What is an ECG test? How does it measure the heart’s electrical activity? Discover the different types of ECG, how to prepare for the test, and what the results can reveal about your heart health.

Measuring the Heart’s Electrical Activity: Understanding the ECG Test

An electrocardiogram (ECG) is a non-invasive medical test that records the electrical activity of the heart. It is a widely used diagnostic tool that can help identify various heart conditions, including abnormal heart rhythms, coronary heart disease, and heart attacks.

Types of ECG: Resting, Ambulatory, and Exercise Stress Test

There are three main types of ECG tests: resting ECG, ambulatory ECG, and exercise stress test. A resting ECG is performed while the patient lies down, with no movement allowed during the 5-10 minute test. An ambulatory ECG involves wearing a portable recording device for at least 24 hours, allowing the patient to move around freely. An exercise stress test is conducted while the patient is physically active, such as riding a stationary bike or walking on a treadmill.

Preparing for an ECG: What to Expect

Preparing for an ECG is generally simple. Patients can eat and drink as normal, unless otherwise instructed by their doctor. It’s important to inform the doctor about any medications being taken and any allergies to adhesive tapes, as these may be used to attach the electrodes to the skin. Patients may need to remove any upper clothing and, in some cases, remove underwire bras, as these can interfere with the ECG reading.

Interpreting ECG Results: Identifying Heart Conditions

An ECG records the electrical activity of the heart, which can be analyzed by a doctor to detect any abnormalities. Specific features of the ECG trace can indicate various heart conditions, such as abnormal heart rhythms, heart attacks, poor blood supply to the heart, and heart inflammation.

Monitoring Heart Health with ECG

ECG tests can be used not only to diagnose heart conditions, but also to monitor the effects of certain medications or implantable cardiac devices, such as pacemakers. Doctors may recommend an ECG for patients who have been diagnosed with a heart condition or are experiencing symptoms of an abnormal heart rhythm or a potential heart attack.

Importance of ECG in Cardiovascular Health

The ECG test is a crucial tool in the diagnosis and management of various heart conditions. It provides valuable information about the heart’s electrical activity, which can help doctors identify and treat heart problems early, potentially improving patient outcomes and overall cardiovascular health.

Why is an ECG important?

An ECG is an important diagnostic tool because it can help identify a wide range of heart conditions, including abnormal heart rhythms, coronary heart disease, and heart attacks. By analyzing the electrical activity of the heart, doctors can detect any irregularities or abnormalities that may indicate a problem.

How does an ECG work?

An ECG works by measuring the electrical activity of the heart using small electrodes attached to the skin on the chest, arms, and legs. These electrodes detect the electrical signals generated by the heart muscles as they contract and relax, and the ECG machine then records these signals as a waveform on a paper or digital display.

What can an ECG diagnose?

An ECG can help diagnose a variety of heart conditions, including:

• Abnormal heart rhythms (arrhythmias)
• Coronary heart disease, including heart attacks and angina
• Heart inflammation (pericarditis or myocarditis)
• Cardiac arrest

When is an ECG recommended?

Doctors may recommend an ECG for patients who are experiencing symptoms such as chest pain, dizziness, fainting, fatigue, or palpitations. An ECG may also be recommended for patients who have been diagnosed with a heart condition, to monitor the effects of treatment or devices like pacemakers.

How long does an ECG take?

The duration of an ECG test can vary depending on the type of ECG being performed. A resting ECG typically takes 5-10 minutes, while an ambulatory ECG can last for 24 hours or more. An exercise stress test, on the other hand, usually takes 15-30 minutes to complete.

What happens after an ECG?

After an ECG, the electrodes are removed from the patient’s skin, and they can resume normal activities immediately. The doctor will then analyze the ECG results and discuss any findings with the patient, as well as any recommended treatments or follow-up actions.

ECG test – Better Health Channel

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Summary

Read the full fact sheet

• An electrocardiogram (ECG) is a simple, non-invasive test that records the electrical activity of the heart.
• An ECG can help diagnose certain heart conditions, including abnormal heart rhythms and coronary heart disease (heart attack and angina).
• A doctor may recommend an ECG if you are experiencing symptoms like chest pain, breathlessness, dizziness, fainting or a feeling of your heart racing, fluttering, thumping or pounding in your chest (palpitations).
• An ECG can also help monitor how treatments for a heart condition, like medicines or implantable cardiac devices, are working.

