When you get your ECG you will notice that the following letter symbols are labeled on the different groups of graphs on it: I, II, III, aVR, aVL, aVF, V1-V6, and so on. Each of these symbols represents a lead of the ECG. A lead is a specific connection that is set up according to international standards to connect ECG information into the ECG machine. By setting up different leads, you want to view the size, direction, and duration of the ECG information at the same time from different angles and directions. A few more angles will always tell you more about the overall ECG information than a single angle. Just like if you’ve never seen a person before, and someone takes a series of pictures of that person from multiple angles, you can get an overall image of the front of his face, the top of his head, the back of his head, and so on. If only the front photos were taken, you would only know the front features of his face. Generally speaking, since the atrial wave (P wave) is higher in leads II and V1, the ECG recordings in these two leads can be lengthened if necessary in order to observe and analyze arrhythmias, especially complex arrhythmias. Leads Ⅰ and aVL reflect the electrocardiographic information of the high lateral wall of the left ventricle, leads Ⅱ, Ⅲ, and aVF reflect the electrocardiographic information of the lower wall of the left ventricle (the side of the heart muscle that is immediately adjacent to our diaphragm), and leads V1 to V6, the six leads, mainly reflect the electrocardiographic changes of the anterior wall of the left ventricle (including the lateral wall). These localizations are particularly important in terms of where exactly the myocardial infarction is occurring in that location.