Electrocardiogram, What is an electrocardiogram

The heart is an important organ in the circulatory system. Because the heart is constantly performing rhythmic contraction and relaxation activities, blood can flow continuously in the closed circulatory system. Before the heart mechanically contracts, it first generates electrical excitation. The tiny current generated by myocardial excitation can be transmitted to the body surface through body tissues, causing different potentials to be generated in different parts of the body surface. If two electrodes are placed on the body surface and connected to the two ends of an electrocardiograph (i.e., a precise galvanometer) with wires, it will record the potential difference between the two points on the body surface in the order of the heart's excitation time, forming a continuous curve, which is the electrocardiogram.

The basic electrocardiogram is shown above and contains the following bands:
P wave - the time of depolarization of the two atria
PR interval - the time from the beginning of atrial depolarization to the beginning of ventricular depolarization
QRS complex - the potential change of the whole ventricular depolarization
ST segment - the time of slow repolarization just after the ventricular depolarization
T wave - the time of rapid ventricular repolarization
Ordinary electrocardiograms have the following uses
1. It has important diagnostic value for arrhythmias and conduction disorders.
2. It has a high accuracy in diagnosing myocardial infarction. It can not only determine whether myocardial infarction exists, but also determine the pathological site, scope and evolution process of the infarction.
3. It is of great help in the diagnosis of atrioventricular myocardial enlargement, myocarditis, cardiomyopathy, coronary artery insufficiency and pericarditis.
4. It can help understand the effects of certain drugs (such as digitalis, quinidine) and electrolyte disorders on the myocardium.
5. As a time mark of electrical information, the electrocardiogram is often synchronized with cardiac function measurements such as phonocardiogram, echocardiogram, impedance blood flow diagram and other cardiac electrophysiological studies to facilitate the determination of time.
6. ECG monitoring has been widely used in ECG monitoring in surgery, anesthesia, medication observation, aerospace, sports, etc. and the rescue of critically ill patients.