Holter and Event Monitors

  • Holter and event monitors are medical devices that record the heart’s electrical activity. Doctors most often use these monitors to diagnose arrhythmias (ah-RITH-me-ahs).
  • Arrhythmias are problems with the rate or rhythm of the heartbeat. During an arrhythmia, the heart can beat too fast, too slow, or with an irregular rhythm.
  • Holter and event monitors are also used to detect silent myocardial ischemia (is-KE-me-ah). In this condition, not enough oxygen-rich blood reaches the heart muscle. “Silent” means that no symptoms occur.
  • The monitors can also check whether treatments for an arrhythmia or silent myocardial ischemia are working.
  • Our office performs three types of monitors: Holter, Event, and an implantable loop recorder.


  • Holter monitors sometimes are called continuous EKGs (electrocardiograms). This is because Holter monitors record your heart rhythm continuously for 24 to 48 hours.
  • A Holter monitor is about the size of a large deck of cards. You can clip it to a belt or carry it in a pocket. Wires connect the device to sensors (called electrodes) that are stuck to your chest using sticky patches. These sensors detect your heart’s electrical signals, and the monitor records your heart rhythm.


  • Event monitors are similar to Holter monitors. You wear one while you do your normal daily activities. Most event monitors have wires that connect the device to sensors. The sensors are stuck to your chest using sticky patches.
  • Unlike Holter monitors, event monitors don’t continuously record your heart’s electrical activity. They only record during symptoms. For many event monitors, you need to start the device when you feel symptoms. Some event monitors start automatically if they detect abnormal heart rhythms.
  • Event monitors tend to be smaller than Holter monitors because they don’t need to store as much data.
  • Different types of event monitors work in slightly different ways. Your doctor will explain how to use the monitor before you start wearing it.


  • You can’t get your monitor wet, so you won’t be able to bathe or shower. You can take a sponge bath if needed.
  • A good stick between the patches and your skin helps provide a clear signal. Poor contact leads to a poor recording that’s hard for your doctor to read.
  • Oil, too much sweat, and hair can keep the patches from sticking to your skin. You may need to shave the area where your doctor will attach the patches.
  • The sticky patches used to attach the sensors (electrodes) to your chest have a small risk of skin irritation. You also may have an allergic reaction to the paste or gel that’s sometimes used to attach the patches. The irritation will go away once the patches are removed.
  • Too much movement can pull the patches away from your skin or create “noise” on the EKG strip. An EKG strip is a graph showing the pattern of the heartbeat. Noise looks like a lot of jagged lines; it makes it hard for your doctor to see the real rhythm of your heart.
  • When you have a symptom, stop what you’re doing. This will ensure that the recording shows your heart’s activity rather than your movement.
  • While using a Holter or event monitor, your doctor will advise you to keep a diary of your symptoms and activities. Write down what type of symptoms you’re having, when they occur, and what you were doing at the time.
  • Make sure to note the time that symptoms occur, because your doctor will match the data with the information in your diary. This allows your doctor to see whether certain activities trigger changes in your heart rate and rhythm.
  • Also, include details in your diary about when you take any medicine or if you feel stress at certain times during the testing period.
  • When the testing period is done, you’ll return the device to your doctor’s office. Your doctor will tell you when to expect the results. Once your doctor has reviewed the recordings, he or she will discuss the results with you.