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.
This section is meant only as an introduction to the 12-lead ECG. It will take much practice of you to be able to interpret a 12-lead ECG tracing. This section will give you a basic understanding of how to take a 12-lead EKG, how to place the leads, and how to begin to interpret the tracing.