About an ECG test

An electrocardiogram (ECG) is a test that can help diagnose certain heart conditions by measuring the electrical activity of the heart.

Small sticky dots (electrodes) and wire leads are placed on your chest, arms and legs. The leads attach to the ECG machine (electrocardiograph) which records the electrical activity of the heart muscle and displays this as a trace on a screen or on paper.

Any abnormality in the heart rhythm or rate, or damage to the heart muscle, can change the electrical activity of the heart. A doctor will examine the trace and look for specific features of different heart conditions.

An ECG can help diagnose:

• conditions involving the heart’s electrical system
• heart attacks
• abnormal heart rhythms (arrhythmia) – rapid, slow or irregular heart beats
• poor blood supply to the heart
• heart inflammation (pericarditis or myocarditis)
• cardiac arrestExternal Link.

A doctor may recommend an ECG for a person:

• experiencing symptoms of an abnormal heart rhythm such as:
  • chest pain
  • dizziness
  • fainting
  • fatigue
  • feeling of your heart racing, fluttering, thumping or pounding in your chest (palpitations)
  • shortness of breath
  • sweating
• experiencing warning signs of a heart attack or anginaExternal Link such as:
  • discomfort or pain in your chest, arms, shoulders, neck, jaw or back
  • dizziness, light headedness, feeling faint or feeling anxious
  • nausea, indigestion, vomiting
  • shortness of breath or difficulty breathing
  • sweating or a cold sweat
• who has been diagnosed with a heart condition, to monitor the effects of certain medicines or implantable cardiac devices (like a permanent pacemakerExternal Link).

Types of ECG

The three major types of ECG are:

• resting ECG – you lie down for this type of ECG. No movement is allowed during the test, as electrical impulses from other muscles can interfere with the test. This type of ECG usually takes five to 10 minutes.
• ambulatory ECG – for an ambulatory ECG you wear a portable recording device for at least 24 hours. You are free to move around normally while the device is attached. A doctor may arrange this type of ECG if you have symptoms that are intermittent (stop-start) which may not show up on a resting ECG. Your doctor may also recommend an ambulatory ECG if you are recovering from heart attack, to ensure your heart is working properly. You may be asked to write down or record any symptoms you experience while wearing the device, including when they occur, so that your own experience can be compared with the ECG.
• exercise stress test/stress test – this type of ECG helps your doctor see how well your heart is working during physical activity. It involves having an ECG while you ride a stationary exercise bike or walk on a treadmill. This type of ECG takes about 15 to 30 minutes to complete. A stress test can also involve medicines, to understand their effects on the heart.

Having an ECG

An ECG is a simple test that usually doesn’t need any special preparation.

• You can eat and drink as normal before having an ECG (unless your doctor has advised otherwise).
• Always let your doctor know what medicines you are taking before you have an ECG.
• Let your doctor know if you have any allergies to adhesive tapes, as an adhesive is needed to attach the electrodes to the skin.
• You will need to remove your upper clothing so that electrodes can be attached to your chest, arms and legs. Wearing a separate top with trousers or a skirt can allow easy access to the chest. Underwire in a bra can interfere with the ECG reading – you may be asked to remove it before the test.
• An ECG works best when the skin is clean and dry, and free of oils and lotions. Sometimes the skin is shaved if necessary because hair prevents the electrodes from sticking properly to the skin.

After an ECG

After an ECG, the electrodes are removed from the skin. You can resume normal activities immediately.

A doctor can usually interpret the results of your ECG straight away based on your medical history, symptoms and clinical examination.

The results of your ECG will help determine what treatment you need, if any.

Your doctor will discuss the various treatments available to find the treatment most suitable for you.

A person with a heart condition may have a normal ECG result if the condition does not cause a problem with the electrical activity of the heart.

