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.
As long as the electrical impulse is transmitted normally, the heart pumps and beats at a regular pace. In an adult, a normal heart beats 60 to 100 times a minute. Electrocardiography (ECG or EKG) is a painless, non-invasive procedure that records the heartâs electrical activity and can help diagnose arrhythmias.