Coronary Artery Disease (CAD) or Myocardial Infarction (MI) can be diagnosed by a MIBI stress test. CAD occurs when one or more of the coronary arteries are partially blocked due to plaque formation along their walls. When your coronary arteries are blocked, not enough blood can get to your heart causing shortness of breath or chest pain. If this condition is not corrected, it can lead to a heart attack, or myocardial infarction. A MIBI scan can diagnose either of these conditions less traumatically than angiography.
You will be injected with a small amount of radioactivity into a vein in your arm. This injection is no more traumatic than a routine blood test. You will not feel dizzy or nauseous from the radioactivity. The amount of radioactive exposure you will receive is less than from an angiogram. The radioactive tracer we use is called Technetium-99m-NUBI. For those patients with a background in Chemistry, MIBI is an acronym for 2-methoxy isobutyl isonitrile. Once injected, MIBI travels to your heart via the blood supply and then becomes trapped within healthy, active muscle cells in the heart. You cannot feel this happening, but we can take pictures of it with a Gamma Camera. If you have an MI, then some of the muscle cells will not trap the MIBI. The same effect occurs with CAD except the lack of MIBI in some of the muscle cells is due to inadequate blood supply to the heart on exercising. Our physicians can differentiate between the two diseases by comparing your "Rest" pictures with your "Stress" pictures. Patients with CAD will have an abnormal "Stress" picture and a normal "Rest" picture. Both pictures are abnormal for MI. The test is especially accurate for differentiating old MI’s from new CAD.
This test involves visits over two days to our department. Your doctor's office will let you know whether you are having your "Stress " or 'Rest " part first, as the order varies due to our schedule. The "Rest" part involves coming in for a small injection in your arm and then returning about 1-2 hours later for pictures. The pictures take about 30 minutes. The technologist injecting you will inform you of your return time for pictures. The "Stress" part is slightly more involved. First you must have an IV set up in your right forearm. Then you will be sent to Cardiology where you will walk on a treadmill or be given Persantine or Dobutamine--drugs that make your heart think you are exercising. Afterwards, you will have pictures taken in Nuclear Medicine of your heart. We try our best to keep on schedule and we will notify you if we are running a little late. If you are pregnant, please let us know.
Unless you are diabetic, you must be fasting at least 4 hours before each test. In addition, you must avoid caffeine (coffee, decaf, tea, chocolate, Coke, Tylenol, etc.) for 24 hours prior to the "Stress" part of your test. Some medications should be discontinued prior to the "Stress" part as well. Please consult the physician ordering your test if you should stop any medication. You may wish to wear comfortable clothing for the "Stress" part as you may be walking on a treadmill. The pictures require you to he still with your arms above your head. Only metal objects around your chest such as chains, bras, Kirpans need to be removed. During the break between the injection and pictures, you may be requested to eat something--such as a muffin, milk, cheese. A meal helps us to get clearer pictures of your heart by causing your liver to empty. This is because your liver cells also collect MIBI and it sits just under your heart, and thus can sometimes block our view of your heart.