​Children's Heart Center

Holter/Event Monitor

When symptoms such as dizziness, fainting, low blood pressure, prolonged fatigue or palpitations continue to occur without a definitive diagnosis obtained with a resting EKG, the patient’s doctor may request an EKG tracing to be run over a long period of time to try to detect arrhythmias. Certain arrhythmias may occur sporadically or only under certain conditions, such as stress. Arrhythmias of this type are difficult to obtain on an EKG tracing that only runs for a few minutes.

A prolonged type of EKG tracing called a Holter monitor provides a better method of capturing abnormal heartbeats or rhythms that may be causing patients’ symptoms. The Holter monitor records the patient’s EKG tracing continuously for a period of 24 hours or longer. Patients are provided instructions on how long to wear the recorder, how to keep a diary of activities and symptoms during the test, and personal care/activity instructions.

Another similar method of capturing abnormal heart rhythms is called event monitoring. This is often preferred for the same reasons. Once connected to the patient, this monitor also records EKG tracings over a period of 24 or more hours – in some cases, up to 30 days – the difference being that event monitors do not record continuously. Instead, they only record when the patient feels symptoms and manually triggers the device to record the EKG tracing at that moment in time.


Holter/Event Monitoring is often useful in:

  • Evaluating chest pain
  • Evaluating other signs and symptoms which may be heart-related, such as fatigue, shortness of breath, dizziness or fainting
  • Helping to identify irregular beats
  • Evaluating abnormal rhythms previously identified during a resting EKG

Performing Holter/Event Monitoring

  • EKG electrodes are placed on the patient’s chest and lead wires are attached from the electrodes to the monitoring/recording device.
  • The EKG monitor is small and portable, approximately the size of a small paperback book or not much larger than the average cell phone. The monitor may have a strap so it may be worn over the shoulder, or it may be clipped to a belt or pocket.
  • Patients are given instructions on:
    • How to keep the electrodes attached to the patient’s skin
    • How to check the monitor for problems
    • When to call the physician’s office for help
    • Keeping the electrodes and monitor dry by having the patient not take a shower or tub bath (a sponge bath is usually allowed) or go swimming
    • Avoiding situations where the patient may perspire excessively, causing the leads to detach
    • How to keep a diary during the procedure, noting the date and time of day of any changes in activity and symptoms
    • For Event Monitors only – How to trigger a recording on the monitor when the patient feels one or more symptoms, such as chest pain, dizziness or palpitations. The patient or home caregiver will push a button on the event monitor recorder. Some monitors have a feature called “memory loop recording” that can include a recording of a short period of time prior to the moment of the triggered recording and afterwards. This feature can help provide more details about the possible change in EKG at the time the symptoms started and what was happening with the patient just before the monitor was triggered to record. Other event monitors, called “post-event recorders” simply start recording the EKG from the moment the trigger is initiated.
    • How to transmit the event to a central monitoring center
    • How to maintain a handwritten diary, as well as key information to include, such as symptoms and corresponding activities at the time of the event
    • The importance of avoiding the use of electrical appliances, such as electric razors, hair dryers or electric toothbrushes near the patient so the EKG signal will not receive electrical interference on the recording. If these appliances are used near the patient, it should be noted in the diary.
    • The importance of avoiding magnets, metal detectors, areas with high-voltage electrical wires and electric blankets during the time the monitor is connected as these can also create electrical interference on the recording.
  • Once the monitor has been connected to the patient and given instructions, the patient is allowed to return to normal activities unless instructed otherwise by the doctor.
  • Patients are provided a telephone number to call in case one or more of the electrodes comes off or if the monitor starts beeping.
  • When documenting in the diary, it’s important to write down the date and time of any symptoms experienced by the patient, as well as what the patient was doing at the time, including any unusual circumstances that might have occurred at the time.
  • At the end of the monitoring period, the patient will return to the doctor’s office to have the electrodes removed and the monitor discontinued. Alternatively, patients may be instructed to do this themselves at a certain time and date, and return the monitor by mail or other specified package delivery service.