The ECG is valuable in the diagnosis of myocardial infarction (MI), is affordable, quick and easy to perform, non-invasive, and can be localized. It can be used to assess which artery is causing the infarction, and to assess whether the artery is completely occluded, partially occluded, or has the potential for stenosis; and to determine whether to intervene immediately or to take anticoagulation therapy. I. General significance of pathologic Q wave 1, Q wave width ≥ 0.04s; 2, Q wave amplitude is greater than 1/4 of the R wave in the same lead; 3, Q wave appeared in the lead that should not appear Q wave. Electrostatic regions in leads where Q waves should not occur are: (1) Q wave amplitude >1/2R in the aVL lead, and Q wave amplitude >60% R in the lower wall; (2) Q wave duration >0.02s, amplitude >1/4R; (3) Q waves in leads V1 and V2; (4) QS in leads V1 and V2.The traditional diagnostic criteria for Q waves are the diagnosis of MI in which a pathologic Q wave occurs, which are standardized enough so that it is not difficult to diagnose. Since it is standardized enough, it is not difficult to diagnose. At the same time, how to diagnose those that are not standardized? What about MI without Q waves, without symptoms, or with symptoms but no Q waves? Therefore, on the basis of the traditional meaning of pathological Q-wave, the concept of isotonic Q-wave was proposed. Q waves or similar isotonic Q waves caused by non-MI diseases are also called pseudo-MI. non-MI Q waves are abnormal Q waves caused by reasons other than MI. It is mostly seen in leads II, III, aVF, V1-V3, etc. The mechanism of occurrence may be related to the shift of the cardiac electrical axis, cardiac transposition, abnormalities of cardiac agonistic conduction pathways, acute myocardial ischemic injury, limited electrostatic quiescence, fibrosis, or other components instead of the myocardium, hypertrophy of the interventricular septum, and autonomic nerve or indirect stimulation, etc., but it is not a pathologic Q wave or isotropic Q wave caused by MI. Common non-MI diseases include myocarditis, cardiomyopathy, myocardial contusion, progressive myotonic dystrophy, scleroderma, amyloidosis, primary or metastatic cardiac tumors, hypertrophic cardiomyopathy, left ventricular hypertrophy, right ventricular hypertrophy, emphysema, pulmonary heart disease, massive pericardial effusion, left bundle-branch block, left anterior branch block, right-located heart, left ventricular pseudo-bonded cord. Third, positional Q wave: also known as non-pathological Q wave Due to the different cardiac location and changes, normal people in some leads can also appear more than the normal standard Q wave, such as aVL, Ⅲ, aVF, V1, V2 and other leads appeared QS-type or QR-type (Q wave time limit ≥ 30ms, amplitude ≥ 1/4R) is called the cardiac positional Q wave. The electrocardiographic manifestations are: Ⅰ, aVL, V5, V6 leads, when the initial vector of the QRS wave group and the frontal plane electrical axis is close to 90 °, the initial vector of the QRS wave group and the aVL lead is almost perpendicular to the aVL lead, can be projected on the negative side of the aVL lead, so that the QRS wave group is QS-type, and occasionally Qr-type belongs to a normal variant, which always accompanies the inversion of P-wave and T-wave, and there is no Q-wave in the Ⅰ and V5, V6 leads, without ST-segment changes. This condition is always accompanied by P-wave and T-wave inversion, no Q-wave in leads I and V5 and V6, and no ST-segment changes. Leads Ⅱ, Ⅲ, aVF: when lead Ⅲ is approximately perpendicular to the QRS wave lead axis, Q wave can be formed with a slight change in the position of the heart, therefore, most of the Q waves in lead Ⅲ are normal, and should be analyzed in combination with the ST-T changes and the Q waves in leads Ⅱ and aVF.Leads V1 and V2: the Q waves should be recorded in most of the right anterior thoracic positions, and the edge of them is close to the site of lead V1, therefore, this electrode can be used in V1 with a slight change in the position. Therefore, a slight change in the position of the electrode will allow the recording of Q waves or QS waves in lead V1. Normal variants: There are changes in the position of the heart due to obesity, chicken breasts, etc. Positional Q waves are not pathologic Q waves; they are not caused by MI or other organic diseases and have no pathologic significance. However, clinically there are people who do not have a deep understanding of this and diagnosed as “pathologic Q wave”, become “medical origin MI”, and even lose the ability to work. Artificial Q wave 1, the operation of the irregularity and the mistake of reading the map, the recording voltage is too attenuated, resulting in the QRS wave at the beginning of the small r-wave can not be recognized and mistaken for q-wave, and on the other hand, the small q-wave should be lost and there is a leakage of diagnosis and even a delay in the condition. 2. Operational errors, reversing the left and right hands, and misidentifying the left and right chests will lead to pathologic Q waves or isotropic Q waves, resulting in misdiagnosis. Up to now, routine ECG is the most widely used non-invasive examination technique in the clinic, and it is one of the important means to diagnose MI arrhythmia. the identification and diagnosis of Q wave is very important. At present, in addition to the experience of electrocardiography, it is necessary to combine the history and laboratory tests, clinical manifestations, and necessary noninvasive tests such as cardiac ultrasound, head and chest lead electrocardiography, and further invasive tests such as coronary angiography can be done to identify the abnormal Q-wave method. As a clinical electrocardiogram examiner if you can correctly differentiate between pathologic Q waves, isotropic Q waves, non-infarct disease Q waves, positional Q waves and elimination of artificial Q waves, it will reduce the diagnosis of medically induced Q waves. In particular, isotonic Q waves combined with ST-T changes, clinical presentation and laboratory tests will lead to early MI intervention and treatment. The recognition of Q waves due to non-infarctive disease facilitates the treatment of the primary disease. Avoid clinical misdiagnosis caused by the appearance of artificial Q waves, and avoid delayed treatment due to the artificial disappearance of pathologic Q waves.