An electrocardiogram (also referred to as an EKG or ECG) is a recording of the electrical activity in your heart. The ECG or EKG results can be seen immediately on a print out or on a computer screen.
The EKG or ECG reading gives your doctor information about
Although the EKG is extremely valuable in identifying issues, if you have abnormal EKG or ECG results, additional tests will likely be needed to confirm the diagnosis.
For an in depth description of electrocardiograms, I recommend the Mayo Clinic Heart Book, Revised Edition: The Ultimate Guide to Heart Health. For really detailed scientific information, check out Wikipedia
Note that the EKG cannot reliably measure the pumping ability of the heart - see echocardiography.
The EKG or ECG test is a simple and painless process. It can be done in a doctor's office, at a clinic, or at the hospital. You may be asked to remove your clothes from the waist up and put on a hospital gown. Women will have to remove pantyhose or tights.
You lie on a bed or cot and 12 to 15 adhesive patches containing electrodes will be attached to your arms, legs, on the left side of your chest, and possibly some other spots on your chest, neck, or back. A gel is applied to your skin before the patches are attached to improve conductivity of the electrical impulses.
If your skin is very hairy, they may need to shave the spots where the electrodes will be attached. Fine sandpaper to roughen the skin to ensure the patch sticks may be used as well.
Once all the electrodes are attached, all you need to do is lie quietly for 30 to 60 seconds while the technician records your heart activity.
In some cases your doctor will want to monitor your heart's activity over the course of 24 hours (sometimes longer). To do this, you will wear a portable device called a Holter monitor (after Norman Holter who designed it in 1961).
The device is about the size of a glasses case or large wallet and you wear it on your belt. It is connected by wires to the electrode patches attached to your skin.
You wear the monitor 24 hours a day for all your regular activities - even sleeping.
When you return the Holter monitor to the clinic or hospital, they will download the readings into their computer. You will likely be asked to keep a diary of everything you do while wear the monitor so your doctor can correlate the readings with your activities.
There is nothing to do to prepare for an electrocardiogram other than to wear clothing that will allow easy access to attach the electrodes.
There are no risks to this procedure.