How can we determine our individual risk for heart disease? Traditionally, doctors typically estimate your heart risk using a risk estimator or calculator, which takes into account risk factors such as age, smoking, high blood pressure, cholesterol, and other known risk factors. This gives us probabilities of heart disease, based on individuals with your similar risk factors. However, tests like the coronary artery calcium score (CAC) or coronary calcium scan can give you a better assessment of your unique, personal risk for heart disease. So what exactly is a coronary calcium scan and who should get one?
Is a coronary artery calcium score (CAC) the best heart test?
A coronary artery calcium score (CAC) is a special type of CT scan that measures calcified plaque in the arteries of your heart. It looks for calcium depositions, or plaque, in your arteries and quantifies it.
Over time plaque, or blockages, build up in the arteries of the heart when cholesterol deposits into the blood vessel wall and gets oxidized. As a blockage gets older, it becomes calcified and appears bright white on a CT scan. The amount of calcium in the arteries of the heart can be measured or quantified.
The amount of calcium in your arteries can then be compared to an “average” person your age and gender, as well as give you a better idea of your overall risk of a heart attack. Studies have shown that the higher the calcium score, the higher your risk of a heart event.
The absolute CAC score is the best predictor of near-term risk, ie your risk of a heart attack in the next 5-10 years, while the CAC percentile score is the best predictor of lifetime risk, and so is particularly useful in younger people (ie less than 50 years old).
The procedure takes about 10 minutes and delivers about 1 mSv of radiation, which is similar to a mammogram (it is also about one third to one half of the annual background radiation exposure in the United States). No contrast or dye is used. It is often not covered by insurance, and typically costs $100-150 out of pocket.
Should I get a coronary calcium scan?
A coronary artery calcium score is most often considered in individuals who are thought to be of borderline or intermediate risk for a heart problem by their doctor.
It can help both the doctor and you, the patient, decide if you would benefit from certain medications, like statins, or intensification of lifestyle changes to lower their risk.
Other patients who should consider getting the test
- those with a strong family history of heart disease
- those who wish to better understand their personal risk/benefit of starting a statin
- those who have been recommended to take statin therapy based on their risk but want to better assess their personal risk first – particularly older individuals with low risk factor burden and whose risk is largely driven by age
It is not an appropriate test for someone who already knows they have coronary artery disease. It is also not the right test for those with symptoms of heart disease. It is to help better understand your future risk, not assess what is happening right now.
Is CAC a good test in young people?
It is typically not recommended in those younger than 40 years of age because of the overall low risk of heart attack and stroke in those individuals in the short-term. However, it may be considered in those with multiple risk factors for heart disease or a strong family history of heart disease who would otherwise not be given medications. One study followed over 20,000 individuals aged 30-49 years of age for 12 years, and they found a 3-fold increased risk of cardiovascular mortality in those with a CAC score of >100. A CAC>0 in a young person should prompt a conversation regarding preventive medications or used as a motivating factor for aggressive lifestyle changes.
Importantly, a CAC of 0 in younger individuals, particularly those with risk factors, should not be reassuring that nothing needs to be done. Lifetime risk is likely still high and soft plaque, which is plaque that has not yet been calcified and predominates in young people, is not visualized on this test.
What does a score of 0 mean?
A coronary artery calcium score of 0 in individuals aged 40-75 years of age can be used as a strong “negative risk factor.” This is one of the most powerful ways it can change recommended treatment!
Studies have shown that those with a CAC of 0 have a very low 10 year risk, with a mortality rate of about 1% over the next 10 years.
Guidelines suggest that in those with a CAC of 0 who do not have diabetes, smoke, or have a strong family history of heart disease, statins confer limited short to intermediate term benefit, and so it is reasonable to defer statin therapy in this group.
I’ve had a CAC score done. When should I repeat it?
The recommended timing to repeat a CAC varies based on the score and underlying risk, but recommendations range anywhere from 3 to 7 years. This should be decided on an individual basis with your doctor.
Importantly, it should be noted that repeating a CAC score in individuals who are taking statins should be done cautiously. Statins actually modestly increase calcium scores, as they actually deplete plaques of their cholesterol and accelerate calcification (which tends to be stabilizing). Thus, CAC progression shouldn’t be used as a sign of ineffectiveness of statin therapy.
In summary
Coronary artery calcium tests are a safe, effective test to better assess your personalized risk of heart disease. If zero, in the appropriate situation, it can be quite reassuring and reasonable to hold off on initiating medications. On the other hand, if markedly elevated, they can be an early warning sign that heart disease is brewing and an effective motivator for aggressive lifestyle changes and medications if indicated. While they do involve some (low dose) radiation and thus shouldn’t be done annually, they can be a really powerful window into the health of our heart and give us a chance to make healthful changes to prevent a heart attack.