ECG Test: Purpose, Procedure, Preparation and Results

What is an electrocardiogram (ECG)?

An electrocardiogram, or ECG, is a simple, painless and non-invasive test that captures the electrical signs of your heart.

Your heart produces an electrical signal that controls its rhythm and helps to pump blood. An ECG records these impulses and displays them in a graphical format that doctors can use to determine how well your heart is doing.

Your doctor uses it to identify abnormal heart rhythms, to help diagnose heart disease, and to monitor your heart conditions or treatments.

What information does ECG provide?

An ECG provides important information about your heart rhythm, heart rate, and overall well-being. It is usually used to diagnose and monitor your heart over a period of time. The patterns on an ECG help doctors understand:

Heart rhythm and conduction

• Irregular heartbeats

  • An ECG can identify irregular heartbeats, including atrial fibrillation (fast heartbeats), ventricular tachycardia (fast heartbeats), bradycardia (slow heartbeats), or premature ventricular contractions (extra beats).

• Conduction problems

  • The test can identify issues with your heart's electrical conduction system, such as heart block, where electrical impulses slow down or are interrupted when passing through your heart.

Heart structure and damage

• Heart attacks

  • An ECG can show whether you have had a heart attack in the past or recently. It does so through identifying changes in your heart's electrical patterns that take place when heart muscle has been damaged.

• Heart enlargement

  • It will be able to tell if certain chambers of your heart are enlarged, which can occur due to conditions like high blood pressure or heart valve problems.

• Heart disease

  • It can be used to detect conditions including coronary artery disease (blockage or narrowing of arteries) through identifying abnormal patterns in your heart electrical signals.

• Heart valve problems

  • Although not the primary test to identify valve issues, an ECG might sometimes provide clues about the performance of your heart valves.

Blood flow and electrolyte balance

• Reduced blood flow (ischaemia)

  • An ECG can detect reduced blood flow to the heart, often caused by blocked coronary arteries.

• Electrolyte imbalances

  • The test can reveal abnormalities in your heart's electrical activity caused by imbalances in key electrolytes (like potassium, calcium, and sodium) in your blood.

Treatment monitoring

• Medication effects

  • An ECG can be used to monitor the impact of medications (such as antiarrhythmics) on your heart.

• Device effects

  • The test can be used to evaluate the function of implanted devices like pacemakers or defibrillators.

General heart health and symptom evaluation

• Symptom evaluation

  • It helps to investigate symptoms such as chest pain or discomfort, palpitations (feeling of skipped or racing heartbeats), shortness of breath, dizziness or fainting

• General heart health

  • Some routine check-ups or pre-surgery evaluations include an ECG to ensure your heart is functioning well.

Why would I need an ECG?

You might need an ECG if you're experiencing symptoms or have risk factors that suggest potential heart issues. Here are the most common reasons a doctor may recommend this test:

When you have symptoms of heart problems

• Chest pain or discomfort

• Shortness of breath

• Dizziness or fainting

• Palpitations (feeling like your heart is racing, fluttering, or skipping beats)

• Unexplained fatigue or weakness

If you have or suspect irregular heartbeat (arrhythmias)

If you notice that your heart feels like it's beating too fast, too slow, or irregularly, it could be a sign of an arrhythmia, which is an abnormal heart rhythm. An ECG can help detect various types of arrhythmia, such as:

• Atrial fibrillation (AFib)

  • This condition causes an irregular and often rapid heartbeat. It raises the risk of stroke, heart failure, and dementia.

• Ventricular tachycardia

  • This condition is characterised by a dangerously fast heart rate, which originates in your heart's lower chambers. It can cause dizziness, palpitations, and fainting.

For monitoring existing heart conditions

• If you've had a heart attack in the past or have been diagnosed with heart disease, an ECG can monitor your heart's recovery or detect new problems.

• If you've had a heart surgery or procedure, your doctor might use an ECG to check how well your heart is functioning afterwards.

If you have risk factors for heart disease

An ECG can be used as a preventive measure to monitor your heart health if you have risk factors like:

• High blood pressure

• High cholesterol

• Diabetes

• Family history of heart disease

For medical evaluations and treatment monitoring

• Pre-surgery or physical exams

  • Some routine health exams, like those before surgery, may include an ECG. This checks if your heart is healthy enough for the procedure or physical activity.