In this case, your doctor may recommend other tests, including:

• physical examination (listening to heart sounds)
• chest X-ray – to produce an image that shows the location, size and shape of the lungs, heart and major blood vessels
• echocardiogram (ultrasound of the heart)
• magnetic resonance imaging (MRI) or computerised tomography (CT) scans of the chest – to create 3D images of the organs and structures in the chest, including the heart and lungs
• blood testsExternal Link
• coronary angiogramExternal Link (a test to examine the coronary arteries, often used to investigate chest pain or suspected heart attack).

Possible complications of an ECG

An ECG is very a safe test. It does not send electric currents to the body. Some people may be allergic or sensitive to the adhesive used to stick the electrodes to the skin. This might cause some mild skin itchiness and redness which usually resolves on its own and doesn’t require any treatment.

Where to get help

• In an emergency, always call Triple Zero (000)
• Emergency department of your nearest hospital
• Your GP (doctor)
• Your cardiologist
• NURSE-ON-CALL Tel. 1300 60 60 24 – for expert health information and advice 24 hours a day, 7 days a week

• Chew DP, Scott IA, Cullen L et al. National Heart Foundation of Australia & Cardiac Society of Australia and New Zealand: Australian clinical guideline for the management of acute coronary syndromes 2016. Heart Lung Circ. 2016;25:895-951. doi: 10.1016/j.hlc.2016.06.789
• Brieger D, Amerena J, Worthington J et al. National Heart Foundation of Australia and the Cardiac Society of Australia and New Zealand: Australian clinical guidelines for the diagnosis and management of atrial fibrillation 2018. Heart Lung Circ. 2018;27(10):1209-1266. doi: 10.1016/j.hlc.2018.06.1043

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Content on this website is provided for information purposes only. Information about a therapy, service, product or treatment does not in any way endorse or support such therapy, service, product or treatment and is not intended to replace advice from your doctor or other registered health professional. The information and materials contained on this website are not intended to constitute a comprehensive guide concerning all aspects of the therapy, product or treatment described on the website. All users are urged to always seek advice from a registered health care professional for diagnosis and answers to their medical questions and to ascertain whether the particular therapy, service, product or treatment described on the website is suitable in their circumstances. The State of Victoria and the Department of Health shall not bear any liability for reliance by any user on the materials contained on this website.

Reviewed on: 09-01-2023

What is an electrocardiogram (ECG)? – InformedHealth.org

Created: January 31, 2019; Next update: 2022.

Whether during routine examinations or heart diagnostics, many people have already had an electrocardiogram (ECG or EKG). But what does it actually measure, and what does the ECG curve show us?

Our nerve and muscle cells communicate with each other using electrical and chemical signals. Regular electrical signals also control our heartbeat. These signals are sent by a group of cells in the right atrium of the heart known as the sinoatrial node (SA node), and they spread through the heart muscle tissue as tiny electrical impulses. This causes first the atria and then the ventricles of the heart to contract. The way that these signals spread through the heart can also be measured on the surface of our skin. An ECG measures these changes in electrical signals (or, in fact, voltage) on different areas of skin and plots them as a graph. The resulting ECG graph is called an electrocardiogram.

When is this test offered?

An ECG is used to see how the heart is functioning. It mainly records how often the heart beats (heart rate) and how regularly it beats (heart rhythm). It can give us important information, for instance about possible narrowing of the coronary arteries, a heart attack or an irregular heartbeat like atrial fibrillation.

What does an ECG show?

If the heart is beating steadily, it will produce the typical ECG pattern: The first peak (P wave) shows how the electrical impulse (excitation) spreads across the two atria of the heart. The atria contract (squeeze), pumping blood into the ventricles, and then immediately relax. The electrical impulse then reaches the ventricles. This can be seen in the Q, R and S waves of the ECG, which is called the QRS complex. The ventricles contract. Then the T wave shows that the electrical impulse has stopped spreading, and the ventricles relax once again.

Heart diseases and irregular heartbeats can be detected in ECGs. What they look like and how they develop can help us find out what the underlying causes are.

Course of the QRS complex in a normal heartbeat

What does the test involve?

