What Is Electrocardiogram – Indications, Procedures, Results

ECG; EKG

An electrocardiogram (ECG) is a test that records the electrical activity of the heart.

How the Test is Performed

You will be asked to lie down. The health care provider will clean several areas on your arms, legs, and chest, and then will attach small patches called electrodes to those areas. It may be necessary to shave or clip some hair so the patches stick to the skin. The number of patches used may vary.

The patches are connected by wires to a machine that turns the heart’s electrical signals into wavy lines, which are often printed on paper. The doctor reviews the test results.

You will need to remain still during the procedure. The provider may also ask you to hold your breath for a few seconds as the test is being done.

It is important to be relaxed and warm during an ECG recording because any movement, including shivering, can alter the results.

Sometimes this test is done while you are exercising or under light stress to look for changes in the heart. This type of ECG is often called a stress test.

How to Prepare for the Test

Make sure your provider knows about all the medicines you are taking. Some drugs can interfere with test results.

DO NOT exercise or drink cold water immediately before an ECG because these actions may cause false results.

How the Test will Feel

An ECG is painless. No electricity is sent through the body. The electrodes may feel cold when first applied. In rare cases, some people may develop a rash or irritation where the patches were placed.

Why the Test is Performed

An ECG is used to measure:

  • Any damage to the heart
  • How fast your heart is beating and whether it is beating normally
  • The effects of drugs or devices used to control the heart (such as a pacemaker)
  • The size and position of your heart chambers

An ECG is often the first test done to determine whether a person has heart disease. Your provider may order this test if:

  • You have chest pain or palpitations
  • You are scheduled for surgery
  • You have had heart problems in the past
  • You have a strong history of heart disease in the family

Normal Results

Normal test results include:

  • Heart rate: 60 to 100 beats per minute
  • Heart rhythm: Consistent and even

What Abnormal Results Mean

Abnormal ECG results may be a sign of:

  • Damage or changes to the heart muscle
  • Changes in the amount of the electrolytes (such as potassium and calcium) in the blood
  • Congenital heart defect
  • Enlargement of the heart
  • Fluid or swelling in the sac around the heart
  • Inflammation of the heart (myocarditis)
  • Past or current heart attack
  • Poor blood supply to the heart arteries
  • Abnormal heart rhythms ( arrhythmias )

Some heart problems that can lead to changes on an ECG test include:

  • Atrial fibrillation/flutter
  • Heart failure
  • Multifocal atrial tachycardia
  • Paroxysmal supraventricular tachycardia
  • Sick sinus syndrome
  • Wolff-Parkinson-White syndrome

Risks

There are no risks.

Considerations

The accuracy of the ECG depends on the condition being tested. A heart problem may not always show up on the ECG. Some heart conditions never produce any specific ECG changes.

Holter monitor (24h)

Ambulatory electrocardiography; Electrocardiography – ambulatory; Atrial fibrillation – Holter; Flutter – Holter; Tachycardia – Holter; Abnormal heart rhythm – Holter; Arrythmia – Holter

A Holter monitor is a machine that continuously records the heart’s rhythms. The monitor is worn for 24 to 48 hours during normal activity.

How the Test is Performed

Electrodes (small conducting patches) are stuck onto your chest. These are attached by wires to a small recording monitor. You carry the Holter monitor in a pocket or pouch worn around your neck or waist. The monitor runs on batteries.

While you wear the monitor, it records your heart’s electrical activity.

  • Keep a diary of what activities you do while wearing the monitor, and how you feel.
  • After 24 to 48 hours, you will return the monitor to your health care provider’s office.
  • The provider will look at the records and see if there have been any abnormal heart rhythms.
  • Holter heart monitor

It is very important that you accurately record your symptoms and activities so the provider can match them with your Holter monitor findings.

Electrodes must be firmly attached to the chest so the machine gets an accurate recording of the heart’s activity.

While wearing the device, avoid:

  • Electric blankets
  • High-voltage areas
  • Magnets
  • Metal detectors

Continue your normal activities while wearing the monitor. You may be asked to exercise while being monitored if your symptoms have occurred in the past while you were exercising.

How to Prepare for the Test

You DO NOT need to prepare for the test.

Your provider will start the monitor. You’ll be told how to replace the electrodes if they fall off or get loose.

Tell your provider if you are allergic to any tape or other adhesives. Make sure you shower or bathe before you start the test. You will not be able to do so while you are wearing a Holter monitor.