• Check for heart damage

  • If your doctor suspects heart damage from conditions like coronary artery disease, a previous heart attack, or chronic high blood pressure, an ECG can reveal underlying issues.

• Electrolyte imbalances

  • If your doctor suspects electrolyte imbalances, such as low potassium or calcium, an ECG can show how these affect your heart's electrical system.

• Monitoring treatment

  • If you're on medication for heart issues or treatments like chemotherapy (which can affect the heart), your doctor might suggest regular ECGs. This helps track any side effects or changes in your heart's rhythm.

If you’re experiencing any of the symptoms or risk factors mentioned above, request an appointment with Thomson Medical. Our specialists can help diagnose your condition, including performing an ECG test to determine the underlying causes and providing personalised care.

How to prepare for an ECG?

An ECG is a straightforward diagnostic test that doesn't require much preparation. Following these simple guidelines will help ensure accurate results:

• Wear comfortable clothing

  • Since you may need to remove clothing from the waist up, wear something easy to take off.

• Avoid lotions or oils

  • Do not apply body lotions, oils, or creams to your chest on the day of the test, as it can interfere with the electrodes ability to stick properly to your skin.

• Inform the technician about medical conditions

  • If you have a pacemaker, defibrillator, or other implanted devices, or if you are pregnant, let the technician know.

• Avoid stimulants

  • It's best to avoid caffeinated drinks (coffee, tea, energy drinks) or smoking right before the test, as they can affect your heart rate.

• Bring your medications list

  • It may be helpful to bring a list of medications you're currently taking, especially if they're related to heart conditions.

What happens during an ECG?

During an ECG, you'll lie comfortably on an exam table where you'll need to stay still and relaxed to ensure accurate results. The entire procedure is quick and straightforward:

• The technician will place small, sticky patches called electrodes on specific locations on your chest, wrists, and ankles.

• These electrodes act as sensors, detecting the electrical signals generated by your heartbeat.

• The electrodes are connected to an electrocardiograph machine, which records these signals and converts them into wave patterns.

• These patterns are displayed on a screen or printed on paper for your doctor to analyse.

The procedure usually lasts only 5–10 minutes from start to finish.

What can I do/not do after an ECG test?

What can you do?

• Go back to your normal activities

  • An ECG is non-invasive, so there are no restrictions afterwards. You can resume your regular activities immediately.

• Ask about the results

  • Your doctor may discuss the results right away or schedule a follow-up appointment if further analysis is needed.

• Continue taking medications

  • If you're on heart medications, continue taking them as prescribed unless your doctor advises otherwise.

What should you not do?

• No restrictions afterwards

  • There are no specific limitations after an ECG, and you can return to your daily routine.

• Don’t worry (if results are delayed)

  • If your doctor needs more time to review the test or suggests further tests, don't worry — it doesn't necessarily mean anything is wrong. Some results simply require more detailed analysis.

How do doctors interpret ECG results?

When interpreting an ECG, healthcare providers assess the strength and timing of electrical impulses that regulate your heartbeats. The waveforms on an ECG correspond to specific phases of the heart's electrical cycle:

• The P wave represents the electrical activity in the atria (upper heart chambers), where each heartbeat originates.

• The QRS complex reflects the electrical impulses in the ventricles (lower heart chambers), which are responsible for pumping blood.

• The T wave indicates the recovery phase of the ventricles as they prepare for the next heartbeat.

These waveforms allow doctors to evaluate your heart's rhythm, detect abnormalities, and assess overall cardiac function.

Possible complications of an ECG

An ECG is a very safe diagnostic test. Complications are extremely unlikely to occur. The only effects you might experience are listed here:

• Mild skin irritation

  • The adhesive used to attach the electrodes to your skin can sometimes cause slight redness or itching, similar to removing a bandage.

• Minor discomfort

  • You might feel mild discomfort when electrodes are placed or removed, especially in areas with hair.

• Allergic sensitivity

  • Some individuals may have a sensitivity to the adhesive or gel used with the electrodes, which could cause a temporary rash.

False results

Even though not a direct complication to your health, there can be situations where the ECG provides false readings or readings that cannot be interpreted with certainty. This can happen due to:

• Movement during the test

• Poor contact between the electrodes and the skin

• Skin conditions or excessive body hair

• Electrical interference from nearby equipment

If this happens, the test may need to be repeated to ensure accurate results.

