What is it? A heart scan is a noninvasive procedure that shows the amount of calcified plaque you have in your coronary arteries. Currently, two types of heart scanners are being used. The first is the multislice computed tomography (CT) scanner, which creates an extremely detailed cross-sectional image of your arteries using x-ray cameras. The second is the electron-beam tomography (EBT) scanner, which creates images of the heart using an electron gun. Both types of scanners are excellent, and the one you choose depends on what your doctor recommends and what type of equipment is available at your medical center. It may also depend on how much money you are willing to spend.
There are advantages to each. The advantage of the EBT scanner is that it acquires images faster than a multislice scanner. This is particularly important when imaging a moving organ such as the heart. But while an EBT scan will provide an accurate Calcium Score and show the extent of your coronary disease, it cannot consistently show the presence and extent of soft plaque. That is the true benefit of the state-of-the-art 64-slice scan. Remember, it is the cholesterol-filled soft plaque that can grow, rupture, and cause a heart attack, so it is good to know if there is soft plaque lurking inside the lining of your artery walls.
The 64-slice scanner is simply the latest in a long line of multislice scanners, many of which are still being used. The first multislice scanner was the 4-slice, introduced in the early 1990s. It was followed by 8-, 16-, and 32-slice scanners. Some centers are still using this earlier technology but, while some of these scans can give you an accurate Calcium Score, the 64-slice scan is the best at imaging soft plaque with a dye injection (as I mentioned earlier, this is called a noninvasive angiogram). You may have been told that the 64-slice scanner can actually quantify the percentage of obstruction in your arteries. While it may be able to do this in certain patients, results are often unreliable. The invasive angiogram is still the best technique for determining the percentage of blockage. That said, a noninvasive angiogram is useful for excluding obstruction. In other words, if your scan looks completely normal, you can be confident that it is accurately showing that there are no blockages.
From a patient's perspective, getting a heart scan is quite easy. You lie down fully clothed on an examination table, the scanner passes over you for a minute or two, and then it's over. If a contrast dye is used, you may have to fast beforehand and the examination can take a little longer. One caveat: If you've ever had an allergic reaction to a contrast dye or iodine or have an allergy to shellfish, you should consider a scan that involves contrast dye injection only under special circumstances. Be sure to tell your doctor about any such allergies or reactions. Premedication can be used to minimize an allergic reaction to the dye. Caution must also be used in patients with compromised kidney function (often found in people with diabetes) since the dye can worsen the situation. You should also tell your doctor if you are or might be pregnant; if so, you should not have a scan at all. Once the scanned image of your heart has been analyzed, it's converted into a number ranging from 0 to several thousand. This number is called your Calcium Score. The higher your score compared to others of your age and sex, the more calcified plaque you have in your arteries and the greater your risk for a future heart attack.
UNDERSTANDING YOUR CALCIUM SCORE
Calcium Score for a 55-Year-Old Man or Woman
Relative Amount of Plaque
As I mentioned earlier, one of the real benefits of the heart scan is that I can show my patients pictures of their actual coronary arteries and the extent of plaque buildup. It's one thing to tell patients — especially those who don't have any overt symptoms — that there's a buildup of plaque in their artery walls and that they have to take a medication and make some lifestyle changes. It's quite another to have them see their plaque firsthand (coronary calcium shows up as bright white spots on the scan). I've found that a compelling visual provides strong motivation for patients to stay on their treatment program, and in particular to keep taking their medications. Moreover, follow-up heart scans can help you and your doctor keep track of your progress and make the necessary adjustments to your treatment program if need be.
Follow-up. If you have few or no calcium deposits, you need not repeat the heart scan for at least 5 years. If you do have signs of calcium buildup, the test can be repeated every 2 to 5 years, depending on your other risk factors.
Learn more in the Everyday Health Heart Health Center.