Myocardial Perfusion Imaging (MPI)
This nuclear imaging study is a non-invasive,time tested procedure to screen for critical coronary stenosis. With improved diagnostic accuracy over regular stress tests, abnormal perfusion scans are highly indicative of coronary artery disease.
PURPOSE OF MPI
This diagnostic and prognostic study determines the degree and location of compromised blood flow to the heart as well as pumping function and existence of scarred heart tissue. Healthy heart muscle, receiving normal blood flow, will accumulate more imaging agent than cardiac muscle supplied by diseased coronary arteries.
MPI is used to determine the need for invasive procedures, to avoid unwarranted hospital admissions or discharges, and to assess for long term prognosis.
CANDIDATES FOR MPI
The study is indicated for patients with known or suspected coronary artery disease, including those who have had cardiac events or may be at risk. Populations at an increased risk for heart disease include patients with diabetes, hypertension, elevated blood cholesterol and triglycerides, smoking, and a family history of premature heart disease. In addition to the more commonly known symptoms of chest pain and shortness of breath, several of the lesser-known symptoms of heart disease may include nausea, indigestion, fatigue, and pain in the arm, back and neck.
WITH IMPROVED DIAGNOSTIC ACCURACY OVER REGULAR STRESS TESTS, ABNORMAL PERFUSION SCANS ARE HIGHLY INDICATIVE OF CORONARY ARTERY DISEASE.
PROCEDURE DESCRIPTION
MPI is performed during stress while monitoring for blood pressure and heart rhythm via ECG. Patients’ arteries are dilated when they are subjected to stress conditions, usually though exercise, but a pharmacologically induced stress test may be performed when patients cannot exercise. A small dose of a radiopharmaceutical is injected into the bloodstream at maximum exercise. Patients then undergo a scan using a gamma camera (SPECT technology) which produces images representing blood flow to the heart during stress. Scanning is repeated at rest, with no significant changes appearing in healthy hearts during either study.
TECHNOLOGICAL CAPABILITIES
The radioactive tracer distributes in proportion to blood flow, with greater concentration where there is better blood flow. These sophisticated imaging agents significantly increase the accuracy of nuclear cardiac testing. The gamma camera further improves diagnostic accuracy because SPECT images are reformatted to identify areas of a decrease in blood flow.
Instructing your patients
To ensure accurate results, patients should not ingest caffeine, drinks labeled “caffeine-free,” chocolate, theophylline, dipyridamole or aspirin for 12 hours prior to testing. You should have nothing to eat except water and juice for four hours prior to the first part of the test. Check with your doctor concerning discontinuing of medication prior to testing. Diabetic and insulin dependent patients will require consultation on dietary restrictions and insulin use.
To prepare patients for testing, please provide them with the additional information below:
- Myocardial perfusion imaging determines if patients have coronary artery disease or “heart blockages”.
- The testing is usually performed in two phases:after exercise and again during rest. There is a break of 2 to 4 hours with the first phase taking approximately one hour and the second “scanning” phase about 25 minutes.
- Patients are injected thru an intravenous during exercise with a small amount of a radioactive substance that can show blood flow in the heart muscle.
- The patient exercises and then is scanned with a special camera to determine which areas of the heart are receiving enough blood.
- For patients who cannot exercise, there are alternative ways to perform the test with medication.
- Patients should wear loose-fitting, comfortable clothing suitable for exercise.
- Women who suspect they may be pregnant should tell their doctors prior to testing.
