Patients with angina pectoris may show ischemic changes on the ECG, manifesting as a transient horizontal or downward sloping shift of the ST segment, usually more than 0.1mv, and some patients may show changes such as bidirectional and inverted T waves. Some patients may also show myocardial infarction patterns, with pathological Q waves or QS waves. Some patients may have a normal ECG after an angina attack, and the patient’s angina symptoms may have resolved by the time the ECG is done. Another situation is that the patient’s usual ECG may itself have T-wave changes, and after the onset of angina pseudo-normalization of T-wave instead, showing a normal ECG, which must be compared with the previous ECG to make a clear diagnosis and avoid delaying the disease.