Your physician may be interested in learning whether a patient who has cardiac risk factors for coronary artery disease (“blockage of the arteries”) does in fact have any CAD. In order to avoid invasive studies such as coronary angiography (or “angiograms”), we are able to offer our patients a non-invasive, less risky procedure initially called a myocardial perfusion SPECT study.
The myocardial perfusion SPECT study involves the injection of a tiny amount of radioactive tracer material that is taken up by the muscle cells of the heart. This tracer material gives off a small, weak pulse of energy that is detected by a special camera that we have in our office. This camera, using a sophisticated computerized method, then assembles the images of the heart muscle and allows our nuclear cardiologist to make a determination as to the presence of any decreased blood flow in the heart. Decreased blood flow may imply narrowed or blocked coronary arteries.
This SPECT study has been shown over the past thirty years to be remarkably useful for defining patients who have increased risk of having heart attacks or other serious effects from underlying, as yet undiscovered coronary artery disease. Perhaps most importantly, a SPECT study that shows no areas of ischemia, or lack of blood flow, is very reassuring in terms of prognosis; that is, a normal SPECT study helps us to confidently and comfortably predict which patients are at low risk for major adverse cardiac events.
Technically, the SPECT study uses the physiologic phenomenon of blood flow to the heart muscle to deliver the tracer material (the “isotope”) to the heart muscle.Two sets of images are obtained: one at stress and the other at rest. The isotope travels to the heart with the blood flow during both stress and rest. An area of diminished blood flow may appear on the stress images obtained by the camera. Such an area of diminished blood flow may indicate the need for further testing and possible intervention, such as angiography and “angioplasty” or the placement of a stent in a coronary artery.
Specifically, the test lasts about three hours and involves the placement of a small intravenous (IV) line prior to getting started. The tracer material is then given through the IV. 30-60 minutes later, the resting images are obtained; the patient rests comfortably in a special chair attached to the camera. After this, the stress images are obtained. Stress is accomplished in one of two ways: a patient may either exercise on a treadmill or may be given a medicine that will open the coronary arteries to provide maximal blood flow to the heart in order to mimic an exercise state if unable to exercise.
On the day of the study, please refrain from drinking any caffeinated beverages such as coffee, tea, hot chocolate etc. Do not eat anything for four hours before the test. Your usual medications should be taken unless specifically instructed by the physician at the time the test is ordered. It is best to wear comfortable walking shoes and loose, comfortable clothing to the test. Underwire bras and jewelry should not be worn.
Frequently Asked Questions
My doctor has recommended a MPS SPECT study. What is this study designed to do?
This is a test which involves an injection of a very small amount of radioactive tracer material into the bloodstream which will circulate with the blood cells and allow our technicians to take pictures of the heart muscle and the blood flow to the heart muscle. The study is designed to provide accurate information about the adequacy of blood flow to the heart as well as heart muscle function. The blood cells are photographed as they travel throughout the heart, leaving a small short-lived trail of tracer behind, and any blockages in the path of the blood cells is recorded. The study is then interpreted by an expert in nuclear cardiology in order to determine if there are any serious blockages in the arteries that supply blood to the heart.
Will I need to exercise for the study?
Not necessarily; we may obtain SPECT images of the heart at rest if exercise is difficult for a patient. We use a medication called adenosine which is safe and which causes the heart to behave as it does during exercise without raising the heart rate.
What can I expect on the day of the study?
On the day of the study, you will be asked to sign an informed consent form. Then, an IV line will be placed in order to administer the radioactive substance. After a 30-60 minute waiting period, a 30 minute scan will be taken. The stress test will be next and you will either walk on a treadmill or be given a medication which will mimic the effect of exercise on the heart. After another 15-30 minutes, another scan will be taken. You can expect to spend three or four hours in the office.
Why do I need this study?
Your physician has determined that your clinical history combined with the presence of cardiac risk factors (such as hypertension, high cholesterol, smoking or diabetes) puts you at increased risk for a heart attack. The SPECT study can help to further clarify your risk and guide any further procedures or testing.
Is there something about my case that indicates that I need this study?