The electrical activity of the heart can be measured on the surface of the skin – even as far from the heart as on your arms or legs. The standard “12-lead ECG” uses a total of ten electrodes: six on your chest, and then one each on your lower arms and calves. If there is too much body hair, these areas are shaved first; other than that, no preparation is needed. These electrodes are connected by cables to an ECG machine. The machine converts the signals it receives into an ECG graph and saves it. Some machines can also print the graphs out.

What types of ECG tests are done?

Resting ECG: This involves lying still on your back with a bare chest. It is important that you lie calmly and comfortably during the test because tensing your muscles, moving, coughing or shaking can affect the results. The actual measurement takes about one minute, or five minutes at most.

Exercise ECG: Here the electrical activity of your heart is measured while you are physically active. This usually involves riding an exercise bike. The amount of exertion is steadily increased to a high level by making it increasingly difficult to turn the pedals. The test is stopped earlier if any irregularities in the ECG occur. In addition to the ECG graph, this test also provides data on the power that was generated in Watts. Your blood pressure is also checked regularly.

Holter monitor: The electrical activity of the heart is typically recorded over a period of 24 hours. Three or four electrodes are attached to your chest, and a small recording device is worn on a belt or hung around your neck. The ECG data are then transferred to a computer later on at the doctor’s office for analysis. To do this, the doctor also needs information about your daily schedule (like unusual events, physical activity and sleep). A Holter monitor may be used if, for instance, you only have an irregular heartbeat some of the time and it doesn’t show up in a “normal” ECG.

What do the results of a 12-lead ECG show?

The 12-lead ECG takes advantage of the fact that signals sent by the heart don’t travel evenly over your skin. The device compares the strength of the signals between two electrodes – doctors call these measurements “leads.” For example, one of the leads is measured based on the two electrodes on your arms. A 12-lead ECG, as its name implies, is used to measure twelve leads.

Depending on which lead shows irregularities, experts can find out things like in which part of the heart muscle an infarction has occurred, or whether a heart rhythm problem is coming from the left or right ventricle.

Normal ECG – Left: the leads from the arms and legs, Right: the leads from the chest wall. Source: CCB Frankfurt a.M.

Sources

• Schmidt R, Lang F, Heckmann M. Physiologie des Menschen: mit Pathophysiologie. Berlin: Springer; 2017.

• Trappe HJ, Schuster HP. EKG-Kurs für Isabel. Stuttgart: Thieme; 2017.

• IQWiG health information is written with the aim of helping
  people understand the advantages and disadvantages of the main treatment options and health
  care services.

  Because IQWiG is a German institute, some of the information provided here is specific to the
  German health care system. The suitability of any of the described options in an individual
  case can be determined by talking to a doctor. We do not offer individual consultations.

  Our information is based on the results of good-quality studies. It is written by a
  team of
  health care professionals, scientists and editors, and reviewed by external experts. You can
  find a detailed description of how our health information is produced and updated in
  our methods.

Taking an electrocardiogram using the ECG app on Apple Watch

Using the ECG app, you can take an electrocardiogram.

What is an ECG

An electrocardiogram (ECG) is a test result that reads the duration and strength of the electrical signals generated by the heartbeat. By examining the ECG, the doctor can get detailed information about your heart rhythm and identify irregularities.

• ECG Application Instructions 9Important information

• How the ECG app works

Instructions for use

ECG app

The ECG app can record your heartbeat and heart rate using the electrical heart rate monitor available on your Apple Watch Series 4, Series 5, Series 6, Series 7, Series 8, or Ultra* and check the result for signs atrial fibrillation, a type of irregular heart rhythm.

The ECG application creates an electrocardiogram that displays the electrical impulses that occur during a heartbeat. The ECG app checks these pulses to calculate your heart rate and detect out of sync between the upper and lower chambers of the heart. Such desynchronization may indicate atrial fibrillation.

Here’s what you need

Installing and configuring the ECG app

The ECG app is installed during the ECG app setup process in the Health app. To install the ECG app, follow these steps:

1. Open the Health app on iPhone.
2. Follow the instructions on the screen. If you don’t see setup prompts, go to the Overview tab, then select Heart > Electrocardiograms (ECGs) > ECG App Setup.
3. After setup, open the ECG app to take an ECG.

