Nuclear Cardiac Stress Test

What is a nuclear cardiac stress test?

A nuclear cardiac stress test is used to assess the blood flow to your heart muscles during exercise and rest. It is also called a nuclear perfusion scan or myocardial perfusion imaging.

A nuclear cardiac stress test is a common test used to diagnose heart problems. It may be used to complement a regular electrocardiogram (ECG), which detects abnormal electrical activity in the heart and pinpoints heart blockages exactly.

How it works

During the procedure, your doctor will inject a small amount of a radioactive compound (called a tracer) into a vein in your arm. The tracer will be swept from your blood quickly by heart muscle cells.

Your doctor will take 2 sets of images of your heart using a gamma camera — when you are resting and after you exercise. If radioactivity is not seen in parts of the heart, this means that there is a lack of blood supply to that part.

Why do you need a nuclear cardiac stress test?

Your doctor may request a nuclear cardiac stress test to:

• Assess blood flow to your heart walls.
• Determine the cause of chest pain if you experience chest pain for no clear reason or during exercise.
• Check if any coronary (heart) arteries are blocked and the extent of any blockage.
• Find out the extent of damage to your heart if you experienced a heart attack. If the tracer cannot be detected in some areas of the heart, this could indicate scar tissue, or damaged heart tissue from a heart attack.
• Assess blood flow to your heart after a heart bypass surgery or angioplasty (re-opening of blocked heart arteries using a balloon or a stent).

Who should not undergo a nuclear cardiac stress test?

You should not undergo this test if you:

• Have a flu with fever.
• Have an infectious disease such as sore eyes or chicken pox.
• Are pregnant or breastfeeding, to avoid exposure to radiation.
• Are feeling lethargic.

What are the risks and complications of a nuclear cardiac stress test?

A nuclear cardiac stress test is generally safe. Rare complications include:

• Abnormal heart rhythms (arrhythmias) occurring during a stress test. This is usually temporary. Life-threatening arrhythmias due to the test are rare.
• Dizziness or chest pain can happen during a nuclear cardiac stress test. Other mild and brief symptoms may include feeling anxious, feeling out of breath, nausea, shakiness, headache and flushing during the test.
• Heart attack due to the test. This is extremely rare.
• Low blood pressure during or immediately after the exercise. You may feel dizzy or faint but will recover after the stress test.

How do you prepare for a nuclear cardiac stress test?

To prepare for the test:

• Stop taking medications containing theophylline 48 hours before the test.
• Avoid taking medications and food and drinks containing caffeine 12 hours before the test.
• Shave your chest if you are a male patient. This allows the electrodes to stick to your skin better.
• Wear or bring along exercise attire and shoes for exercising, or walking on the treadmill.
• Have a light meal before the test.

What can you expect in a nuclear cardiac stress test?

The nuclear cardiac stress test has 2 parts:

1. Rest scan
2. Stress scan

Estimated duration

Depending on the type of nuclear tracer used, the complete test may take 2 – 6 hours.

Before the procedure

Your doctor will insert an intravenous line into your arm to inject the radioactive tracer.

During the procedure

If you are undergoing a rest scan, your doctor will:

• Inject the radioactive tracer.
• Wait for the tracer to circulate through your heart's blood vessels.
• Take images of your heart.

If you are undergoing a stress scan, your doctor will:

• Inject the radioactive tracer.
• Place electrodes on your chest. The electrodes are connected to an electrocardiogram to monitor electrical signals that trigger your heartbeat.
• Ask you to exercise on a treadmill. If you are unable to exercise, your doctor will inject a medication to increase blood flow to your heart instead.
• Monitor your blood pressure during the test.
• Take images of your heart when your heart rate peaks.

After the procedure

Your doctor will compare the 2 sets of images to see how blood flows through your heart.

Care and recovery after a nuclear cardiac stress test

After the test, you may return to normal activities. Take note to:

• Drink lots of fluid for the next 1 – 2 days to flush out any remaining radioactive tracer from your body.
• Minimise contact with infants and pregnant mothers for 24 hours after the test. This avoids any risk of radiation exposure to them.
• (If you are breastfeeding) Only resume breastfeeding 24 hours after the test.