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.
A 12-lead ECG detects and amplifies these voltage changes between two electrodes as wavy lines on paper or a monitor screen. Electrodes are commonly placed in pairs, such as on the right leg and left leg. Each pairâs output is called the lead, and it captures heart information from different angles. Unlike 12-lead ECGs, the information recorded by 3- and 5-lead ECGs is rarely printed out and generally is used as a form of continuous monitoring via a screen during ambulance transport or hospitalization.