Holter ECG daily monitoring (HM): what is it, how to do and decipher

What is Holter

This is a method of continuous ECG recording during normal daily activities with the recording of the results on a memory card and further analysis of the data obtained.

The main idea of ​​outpatient electrocardiography is to increase the duration and possibility of recording an ECG in the natural environment for the patient, which implies an increase in the diagnostic value and sensitivity of the method to disturbances in the rhythm and conduction of the heart.

A Holter monitor is a portable cardiograph, the size of a mobile phone, that connects wires to sensors that are attached to the surface of the body. This device continuously records an electrocardiogram at a 24-48 hour interval.

Unlike short-term ECG recording with a standard cardiograph, long-term Holter cardiac monitoring helps:

1. To assess the relationship between the occurrence of arrhythmias and clinical symptoms, including syncope.
2. To identify transient cardiac arrhythmias in patients with appropriate clinical symptoms.
3. To register the moments of the appearance and termination of paroxysms, which makes it possible to identify the mechanism of arrhythmias and to carry out differential diagnostics.
4. Make a quantitative and qualitative assessment of arrhythmias necessary for risk stratification (assigning a patient to a particular group, taking into account the likelihood of complications).
5. Establish the dependence of the occurrence of arrhythmias on the deficit of coronary blood flow.
6. Check the efficacy and safety of drug therapy for arrhythmias.
7. To assess the functioning of implanted devices (pacemakers, cardioverter-defibrillators).

Mechanism of work

The result of the latest developments was the appearance on the market of devices with multifunctional monitoring, which, in addition to ECG, record the level of blood pressure and other physiological parameters.

The mechanism of work of daily heart rate monitors is identical to the ECG apparatus. Sensors are fixed on the patient's body, with the help of which there is a continuous (or episodic, with multi-day fragmentary monitoring of events) recording of the electrical activity of the myocardium. The indicators are transmitted through the wires to the recorder with a memory card. The latest models have an online data transfer function.

How the device works and what types of it are

Holter heart monitoring device provides:

• long-term registration of ECG in conditions of daily standard activity of the patient;
• reproduction of registered signals;
• decoding and interpretation of the received data.

Most modern systems for daily ECG monitoring consist of:

1. Recording device:
   • Electrodes (sensors attached to the surface of the body).
   • Connecting wires.
   • The main cable.
   • Pressing signaling device.
   • Registrar.
2. Analyzing part. Software that performs systematic analysis of recorded data.

The recorder is fixed to the subject's body for the entire monitoring period. The device is powered by a rechargeable battery or batteries. The indicators are usually recorded on a removable storage medium (flash card).

Most recorders have an “event marker” button on the body that the patient presses when certain symptoms appear.

For convenience and preservation of research results, the reading part of the device transfers and converts the information contained on the removable medium to the analyzing element (a computer with special programs for decoding and characterizing the ECG signal).

Continuous contact of the recorder with the patient's torso is provided with the help of disposable self-adhesive electrodes, consisting of silver-chlorine alloys.

Comparative characteristics of devices for outpatient cardiogram monitoring:

There are also cardiorespiratory systems, in which, in addition to the ECG, sensors for monitoring respiration, oxygen in the blood, and patient movements are mounted. Such a study is often carried out during sleep, the somnologist deciphers the results.

Main manufacturers and their features

The leaders in the production of heart monitors are Great Britain, Germany and the Czech Republic. There are also several companies in Russia offering Holter monitors at a lower cost.

The price of the device depends on the set of additional functions, ease of use, battery and memory card capacity, as well as the duration of continuous operation, the possibility of online transmission of indicators and software for decrypting data.

As you know, in some patients episodes of arrhythmia are rare and it is impossible to register them during Holter. For this purpose, a cardiac technique was developed for fragmentary ECG monitoring. So-called “event recorders” record a short ECG episode after activating the device by a patient who was experiencing symptoms at the time. At the end of the recording, the data is saved in the memory and sent to the doctor using the phone.

Comparison of the latest devices for daily ECG monitoring:

Indications for 24-hour ECG monitoring

Continuous ECG monitoring throughout the day helps to identify the pattern of arrhythmias, their specificity, additional phenomena that develop when the normal heart rate resumes. This allows you to determine the tactics of treatment.

Holter ECG 24-hour monitoring is indicated for:

1. Complaints indicating arrhythmias (palpitations, interruptions, fading, loss of consciousness, dizziness, chest pain).
2. Risk stratification of life-threatening arrhythmias in patients without characteristic signs of pathology, but with:
   • Hypertrophic cardiomyopathy.
   • Recently suffered acute coronary syndrome complicated by circulatory failure or arrhythmia.
   • Long Q-T syndrome.
3. Verification of the diagnosis of arrhythmia in patients with latent course of the disease.
4. The need to test the effectiveness of selected antiarrhythmic drugs.
5. Evaluation of the functional state of the implanted cardiac device:
   • In patients with complaints of interruptions in the heart.
   • With individual device settings.
6. Assessment of insufficient blood supply to the myocardium in case of suspicion of:
   • Prinzmetal's angina.
   • Acute coronary syndrome.
   • Ineffectiveness of drug therapy for coronary artery disease.
7. To characterize the lability of the heart rate in patients with diabetes mellitus and sleep apnea who have undergone acute coronary syndrome, which is complicated by heart failure, as well as to determine disorders of autonomic innervation.
8. Tracking the 24-hour dynamics of the Q-T interval in case of suspected long Q-T syndrome.