Coronary artery disease (CAD) is very common in the United States. In order to better understand who has significant CAD, cardiologists have developed an understanding of what are known as risk factors. People with several risk factors or with symptoms suggesting heart disease are often referred for a myocardial perfusion study.
How quickly can I learn the results of the study?
Generally, the images are available for review the day of the study and will be interpreted within about 48 hours.
Do I need to take any special precautions for the study?
The use of caffeine can interfere with the ability of the tracer material to bond with the heart muscle cells. Avoiding the use of caffeine for 12 hours preceding the study is very important.
Will the study tell me if I have a blockage in my arteries?
The scan will allow the nuclear cardiologist to understand the pattern of blood flow in your heart. If there is diminished blood flow to a particular region of the heart, this may imply the presence of narrowed or blocked arteries.
Can this study accurately predict a heart attack?
The perfusion scan can help to define risk of a heart attack. Perhaps most importantly, a negative scan can be very helpful in defining patients at very low risk for heart attacks.
What other information can be learned from this study?
Our best test for understanding of the function of the heart muscle function and pumping capacity is the perfusion (or SPECT) scan. The pumping capacity of the left ventricle is the single most important prognostic parameter in people with any type of heart disease.
The testing center has required that I leave a deposit for the study. Why is this?
Unfortunately, occasionally patients fail to come in for their scan. The radioactive tracer material is quite expensive and is ordered for a specific date in a dose that is tailored to the individual patient. This tracer is only useful for a few hours. In order to continue to offer this service to our patients, a deposit must be taken in order to insure that our imaging center can continue to operate. The deposit is held until the day of the procedure. The only time the deposit is withheld is if a patient fails to appear for the test or does not cancel the test within 48 hours. If the patient appears for the test, the deposit is returned to the patient on the day of the study and the insurance company will be billed for the test and the isotope. Because of the way the insurance companies work, the tracer material is paid for only if the study is completed. If the study is not completed due to failure of the patient to come in for the test, the patient will pay for the tracer using the deposit.
Is the study safe?
Yes. Many people are concerned about the idea of introducing a radioactive material into the body. In fact, the amount of radioactivity is quite small. This is a study which has been approved and shown to be safe for decades. Thousands of people undergo myocardial perfusion scanning annually.
I have a friend or relative who has had an angiogram. Why not just go straight to this test if it is more accurate?
While generally safe, angiography, like all invasive procedures, carries a small risk of complication. We feel that procedures which involve any risk at all should be reserved for individuals who clearly require the procedure. In our office, this means using screening non-invasive studies to more clearly define the patients who will benefit from invasive procedures such as angiography.
Why not get a HeartScan?
A heart scan or CT scan of the heart has not been shown to predict what are know as “events” such as heart attacks or heart failure. Heart scans simply show blockages in the coronary arteries and tell us nothing about the risk of those blockages. This is known as an “anatomical” test. In order to better understand the significance of blockages in the arteries, a “functional” study is required. Perfusion scanning accurately and demonstrably shows the effect blockages have on blood flow which is far more important than simply demonstrating the presence of narrowing of arteries. In general, if a heart CT finds blockages in the arteries, a patient is then referred for a myocardial perfusion scan anyway. Obtaining the perfusion scan without the CT scan avoids the expense, inconvenience and exposure to radiation caused by the use of multiple tests.
Echocardiography or cardiac ultrasound has been used in cardiology for over 40 years. This is a painless and simple test which can be done in a cardiologist’s office. The test requires no medications or injections and the results are immediately available to the cardiologist, primary card doctor, and patient.
The test requires the patient to rest quietly on a procedure bed while disrobed from the waist up. The expert technician, or sonographer, will use a transducer, or probe, and a small amount of liquid gel to aid in transmission of the sound waves across the chest toward the heart muscle and valves. The transducer sends out sound waves that are reflected off the heart and back toward the transducer in the same way that a voice “echoes” back across a canyon.
The test is quite safe; there are no known risks. The technology used is identical to that used when examining a pregnant woman’s baby as it develops in the uterus at 12 and 20 weeks.
Occasionally, because of individual anatomical differences, underlying disease processes or when using echocardiography for specific reasons such as the location of “hole in the heart”, an intravenous line (an IV) may be required in order to inject contrast material into the chambers of the heart.