrocardiogram, and it is not clear whether it is coronary artery disease or not. The ECG can reflect myocardial ischemia, as well as the rapidity of heart rate, conduction problems of the heart, and whether there are arrhythmias, etc. However, the diagnosis of coronary heart disease cannot be made definitively by the ECG alone, but also by the patient’s medical history, symptoms, signs, and cardiac ultrasound. In addition, a chest x-ray should be done to rule out that the chest pain is caused by a lung problem. Finally, CTA or angiography of the coronary arteries should be done to clarify the presence of coronary artery disease after all the above tests. Coronary angiography is the gold standard for the diagnosis of coronary artery disease. Other tests, such as cardiac ultrasound, can also rule out valve disease, and can provide information about the structure of the heart, the size of the heart chambers, and the blood flow and function of the heart, which are also important tests essential for coronary artery disease.