For many decades, doctors have used the traditional coronary disease “risk factors” to predict an individual’s risk of developing heart attacks or other major coronary events. These include smoking, diabetes, high blood pressure, and elevated cholesterol.
These factors can be plugged into various formulas to predict the likelihood of a coronary event occurring in the next 10 years and are used to decide if a person should be started on lipid-lowering therapy.
If the calculated risk is very low or very high, no other information is needed. Many people, however, fall into an intermediate risk range. In some instances, even those with high risk of coronary disease may not want to start a statin drug because of feared side effects (which are uncommon).
Such situations suggest the use of a coronary artery calcium (CAC) score.
As plaque (cholesterol deposits) builds up in coronary arteries, calcium is also deposited. A low-dose CT scan can measure the amount of calcium. Ideally, you would have a score of 0, and the higher the score, the higher the risk of developing symptomatic coronary disease.
Who might benefit from this testing?
If your doctor has recommended you start a statin, but you are hesitant, a zero score would allow you to postpone the drug while a score over 100 would strongly suggest you take it.
If your calculated risk is intermediate, a zero score would suggest you do not need to begin cholesterol-lowering therapy while a non-zero score would push you to do so.
If your cholesterol is not bad but you have other risk factors for coronary disease, a CAC score will give useful information. If several family members had early heart attacks, a non-zero CAC score suggests that even if your cholesterol is not high, a statin might be a good idea.
If you have not tolerated a prescribed statin and stopped it, a CAC score may help you to decide whether to try a different statin or one of the newer injectable cholesterol-lowering drugs.
Who should not get a CAC score done?
If you are under 40, a zero score is expected and will not impact decision-making; use the traditional risk factors to guide your thinking. If you are over 80, and not on a statin, the results are unlikely to change recommendations to begin.
If your risk for coronary disease based on the traditional risk factors is high, a CAC is a waste of money: take a statin. If you are on a statin and doing well, be happy and do not get a CAC test.
Finally, if your score is zero, repeating the test can wait at least three and probably five years.
Edward Hoffer MD is Associate Professor of Medicine, part-time, at Harvard.
What Does The Doctor Say?
By Dr. Edward Hoffer