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.
The standard 12-lead electrocardiogram is a representation of the heart's electrical activity recorded from electrodes on the body surface.This section describes the basic components of the ECG and the lead system used to record the ECG tracings.Topics for study:1  ECG Waves and Intervals.he standard 12-lead electrocardiogram is a representation of the heart's electrical activity recorded from electrodes on the body surface.