In most cases, these issues are minor and easily managed. If you experience any discomfort or unusual symptoms during or after the test, you should inform your healthcare provider immediately.

FAQ

What does an ECG test tell you?

An ECG can show:

• Heart rate

  • How fast or slow your heart is beating

• Heart rhythm

  • Whether your heartbeat is regular or irregular

• Electrical conduction

  • How well electrical signals are moving through your heart

• Signs of damage

  • Evidence of past or current heart attacks, ischaemia (lack of blood flow), or other heart conditions

Can an ECG detect most heart problems?

An ECG is a powerful tool for detecting many heart problems, but it does not detect all heart conditions.

It primarily focuses on the electrical activity of your heart, so it can reveal issues related to your heart's rhythm, structure, and electrical conduction.

An ECG cannot detect:

• Structural problems (e.g., heart valve disease)

  • An ECG test does not directly show problems with heart valves, such as valve leaks or narrowed valves. These are typically diagnosed with imaging tests like an echocardiogram.

• Coronary artery blockages

  • While an ECG might be able to detect ischaemia (lack of oxygen in the heart), it does not provide a detailed picture of the extent of coronary artery disease (blockages in the arteries). A stress test, an angiogram, or a CT scan will be needed to do so.

• Heart failure

  • An ECG does not always show heart failure but can detect conditions that might be causing it, such as heart attack or arrhythmias. Heart failure diagnosis typically includes a clinical examination and imaging tests like echocardiograms or chest X-rays.

• Blood clots or pulmonary embolism

  • If you have a blood clot in your lungs (pulmonary embolism), an ECG might show signs that could be interpreted as heart-related issues, but it won’t directly detect the clot. A CT scan or ultrasound is then needed to confirm the clot.

• Aneurysms (e.g., aortic aneurysm)

  • While an ECG may detect a change in your heart electrical activity due to an aneurysm, it cannot be employed to diagnose one. Aneurysms must be diagnosed with imaging tests like CT scans or MRIs.

What is a normal ECG result?

A normal ECG result shows that your heart is functioning properly with:

• Normal heart rate (60-100 beats per minute)

• Regular rhythm

• Smooth P waves (representing electrical activity of the atria as they contract)

• Narrow QRS complexes (representing electrical activity of the ventricles)

• No abnormal waveforms

• No ST segment elevation

• No signs of ischaemia or arrhythmias

What happens if the ECG is abnormal?

After an abnormal ECG, your doctor will typically:

• Evaluate your symptoms and medical history

  • They'll consider your symptoms (such as chest pain, shortness of breath, and dizziness) and any risk factors (like high blood pressure, diabetes, smoking, or family history of heart disease).

• Order additional tests

  • Depending on the abnormality, your doctor may recommend further tests such as:

    • Blood tests (to check for heart damage or electrolyte imbalances)

    • Echocardiogram (to assess your heart structure and function)

    • Stress tests (to check for heart problems during exercise)

    • Holter monitor (to monitor your heart rhythm over 24-48 hours)

    • Coronary angiography (to check for blocked arteries)

• Determine treatment

  • If a specific heart condition is diagnosed, your doctor will recommend appropriate treatment, which could include:

    • Medications to regulate heart rate, manage blood pressure, or treat underlying conditions

    • Lifestyle changes including diet, exercise, and quitting smoking

    • Procedures such as angioplasty, stent placement, or pacemaker implantation in some cases

• Follow-up care

  • Regular monitoring or check-ups to ensure that the treatment plan is effective

Can an ECG detect high cholesterol?

An ECG will not identify high levels of cholesterol. The test measures the electrical activity of your heart and identifies issues with arrhythmias, heart attacks, or electrical conduction problems. It doesn't provide information about cholesterol levels or lipid imbalances in your blood.

Are there any side effects from an ECG?

There are no significant side effects associated with an ECG. Some individuals may experience mild skin itchiness where the electrodes were placed, but this discomfort is usually temporary and will go away on its own.

The information provided is intended for general guidance only and should not be considered medical advice. For personalised recommendations based on your medical conditions, request an appointment with Thomson Medical.