An electrocardiogram (ECG) is the most commonly used type of cardiac test. It measures the rhythm and electrical activity of your heart and is used to detect a variety of heart conditions. ECGs are also used to assess how well your heart is functioning and your overall heart health.
Electrical signals are formed in the sinus node (SAN) and transmitted to different areas of your heart. These signals coordinate the contractions in the upper chambers (the left and right atria) and lower chambers (the left and right ventricles) of your heart. The rate at which these electrical signals are sent out determines the rate your heart beats and how blood is pumped around your body. During an An electrocardiogram (ECG) test, the cardiologist will measure these electrical signals to assess:
· The rhythm of your heartbeat.
· The strength, timing and pattern of the electrical signals.
· The size and positioning of the chambers of your heart.
ECGs examine the electrical signals when the upper and lower chambers relax and contract and pump blood out of your heart and around your body.
There are several different types of ECG. The ECG you require will depend on multiple factors, such as:
· The types of symptoms you experience.
· How frequently your symptoms occur.
· Any previous cardiac or medical testing you have undergone.
· Whether a specific heart condition is suspected.
The most common ECGs are:
Resting Electrocardiogram (ECG):
A resting ECG is done while you are lying down in a comfortable position and while your heart rate is at rest. You will be asked to keep as still as possible to ensure that your movement doesn’t interfere with the test and that your heart rate remains at rest. The cardiologist will be able to see the electrical activity of your heart at rest and information about your heart rate and rhythm. A resting ECG is typically used to diagnose heart conditions such as arrhythmias.
Stress ECG/ Exercise Tolerance Test (ETT):
Stress ECG and exercise tolerance test (ETT) are different names for the same cardiac test. It is a type of ECG that is conducted while you are exercising on a treadmill or a stationary exercise bike and is used to assess the electrical activity of your heart and how well it functions while it is under physiological stress. A stress ECG will likely be recommended if you experience symptoms while you are exercising or under physical exertion.
ECG Holter Monitor:
ECG Holter monitors (sometimes called ambulatory ECGs) are usually recommended if your symptoms occur intermittently and are unpredictable. It is a small ECG machine that you wear for an extended period(between 24 hours and 14 days) while continuing your usual activities. The monitor will record your heart rate and rhythm and your heart’s electrical activity continuously while you are wearing the monitor.
There are several reasons why you may require an ECG. For example:
· If you are experiencing concerning symptoms, such as chest pain, dizziness, shortness of breath or heart palpitations.
· To assess or monitor your heart rate.
· To diagnose an arrhythmia or another heart condition, such as coronary heart disease.
· To determine if you are having a heart attack.
· To detect any damage following a heart attack.
· To monitor an existing heart condition.
· To monitor the effectiveness of heart medication or a pacemaker.
· To determine your heart health before surgery or another medical treatment.
Before the ECG begins, you will likely be asked to remove any clothing from your upper body, and you may need to have parts of your chest shaved or cleaned (to remove any dirt or products). The cardiologist will attach several electrodes (small, sticky sensors) to your chest, arms and legs. These electrodes will then be connected to the ECG machine.
The electrodes record the electrical signals that occur every time your heart beats. During a resting ECG, you will be asked to lies till while the ECG machine records the electrical activity of your heart. If you are having a different type of ECG, the cardiologist will give you different instructions.
Once the test is finished, the cardiologist will carefully examine the ECG and interpret the result.
Because you will be engaging in physical activity, you should wear comfortable clothes and trainers for your exercise tolerance test. To measure the electrical activity of your heart, small electrodes will be attached to your chest and then connected to an ECG machine.
You will either be asked to walk on a treadmill, initially at a slow pace before the incline or speed is steadily increased. Alternatively, you will be asked to cycle on an exercise bike, increasing the speed and difficulty as directed. The exercise is designed to become more strenuous to increase your heart rate. You will then be encouraged to run or cycle as hard as you can to increase the stress on your heart. This allows the cardiologist to assess your cardiac function during physical exertion.
Your heart rate, breathing and blood pressure will be monitored throughout the test to ensure they do not rise to a dangerous level. However, ensure you tell the doctor if you begin to feel chest pain or other concerning symptoms.
ECGs usually take between five and 10 minutes. However, don’t be alarmed if the test takes more or less time.
An ECG is a quick, painless, non-invasive cardiac test. The risks associated with an ECG are minimal and occur extremely rarely.
A small number of people experience skin irritation or a rash where the electrodes are attached to their skin. Some people may also experience an allergic reaction to the sticky substance or the gel that is used to attach the electrodes. However, in this situation, the cardiologist will remove the electrodes and your symptoms will usually subside.