There are three common tests for the heart: electrocardiogram, cardiac ultrasound, and coronary angiography, and the roles of these three tests rarely overlap with each other and cannot replace each other. If we compare the heart to a house, then ECG is to check the circuit of the house. For example, arrhythmia, premature beats, and acute myocardial infarction can all be diagnosed by ECG. These diseases are accompanied by changes in the electrical activity of the heart. However, the diagnosis of ECG depends on the onset or not. For example, in the case of panic attacks, the ECG may be altered during the attack period, but it may return to normal during the remission period. Therefore, when you feel uncomfortable with your heart, the first thing you should do is not to go to a big hospital to find a specialist, but to capture an ECG at the onset of the disease, and it is not too late to find a specialist after capturing the ECG at the onset. There is also a 24-hour ECG called holter, which requires you to record the time of your onset to compare the similarities and differences between the ECG at the time of onset and the time of remission. One type of acute myocardial infarction has a very specific presentation, which can manifest as stomach pain. That is why all middle-aged and elderly people who visit the doctor with stomach pain should be scheduled for an ECG. Many patients do not understand why they need to check ECG for stomach pain and think it is over-medication, but it is not. Second, the heart ultrasound The heart ultrasound is to check the walls of the house. Some heart diseases do not affect the ECG, but only the structure of the heart. For example, if the heart is enlarged, if the heart contraction is weak, or if the door of the house is not closed properly, the diagnosis and detection of these diseases are more dependent on the cardiac ultrasound. Coronary angiography Coronary angiography is to check whether the water pipes of the house are open or closed. The coronary artery is the blood vessel that supplies blood to the heart. When this vessel or its branches are diseased, we will suffer from coronary heart disease, which is often called myocardial ischemia, angina pectoris, myocardial infarction, etc. In mild lesions, there will be no symptoms or angina pectoris. In severe lesions, there is a risk of myocardial infarction. Although the ECG can reflect some of the ischemic lesions of the heart, there are still some patients who have normal ECGs even with coronary artery disease. Therefore, patients with coronary artery disease should have this test done to understand the extent of the lesion and to determine the treatment plan in a targeted manner. So a significant portion of the common symptoms such as panic, chest tightness and chest pain are caused by changes in the electrical activity of the heart, changes in the structure of the heart and changes in the arteries supplying blood to the heart. And all these changes depend on different tests, so it is not that checking one can replace all tests.