Myocardial Perfusion and Cardiac Viability Imaging

What is Myocardial Perfusion Imaging?

Myocardial Perfusion Imaging (MPI) is a specialized test that shows how blood flows to your heart muscle. This test helps your doctor:

• Detect blockages in your coronary arteries
• Assess the impact of these blockages on your heart
• Evaluate the effectiveness of previous treatments like stents or bypass surgery
• Determine your risk for future heart problems

The test uses small amounts of radioactive tracers (such as Tc-99m Sestamibi) that travel through your bloodstream to your heart. A special camera detects these tracers, creating images that show how blood flows to different areas of your heart muscle both during stress and at rest.

What is a Viability Scan?

A viability scan determines whether areas of your heart muscle that appear damaged are:

• Dead tissue from a previous heart attack, or
• “Hibernating” tissue (alive but not functioning properly) that could potentially recover with improved blood flow

This distinction is crucial because hibernating heart tissue may benefit from procedures to restore blood flow, while dead tissue will not.

Why Might I Need These Tests?

Your doctor may recommend these tests if:

• You have symptoms like chest pain, shortness of breath, or fatigue
• You have known coronary artery disease
• You’ve had a previous heart attack
• You’ve had treatments like stents or bypass surgery
• Other tests have been inconclusive
• Your doctor needs to determine if heart surgery would be beneficial

Preparing for Your Test

Before Your MPI (myocardial perfusion imaging) Scan:

• Fast for 4-6 hours before the test (specific instructions will be provided)
• Avoid caffeine (coffee, tea, chocolate, cola) for 24 hours before the test
• Do not smoke on the day of the test
• Certain medications may need to be temporarily stopped, including:
  • Beta-blockers
  • Calcium channel blockers
  • Nitrates
  • Aminophylline derivatives
• Important: Consult with your doctor before stopping any medications
• Wear comfortable clothes and walking shoes if you’ll be exercising
• Bring a snack to eat after the test is complete

Before Your Viability Scan (if needed):

• For PET-CT viability scans, you’ll need to fast overnight

What to Expect During the MPI Procedure

The MPI Test (Two Parts):

Part 1: Stress Test

1. Preparation
   • An IV line will be placed in your arm
   • Monitoring equipment will be attached to check your heart rate and blood pressure
2. Stress Portion (one of the following):
   • Exercise Stress: You’ll walk on a treadmill that gradually increases in speed and incline
     • The goal is to exercise until you reach your target heart rate or experience symptoms
     • If you have mobility issues, please inform us in advance
   • Medication Stress: If you cannot exercise, you’ll receive a medication that mimics the effects of exercise on your heart
     • You may feel flushing, shortness of breath, or chest discomfort – this is normal
     • These sensations will disappear quickly after the medication is stopped
3. Tracer Injection
   • At peak stress, the radioactive tracer will be injected through your IV
   • You’ll continue exercising or receiving the medication for a short time
4. Imaging
   • After 45-60 minutes of waiting, you’ll lie on an examination table
   • A camera will rotate around your chest, taking pictures of your heart
   • This imaging takes approximately 25 minutes
   • You’ll need to lie still with your arms above your head

Part 2: Rest Test

1. Usually performed on a different day or earlier on the same day as the rest study
2. You’ll receive the same radioactive tracer while at rest
3. After waiting 60-90 minutes, imaging will be performed for about 25 minutes
4. No exercise or medication stress is involved in this portion

What to Expect During a Viability Scan (If Needed)

PET-CT Viability Scan:

1. You’ll receive a glucose-rich meal upon arrival
2. Your glucose levels will be monitored with a glucose monitor that requires a pin-prick blood sample
3. A radioactive glucose tracer will be injected
4. After 40 minutes, imaging will be performed for approximately 30 minutes

For Diabetic Patients:

• Your blood sugar will be carefully monitored with a glucose monitor
• You may receive insulin to bring your blood sugar to an optimal level
• The scan proceeds as above once your blood sugar is properly controlled

After Your Test

• You can resume normal activities immediately
• Drink plenty of fluids to help flush the tracer from your body
• You can resume taking any medications that were stopped for the test
• The small amount of radiation used will leave your body naturally within 1-2 days
• A nuclear medicine specialist will analyze your images and send a report to your doctor
• Your doctor will discuss the results with you at your next appointment

Results and Follow-up

Your doctor will receive a detailed report that shows:

• How blood flows to different areas of your heart muscle
• Whether there are areas with reduced blood flow
• If reduced blood flow occurs only during stress or also at rest
• Whether areas of your heart muscle are viable (alive) or non-viable (dead)

This information helps your doctor determine the best treatment plan for your specific condition.

If you have any questions or concerns about your myocardial perfusion or viability scan, please discuss them with your healthcare provider.