Holter Monitoring

Holter Monitoring

A Holter monitor is a portable device for continuously heart activity (ECG). Its extended recording period is sometimes useful for observing occasional cardiac arrhythmias which would be difficult to identify in a shorter period of time. For patients having more transient symptoms, a cardiac event monitor which can be worn for a month or more can be used.

Much like standard electrocardiography the Holter monitor records electrical signals from the heart via a series of electrodes attached to the chest. Electrodes are placed over bones to minimize artifacts from muscular activity. The number and position of electrodes varies by model, but most Holter monitors employ between three and eight. These electrodes are connected to a small piece of equipment that is attached to the patient’s belt or hung around the neck, and is responsible for keeping a log of the heart’s electrical activity throughout the recording period.

Modern units record onto digital flash memory devices. The data are uploaded into a computer which then automatically analyzes the input, counting ECG complexes, calculating summary statistics such as average heart rate, minimum and maximum heart rate, and finding candidate areas in the recording worthy of further study by the technician.

Although there are many patients having fear of Holter examination, there is nothing to be worry about. There are no contraindications for this examination and it doesn’t interfere with the normal daily life much.

The recording device can be worn on a belt or in a case on a strap worn across the chest. Individuals who want to minimize the visibility of the device can wear layers or bulky clothes so the case is not as obvious. Also, because of the placement of the electrodes, individuals wearing a Holter monitor may wish to wear shirts with a high neck.

Patient wearing the monitor should act as he/she wouldn’t have any device with him/her self and not limit his/her normal daily activities. That’s because it is the intention to do the monitoring in normal life style conditions. Exceptions relate only to activities associated with water such as showering – although removal of the device and connected electrodes can be done occasionally. These situations can also happen during the batteries or electrodes change (both in case of multiple day monitoring).

When the recording of ECG signal is finished (usually after 24 or 48 hours), it is up to the physician to perform the signal analysis. Since it would be extremely time demanding to browse through such a long signal, there is an integrated automatic analysis process in each Holter software which automatically determines different sorts of heart beats, rhythms, etc. However the success of the automatic analysis is very closely associated with the signal quality. The quality itself mainly depends on the attachment of the electrodes to the patient body. If these are not properly attached, the electromagnetic disturbance surrounding us will influence the ECG signal resulting thus in a very noisy record. If the patient moves rapidly, the distortion will be even bigger. Such record is then very difficult to process. Besides the attachment and quality of electrodes, there are other factors affecting the signal quality, such as muscle tremors, sampling rate and resolution of the digitized signal.

The automatic analysis commonly provides the physician with information about heart beat morphology, beat interval measurement, heart rate variability, rhythm overview and patient diary (moments when the patient pressed the patient button). Another requirement is the ability of pacemaker detection and analysis. Such ability is useful when one wants to check the correct pacemaker function.