One of the most common questions I get as a health consumer advocate is, “Should I have a heart scan?” What has been portrayed as a complex question really boils down to answering a few simple questions about your health and your philosophy about managing your health. But first, I think it is helpful to define exactly what we mean by a heart scan.
The many kinds of heart scans
Heart scans have come to mean many things depending on who you are talking to. Here is a list of “heart scans” commonly available and used in modern cardiology.
1. Nuclear cardiac perfusion scan. This type of scan is used when doing a nuclear stress test (also known as a myocardial perfusion scan, myocardial perfusion imaging, thallium scan, cardiac perfusion scan, and sestamibi cardiac scan, among others). This type of test has been the gold standard of non-invasive methods to test whether blockages are developing in coronary arteries.
First, your doctor will inject a short-lived, radioactive tracer-drug into your veins. The scanner tracks the amount of tracer-drug (and therefore blood) that enters the heart tissue while at rest. Once the radioactive drug wears off, (about an hour later if the newest drugs are used) you will be put on a treadmill just like a regular stress test and once again receive an injection. A second scan determines how much “radioactive blood” enters various parts of the heart under physical stress and is compared to the at-rest scan. Areas of insufficient blood flow can be indicative of blockages in the arteries that feed that part of the heart. Blockages of about 80 percent or greater can be detected without doing an invasive catheterization. The obvious disadvantage of this scan is you are twice subjected to low levels of radioactive substances.
This test has received a modern upgrade in recent years. I had this test many years ago and had to wait three hours between scans (waiting for the radiation to wear off). I was literally bandaged to make sure I remained motionless for half an hour! Newer technologies have reduced these drawbacks.
2. Stress-echo scan. This scan is similar in procedure and diagnostic value as the nuclear cardiac perfusion scan with several important differences. This test features no radiation or drugs and is typically less expensive as well as faster. The procedure is the same (but without the radioactive drug) but the scan is actually a simple echocardiogram that measures movement of the heart muscle. If there is no increase in heart movement (not heart rate, but actual amount of heart wall expansion and contraction) after running on a treadmill, it may be indicative of a blockage. I now have this test performed yearly.
3. Virtual angiogram. A virtual angiogram (also known as a CT angiogram) is a special form of CAT scan that is able to create a 3-D reconstruction of the heart and its arteries. Any significant internal narrowing of an artery is a strong indication of a blockage and usually leads to the patient having a traditional cardiac catheterization to more fully examine the suspected blockage, at which time a stent might be placed to open the narrowing. The obvious advantage is the ability to detect blockages without the risk, cost, and discomfort of performing an invasive surgical procedure to thread a catheter into the heart. The primary drawback of this procedure is the high level of radiation exposure (two to three times higher than a cardiac catheterization).
4. Coronary calcium scan. This test is another specialized CAT scan that detects traces of calcium in the arteries. When you hear the generic term “heart scan,” it typically refers to a coronary calcium scan. Cardiac imaging pioneer Dr. John Rumberger examined the plaque in coronary arteries of numerous persons who had died from coronary artery disease (CAD). He found that, regardless of age or sex, calcium comprised about 20 percent of the volume of atherosclerotic plaque. Therefore, a calcium score can determine how much plaque you have in your coronary arteries.
Later studies have shown that calcium scores are highly associated with increased heart attack rates. Most tests such as cholesterol blood tests only determine your risk of developing CAD. A calcium score can tell you if you have CAD without regard to such risk factors. For example, if you have high cholesterol but a zero heart scan score, your heart attack risk is still very low. However, even if your cholesterol is low, your heart attack risk is high in the presence of a high calcium score.
Like any other type of CAT scan, a coronary calcium scan does impart a significant radiation dose so the benefit must be weighed against the risk. The newer “256-slice” scanners deliver a dose equal to about six to 15 chest X-rays.
To scan or not to scan
There is significant disagreement as to whether the “average” person should have a heart scan. Many authorities would agree that a coronary calcium scan can add useful information for patients whose risk factors such as cholesterol or family history are borderline or contradictory.
For example, my cholesterol was low (about 110 mg/dL) but after several relatives had sudden heart attacks, I decided to have a coronary calcium scan, which determined I did indeed have CAD and it led me to search for and find that I had other significant risk factors which my doctor had not tested for. Once I discovered these new risk factors, I was able to successfully treat them. Without the heart scan, I might never have uncovered them.
At the beginning of this article, I suggested the answer as to whether a heart scan is right for you should be based on your current health and your health management philosophy. As always, you should first discuss your health and diagnostic options with your doctor. Here are some guidelines to help you have that discussion.
1. CAD is primarily a disease of age. Most experts seem to agree that it makes little sense for men under 40 or women under 50 to seek a heart scan under normal conditions. Ask your doctor whether you fit into this category.
2. Even in the absence of normal risk factors such as high cholesterol, a family history of CAD suggests it might be useful to consider a more aggressive approach in favor of early detection. Remember, a coronary calcium scan can non-invasively determine if you have CAD regardless of risk factors. Be certain to thoroughly discuss your family health history with your doctor in addition to your own history.
3. For some, the fear of not knowing whether they have CAD, regardless of their health condition or history, can be debilitating. If this is the case, it might be beneficial to discuss having a heart scan with your mental health professional well as your doctor.
4. It is important to understand that a heart scan has radiation risk. Ask your doctor whether there are any special radiation concerns you should consider.