The Holter monitor or continuous electrocardiography
or ambulatory electrocardiography was developed by Norman J. Holter, an American researcher in the 1940s, and is used to continuously record the electrical activity of the heart (continuous ECG or EKG) over a period of 24 hours to 48 hours. The Holter monitor is a home monitor and is used to understand conditions, such as arrhythmia of the heart, fatigue, fainting, palpitations, and dizziness. Such conditions may not be detected with the standard ECG. This is due to the fact that many of these conditions, such as dizziness, occur suddenly and subside after a period of time. If the standard ECG recording is not taken during the events, it is difficult to detect these conditions. Hence, continuous monitoring of the electrical activity of the heart is preferred.
Procedures in a Holter Monitor Test
There is no pain involved in this procedure. The general procedure in the use of a Holter monitor involves carrying a monitor (weight- ~190 g; dimensions – 70 x 95 x 20 mm) that is equipped with a flashcard to record data from 2 to 3 electrode adhesive patches connected to the monitor by lead wires. These electrodes are stuck on the chest, and the electric activity is recorded and stored on the flashcard for a period of 24 to 48 hours. The monitor is battery-operated. The analysis of the data is in digital format. Patients can carry the Holter monitor in a pouch around the neck or the waist. Patients are requested to maintain a diary to note down the symptoms. The exact time of occurrence of the symptoms should be noted. This helps in comparing heart activity irregularities in the data recordings with the symptoms.
The doctor first explains the procedure to the patient and lets the patient clarify any doubts regarding the procedure. The doctor also assesses the patient’s medical history to identify any additional procedures to be followed before using the monitor. The patient is requested to remove jewellery and other accessories on the upper half of the body. The clothes from the upper half of the body are removed and the adhesive electrodes are stuck onto the chest. The patient should inform the doctor of any allergies to adhesives before the electrodes are stuck to the chest. Some patients may need to have their chest shaved in order to fix the electrodes to the chest. The patient should shower before the electrodes are attached. Once the monitor is attached, the patient cannot shower until the monitor is removed. The patient is educated on the use of the monitor and how to replace and attach the electrodes if they fall off. The monitor should always be kept close to the body. The patients can resume their normal activities after being fitted with the electrodes.
When the data is analyzed, any abnormality in the data is compared with the symptoms recorded by the patient. Since the monitor records the electrical activity of the heart, the patient is advised to keep clear of high-voltage areas, magnets, and electrical appliances, such as hair dryers, shavers, toothbrushes, and electric blankets.
Uses of a Holter Monitor
The Holter monitor may be used for the following purposes:
- To check the condition of a pacemaker
- To detect arrhythmias of the heart
- To detect possible cardiac cause of dizziness, fatigue and fainting
- To detect the risk of cardiac events in certain conditions affecting the heart, such as Wolff-Parkinson-White syndrome (abnormal electrical activity within the heart), weakness of the walls of the heart following a heart attack, or thickening of the heart walls (idiopathic hypertrophic cardiomyopathy)
- To monitor chest pain that does not occur due to exercise
- To analyze the effectiveness of drugs used to treat the heart for conditions, such as cardiac arrhythmia
- To detect slow heart beat rate (bradycardia) or fast heart beat rate (tachycardia).
Limitations of a Holter Monitor
- Abnormalities in the heart rate need to be correlated with patient symptoms. When the patient does not log in the symptoms correctly, it is difficult to correlate and identify the condition of the heart.
- The data is recorded over time and does not give data collected at a specific time or in other words, real-time analysis.
- The diagnostic efficiency of Holter monitors is high for patients who exhibit daily symptoms. However, it is low compared with the newer continuous recording devices.
- Certain medications and smoking can interfere with the recording of data in the monitors.
- Perspiration can cause the electrodes to fall off from the chest. On the other hand, sensitive skin on the chest may be inflamed or irritated with continuous application of the electrodes.
Advantages of a Holter Monitor
- A Holter monitor test is a non-invasive test and can be used o an outpatient basis.
- The Holter monitor can record ECG continuously providing an overall picture of the heart activity. The digital data can be obtained without any additional effort from the patient.
Costs of a Holter Monitor Test
In the USA, a Holter monitor scan can cost ~357 dollars, while a Holter monitor recording can cost ~395 dollars. In India, it costs anywhere between Rs. 1000 to Rs. 4000.
Recent Advances in Holter Monitors
There are new Holter monitors that can record data for nearly 2 weeks. In addition, Holter monitors with 12-lead electrodes have been used to analyze heart rate irregularities in underwater divers at different stages (pre-diving, diving, and post-diving).