Cardiac Positron Emission Tomography (PET) Myocardial Perfusion Stress Test

Definition

A Cardiac PET scan is a non-invasive nuclear imaging test using radioactive tracers (eg Rubidium37) to produce pictures of heart.

A radioactive tracer produced from natural body compounds such as glucose, water or ammonia, tagged with a small amount of radioactive material (eg rubidium37) is injected into your bloodstream and taken up by your heart. The radioactive tracer produces a type of energy called a gamma ray inside your body and these are detected by a gamma detector which then produce a series of clear images of your heart. Areas of your heart that have good blood flow will be light, and areas with poor blood flow will be dark. The different colors represent different amounts of tracer uptake.

Using state-of-the-art PET methods, this test allows your physician to assess for coronary artery disease and the degree of ischemia (lack of oxygen) your heart muscles is subjected to due to the heart artery blockages. It also assesses the degree of damage due to a heart attack and will help your physician decide if you will benefit from a percutaneous coronary intervention (PCI) such as coronary angioplasty and stenting, coronary artery bypass surgery (CABG) or another procedure.

What are the benefits of this test?

This test is used to:

  1. 1
    Diagnose the presence of coronary artery disease
  • Using radioactive tracers taken up by your heart muscles, this test is a very accurate way to diagnosed coronary artery disease and detect areas of low blood flow in your heart.
  1. 2
    Assess the severity of narrowing of the coronary arteries
  • Narrowed arteries will reduce the uptake of radioactive tracer into the heart muscle and it will appear as a perfusion defect. The greater the degree of narrowing of the heart arteries, the greater the perfusion defect.
  • The need for revascularization (via stenting or bypass surgery) is determined largely by the degree of perfusion defect detected.
  1. 3
    Determine the benefit from a cardiac procedure
  • Different colors or degrees of brightness on the PET scan show different levels of tissue function.
  • Dead heart tissue (non-viable myocardium) or scars from a prior heart attack will appear dark and while injured but still living (viable myocardium) heart muscles will appear bright.
  • The higher the degree of muscle tissue that is alive (viable myocardium), the higher the benefit you will receive from going through a cardiac procedure to improve the blood flow to your heart muscles.
  • This will help in the decision process of whether the benefits of going through a stenting procedure or bypass surgery outweigh the risks.

Who will benefit from this test?

  • Patients with atypical chest pain and intermediate risk for coronary artery disease with the following risk factors.
  1. Family or personal history of coronary artery disease
  2. Male over 45 years of age
  3. Females over 55 years of age
  4. Past or present smoker
  5. History of high cholesterol, diabetes or high blood pressure
  6. Elevated body mass index (BMI)
  7. Inactive lifestyle
  • Patients with new or worsening symptoms (eg Chest pain or shortness of breath) with a previous normal stress test result
  • Patients with inconclusive stress test results (eg borderline positive treadmill test)

Are there any side effects of this test?

Cardiac PET is generally safe for most people. The amount of radiation is minimal and your body will get rid of it through your kidneys within about 24 hours. If you’re pregnant or think you might be pregnant, or if you’re a nursing mother, tell your doctor before you have this test as it could harm your baby.

How to prepare for the test

  1. 1
    Before the day of the test
  • Take the morning off so that you can complete this test in a more relaxed state of mind. Stress increases your heart rate and it can make this test less accurate.
  • Keep yourself well-hydrated. This will reduce the risk of kidney impairment due to the injection of the dye.
  • Stop diabetic medications containing Metformin (eg Glucophage).
  1. 2
    On the day of the test
  • You may drink water and consume all your medications (except Metformin) but do not eat for 4 hours prior to your scheduled appointment.
  • Avoid any caffeinated drinks (eg coffee, tea, mountain dew, energy drinks) for 24 hours before and during the day of the test.
  • Do not smoke on the day of your test as nicotine will interfere with the results of your test.
  • You may consume your oral medications except:
  • Over the counter medications that contain caffeine (eg Panadol extra)
  • Isosorbide dinitrate (eg ISDN)
  • Isosorbide mononitrate (eg Imdex or Imdur)
  • Dipyridamole (Persantin)
  • Beta-blockers (Atenolol, Concor, Metoprolol, Carvedilol, Nifetex)
  • If you take pills for your diabetes, do not take them until after the test is complete. If you take insulin to control your blood sugar, ask your physician how much insulin you should take during the day of your test.
  • If you own a glucose monitor, bring it with you to check your blood sugar levels before and after your test. If you think your blood sugar is low, tell the lab personnel immediately. Plan to eat and take your blood sugar medication following your test.
  • If you use an inhaler for asthma or other breathing problems, please bring it along with you and highlight it to our cardiac technician & doctor.

How is the test performed?

A doctor and a nuclear medicine technologist usually perform the scan in a hospital or at a PET center using special equipment.

  1. 1
    Before the test
  • You will change into a hospital gown.
  • The nurse will record your height, weight and blood pressure and insert an intravenous (IV) cannula into a vein in your arm.
  • You will lie on a special scanning table connected to the PET scanner shaped like a giant dougnut and a computer.
  • Three electrodes (small flat sticky patches) will be placed on your chest wall and attached to an ECG monitor that charts your heart’s electrical activity during the test.
  1. 2
    During the test
  • You will feel the table move inside a donut-shaped scanner and doctors will take a baseline picture of your heart before the tracer is injected. This takes about 15 to 30 minutes. 
  • The tracer will then be injected and your heart will be scanned once again.
  • You will then get a medicine that increases the blood flow in your heart, similar to what happens during exercise. These medicines may include adenosine, dipyridamole (Persantine) or dobutamine. 
  • Another small amount of tracer will be given and your heart will be scanned once again to assess how well your heart takes up the tracer before and after the medications are given.
  • If you have severe coronary artery disease, some areas of your heart may not get enough blood during a stress so the tracer won’t show up in those areas.
  • The entire procedure may take between 1-3 hours.
  1. 3
    After the test
  • You may resume your normal daily activities after the exam.
  • Drink plenty of water for the next 24 hours to flush the radioactive material from your body.
  • You Cardiac PET with be reviewed by our doctor and a summarized report will be provided and explained to you during your review.

How does the doctor use this test to treat me?

1. Normal exam

  • No further testing may be needed.

2. Abnormal exam

  • Further investigations such cardiac catheterization may be needed.
  • Lifestyle changes and treatment with cardiac medications to optimize your condition will be given by your physician.

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