The most common indication for Holter is symptoms suggestive of arrhythmia:

• recurrent rapid heartbeat;
• dizziness;
• fainting conditions of unknown origin;
• periodic chest discomfort, shortness of breath, weakness.

Daily monitoring of the heart according to Holter has no absolute contraindications.

Examination rules

Before starting the study, the patient gets acquainted with the information:

• date and time of the next visit to remove the device;
• the rules for keeping records in the diary;
• cases of using the button analyzer;
• prohibition of bathing, the use of electrically heated bedding;
• prohibition on self-configuration of the registrar;
• constant monitoring of the position and contact of sensors, wires and the timely restoration of the normal operation of the device.

If there is excessive hair growth on the skin of the investigated person in the places of planned imposition of sensors, it must be got rid of. Then the skin is treated with isopropanol or acetone and wiped with a special sponge or abrasive paste for complete degreasing. This reduces skin resistance, which improves the recording quality and prevents the electrode lagging during physical activity. After gluing the sensors, their resistance is checked (no more than 8 kOhm).

The electrodes are connected to the recording device using wires 85-95 cm long. Then they are fixed on the patient's skin with a plaster, twisting into a loop (better shock absorption during movement). In the hot season, the sensors are fixed with a double amount of plaster. During sleep, the subject wears tight underwear.

Sensors are usually applied to areas of the body with a small volume of muscle to avoid artifacts and signal distortion during active movements.

After installing the device, a functional test is made to determine the reliability of the contact of the sensors with the skin. To do this, an ECG record is displayed on a computer monitor, while the patient changes the position of the body in space.

Then a power source is inserted into the recording device, which is placed in a case and fastened to a belt.

Patient diary keeping

For the period of daily monitoring of the ECG according to Holter, the patient is obliged to keep a diary, where it is necessary to fill in the necessary columns in detail.

This document is divided into two halves:

1. Part A, where the patient indicates:
   • Activity type (sleep, walk, physical work, car driving, stress).
   • Signs of pathology (pain, heartbeat, shortness of breath, chest tightness, dizziness, sudden weakness).
   • Time of drug use (name and dose).
   • Hours of start and end of activity and complaints (from - to).

Example:

2. Part B (the patient fills in only for chest pain):
   • Character (dull, oppressive, stabbing).
   • Time of appearance (rest, work, stress, sleep).
   • The intensity of pain decreases on its own (when), after the termination of the load, taking nitrates.

Additionally, on the model of the patient's torso, he indicates the localization of pain sensations.

Interpretation of results and conclusion

The findings of the Holter study indicate:

1. Examination conditions (inpatient or outpatient).
2. Leads used
3. Sinus rhythm parameters.
4. The quantitative and qualitative characteristics of the detected pathology (how many times occurred and how long the episodes lasted).
5. Description of repolarization disorders in the myocardium.
6. Fragments of maximum elevation and depression of the S-T segment.
7. Clarification of the relationship of arrhythmic and ischemic phenomena with the presented complaints.

The software on the computer decodes the ECG and keeps track of:

• the amount of QRS complexes recorded during the study period;
• sections of the fastest and slowest heart rate with the exact time of its registration;
• the number of occurrence of tachy- and bradycardia;
• the number of extrasystoles, their proportions per 1000 cardiac cycles;
• episodes of ventricular arrhythmias.

Sometimes the doctor issues an extended protocol, which further describes:

1. Detailed analysis of cardiac disorders.
2. Analysis of the Q-T interval, rhythm variability.
3. The functional state of the implanted pacemakers.
4. Graphs of hourly heart rate variability, S-T segment, Q-T segment changes during the study.

Table. Elements of the cardiological conclusion of daily monitoring of the ECG.

After the main part of the conclusion, the doctor suggests examples that illustratively characterize cardiac arrhythmias and repolarization. The duration of these fragments is 7-10 seconds.

In some cases, the daily study is printed in full on sheets of 30 minutes of recording each.

There is also a separate direction in long-term ECG monitoring - quantitative assessment of heart rate variability (HRV), S-T segment deviations, assessment of pacemaker function, duration and fluctuations of the Q-T interval.

Conclusions

It is obvious that Holter is far from the only possible method for diagnosing arrhythmias. In many cases, a 12-lead ECG or short-term monitoring is sufficient.Conversely, in some patients, the duration of the Holter study is insufficient due to rare episodes of clinical symptoms. Therefore, a long fragmentary ECG monitoring is required, or more aggressive diagnostic methods (stress tests, transesophageal diagnostics, coronary angiography).