If a patient shows partial ST-segment depression on the ECG, it is usually a reference indicator of a change in ECG vectorology, with physiological or pathological causes. For physiological causes, partial ST-segment depression often occurs when the patient is overly tired, nervous, anxious, irritable, has consumed large amounts of strong coffee, alcohol, strong tea, or has had adverse reactions to certain medications. For pathological factors, for example, patients with cardiogenic diseases, such as coronary angina, acute myocarditis, pericarditis, severe arrhythmia, or heart failure, will have partial ST-segment depression. In addition, for endocrine metabolic disorders, this change is often seen in thyroid dysfunction and adrenal cortical dysfunction. Finally, if the patient has an internal environmental disorder, in which the water-electrolyte and acid-base balance is impaired, there will also be an ECG showing ST-segment depression.