Ambulatory monitors are small, portable electrocardiograph machines that are able to record the heart’s rhythm. Each type of monitor has unique features related to length of recording time and ability to send the recordings over the phone.

Your doctor uses ambulatory monitors to:

  • assess your heart rhythm over time
  • correlate your symptoms with your heart rhythm
  • diagnose abnormal heart rhythms: what kind they are, how long they last, and what may cause them
  • guide treatment for abnormal heart rhythms

To prepare:

  • Avoid oily or greasy skin creams and lotions where the monitor is applied. They interfere with the electrode-skin contact.
  • Wear a shirt that can be easily removed to place the electrodes on the chest.

Holter Monitor (Ambulatory ECG)

  • A Holter monitor is a portable ECG recorder that you wear during your normal daily activities, including sleeping.
  • It can be worn up to 24 hours.
  • Electrodes (sticky patches) are placed on the skin of your chest. Wires are attached from the electrodes to a box about the size of a portable tape player and worn on a belt or shoulder strap. The electrical impulses are continuously recorded and stored in the Holter Monitor.
  • While you are wearing the monitor, you will be asked to keep a diary of your activities and your symptoms, such as fluttering feelings in your chest (palpitations), rapid heartbeats, and any episodes of dizziness or faintness. It's important to keep track of the activities you were doing when your symptoms occurred, so your doctor can see what kinds of events are bringing them on.

Holter Monitor

  • When the Holter monitor test is complete, you will return the Holter Monitor. A technician plays the tape on a special computer that analyzes the recording and looks for any abnormalities of the rhythm. The technician prepares a full report for the doctor, including a printout of abnormal heart rhythms.

Event Monitor (Event Recorder)

  • This device, similar to a Holter monitor, is worn during normal daily activities including sleeping; however, it is worn for a longer period of time. You will learn how to take the device off during showers and baths. It is used for arrythmias that occur less frequently.
  • Small electrodes are attached to your chest. Wires are attached from the electrodes to a box about the size of a portable tape player and worn on a belt or shoulder strap.
  • When you feel symptoms, you depress a button and the recorder is activated. The monitor records the event for the 60 seconds prior to your pushing the button and up to 40 seconds after the arrhythmia is over. The event monitor can store up to three events.
  • The rhythm can be sent immediately or saved and transmitted later, over the phone line. The technician will give the recordings to your doctor for review. If the reading indicates an emergency, the technician will instruct you to go to the emergency room.

CardioNet (Mobile Cardiac Outpatient Telemetry)


Technician instructing on event monitor

  • CardioNet mobile telemetry allows continuous heartbeat monitoring as you go about your daily activities. Most people are on the CardioNet service from seven to 14 days.
  • This device consists of a small sensor attached to three electrode pads, worn either as a lavalier, which is invisible under clothing or on a belt clip.
  • The sensor sends each heartbeat to a handheld monitor that can be tucked into a pocket or purse.
  • When the monitor detects a heart rhythm problem — whether you feel it or not — it automatically transmits your ECG to the CardioNet monitoring center. At the CaridoNet Center, which operates around the clock, certified cardiac technicians analyze each transmission, respond appropriately to each event and transmit diagnostic reports to your doctor.
  • If you feel a symptom, you use the touch screen on the CardioNet monitor to report it. The monitor transmits the symptom you entered and your ECG to the CardioNet monitoring center. Integrated symptom and ECG data can help doctors rule in, or rule out, cardiac causes for symptoms such as dizziness and fainting.

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Transtelephonic Transmitter

  • Transtelephonic transmitters are not worn continuously. They are used only during the phone-monitoring period.

Transtelephonic Transmitter

  • In the past, this type of transmitter was used for monitoring pacemaker function. However, now it is used for patients with arrhythmias to monitor certain events indicated by their doctor.
  • When you are ready to call the Pacemaker-Arrhythmia Center, use the electrode transmitter as directed. The electrode may be a finger electrode, wrist bracelet or chest plate.
  • You will dial the center and place the telephone into a transmitter. Hold as still as possible during the transmission. After you have completed the transmission, the nurse or technician will ask you questions about your symptoms and current medications.
  • Your doctor will review the recordings and information provided by the arrhythmia-pacemaker clinic.

Reviewed: 09/13 This information is about testing and procedures and may include instructions specific to Cleveland Clinic. Please consult your physician for information pertaining to your testing.