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.
In many cases, patients in the intensive care unit will be monitored continuously using an EKG machine. A precordial lead is one of the leads placed on the chest for an electrocardiogram. During an electrocardiogram, electrodes are placed on the skin to monitor electrical impulses inside the heart. A heart attack results in evolving changes to different precordial leads.