The stress test can also help a doctor advise patients on the best type of physical activity for them.
Some patients will not be able to do the activities involved in an exercise stress test, for example, those with arthritis.
Instead of exercising, the patient can take a drug to make the heart work harder, as it might during exercise.
Why take a stress test?
The stress test captures the state of your cardiac health during heightened physical activity.
The doctor may recommend a stress test to find out if the patient:
- has heart-related symptoms, such as difficulty breathing or chest pain
- is suitable for an exercise program or cardiac rehabilitation program, and if so, how hard they should exercise
- is responding to heart treatment
- needs other tests to detect narrowed arteries, such as a coronary angiogram
- has arrhythmia, an irregular heartbeat or abnormal heart rhythm.
When the heart pumps harder during exercise, the stress test can reveal problems, such as poor blood supply through the coronary arteries. These problems might not be apparent at other times.
When the electrical impulses that coordinate heart rhythm are faulty, the heart may beat irregularly.
What to expect
The patient may have to refrain from eating, drinking, or smoking for 2 hours before the test. Sometimes, the physician will advise the patient not to take their usual medications beforehand or consume caffeine, as these can affect the results.
If the patient normally has an inhaler, they should bring this to the test, and make sure the doctor knows about it.
For an exercise stress test, the patient should wear comfortable clothes and walking shoes.
This test will take about an hour.
The stress test can be performed in different ways depending on the needs of the patient.
Exercise stress test
During a stress test, the doctor aims to find out the patient's heart rate, blood pressure, breathing, and how tired they feel under different levels of physical activity.
The test also involves an electrocardiogram (ECG or EKG) test. This is a simple test that records the heart's electrical activity. It helps the doctor understand how well the heart is working.
An ECG shows how fast the heart is beating. It also analyzes heart rhythm and measures the strength and timing of electrical signals as they pass through each part of the heart. Wires with electrodes are hooked up to the patient's chest, arms, shoulders, and legs. Toward the end the patient may have to breathe into a mouthpiece.
Here is a step-by-step description of what happens during a stress test using a treadmill:
- The patient is hooked up to the device that monitors the heart
- A blood pressure cuff is wrapped around the upper part of one arm
- The patient stands on the treadmill
- The treadmill starts to move, and the patient walks slowly
- The treadmill speed gradually increases
- The treadmill may go into an uphill, or incline, position
- The patient breathes into a tube for a minute or two
- After slowing down, the patient gets off, stands still for a few seconds and then lies down
- The medical team takes further readings of blood pressure and so on
The patient can hold the railing of the treadmill for balance, but holding onto it all the time may affect the reliability of the readings. Sometimes the doctor will advise the patient to hold on.
Blood pressure is one of the closely-examined elements of the stress test.
A stress test will last no more than 15 minutes. The doctor needs to work the heart harder than normal for 8 to 12 minutes.
If patient has any of the following signs or symptoms, the doctor will stop the test:
- severe panting
- high or low blood pressure
- chest pain
- abnormal changes detected by the ECG device
Qualified medical professionals are always on hand in case of adverse effects.
Stress test without exercise
If a person cannot do the exercise involved in an exercise stress test, the doctor may use medication to trigger the same process.
A technician will attach electrodes to their chest, legs, and arms, using sticky patches.
They will put an intravenous (IV) line into the patient's arm, and a medication will be given through this line. The medication will stimulate the heart, and it may cause side effects similar to those experienced during exercise, for example, flushing or shortness of breath.
Exercise stress echocardiogram test
A nurse will carry out an exercise stress echocardiogram by creating an image of the heart both before and after physical exertion.
The main instrument used is a transducer. Transducers emit a high-frequency soundwave that forms a picture of the heart once the echoes reach the organ. Bats and dolphins navigate their surroundings using a similar principle.
The sonographer (specialist ultrasound technician) will rub a gel onto the chest and then move the transducer around against it to create the clearest picture.
Some sonographers will request that the patient lies on their side for the test. Others may use an intravenous dye to enhance the clarity of the image. If so, this will be injected into the bloodstream during the test.
Nuclear stress test
If the initial symptoms persist or get worse, the doctor may recommend a nuclear stress test.
This will probably give a more detailed and accurate assessment of the patient's heart.
The results of a stress test will dictate what treatment can be provided to help the patient's heart problems.
The process is the same, but a dye is injected into the patient's arm that will show up the heart and blood flow on an image.
It will also show the areas of the heart where blood is not flowing. This can suggest a blockage.
This can be captured by an x-ray, or single photon emission computer tomography (SPECT) or cardiac positron emission tomography (PET).
Two sets of images will be taken, each lasting 15 to 30 minutes. The first will be taken just after exercising, and the second will be taken when the body is at rest, either later that day or the next day.
This allows a doctor to compare how the heart looks and functions normally and under stress.
The test will take from 2 to 5 hours.
Both the stress test and the nuclear stress test are normally safe.
Rarely, an adverse reaction may occur, including:
- abnormal heart rhythms, but these usually end when the test does
- flushing or chest pain
- an allergic reaction to the dye, in a nuclear stress test
Very rarely, it could trigger a heart attack, or myocardial infarction.
What might the results show?
Possible results of the test include:
- normal blood flow during exercise and rest
- normal blood flow when resting but not during exercise, possibly indicating a blocked artery
- low blood flow when exercising and resting, suggesting coronary artery disease
- no dye in some parts of the heart, implying tissue damage
If the stress test is normal, no further tests will be needed.
If results suggest a coronary artery blockage, further tests or surgical intervention may be necessary. This could be a balloon angioplasty and stent placement, or a coronary artery bypass.