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 test is sometimes called an EKG, electrocardiography and a 12-lead EKG/ECG (because the heart's electricity activity is monitored in 12 parts of the body). The printout after the test shows a graph of the electrical activity and rhythm of each heartbeat over the time of the test.