A Holter monitor is a portable electrocardiogram (EKG) that monitors the electrical activity of an ambulatory (freely moving) patient’s heart while the person goes about daily activities. There are a few reasons a physician might request that a patient wear a Holter monitor, but the most common is to diagnose an abnormal heart rhythm (arrhythmia). They are also sometimes used to monitor existing pacemakers, diagnose a lack of oxygen-rich blood flowing to the heart (cardiac ischemia) and measuring variability in the heart rate.

There is no special preparation for this painless test. Wires (electrodes) from the Holter monitor are taped to thoroughly cleansed areas on the patient’s skin, and the patient is sent home to go about his or her regular daily activities (except for showering/bathing). Patients will be asked to keep a diary of their activities and any symptoms they may experience. The test will last about 24 hours or up to five days, depending on the kind of Holter monitor and the patient's symptoms. Depending on the results output from the Holter monitor, the physician may order additional tests or treatment (e.g., antiarrhythmics).

A Holter monitor is a portable electrocardiogram (EKG) that monitors the electrical activity of an ambulatory (freely moving) patient’s heart for one to five days, 24 hours a day. The sensitive Holter monitor can be used to detect abnormal heart rhythms (arrhythmias) as well as cardiac ischemia – a usually temporary situation in which the heart is not getting enough oxygen-rich blood. Holter monitors may be especially useful to detect transient and short cardiac arrhythmias that might not be present during in-office EKG monitoring.

The device can also help to monitor pacemakers or evaluate how well medications are working, especially antiarrhythmics. Finally, Holter monitors or other forms of ambulatory EKG monitoring might be recommended for heart attack patients and patients with cardiomyopathy. The results of the Holter monitor may be compared to future results should further diagnosis or testing become necessary.

Holter monitors are important in the diagnosis and treatment of premature ventricular contractions, or PVCs. Research has shown that people who experience premature ventricular contractions are more likely to suffer from ventricular tachycardia and ventricular fibrillation. In these conditions, the ventricles beat too rapidly. Ventricular fibrillation is a medical emergency that requires rapid defibrillation to prevent sudden cardiac death. By detecting premature ventricular contractions with a Holter monitor, physicians are better able to design effective antiarrhythmic treatment programs, usually using various antiarrhythmic medications.

Holter monitors consist of electrodes that are attached to the chest of the patient. The electrodes are connected to a small unit that can be worn on a belt or over the shoulder using a shoulder strap. The unit records the data that the patient produces.   

After a patient is outfitted with a Holter monitor, he or she is sent home and instructed to go about usual daily activities while the heart’s electrical activity is recorded on a tape inside the machine. Patients are also told to keep a written diary of their activities and any physical symptoms they may have, such as palpitations (strong, fast or “galloping” heartbeat) or any chest pain. The diary is very helpful to the physician, who will match any written symptoms with the corresponding heart activity when evaluating the printout results.

In recent years, Holter technology has advanced and, in some cases, the devices are capable of transmitting their results over a telephone to the physician's office, called transtelephonic monitoring. Once transmitted, the results can be printed out as a standard EKG and interpreted. Although most of these transtelephonic devices are not equipped continuous monitoring, that option is sometimes available.

No special preparation is required for a Holter monitor, although patients may wish to shower or bathe before the monitor is fitted because they will not be able to while wearing the monitor. The patient should also inform the physician about any allergies to tape or adhesives.

As with the in-office EKG, this is a painless test in which electrodes connected by wires to the Holter monitor are taped to thoroughly cleansed areas on the patient’s skin. For men, a nurse may shave the necessary areas of the chest.

Once the electrodes are firmly in place, patients are instructed on how to use the monitor and then sent home to go about their usual daily activities. The only activities that must be avoided are the following:

Patients are also told to keep a diary of activities and any physical symptoms that take place while they are being monitored.

After the prescribed testing period is over, the recorded results are analyzed. Depending on the results, further testing or treatment (e.g., taking medications called antiarrhythmics) may be advised.

Additional tests that may be ordered after the Holter monitor results have been analyzed include:

Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions related to Holter monitoring:

1. How long will I be wearing the Holter monitor?
   
   
2. What are we looking for?
   
   
3. Will I feel anything when it is working?
   
   
4. Can I shower? Be exposed to water?
   
   
5. Is there any danger that electronic devices might interfere with my Holter monitor?
   
   
6. Will I know if it stops working? How?
   
   
7. What happens if one of the electrodes comes off?
   
   
8. What happens if I remove the device? Will I have to start over?
   
   
9. If these results are inconclusive, what is the next step in my diagnosis?
   
   
10. If these results reveal an abnormal heart rhythm, what are my treatment options?