The best screening tool for people at intermediate risk for heart attack
When your doctor assesses your risk of having a heart attack, he or she usually places you in one of three risk categories: low, intermediate or high. Doctors have a pretty good idea of what to recommend if you're at low or high risk. For example, your doctor may emphasize lifestyle measures if you're in the low-risk category, where your chance of having a heart attack or dying from heart disease within 10 years is less than 10 percent. Or, he or she may also prescribe medications if you're at high risk, where you stand a more than 20 percent chance of heart attack or death from coronary heart disease (CHD).
But if you're one of the estimated 23 million Americans who fall in the intermediate-risk categorywhere your chances of heart attack within 10 years range from 10 to 20 percentyour doctor's choices may not be so clear cut.
That's because if you don't have any heart disease symptoms like shortness of breath or chest pain, it's hard to tell at which end of the range your risk falls and how aggressively you should be treated.
Assessing your risk
Your doctor typically estimates your risk of heart attack using an assessment tool such as the Framingham Risk Score (FRS) that takes into account your age, gender, cholesterol levels, smoking history and blood pressure. In addition to these traditional risk factors, your doctor may also consider your family history of heart disease, body mass index, belly fat and levels of triglycerides (other fats that circulate with cholesterol in the bloodstream).
But this routine screening doesn't always tell the whole story if your score lands you in the intermediate category. Further testing may reveal that you should be reclassified in another category. In this case, your doctor may suggest an additional screening to better predict your risk and subsequently guide his or her treatment decisions to intensify or reduce your therapy. (If you’re at low or high risk, more testing is unnecessary because the results shouldn't change your current treatment plan.)
According to a new study, the best method to detect asymptomatic heart disease for those at intermediate risk is to look for measurable amounts of coronary artery calcium (CAC) using computed tomography (CT). Earlier studies have shown the benefits of CAC scans to reclassify intermediate-risk patients, but this is the first time researchers have compared CAC scans head to head with five other popular diagnostic tools.
More than 1,300 men and women ages 45 to 84 with intermediate risk of heart disease were followed over an average of seven and a half years. At the beginning of the study, each participant was assessed for six risk markers
- coronary artery calcium
- ankle-brachial index
- high-sensitivity C-reactive protein
- carotid intima-media thickness
- brachial flow-mediated dilation and
- family history of coronary heart disease
Writing in the August 22, 2012, issue of the Journal of the American Medical Association, the researchers concluded that CAC was the best predictor of heart attack or death from CHD after the seven-and-a-half-year follow-up. During the follow-up period, the researchers were able to reclassify 25 percent of intermediate-risk patients to high risk and another 40 percent to low risk as a result of their CAC scan. This should have ideally led to more appropriate care for those reclassified.
James L. Weiss, MD, Michael J. Cudahy Professor of Cardiology, Johns Hopkins University School of Medicine
Coronary artery calcium scans should never be considered as "routine" screening for the general population or for people at low or high risk of coronary heart disease. But for those individuals categorized at intermediate risk of CHD, the benefits may outweigh the risks if it leads to improved management of the disease.
It's also helpful to understand that because coronary artery calcium scans don't track progress of heart disease, they're beneficial only as a one-time measurement. Just as important are regular visits with your doctor to reassess your risk and adjust your treatment, if necessary.
Source: Prepared by the Editors of The Johns Hopkins Medical Letter: Health After 50