1 Most episodes of acute lower back pain are caused by muscle strain, such as from lifting a heavy object, a sudden movement or a fall. 2  The low back pain can be very severe and last for several hours, several days or even a few weeks.
3. Characteristics of the Normal ECG. It is important to remember that there is a wide range of normal variability in the 12 lead ECG. The following normal ECG characteristics, therefore, are not absolute. It takes considerable ECG reading experience to discover all the normal variants.
Chest Leads. There are 10 wires on an ECG machine that are connected to specific parts of the body. The 6 leads are labelled as V leads and numbered V1 to V6. They are positioned in specific positions on the rib cage. To position then accurately it is important to be able to identify the angle of Louis, or sternal angle.