If the app still doesn’t show up on Apple Watch, open the Watch app on iPhone and select Heart. In the “ECG” section, click “Install” to install the “ECG” application.

Taking an ECG

If you are experiencing symptoms such as palpitations or irregular heartbeats, you are just worried about your heart condition, or you receive an irregular heart rate notification, you can take an ECG at any time.

1. Make sure your Apple Watch fits snugly on the wrist you select in the Apple Watch app. To check this, open the Apple Watch app, navigate to the My Watch tab, and select General > Watch Position.
2. Open the ECG app on your Apple Watch.
3. Place your hands on a table or on your knees.
4. Touch the Digital Crown with your finger without a watch. You do not need to press the Digital Crown during a session.
5. Please wait. The recording lasts 30 seconds. Once you have a classified result at the end of the recording, you can click “Add Symptoms” and select your symptoms.
6. To capture symptom information, click Save and then Finish.

Interpretation of results

After a successful reading, you will receive one of the following results in the ECG application. Regardless of the outcome, if you feel unwell or experience any symptoms, you should consult with your healthcare provider.

Sinus Rhythm

Sinus Rhythm means that the heart is beating at a steady rate of 50-100 beats per minute. This is a sign that the upper and lower chambers of the heart are working in sync. Sinus rhythm refers only to that particular reading and does not mean that your heart is constantly beating at the same rate. This result also does not mean that you are healthy. If you feel unwell or have any symptoms, you should consult with your healthcare provider.

Atrial fibrillation

This result means that the heart is beating unevenly. Atrial fibrillation is the most common form of serious arrhythmia or abnormal heart rhythm. If you get this result, but you have not been diagnosed with atrial fibrillation, you should consult with your doctor. In the ECG version 1 application, you can check for the presence of atrial fibrillation with a frequency of 50-120 bpm. In the “ECG” application version 2, you can check for the presence of atrial fibrillation with a frequency of 50-150 bpm.

Learn more about ECG app version availability and check which version you are using.

Low or high heart rate

Heart rate below 50 or above 120 bpm in the ECG version 1 app affects the ability of the ECG app to check for signs of atrial fibrillation. In the ECG app version 2, heart rates below 50 or above 150 bpm can affect the ability of the ECG app to check for signs of atrial fibrillation.

• The pulse may be low due to certain medications or poor conduction of electrical signals in the heart. A low heart rate can also be associated with professional sports.
• High heart rate may result from exercise, stress, nervousness, alcohol consumption, dehydration, infection, atrial fibrillation or other forms of arrhythmias.

Ambiguous result

An ambiguous result means that the read cannot be classified. This may be due to one of the following situations:

• In the ECG version 1 app, your heart rate is between 100 and 120 bpm and there is no atrial fibrillation. The ECG version 2 app has also been tested in clinical trials with approximately 546 participants. The level of accuracy in relation to sinus rhythm was 99.3%, and in relation to atrial fibrillation – 98.5%.
• You are using a pacemaker or an implantable cardioverter defibrillator.
• The reading may indicate signs of other forms of arrhythmias or heart conditions that are not recognized by the application.
• For a small percentage of users, due to certain physiological conditions, the signal may be too weak to obtain a quality result.

In the ECG version 1 app, you can also get an ambiguous result if you do not rest your hands on the table during the recording or if the Apple Watch is loose on your arm. Learn how to get the most accurate results.

Poor recording

This classification is unique to ECG version 2. A poor recording means that the result cannot be classified. If you receive a poor quality reading, the following suggestions may help improve the quality of the reading:

• Place your hands on the table or on your knees while reading. Try to relax and stay as still as possible.
• Make sure your Apple Watch is not too loose on your wrist. The strap should be tightened so that the back of the Apple Watch is in contact with your wrist.
• Make sure your wrist and Apple Watch are clean and dry. Water and sweat may cause poor recording quality.
• The Apple Watch must be worn on the hand specified in the settings.
• Sit away from any plugged-in electrical appliances to avoid electromagnetic interference.

If you need help, contact Apple Support.

