Written by Dimitrios Vrachatis, Specialist Cardiologist, PhD, National and Kapodistrian University of Athens.
What is Holter ECG monitoring?
Holter ECG monitoring, also called cardiac rhythm monitoring or a rhythm recorder, records the electrical activity of the heart over a prolonged period — 24, 48 or more hours. It is named after its inventor, the American physicist Norman J. Holter, who devised it in 1949.
When is Holter monitoring needed?
The examination may be needed to:
- Investigate palpitations, such as a noticeable heartbeat or fluttering sensation.
- Investigate fainting or near-fainting episodes.
- Investigate episodes of dizziness.
- Diagnose or monitor arrhythmias such as atrial fibrillation.
- Detect life-threatening arrhythmias early in people at high arrhythmic risk, for example those with coronary artery disease.
- Measure the burden of premature beats.
- Diagnose bradyarrhythmias.
- Monitor heart rate in patients taking medicines that slow the heart, and in other situations.
What does a Holter ECG show?
It provides information about heart rate, heart rhythm and premature beats, helping diagnose or monitor different arrhythmias.
Although recording lasts much longer than a standard electrocardiogram, it may still fail to establish a diagnosis if the suspected or known arrhythmia does not occur during that period.
The examination may then be repeated one or more times, or the doctor may recommend an implantable loop recorder for continuous cardiac recording over 2–3 years.
The clinical suspicion and differential diagnosis guide further investigations, such as an electrophysiological study, according to the findings and each patient’s circumstances.
How is a Holter fitted, and what does the examination involve?
Fitting the Holter takes only a few minutes. You will need to uncover your chest.
The device has a very lightweight central unit carried in a special pouch, connected by 5–7 electrodes (wires) to adhesive patches on the front of the chest. The central unit records the electrical activity of the heart, much like an electrocardiograph, but for a longer period. The patient does not need to remain in the examination room and returns to everyday activities.
Where is the Holter fitted?
It is usually fitted at the clinic. If the person cannot travel, it can be fitted at home.
What should I be aware of while wearing a Holter?
Depending on the device, a Holter can record for 24 or 48 hours, or longer. Follow your usual activities and note the time of any symptoms. Modern devices allow you to mark the time of a symptom by pressing a dedicated button.
No special precautions are needed, except that you must not bathe or shower because the device is usually not waterproof and could be damaged. Do not move the electrodes during the examination.
Although modern devices are small, loose, comfortable clothing can prevent discomfort from the device and electrodes.
Is any preparation needed before Holter monitoring?
No special preparation is required. Increased chest hair can sometimes prevent the adhesive patches from staying in place. In that case, a small area may need to be shaved to keep the electrodes secure.
As bathing is not permitted during the recording, it is advisable to bathe or shower before the appointment.
Medication is usually continued unless the doctor advises otherwise.
How and when is the Holter removed?
At the end of the scheduled recording period, the electrodes are removed by the patient or the doctor, according to detailed instructions provided beforehand. The cardiologist then connects the central unit to a computer and transfers the data.
Holter ECG results
Using specialised software, the cardiologist analyses the complete recording and looks for potentially significant clinical events. The times of symptoms identified by the patient are also reviewed separately.
The process is computer-assisted but is not automatic. Results are available only after the doctor has processed and interpreted the recording, which can take time. The final diagnostic report is usually provided the following day.
This highlights the importance of the human factor: the cardiologist interpreting the recording needs to know why the test was requested and which arrhythmia is being sought. A Holter ECG does not simply generate an automatic number. Having the examination performed by the treating doctor therefore has an advantage over an assessment carried out without that personal context at a diagnostic centre.
Are there any risks from Holter monitoring?
Holter monitoring is non-invasive and carries no significant risks. It is completely painless. Very rarely, the adhesive electrode patches may cause skin irritation.