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The electrocardiogram (ECG or EKG) is a test that measures the heart’s electrical activity, and a resting ECG is administered when the patient is at rest. It involves noninvasive recording with adhesive skin electrodes placed on specially prepared spots on the skin, and it plots out the heart's activity on a graph. It is used to determine the health of the heart and circulatory system and to help diagnose issues with associated body systems.
In order to perform the resting ECG, the electrocardiography technician applies up to 12 adhesive electrodes to the skin at specific spots, mostly on the left side of the chest but also on the wrists and ankles. Typically, these electrodes are self-adhesive or applied with a conductive, adhesive gel. The spots used are typically shaved, cleaned with an abrasive cream or both in order to reduce interference or impedance between the skin and the electrodes. After the patient is prepped and the skin electrodes are in place, the test lasts less than a minute, and it is completely painless and noninvasive.
The patient’s resting ECG is of interest because the technician and involved doctors can see what their patient’s natural, “default” electrical heart activity is. The ECG itself is composed of lines plotted on a graph displaying time intervals. At ideally regular intervals, the lines crest up to a peak and then fall down below the line’s starting point, or baseline, into a trough. Peaks and troughs can occur backward as well.
The dimensions and regularity or irregularity of these lines communicates the nature of the patient’s heart activity. A person’s resting ECG can show evidence of recent heart attack, a lack of oxygen to the heart, coronary ischemia, the effects of some drugs and certain genetic faults. A resting ECG likely will be requested in cases of seizure, difficulty breathing or fainting; if the patient has observed unusual heart rhythm; or to determine whether he or she has had a recent heart attack or other cardiac event.
The resting ECG is not the only test using the basic setup of the electrocardiogram. In cases of damage from coronary artery disease, doctors might request an exercise ECG, in which the electrodes are placed as normal, but the patient exercises on a treadmill or stationary bike during the test. This also is referred to as a cardiac stress test, and it can be used to determine the amount of work the heart of a given patient can take by recording the reaction of the heart and associated systems to strenuous physical effort.