Viewing and sharing health data

The ECG waveform, associated classifications, and any noted symptoms are stored in the iPhone Health app. You can also provide the corresponding PDF file to your healthcare provider.

1. Open the Health app.
2. Go to the Overview tab, click Heart > Electrocardiograms (ECGs).
3. Press the graphical representation of the “ECG” result.
4. Click “Export Doctor PDF”.
5. Press button to print or share the PDF.

Instructions for Getting the Most Accurate Results

1. Place your hands on the table or on your knees while reading. Try to relax and stay as still as possible.
2. Make sure your Apple Watch is not too loose on your wrist. You want the strap to fit snugly around your hand and the back of your Apple Watch to touch your wrist.
3. Make sure your wrist and Apple Watch are clean and dry.
4. Make sure the Apple Watch is on the wrist specified in the Apple Watch app. To check this, open the Apple Watch app, navigate to the My Watch tab, and select General > Watch Position.
5. Sit away from any plugged-in electrical appliances to avoid electromagnetic interference.

A small percentage of people may have a signal that is too weak to obtain a good result due to certain physiological conditions. For example, the position of the heart in the chest can affect the power level of the electrical signals, which affects the ability of the ECG app to take measurements.

The ECG application requires the surfaces involved to be completely dry to function properly. If the Apple Watch surface and/or skin is not dry enough, the ECG app may be affected. Make sure your wrist and hands are sufficiently dry before reading. For the most accurate reading after swimming, showering, sweating a lot, or washing your hands, clean and dry your Apple Watch. It may take an hour or more for your Apple Watch to dry completely.

Important information

• The ECG app is unable to detect a heart attack. If you feel pain, pressure or tightness in your chest, or think you are having a heart attack, contact emergency services immediately.
• The ECG application is unable to detect blood clots or stroke.
• The ECG application is unable to detect other heart conditions. This includes high blood pressure, congestive heart failure, high cholesterol, and other forms of arrhythmias.
• If you feel unwell or have any symptoms, talk to your doctor or seek medical attention immediately.

How the ECG app works

The ECG app on your Apple Watch Series 4, Series 5, Series 6, Series 7, Series 8, or Ultra allows you to take readings similar to a single-lead ECG. In medical settings, a 12-pin electrocardiograph is commonly used, which records the heart’s electrical signals from different angles and generates 12 different waveforms. The waveform generated by the ECG app on the Apple Watch is similar to one of these 12 waveforms. A single-lead ECG is able to provide information about heart rate and heart rate, and also allows you to determine atrial fibrillation. However, it cannot be used to identify certain other conditions, such as a heart attack. Doctors often prescribe single-contact electrocardiographs to be worn at home or in medical settings to access pulse rate and heart rate data faster. However, the ECG app on the Apple Watch Series 4, Series 5, Series 6, and Series 7 allows you to take an ECG similar to a single-lead ECG without a doctor’s prescription.

When comparing electrocardiograms taken simultaneously in the ECG application on the Apple Watch and on a standard 12-lead electrocardiograph, the results in relation to sinus rhythm and atrial fibrillation were the same.

The ability of the ECG app to accurately classify readings as sinus rhythm or atrial fibrillation has been proven in clinical testing involving approximately 600 people. The accuracy level in relation to sinus rhythm was 99.6%, and in relation to atrial fibrillation – 98.3%.

Clinical testing conducted in a controlled environment. When using the ECG app in real life, the number of inconclusive or unclassifiable results may be higher.

Additional Information

* The ECG app is not supported on Apple Watch SE or when using Family Setup.

Publication date: September 21, 2022

How the ECG procedure is carried out: indications, preparation, conducting at home

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Article content:

• ECG
• ECG diagnostic algorithm
• ECG technique
• How to read an ECG
• What kind of heart disease shows the ECG
• Holter monitoring: readings
• Ambulatory monitoring technique
• Stress Electrocardiography: Indications and Preparation
• Stress test technique
• Difference between ECG and Echo-KG
• ECG at home

ECG (electrocardiography, or cardiogram) of the heart is the simplest and most commonly used method for assessing the work of the heart. The device for recording a cardiogram is called an electrocardiograph. It captures and registers electrical impulses that occur in the heart muscle. The method is non-invasive – it does not require a violation of the skin, penetration into the cavities of the body.

