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.
Although it is called a 12-lead ECG, it uses only 10 electrodes. Certain electrodes are part of two pairs and thus provide two leads. Electrodes typically are self-adhesive pads with a conducting gel in the center. The electrodes snap onto the cables connected to the electrocardiograph or heart monitor.