Holter and event monitors are medical devices that record the heart's electrical activity. Doctors most often use these monitors to diagnose arrhythmias. These are problems with the speed or rhythm of the heartbeat. During an arrhythmia, the heart can beat too fast, too slow, or irregularly.

Holter and event monitors also are used to detect silent myocardial ischemia. In this condition, not enough oxygen-rich blood reaches the heart muscle. "Silent" means that no symptoms occur.

These monitors also can check whether treatments for arrhythmia and silent myocardial ischemia are working.

Overview

Holter and event monitors are similar to an EKG (electrocardiogram). An EKG is a simple test that detects and records the heart's electrical activity. It's the most common test for diagnosing a heart rhythm problem.

However, a standard EKG only records the heartbeat for a few seconds. It won't detect heart rhythm problems that don't occur during the test.

Holter and event monitors are small, portable devices. You can wear one while you do your normal daily activities. This allows the monitor to record your heart for a longer time than an EKG.

Some people have heart rhythm problems that only occur during certain activities, such as sleep or physical exertion. Using a Holter or event monitor increases the chance of recording these problems.

Although similar, Holter and event monitors aren't the same. A Holter monitor records your heart's electrical activity the entire time you're wearing it. An event monitor only records your heart's electrical activity at certain times while you're wearing it.

How the Test is Performed

Electrodes (small conducting patches) are stuck onto your chest and attached to a small recording monitor. You carry the Holter monitor in a pocket or small pouch worn around your neck or waist. The monitor is battery operated.

While you wear the monitor, it records your heart's electrical activity. You should keep a diary of what activities you do while wearing the monitor. After 24 - 48 hours, you return the monitor to your doctor's office. The doctor will look at the records and see if there have been any irregular heart rhythms.

It is very important that you accurately record your symptoms and activities so that the doctor can match them with your Holter monitor findings.

How to Prepare for the Test

There is no special preparation for the test. Your doctor will start the monitor. You'll be told how to replace the electrodes should they fall off or become loose.

Tell your doctor if you are allergic to any tape or other adhesives. Make sure you shower or bathe before you start the test. You will not be able to do so while you are wearing a Holter monitor.

How the Test Will Feel

This is a painless test. However, some people may need to have their chest shaved so the electrodes can stick.

You must keep the monitor close to your body. This may make sleeping difficult for some people.

You should continue your normal activities while wearing the monitor.

Why the Test is Performed

Holter monitoring is used to determine how the heart responds to normal activity. The monitor may also be used:

  • After a heart attack
  • To diagnose heart rhythm problems
  • When starting a new heart medicine

It may be used to diagnose:

  • Atrial fibrillation/flutter
  • Multifocal atrial tachycardia
  • Palpitations
  • Paroxysmal supraventricular tachycardia
  • Reasons for fainting
  • Slow heart rate (bradycardia)
  • Ventricular tachycardia

Normal Results

Normal variations in heart rate occur with activities. A normal result is no significant changes in heart rhythms or pattern.

What Abnormal Results Mean

Abnormal results may include various arrhythmias. Changes may mean that the heart is not getting enough oxygen.

The monitor may also detect conduction block, a condition in which the atrial electrical activity is either delayed or does not continue into the ventricles of the heart.

Risks

There are no risks associated with the test. However, you should be sure not to let the monitor get wet.