How the Test will Feel

This is a painless test. However, some people may need to have their chest shaved so the electrodes can stick.

You must keep the monitor close to your body. This may make it hard for you to sleep.

Occasionally there may be an uncomfortable skin reaction to the sticky electrodes. You should call the provider’s office where it was placed to tell them about it.

Why the Test is Performed

Holter monitoring is used to determine how the heart responds to normal activity. The monitor may also be used:

  • After a heart attack
  • To diagnose heart rhythm problems that may be causing symptoms such as palpitations or syncope (passing out/ fainting )
  • When starting a new heart medicine

Heart rhythms which may be recorded include:

  • Atrial fibrillation or flutter
  • Multifocal atrial tachycardia
  • Paroxysmal supraventricular tachycardia
  • Slow heart rate (bradycardia)
  • Ventricular tachycardia

Normal Results

Normal variations in heart rate occur with activities. A normal result is no significant changes in heart rhythms or pattern.

What Abnormal Results Mean

Abnormal results may include various arrhythmias such as those listed above. Some changes may mean that the heart is not getting enough oxygen.

Risks

Other than the uncommon skin reaction, there are no risks associated with the test. However, you should be sure not to let the monitor get wet.

EEG

Electroencephalogram; Brain wave test; Epilepsy – EEG; Seizure – EEG

An electroencephalogram is a test to measure the electrical activity of the brain.

How the Test is Performed

The test is done by an electroencephalogram (EEG) technologist in your doctor’s office or at a hospital or laboratory.

The test is done in the following way:

  • You lie on your back on a bed or in a reclining chair.
  • Flat metal disks called electrodes are placed all over your scalp. The disks are held in place with a sticky paste. The electrodes are connected by wires to a recording machine. The machine changes the electrical signals into patterns that can be seen on a monitor or drawn on paper. These patterns look like wavy lines.
  • You need to lie still during the test with your eyes closed. This is because movement can change the results. You may be asked to do certain things during the test, such as breathe fast and deeply for several minutes or look at a bright flashing light.
  • You may be asked to sleep during the test.

If your doctor needs to monitor your brain activity for a longer period, an ambulatory EEG will be ordered. In addition to the electrodes, you will wear or carry a special recorder for up to 3 days. You will be able to go about your normal routine as the EEG is being recorded. Or, your doctor may ask you to stay overnight in a special EEG monitoring unit where your brain activity will be monitored continuously.

How to Prepare for the Test

Wash your hair the night before the test. DO NOT use conditioner, oils, sprays, or gel on your hair. If you have a hair weave, ask your health care provider for special instructions.

Your provider may want you to stop taking certain medicines before the test. DO NOT change or stop taking any medicines without first talking to your provider. Bring a list of your medicines with you.

Avoid all food and drinks containing caffeine for 8 hours before the test.

You may need to sleep during the test. If so, you may be asked to reduce your sleep time the night before. If you are asked to sleep as little as possible before the test, DO NOT eat or drink any caffeine, energy drinks, or other products that help you stay awake.

Follow any other specific instructions you are given.

How the Test will Feel

The electrodes may feel sticky and strange on your scalp, but should not cause any other discomfort. You should not feel any discomfort during the test.

Why the Test is Performed

Brain cells communicate with each other by producing tiny electrical signals, called impulses. An EEG measures this activity. It can be used to diagnose or monitor the following health conditions:

  • Seizures and epilepsy
  • Abnormal changes in body chemistry that affect the brain
  • Brain diseases, such as Alzheimer disease
  • Confusion
  • Fainting spells or periods of memory loss that cannot be explained otherwise
  • Head injuries
  • Infections
  • Tumors

EEG is also used to:

  • Evaluate problems with sleep ( sleep disorders )
  • Monitor the brain during brain surgery

An EEG may be done to show that the brain has no activity, in the case of someone who is in a deep coma. It can be helpful when trying to decide if a person is brain dead.

EEG cannot be used to measure intelligence.

Normal Results

Brain electrical activity has a certain number of waves per second (frequencies) that are normal for different levels of alertness. For example, brain waves are faster when you are awake, and slower in certain stages of sleep.

There are also normal patterns to these waves.

Note: A normal EEG does not mean that a seizure did not occur.