Indications for ECG

Electrocardiography is done for preventive purposes, for the primary diagnosis of diseases and to track the dynamics of the condition in patients with already diagnosed heart pathologies.

Preventive purposes:

• medical examinations of children at a certain age, before entering the children’s

kindergarten, school, sports sections, camps;

• professional examinations of young men of military age;
• professional examinations of employees of enterprises, professional athletes;
• medical examination of citizens;
• commission to obtain a driver’s license, weapons permit;
• examination before hospitalization for planned surgical treatment;
• Examination of pregnant women when registering in a antenatal clinic.

For initial diagnosis, electrocardiography is prescribed for people who have symptoms of heart disease. For patients with an already established diagnosis, the cardiogram is recorded during treatment, at periodic examinations after recovery.

ECG diagnostic algorithm

The human heart spontaneously generates electrical impulses that cause it to contract and relax. Impulses pass through the muscle tissue of the heart from the point of their origin to the point of contraction. It is a cyclical and continuous process. The impulses are captured by the electrodes of the cardiograph, amplified, recorded by a galvanometer and displayed as a graph on special paper – ECG film or in electronic form.

A curve drawn on film will not tell the patient anything. Its decoding is carried out by a cardiologist or special software. Often, in addition to an electrocardiogram, an ultrasound (Echo-KG study) of the heart is done.

Preparing for the procedure

An ECG is usually sent by a cardiologist, internist or pediatrician. The patient must warn the doctor in advance about taking antiarrhythmic drugs, drugs for hypertension, cardiac glycosides. General rules for preparing a patient for an ECG:

• 2-3 ​​hours before the study, do not drink tea, coffee, energy drinks, do not smoke;
• do not take sedatives on the day of the procedure;
• avoid physical activity, do not play sports before recording the electrocardiogram;
• Wear clothing that allows you to easily free your chest, ankles and wrists.

The ECG nurse is responsible for recording the cardiogram. Therefore, if the patient wants to discuss something with the doctor, you need to do this in advance. The result will also be reported by the doctor, some time after the procedure, sufficient to prepare a description. The time of the ECG takes from 5 to 10 minutes (at rest), the ECG with a load is carried out for 15-20 minutes.

ECG technique

The patient lies on a couch, exposing the shins, forearms and upper body. The nurse degreases the skin areas on which the electrodes will be applied by wiping them with a tissue moistened with isotonic sodium chloride solution. The surface of the electrodes is also degreased, a gel is applied to it or to the skin to improve electrical conductivity.

The electrodes are fixed on the patient’s body in a certain order. A red electrode is applied to the right hand, and a yellow electrode to the left. The black electrode is for the right leg, and the green electrode for the left leg. 6 electrodes are applied to the chest in certain positions (V1 – red, V2 – yellow, V3 – green, V4 – brown, V5 – black, V6 – blue) or one electrode is sequentially moved to different points.

Before recording an ECG, the patient needs to calm down, while recording – do not move, do not take deep breaths. An ECG of the heart can be done as often as necessary, the procedure does not have any effect on the body.

How to read a cardiogram

It is almost impossible for people without special medical training to evaluate the result of electrocardiography. The interpretation of the ECG in adults and children is done either by the doctor who sent the patient to this study, or by the doctor of the functional diagnostics department.

The ECG film displays a graph in the form of a broken curve with peaks (teeth) and intervals between them located on a straight line, which is called an isoline. The teeth are indicated by the letters of the Latin alphabet – P, Q, R, S, T, intervals – P-Q, P-R, QRST (QT), QRS, S-T. To interpret the results of the cardiogram, the doctor evaluates the duration of the teeth in seconds and their amplitude in standard leads in millimeters, as well as the duration of the intervals in seconds.

There are established norms for these values. Comparing the ECG result with normal values, the doctor may suspect a deviation from the norm of heart rate, the presence of arrhythmias, diagnose acute conditions such as myocardial infarction, angina pectoris.

