Event monitoring is a method of recording the heart rhythm during symptoms, or an "event."

If you've been having recurrent symptoms such as palpitations, dizziness or fainting spells, your doctor may want to determine whether these symptoms are caused by an arrhythmia–an abnormal heart rhythm in which the heart may beat too rapidly, too slowly or irregularly.

Doctors can diagnose an arrhythmia by obtaining an electrocardiogram, or EKG, a recording of the heart's electrical activity. However, an EKG records activity for a brief period (less than a minute). If your doctor suspects you have an arrhythmia he or she will want to record the EKG over longer periods of time and will order an event monitor.

You will carry a recorder, which is about the size of a pager, over a period of 30 days while performing usual daily activities. Worn day and night, the recorder continuously scans your heart's electrical activity. When you experience symptoms, you will press a button and the device records and stores up to several minutes of the heart's electrical activity before, during and after an event. At your convenience, you can transmit the stored data over the telephone to your doctor's office or to an EKG receiving center.

You will keep a diary during the period you carry the recorder. The information you'll need to enter in the diary includes the date and time of each entry, symptoms you experience and what you were doing at the time of the event. The diary enables nurses and doctors to correlate your symptoms with the EKG recordings.

Once the data have been transmitted, a nurse or doctor will analyze and interpret the recording. The information gained from the test helps your doctor make an accurate diagnosis and develop a treatment plan that's best for you.