Holter electrocardiogram (ECG) measures the electrical activity of a human heart. It is a portable device that continuously records the electrical heart activity of the circulatory system/cardiovascular system for a specified period of time (usually up to 24-48 hours).
The activity is performed by positioning electrodes at explicit locations on the body, such as chest, legs, and arms. This presents a graphical representation of the electrical activity of the heart. Any changes in the activity from the standard tracing may indicate heart-related conditions. Besides, disorders which are not directly connected with the heart conditions can also instigate changes in the electrocardiogram (ECG). 
Holter electrocardiography or Regular ECG Test?
A regular (resting) ECG test traces a very minute portion of the heart’s activity, which is not more than 0.25% of a person’s daily heartbeats. Also, the test is usually performed as a person rests and so, it fails to indicate how the heart acts in response to the normal routine activities. This means, a regular ECG test is generally prescribed by Singapore heart specialist to measure the time intervals of a heart’s wave (i.e., to determine the total time taken by the wave or an electrical impulse to pass through one section of the heart to the other), which in turn, signifies if this electrical activity is irregular, slow, or fast. An ECG test is often regarded as a baseline test that is used to identify various heart problems like changes in the rhythm of heart and heart rate, determines the propensity to particular rhythm disturbance, identifies any abnormalities of the heart’s muscle, and captures injury to the heart prior or during a heart attack. 
Holter monitor, on the other hand, enables a physician to verify the indications of ephemeral cardiac problems (i.e., temporary problems that are momentary or short-lived), which are not apparently identified by a standard ECG test. These problems may include – cardiac ischemia or reduced blood flow to the heart muscles, cardiac arrhythmias or irregular heart rhythms, to name a few. In addition, Holter ECG is also prescribed by doctors in following circumstances:
- during open heart surgeries
- to monitor patient’s cardiac activities post a heart attack
- to evaluate the functionality of a pacemaker
Additional ECG Procedures
Besides Holter monitoring, other ECG tests recommended by a physician include:
- Stress Test or Exercise ECG
- Signal-averaged ECG
Premonitions for Holter Monitoring
Holter Monitoring is also referred as the Ambulatory Electrocardiographic Monitoring or AECG. It is deliberated as a medically acceptable and essential test for seamlessly capturing the ECG abnormalities of a heart in an ambulatory environment. Some of the indications for recommending Holter Monitoring by physicians include:
- Inexplicable syncopal episode experienced by the patient
- Transient cerebral ischemia episode experienced by the patient, which may possibly lead to cardiac rhythm risk
- Frequent palpitations felt by the patient
- Regular ECG examination failed to provide satisfactory explanations of the patient’s complaints, which may include (but are not limited to) breathlessness, chest pain, syncope, skipped heart beats, and palpitations
- Holter ECG is indispensable to evaluate and manage the patient’s significant cardiac condition or disorder
- Patients with serious heart conditions like myocardial ischemia or cardiac arrhythmias, wherein Holter Monitoring is imperative
- The patient’s cardiac medication is affecting his/her heart’s electrical conduction system for which Holter Monitoring is required to check and evaluate the cardiac rhythm
- For clinical assessment to check the possible malfunctioning of pacemaker
In the aforementioned instances, Holter Monitoring is performed as a standard medical practice to diagnose the reflected conditions.
Conditions diagnosed by Holter ECG
Holter monitoring may be performed by the physicians to diagnose:
- Atrial fibrillation or flutter
- Palpitations in the heart
- Multifocal atrial tachycardia
- Ventricular tachycardia
- Diagnose the explanations for fainting
- Paroxysmal supraventricular tachycardia
- Slow heart rate or bradycardia
How Holter ECG Works?
The electrodes or minute conducting patches are directly attached to the patient’s explicit locations on the body (chest, arms, and legs). The patches are further are connected by wires to a recording monitor that operates on batteries. As the patient wears the patch holding the monitor, the device commences recording the electrical activities of the heart. It’s important to:
- Avoid showering, swimming, and bathing while wearing the device.
- Keep a track of these activities while wearing the monitor as it will help the physician to determine changes and movements in the heart, if any.
- While the 24 to 48 hours test is painless, it is essential to record if any pain in the chest or abnormal heart rhythms or other major symptoms is observed.
It is important to check that the electrodes are firmly attached to the patient’s chest, so the device indicates an accurate recording related to the heart’s behavior and movements.
While wearing the machine, always avoid:
- Wearing electric blankets
- Places with high voltage intensity
- Magnetic areas/direct contact with magnets
- Stay away from metal detectors
Apart from above, a person may continue to pursue his/her normal activities whilst wearing the Holter monitor. At times, a physician may instruct the patient to perform certain exercises while being monitored in order to check if the symptoms are the results of exercises performed in the past.
Risks Associated with Holter Monitoring
This test is prescribed as a necessary medical condition by the physicians to identify certain behavior and movements that a regular ECG fails to identify. There are no distinguishable risks associated with the Holter electrocardiogram. Nevertheless, any abnormal result may be the consequence of insufficient oxygen (due to any physical activity performed during the test), or any fault in the monitor. 
Alternative Names to Holter Electrocardiogram
The test is also popularly known as:
- Ambulatory electrocardiography
- Electrocardiography – ambulatory
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