An ECG is an important part of the initial evaluation of a patient who is suspected to have a heart related problem. Small sticky electrodes are applied to the patient's chest, arms and legs. However, with some systems, the electrodes may be applied to the chest, shoulders and the sides of the lower chest, or hips . Wires are used to connect the patient to an ECG machine. You will be asked to remain very still while a nurse or technician records the ECG. The electrical activity created by the patient's heart is processed by the ECG machine and then printed on a special graph paper. This is then interpreted by your physician. It takes a few minutes to apply the ECG electrodes, and one minute to make the actual recording.


The ECG is extremely safe and there is no risk involved. In rare cases, some people may develop skin irritation from the electrode adhesive, but no serious allergic reactions have been reported.

The only preparation for an ECG to wear clothes that allow easy access to your chest. Thus, a blouse or shirt with buttons down the front is a lot more practical than a pantsuit or dress. Once you arrive in your doctor's office or in the hospital, your chest may be cleansed with alcohol to ensure good electrical contact with the ECG electrode. In men with hairy chest, small areas may have to be shaved to allow adequate skin contact with the electrode. This avoids interfering artifacts from being recorded on the ECG and produces a technically satisfactory study.

The ECG can provide important information about the patient's heart rhythm, a previous heart attack, increased thickness of heart muscle, signs of decreased oxygen delivery to the heart, and problems with conduction of the electrical current from one portion of the heart to another. For example, the ECG tracing shown above demonstrates an acute or ongoing heart attack involving the bottom (or inferior portion of the heart). An example of an ECG of a patient with a heart attack is shown below.


It is important to remember that ECGs are not 100% accurate. Normal recordings can be obtained in patients with significant heart disease, or some "abnormalities" may exist in the presence of a normal heart.