Uses of electrocardiogram: I. For confirming diagnosis: 1. Myocardial infarction, especially acute myocardial infarction: it can confirm the diagnosis of most myocardial infarctions relatively accurately, including their location, staging, and diagnosis of certain comorbidities. 2. 2, all kinds of arrhythmia: up to now, the confirmation and discovery of all kinds of arrhythmia mainly rely on the electrocardiogram, while the cardiac ultrasound, imaging, nuclear examination, etc. are far inferior to the electrocardiogram in the accurate diagnosis of arrhythmia. Today, more and more patients are being fitted with pacemakers, which also require frequent monitoring with ECG. When taking certain antiarrhythmic drugs, frequent ECG monitoring is needed to increase, decrease, or stop the drug at any time according to the condition of the patient. This is because improper use of certain antiarrhythmic drugs can lead to new, even dangerous, arrhythmias. Second, for auxiliary diagnosis: 1, other heart disease: all kinds of coronary angina pectoris, asymptomatic myocardial ischemia, hypertensive heart disease, rheumatic heart disease, pulmonary origin disease, congenital heart disease, myocarditis, cardiomyopathy, pericarditis, cardiovascular imaging examination of the guardianship and so on. 2. Thyroid disease, detection of the effect of certain drugs on the heart, detection of electrolyte disorders such as potassium and calcium in the blood, as well as surgical anesthesia and surgical monitoring.