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.
To obtain a 12 lead ecg you would have 4 wires attached to each of the limbs, and six wires placed around the chest, 10 wires in total but you get 12 leads or pictures. In a similar way a combination lock may have 50 numbers but it has thousands of possible combinations.