What Abnormal Results Mean

Abnormal results on an EEG test may be due to:

  • Abnormal bleeding (hemorrhage)
  • An abnormal structure in the brain (such as a brain tumor )
  • Tissue death due to a blockage in blood flow (cerebral infarction)
  • Drug or alcohol abuse
  • Head injury
  • Migraines (in some cases)
  • Seizure disorder (such as epilepsy)
  • Sleep disorder (such as narcolepsy )
  • Swelling of the brain (edema)

Risks

An EEG test is very safe. The flashing lights or fast breathing ( hyperventilation ) required during the test may trigger seizures in those with seizure disorders. The provider performing the EEG is trained to take care of you if this happens.

His bundle electrography

His bundle electrogram; HBE; His bundle recording; Electrogram – His bundle; Arrythmia – His; Heart block – His

His bundle electrography is a test that measures electrical activity in a part of the heart that carries the signals that control the time between heartbeats (contractions).

How the Test is Performed

The bundle of His is a group of fibers that carry electrical impulses through the center of the heart. If these signals are blocked, you will have problems with your heartbeat.

The His bundle electrography is part of an electrophysiology (EP) study. An intravenous catheter (IV line) is inserted into your arm so that you can be given medicines during the test.

Electrocardiogram (ECG) leads are placed on your arms and legs. Your arm, neck, or groin will be cleaned and numbed with a local anesthetic. After the area is numb, the cardiologist makes a small cut in a vein and inserts a thin tube called a catheter inside.

The catheter is carefully moved through the vein up into the heart. An x-ray method called fluoroscopy helps guide the doctor to the right place. During the test, you are watched for any abnormal heartbeats ( arrhythmias ). The catheter has a sensor on the end, which is used to measure the electrical activity of the bundle of His.

How to Prepare for the Test

You will be told not to eat or drink anything for 6 to 8 hours before the test. The test will be done in a hospital. Some people may need to check into the hospital the night before the test. Otherwise, you will check in the morning of the test. Although the test may take some time, most people DO NOT need to stay in the hospital overnight.

Your health care provider will explain the procedure and its risks. You must sign a consent form before the test starts.

About half an hour before the procedure, you will be given a mild sedative to help you relax. You will wear a hospital gown. The procedure may last from 1 to several hours.

How the Test will Feel

You are awake during the test. You may feel some discomfort when the IV is placed into your arm, and some pressure at the site when the catheter is inserted.

Why the Test is Performed

This test may be done to:

  • Determine if you need a pacemaker or other treatment
  • Diagnose arrhythmias
  • Find the specific location where electrical signals through the heart are blocked

Normal Results

The time between electrical signals from the bundle of His are evenly spaced.

What Abnormal Results Mean

A pacemaker will be needed if the test results are abnormal.

Abnormal results may mean you have or had:

  • Chronic conduction system disease
  • Carotid sinus pressure
  • Recent heart attack
  • Atrial disease

Risks

Risks of the procedure include:

  • Arrhythmias
  • Cardiac tamponade
  • Embolism from blood clots at the tip of the catheter
  • Heart attack
  • Hemorrhage
  • Infection
  • Injury to the vein or artery
  • Low blood pressure
  • Stroke

FAQ

What is an EEG test used to diagnose?

  • EEG results show changes in brain activity that may be useful in diagnosing brain conditions, especially epilepsy and other seizure disorders. An electroencephalogram (EEG) is a test that detects electrical activity in your brain using small, metal discs (electrodes) attached to your scalp.

Why EEG test is done?

  • Why It’s Done
  • Most EEGs are done to diagnose and monitor seizure disorders. EEGs also can identify the causes of other problems, such as sleep disorders and changes in behavior. They’re sometimes used to evaluate brain activity after a severe head injury or before a heart transplant or liver transplant.

What should you not do before an EEG test?

  • Do not eat or drink anything with caffeine in it for 12 hours before the test. This includes cola, energy drinks, and chocolate. Shampoo your hair and rinse with clear water the evening before or the morning of the test. Do not put any hair conditioner or oil on after you wash your hair.

Which is better EEG or MRI?

  • MRI has a higher spatial resolution than electroencephalography (EEG). MRI with hyperintense lesions on FLAIR and DWI provides information related to brain activity over a longer period of time than a standard EEG where only controversial patterns like lateralized periodic discharges (LPDs) may be recorded.

Can EEG detect mental illness?

  • Electroencephalography or EEG, technology that measures brain function could encourage earlier diagnoses of common mental and neurological disorders, including autism, ADHD, and dementia, according to findings published in The Neurodiagnostic Journal.

Can EEG detect brain tumors?

