Holter ECG device vs. Resting ECG machine

Although an ECG may be obtained using only three basic electrodes (Positive, Negative and Earth), the bio-electrical signals also occur in more than a single dimension as the heart is three dimensional. For this reason, evaluation of the ECG in all three dimensions will give a more accurate ECG assessment, which is achieved by using higher number of electrodes, placed in various arrangements. While standard resting ECG machine will have 12 leads, providing vital information in 12 views of the heart, after several hours of in-patient monitoring  it will display only few minutes of heart muscle activity. Holter ECG is a portable monitoring device that operates on the same principle as ECG machine but it will acquire ECG recordings from two to five views of the heart, continuously over 24 or 48 hour period.

In practice of ambulatory ECG monitoring, seven lead recording will provide the optimum, three dimensional “picture” of the heart through 3 bipolar channels (each coupling Positive/Negative lead, plus one lead for Earth), further leads would be just unnecessary discomfort for the patient. It is also important to recognize that electrocardiography with ECG machine will be performed in quiet and isolated environment of medical institution,most frequently having patient lying on bed, in resting position. This time limited monitoring modus will not capture the abnormalities in electro-physiological functions of the patients' heart in most cases. The main purpose of monitoring with Holter devices is to have the patient participate in as many daily activities as possible, even in those that might place more demands on his/her heart, carrying Holter equipment without major feeling of discomfort. This way, medical professionals will have more diversified recording of the patients' heart rhythm over longer period and in variety of conditions, with aim to identify those that might trigger cardiac events and functional abnormalities.

Application and use of the monitoring equipment

The Holter monitor is compact and lightweight instrument, which is delivered with a pouch with straps in most cases (over shoulder and waist) to fasten it safely and comfortably to the patients' body or with a clip for clipping it to a belt or pocket edge. It is a battery powered device, storing recorded ECG data on a built-in memory or standard memory card. The Holter equipment has 3 to 7 wires called leads, coming out of the recorder unit, which are attached to disks commonly known as electrodes. The action potential created by the heart contraction spreads bio-electrical currents from the heart throughout the body and these currents induce different potentials at different points of the body.

Electrodes placed on the surface of the skin are sensitive enough to pick up these impulses, using biological transducers. They are made of metal with backing from various, hypoallergenic  materials, often self adhesive and disposable. The electrodes will be placed on the patient's chest in a specific order by the physician or the cardiologist, who will check their placement by running a short “real-time” monitoring session and introduce the last, but not the least important element of the Holter equipment: the Patient diary. In this diary, the patient shall make notes about the changes in his condition, activity or any symptom that may occur during monitoring. The use of the patient diary is of vital importance, since the authenticity of ambulatory monitoring lies in correlation between the symptoms experienced by the patient and the ECG recording. With this reason, its use should be duly explained by the doctor, before the patient goes home to resume his/her daily activities.