Each year in the United States more
than 400,000 persons die of unexpected cardiac death. Our specialists provide
evaluation and treatment of hypertension, coronary artery disease,
and peripheral vascular disease. Evaluation via holter monitoring,
treadmill stress tests, and echocardiograms is available as well.
If indicated, patients are referred for stress thallium testing to further delineate any possibility of
cardiac disease. Patients may also be referred for cardiac catheterization to diagnosis blockage of coronary arteries.
What is a thallium stress test?
This is a type of nuclear scanning test or myocardial perfusion (mi"o-KAR'de-al per-FU'zhun) imaging test. It shows how well blood flows to the heart muscle. It's usually done along with an exercise stress test on a treadmill or bicycle.
The thallium stress test is useful to determine:
- Extent of a coronary artery blockage
- Prognosis of patients who've suffered a heart attack
- Effectiveness of cardiac procedures done to improve circulation in coronary arteries
- Cause(s) of chest pain
- Level of exercise that a patient can safely perform
When the patient reaches his or her maximum level of exercise, a small amount of a radioactive substance called thallium is injected into the bloodstream. Then the patient lies down on a special table under a camera ("gamma camera") that can see the thallium and make pictures. The thallium mixes with the blood in the bloodstream and heart's arteries and enters heart muscle cells. If a part of the heart muscle doesn't receive a normal blood supply, less than a normal amount of thallium will be in those heart muscle cells.
The first pictures are made shortly after the exercise test and show blood flow to the heart during exercise. The heart is "stressed" during the exercise test -- thus the name "stress test." The patient then lies quietly for 2-3 hours and another series of pictures is made. These show blood flow to the heart muscle during rest.
What does the thallium stress test show?
- If the test is normal during both exercise and rest, then blood flow through the coronary arteries is normal. The coronary arteries are supplying sufficient blood to the heart muscle.
- If the test shows that perfusion (blood flow) is normal during rest but not during exercise (a perfusion defect), then the heart isn't getting enough blood when it must work harder than normal. This may be due to a blockage in one or more coronary arteries.
- If the test is abnormal during both exercise and rest, there's limited blood flow to that part of the heart at all times.
- If no thallium is seen in some part of the heart muscle, the cells in this part of the heart are dead from a prior heart attack. (Scar tissue has formed.)
What if I can't perform an exercise test?
Sometimes you can't do an exercise test because you're too sick or have physical problems. In this case, a drug such as deprivable or adenosine is given. This drug increases blood flow to the heart and thus "mimics" an exercise test. Then the thallium test is given.
What Is Cardiac Catheterization?
Cardiac catheterization (KATH-e-ter-i-ZA-shun) is a medical procedure used to diagnose and treat certain heart conditions. A long, thin, flexible tube called a catheter is put into a blood vessel in the arm, upper thigh (groin), or neck and threaded up into the heart. Through the catheter, doctors can perform diagnostic tests and treatments on the heart. Cardiac catheterization is usually performed in a hospital by heart doctors (called cardiologists) that specialize in the treatment of heart diseases.
To diagnose some heart conditions, doctors may put a special dye into the catheter to make the inside of the heart and blood vessels show up on x rays. Doctors may take samples of blood and heart muscle through the tube. They can also treat certain heart problems during this procedure.