What kind of heart disease is shown by ECG

ECG is one of the most accurate methods for diagnosing rhythm disturbances. With its help, you can identify the cause of rhythm disturbance, the location of the pathological focus of excitation, the type of arrhythmia. Partial or complete blockade of the conduction pathways of the heart is also well displayed on the electrocardiogram.

Electrocardiography plays an important role in the diagnosis of acute myocardial infarction. Changes in a heart attack are clearly displayed on the tape, in combination with the clinic, this allows you to start treatment in a timely manner and in many cases save the patient. Therefore, doctors or paramedics on calls to patients with complaints of pain in the heart always have a portable device with them in order to be able to make a cardiogram of the heart at home.

Holter monitoring: indications

For a more accurate diagnosis of certain diseases of the heart and blood vessels, additional types of ECG studies are prescribed. One of them is a continuous recording of an electrocardiogram for 24 (rarely 48, 72) hours, or Holter monitoring. It is indicated in the following situations:

• recovery period after myocardial infarction;
• diagnostics and monitoring of the dynamics of various cardiomyopathies;
• assessment of the work of the cardiovascular system in congenital and acquired heart defects;
• hypertension;
• chronic heart failure;
• suspected arrhythmia;
• pain behind the sternum of an unknown nature without changes on the cardiogram at rest;
• causeless dizziness and fainting.

24-hour monitoring technique

Electrodes are placed on the patient’s chest, just as when taking a cardiogram at rest, they are additionally fixed with an adhesive plaster. The electrodes are connected to a recorder, which the patient wears in a special case all the time of monitoring.

Electrocardiography recording during monitoring can be fragmentary (the patient presses the button on the recorder when the condition worsens) or permanent (all cardiac cycles are recorded for a day or more). At the same time, the subject keeps a special diary, where he records the time of sleep, wakefulness, the presence of physical activity, stress and other significant events. Additionally, the patient can perform stress tests as prescribed by the doctor.

Stress electrocardiography: indications and preparation

ECG under stress (stress test, or treadmill test) is done to clarify the diagnosis of coronary heart disease, to monitor cardiac activity after coronary artery bypass grafting in myocardial infarction, to diagnose and monitor the dynamics of some heart defects.

The study is also conducted for healthy people – professional athletes, pilots of civil and military aviation, candidates for service in law enforcement agencies, contract service in the army.

To prepare for an exercise ECG, avoid tea, coffee, alcoholic and energy drinks, and smoking during the day before the procedure. The last meal should be 3-4 hours before the recording of the electrocardiogram. Intense physical activity must be stopped two days before the study. Three days before the procedure, men should refuse to take potency-improving drugs (Viagra, Cialis).

Stress test technique

An ECG is recorded at rest, then during or immediately after exercise, if necessary, a few minutes after exercise.

Load:

• squats – 20 times in 40-60 seconds;
• ascent and descent of the step platform with feet – 20 times in 40-60 seconds;
• running on a treadmill at a moderate pace for 20-25 seconds;
• three-minute load on a bicycle ergometer.

The doctor evaluates the heart rate, their rhythm at rest, changes in these indicators during exercise and during the recovery period. Sometimes, simultaneously with recording an electrocardiogram under load, blood pressure is measured and the indicators are evaluated in combination.

After the procedure, the health worker should monitor the patient’s condition until the pulse rate returns to normal.

Difference between ECG and Echo-KG

Echo-KG, or echocardiography, which is also called cardiac ultrasound, is a procedure that is fundamentally different from ECG.

Echocardiography is a non-invasive ultrasound examination of the heart and blood vessels. The high-frequency sound emitted by the echocardiograph transducer, passing through the tissues of the heart, is reflected from them and recorded by the same transducer. The result is displayed as an image on the monitor.

Echo-KG data allow to evaluate the size of the heart, the thickness, integrity and structure of the heart muscle, the size of the cavities of the ventricles and atria, myocardial contractility, the condition of the valves and large vessels.

Ultrasound and ECG are different methods, so it cannot be said that it is better to check the condition of the heart with one of them. To assess the activity of the cardiovascular system, these studies are assigned in combination.

ECG at home

ECG at home is possible not only in emergency cases.