  • EEG can also detect abnormal brain waves after a head injury, stroke, or brain tumor. Other conditions such as dizziness, headache, dementia, and sleeping problems may show abnormal brain patterns. It can also be used to confirm brain death.

What happens if EEG is abnormal?

  • An abnormal EEG means that there is a problem in an area of brain activity. This can offer a clue in diagnosing various neurological conditions. Read 10 Conditions Diagnosed With an EEG to learn more. EEG testing is one part of making a diagnosis.

What do you wear to an EEG?

  • Wear comfortable clothing. Shampoo and dry hair without using sprays, gels or oils. No braids or intricate hair designs as they will need to be removed prior to the test. Continue taking medications as prescribed by your physician.

How long does an EEG take to do?

  • This study is generally done by an EEG technician and may take approximately 45 minutes to 2 hours. If you are being evaluated for a sleep disorder, the EEG may be done while you are asleep.

What are 10 conditions diagnosed with an EEG?

10 Conditions Diagnosed With an EEG
  • Seizure Disorders. The primary use of EEG is to diagnose epilepsy and other seizure disorders.
  • Sleep Disorders. Sleep disorders range from insomnia to narcolepsy.
  • Brain Tumors. There are many types of brain tumors.
  • Brain Injury.
  • Dementia.
  • Brain Infections.
  • Stroke.
  • Attention Disorders.

What is a normal EEG?

  • Most waves of 8 Hz and higher frequencies are normal findings in the EEG of an awake adult. Waves with a frequency of 7 Hz or less often are classified as abnormal in awake adults, although they normally can be seen in children or in adults who are asleep

What can an EEG show that an MRI Cannot?

  • A complex organ like the brain can have any number of problems, even without injury. The Brain Foundation lists infections, autoimmune diseases, seizures, and dementia among the most common neurological conditions doctors see.

Does an EEG show brain death?

  • EEGs are performed occasionally to provide supportive evidence of brain death. Although brain death is defined by clinical criteria, some situations preclude complete or definitive examination findings (such as severe open head or eye trauma). In such situations, a confirmatory test is often helpful.

Is an EEG expensive?

  • Average out-of-pocket costs for electroencephalogram (EEG) tests, which can be used to diagnose conditions such as epilepsy, increased from $39 to $112. For MRI scans, they increased from $84 to $242. Office visits increased from an average of $18 to $52.

What medications affect EEG?

  • Before the day of EEG, medications that can affect brain activity may be ceased, but this is not usually necessary. These can include sedatives, tranquilizers, sleeping tablets, and medications for epilepsy. These can affect the test but it is very important that you consult your doctor before you stop them.

Is an EEG the same as an ECG?

  • They may sound similar, but one of these things is not like the other: both ECG and EKG refer to a test of the heart, while EEG is a test of the brain. Electrocardiogram (ECG or EKG) is a painless test that measures the electrical activity in the heart.

What are the possible causes for an abnormal EEG?

Abnormal results on an EEG test may be due to:
  • Abnormal bleeding (hemorrhage)
  • An abnormal structure in the brain (such as a brain tumor)
  • Tissue death due to a blockage in blood flow (cerebral infarction)
  • Drug or alcohol abuse.
  • Head injury.
  • Migraines (in some cases)
  • Seizure disorder (such as epilepsy)

What is the difference between electroencephalography and electroencephalogram?

  • Is that electroencephalogram (neurology) a recording of electrical brain activity (brain waves) made by an electroencephalograph while electroencephalography is (neurology) the measurement and recording of electrical activity in the brain for diagnostic purposes?

What is the difference between EMG and ECG?

  • An ECG determines heart activity by measuring signals from electrodes placed on the torso, arms, and legs.

What is the difference between an ECG, EEG, EMG, and EOG?

Source Amplitude (mV) Bandwidth (Hz)
ECG 1-5 0.05-100
EEG 0.001-0.01 0.5-40
EMG 1-10 20-2000
EOG 0.01-0.1 dc-10

What problems can an EEG detect?

  • The electroencephalogram (EEG) is a medical test used to measure the electrical activity of the brain. A number of electrodes are applied to your scalp. EEG can help diagnose a number of conditions including epilepsy, sleep disorders, and brain tumors.

What is an EMG procedure?

  • Electromyography (EMG) measures muscle response or electrical activity in response to a nerve’s stimulation of the muscle. The test is used to help detect neuromuscular abnormalities. During the test, one or more small needles (also called electrodes) are inserted through the skin into the muscle.