Electrocardiograms and Stress Tests
An electrocardiogram (ECG) is a non-invasive, painless test that records the electrical activity of the heart. A stress test is an ECG performed while the heart is being stressed by medications or exercise.
Who needs an ECG?
Doctors may suggest an ECG to measure:
- Any damage to the heart
- Heart rate and whether it is beating normally
- The effects of drugs or devices used to control the heart (e.g. pacemaker)
- The size and position of heart chambers
An ECG is also useful for determining whether a patient has heart disease. A doctor may request this test for a patient who complains of chest pain or palpitations. The test may be included as part of a routine examination in patients over the age of 40 as the risk of heart-related health complications tends to increase with age.
What preparation is required for the test?
Before the test, the doctor will need to be informed of all non-prescription and prescription medicines taken, as some medicines can distort the ECG results. The doctor will specify how heart medications should be taken before the test. All jewellery should be removed before beginning the test. Men usually perform the test bare-chested, whilst women may wear a bra, T-shirt or gown. A cloth or paper covering will also be provided, as stockings should be taken off.
What are the risks?
An ECG is a safe procedure. Minor discomfort may be experienced only when electrodes are removed, similar to the removal of a band-aid. In some rare cases, electrodes may cause redness or swelling of the skin.
When an ECG is performed during a stress test, the exercise or medication that mimics the effects of exercise, may cause irregular heartbeats. This side effect is caused by the exercise or medication, not the ECG itself.
The risk of electrocution during an ECG is nil. Electrodes placed on the body only record the electrical activity of the heart. They do not emit electricity.
What to expect during the test
- The test requires patients to lie down. Electrodes are then attached to the patient's arms, legs and chest with a gel that helps detect and conduct electrical currents from the heart. If hair is present on parts of the body where the electrodes will be placed, the hair may need to be removed so that the electrodes adhere firmly to the skin.
- The number of patches used may vary.
- In most cases, patients will need to remain still, and may be asked to hold their breath for short periods during the procedure. It is important to be relaxed and relatively warm during an ECG recording. Any movement, including muscle tremors such as shivering, can alter the results.
- The electrodes are connected by wires to a machine that converts the electrical signals from the heart into wavy lines, which are printed on paper and reviewed by the doctor.
- Sometimes this test is done during exercise or under minimal stress to monitor changes in the heart. This type of ECG is often called a stress test.
- Some intermittent heartbeat irregularities may not be captured during an ECG, so the doctor may recommend another type of ECG:
Holter monitor – also known as an ambulatory ECG monitor, a holter monitor records heart rhythms for an entire 24-hour period. Wires from electrodes on the chest are attached to a battery-operated recording device carried in a pocket or worn on a belt or shoulder strap. Whilst wearing the device, patients must keep a diary of activities and symptoms. This diary is compared with the electrical recordings to determine the cause of symptoms.
Event recording – a doctor might suggest this device if symptoms are infrequent. It is similar to a holter monitor, except that it allows the patient to record an ECG just when the symptoms occur.
What happens after the procedure?
If the ECG results are normal, no further testing may be needed. If abnormalities are found, a repeat ECG or other diagnostic test, such as an echocardiogram may be required. Treatment will depend on the causes of the signs and symptoms.
A consistent, even heart rhythm and a heart rate between 50 and 100 beats a minute is considered healthy. Variations provide clues about heart health including:
Heart rate – checking pulse is generally a sufficient measure of heart rate, however, an ECG may be helpful in cases where a pulse is difficult to feel or too fast or irregular to count accurately.
Heart rhythm – when the heart’s electrical system malfunctions, an ECG can help a doctor to identify an unusually fast heartbeat (tachycardia), an unusually slow heartbeat (bradycardia) or other heart rhythm irregularities (arrhythmias). In other cases, medications such as beta blockers, psychotropic drugs or amphetamines can trigger arrhythmias.
Heart attack – an ECG can often identify evidence of a past heart attack or one that is in progress. The ECG patterns may also indicate which part of the heart has been damaged, as well as the general extent of the damage.
Insufficient blood and oxygen supply to the heart – an ECG conducted whilst having symptoms can help a doctor to determine whether the chest pain is caused by inadequate blood flow to the heart muscle.
Structural abnormalities – an ECG can provide clues about enlargement of the chambers or walls of the heart, heart defects and various other health problems.
A stress test helps determine how well the heart works under stress. The test involves exercise on either a treadmill or bicycle. During difficult exercise, the body needs more oxygen, so the heart needs to pump harder to provide it. By showing whether the blood supply is reduced in the arteries that supply the heart, a doctor can use a stress test to determine whether there is coronary artery disease present, and if so, the severity.
Who needs a Stress Test?
Doctors may recommend a stress test in order to:
- diagnose coronary artery disease
- diagnose a complaint relating to chest pain, shortness of breath or light-headedness
- determine a safe level of exercise
- determine the effectiveness of procedures done to improve coronary artery circulation in patients with coronary artery disease
- predict the risk of dangerous heart-related conditions such as heart attacks
What Preparation is Required Before the Test?
- Stress tests generally take about 1 hour, however, allow for 2 hours just to be on the safe side.
- Bring walking shoes and loose-fitting clothing.
- Avoid solid foods for 4 hours before the test.
- Drinking water is ok, however caffeinated drinks should be avoided (i.e. no regular or decaf coffee, tea, chocolate, or soft drink).
- A doctor should be consulted on which medications are ok to take on the morning of the test. Medications should be taken with sips of water only.
What to Expect During the Test?
A technician will be present throughout the test to closely monitor patient wellbeing.
ECG electrodes will be attached to the chest, arms and legs. The recording will show how fast the heart beats, its rhythm (steady or irregular), as well as the strength and timing of electrical signals as they pass through each part of the heart.
A blood pressure cuff will be wrapped around the arm to monitor blood pressure during the test. In addition, patients may be asked to breathe into a special tube so the exhaled gases can be monitored.
During the test, the exercise level will get progressively harder. However, patients can stop at any time, if they feel the exercise is too much. At the end of the test, normal activities may be resumed.
What is Monitored During the Test?
The following measures will be taken during the stress test:
- Heart rate
- Blood pressure
- Electrocardiogram (ECG)
What are the Risks?
There is very little risk - no more than walking fast or jogging up a big hill. At all times, a doctor will be available in the event anything unusual occurs during the test.