What does an EKG show?

Electrocardiogram records the electrical activity of your heart. ---- An EKG (or electrocardiogram) is an electrical representation of the cardiac activity as detected by surface electrodes placed in specific locations across the chest and extremities. These electrodes detect the electrical activity occurring in the heart and these are depicted as deflections of a line. The usual deflections, or waves, are denoted PQRST. There are other waves which are sometimes seen in normal or abnormal states, such as the U wave. The P wave represents atrial depolarization. This is followed by the PR interval, which represents the amount of time the depolarization wave takes to get through the AV node to the ventricular conduction system. The QRS represents ventricular depolarization. ST segment deflection can indicate ventricular injury or ischemia, such as that seen in myocardial infarctions. The QRS is followed by the T wave, which represents ventricular repolarization. The atrial repolarization wave is hidden by the much larger voltage of the QRS. Various abnormal states can cause changes in the usual appearance of the EKG, such as electrolyte abnormalities (e.g. hypo- or hyperkalemia), medications (e.g. digitalis), infections (e.g. myocarditis, pericarditis), and ischemia (e.g. angina or myocardial infarction). This is why the EKG is useful as a diagnostic test. It is not, however, a perfect test and many innocuous conditions can cause abnormalities and an EKG can be normal even when there is serious pathology, which is why other tests are frequently necessary.