February 3, 2009
U.S. News and World Report

CT Heart Scan Risks: 7 Better Ways to Screen for Heart Disease

By Deborah Kotz

The high-tech imaging test poses radiation risks, so what should you do to determine your chances of having a heart attack? When it comes to determining whether you need to worry about heart disease, you probably take certain assumptions for granted. If you have high cholesterol, a nasty smoking habit, and hypertension, your heart is a ticking time bomb; if you have none of those risk factors, you don't need to worry. Unfortunately, it's not that simple: More than one third of folks who drop dead from heart attacks have none of the classic warning signs. But seeking out a high-tech CT heart scan that peers into your arteries, called cardiac CT angiography, may not be the solution either. A new study published in the Journal of the American Medical Association finds that radiation from the test could raise your cancer risk and that many radiologists aren't taking enough protective measures to reduce radiation exposure.

The results underscore an unsettling reality: There is no perfect way to predict a future heart attack—especially if you don't have heart disease symptoms like chest pain or shortness of breath, or you don't already have established heart disease or its close cousin, diabetes. The risk factors outlined above can be mathematically combined to come up with a predictor of your odds of a heart attack over the next 10 years, called a Framingham risk score, but cardiologist Roger Blumenthal, director of the Johns Hopkins Ciccarone Center for the Prevention of Heart Disease, says this assessment is "relatively crude" and frequently misses many men and women of all ages who have dangerous underlying heart disease.

Consider this: Yale University researchers in a study published last month performed CT heart scans on more than 1,600 patients, compared the images of artery plaque with participants' Framingham scores, and found that more than one fifth of the patients who had "low risk" scores actually had enough plaque on their arteries to benefit from low-dose aspirin or cholesterol-lowering statins. "There are many good objections as to why we can't use CT angiography to screen everyone for heart disease," such as cost and radiation exposure, says study author and Yale radiologist Kevin Johnson.

Still, he adds, other imaging tests that use less or no radiation can be very helpful in making treatment decisions. His study also found that more than one fourth of those who were put on statins because of an elevated Framingham risk score actually had perfectly clear arteries and probably didn't need to be on any medications at all. These folks might have benefited, he says, from getting some sort of imaging test before embarking on treatment.

Eventually, the most powerful predictors of heart disease "will come through genetic testing to see not just who is likely to have a heart attack but who is likely to die from one," says heart disease researcher Robert Myerburg, a professor of medicine at the University of Miami School of Medicine. While studies have shown that having a close family member who died suddenly from a first heart attack increases the odds that you will too, scientists are still searching for genetic markers that will tell people for certain whether they need to take aggressive action.

For now, what's the best way to assess your own individual risk? Experts who spoke with U.S. News recommended this seven-step approach:

1. Framingham Risk Assessment: As basic and crude as it may be, it's a good starting point. The assessment takes into account your age, gender, blood pressure, cholesterol, smoking habits, and family history to spit out your risk of having a heart attack in the next 10 years. You can get an estimate of your Framingham score yourself.

2. High Sensitivity C-reactive Protein. This blood test measures a marker for inflammation, thought to be involved in plaque formation. It's often elevated when a person is overweight, out-of-shape, and on the road to diabetes. Many doctors routinely do this blood test nowadays and it can be combined with Framingham risk factors to give you what's known as a Reynolds Risk Score. Research shows it provides more accurate information about heart-disease risk than Framingham and can tell you your heart attack risk out to 40 years and your risk of other heart conditions like strokes. Note: The test isn't accurate for those who already have diabetes, but these folks are already considered to be at high heart disease risk and should be taking a statin.

3. Waist-Hip Ratio: Comparing your waist measurement to your hip measurement tells you whether you've got too much fat in your abdominal area; this fat wrapped around vital organs tends to be more metabolically active than fat on the hips and thighs, spewing out inflammatory chemicals that promote plaque formation. A 2007 study published in the journal Circulation found that men who had the biggest waists in relation to their hips had a 55 percent higher risk of developing heart disease than the men who had the smallest ratios. Women with the highest ratios were 91 percent more likely to develop heart disease than were those with the smallest. The researchers also found that measuring just your waist size was a far less accurate predictor than measuring your waist in comparison with your hips, which suggests that bigger hips might be protective. For women, a waist-hip ratio of 0.80 or below is considered low risk; 0.81 to 0.85 is considered moderate risk; above 0.85 is considered high risk. For men, a waist-hip ratio of 0.95 or below is considered low risk; 0.96 to 1 is considered moderate risk; above 1 is considered high risk. Here's how to measure your waist-hip ratio.

4. Body Mass Index: The comparison of weight and height is generally reliable for assessing body fat, though it can overestimate body fat in athletes who have a lot of muscle and can underestimate body fat in older people who naturally shed muscle mass. Any measurement over 25 means you're overweight and at moderately increased risk of heart disease and 30 or above means you're obese and at greatest risk. Here's how to measure your body mass index.

5. Speed of Menopause Transition: A surprising finding from Cedars-Sinai Heart Institute in Los Angeles shows that women who move through the transition from the first irregular periods of perimenopause to an all-out cessation of menstruation in less than 18 months appear to have a faster accumulation of plaque in their arteries than those who take longer. "Menopause itself doesn't pose a heart risk for women, but those who transition rapidly have more thickness in their carotid artery, an indirect measure of how much plaque is accumulating in the arteries of the heart," says study author C. Noel Bairy Merz. She says the finding could be useful for a woman considering going on hormone replacement therapy to combat hot flashes, mood swings, and other menopausal symptoms. "If she was a former smoker, has a high C-reactive protein level, and went through a rapid transition," Merz explains, "I might be more cautious because previous research has shown that for women who already have clogged arteries, HRT may further increase their heart attack risk."

6. Images of your arteries. Certain cardiac imaging tests can provide even more clues about your individual heart attack risk. The most benign test uses ultrasound (and no radiation) to measure the thickness in the walls of the carotid artery in your neck—something that Merz used in her study. "Newer hand-held devices are very user-friendly and some primary care physicians are starting to do them," Merz says. "It might soon be used like a blood pressure cuff, but we're not there yet."

Another simple heart scan measures calcium in the coronary arteries and uses low-dose radiation, equivalent to the amount in a mammogram. A score of more than 400 means you've got a significantly higher risk of having a heart attack and sudden death and indicates you should probably be taking aspirin and a statin even if you've got no other risk factors, says Blumenthal, who published a study on this. A scan showing no calcium can be useful for ruling out statins if you're already at fairly low risk for heart disease. Most folks, though, have a score somewhere in the middle and the scan may not add too much more information about their heart disease risk.

7. Listen to your body. This is probably one of the most important things you can do to assess your risk. "If you're having heart symptoms—vague chest discomfort, shortness of breath, palpitations, fainting spells, light headedness—don't brush them off just because you've got a low risk profile," warns Myerburg. Seek medical attention as soon as possible. After all, he adds, "a risk profile tells you what may happen in the future, whereas symptoms tell you what's happening now."