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 12-lead electrocardiogram (ECG) is an integral part of the evaluation of coronary artery disease (CAD). It remains the initial test in identifying an acute myocardial infarction (MI) and a remote MI. The ECG records depolarization of the normal ventricular myocardium as the QRS wave and repolarization as the ST segment and T wave.