Sometimes it isn’t possible to “catch” problems with a single ECG and a special device is used to monitor the heart rhythm and rate continuously for a prescribed period of time, such as 24 hours. If you are experiencing abnormal heart rhythms, or arrhythmias, or other symptoms, the test may be used as an "event" monitor and it will be worn for a period of time that enables the problem to be "caught" on an ECG.

The procedure uses basically the same equipment as used for an ECG, but the equipment is not tethered to a stationary monitor. A special recording device called a Holter monitor, can be worn during normal activities and allows you to remain active during the testing period. This lightweight recording device can be attached to a belt or shoulder strap. The ECG is recorded continuously for the period of time your doctor wants to study.

A diary may also be required for the period of time that the monitor is worn. Be sure to correlate the time of day, the activity you are performing, such as taking medication or participating in a meeting at work, and the specific symptoms you notice happening at the time that the target “event” or symptom is happening. The ECG monitor also may have a button to push when symptoms are being experienced. These “symptoms” also should be noted carefully in a diary.

When the evaluation period is over, the electrodes and recording device can be removed and the waveforms evaluated. When a longer period of continuous monitoring is desired, a recording can be “called in” to the doctor’s office or clinic by a special “telemetry” phone attachment.

While you are wearing an ambulatory ECG monitor, certain precautions should be taken:

• If you usually sleep on your stomach, it will be recommended to sleep on your back or side while the monitoring device is in place.

• You should avoid any device or environment that might interfere with the monitor, such as electric blankets, magnets, metal detectors, and high-voltage areas.

• Showers or baths are not approved while the Holter monitor is in place, but sponge baths are. Just be careful not to get the device wet.

• Proceed with your usual activities. Remember, this test gives the best results when the doctor can evaluate your heart during your usual activities.

• Be sure to contact the doctor’s office or clinic if an electrode falls off. Also, some monitors will make a noise which should be reported as well.