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Coronary Artery Calcium (CAC) Scoring
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American College of Cardiology
https://www.cardiosmart.org/topics/high-cholesterol/exams-and-tests/coronary-artery-calcium-scoring
Atherosclerosis [heart disease] is a dynamic process that is constantly changing and morphing. Unchecked, this constant change can lead to advancement and disruption, culminating in ischemic heart disease and myocardial infarction. However, this dynamic nature also offers opportunities to intervene with preventive therapies to halt or reverse course before these adverse outcomes occur. These properties also offer the allure of quantifying change in atherosclerosis to better pinpoint and personalize atherosclerotic cardiovascular disease (ASCVD) risk estimates.
Several novel screening tests have been evaluated to improve ASCVD risk assessment; of these tests, coronary artery calcium (CAC) scanning has emerged as the top contender. High CAC scores are associated with a markedly increased risk of coronary heart disease (CHD) (4- to 10-fold higher) independent of other risk factors, and CAC has been shown to improve clinical reclassification of CHD and ASCVD risk.1-3 In addition, those with no CAC have a relatively good prognosis and may consider deferring preventive therapies such as statins.
Coronary artery calcium (CAC) scoring, also called a coronary calcium scan, is a test that measures the amount of calcium in the walls of the heart's arteries.
Most of the calcium in our body is found in our bones and teeth. It helps keep them strong and healthy. But calcium in the arteries that supply the heart with oxygen and nutrients can spell trouble for our heart health.
That's because deposits of calcium in the coronary arteries are a sign that there may also be a buildup of plaque-a waxy substance that can harden over time and narrow or block the arteries (called atherosclerosis). When this happens, it makes a heart attack or stroke more likely.
So a coronary calcium scan is one way to estimate someone's risk of developing heart disease or having a heart attack or stroke.
Questions To Ask Your Doctor
You may have questions about coronary calcium tests. Some common questions include:
• How exactly does calcium in the arteries relate to heart disease?
• What are the main risk factors for blockages in the heart's arteries? Which ones do I have?
• Based on what we know about my risk, could I benefit from CAC scoring?
• How will knowing my CAC score help guide my care?
• Are there people who wouldn't benefit from CAC scoring?
• What should I do to prepare for the test?
• Do I need to be concerned about the amount of radiation used?
• Will my insurance cover this test?
• Are calcium supplements harmful? Do they play a role?
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A Type of Imaging Test
This test uses a special type of imaging test called a computed tomography (CT) scan of the heart. This scan produces multiple pictures to check if calcium is present and, if so, how much.
CAC scoring may also be called:
• Calcium Scan of the Heart
• Coronary Calcium Score
• Cardiac Scoring
• Cardiac CT for Calcium Scoring
• Calcium Scan Test
"Calcium itself is not necessarily bad. But having it in your arteries is considered a marker of having coronary heart disease. A lot of plaque can lead to a heart attack."- Salim Virani, MD, FACC, and member of the 2018 Cholesterol Guideline writing committee
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Who Should Have CAC Scoring ?
A coronary calcium scan can help you and your clinician better understand your future risk of having a heart attack, stroke or dying from one even if you don't have any symptoms of heart disease.
But it's most helpful in certain cases and for certain patients.
Most of the time, results from a physical exam, bloodwork and other tests will give you and your care team enough information to gauge your future risk of a heart attack or stroke.
The test is another tool that you and your care team can use when deciding what treatment is right for you. It can help determine if there are steps you should consider taking - beyond adopting healthy lifestyle habits - to lower your risk.
CAC scoring really comes into play when there is still some doubt as to whether your risk is enough to warrant taking a statin, which is a medication that lowers cholesterol. Statins are commonly used as the first medication of choice to lower low-density lipoprotein (LDL) cholesterol, or "bad" cholesterol.
"CAC scoring can help give patients and clinicians more information to better inform decisions about whether a statin or other cholesterol medication might help." - Martha Gulati, MD, FACC, CardioSmart editor-in-chief
CAC scoring is not recommended if you have:
• Low risk for heart disease (no risk factors) or
• High risk for heart disease or have heart disease already, or if you've already had a heart attack, stroke, stent or bypass surgery
CAC scoring also shouldn't be used to assess whether treatment is working or not.
According to the 2018 Cholesterol Guideline, CAC scoring should be used only after you and your clinician have:
1. Assessed the likelihood of you having a heart attack, stroke or dying from one of these events in the next 10 years.This is called your 10-year risk score.
2. Taken into account other risk factors that could increase your risk, such as family history or certain diseases.
3. After steps 1 and 2, there is still some doubt about whether you should start a cholesterol-lowering medication.
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CAC Score Is Helpful If You Are At Intermediate Risk ?
If you are at intermediate risk of having a heart attack or stroke, CAC scoring may be helpful.
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What Do The Results Mean ?
The test result is given as a number, called a CAC score. It can range from 0 to over 400. Your clinician can help explain your result and what it means.
Basically, the more evidence of calcium and thickening that is seen in the inside lining of the arteries, the higher the score. The higher your CAC score, the more likely you are to develop heart disease or have an event such as a heart attack or stroke.
Keep in mind, though, this score tells us about the chance of developing disease. It's not a guarantee. So, people with a 0 score could still have a heart attack, but the risk is very low. Similarly, people with a high CAC score aren't certain to have a heart attack. This is why CAC scoring should be used together with other methods for estimating heart disease.
Results
• A score of zero means no calcium is seen in the heart. ...
• When calcium is present, the higher the score, the higher your risk of heart disease.
• A score of 100 to 300 means moderate plaque deposits. ...
• A score greater than 300 is a sign of very high to severe disease and heart attack risk.
The new cholesterol guideline states: "If CAC is zero, treatment with statin therapy may be withheld or delayed, except in cigarette smokers, those with diabetes mellitus, and those with a strong family history of premature ASCVD. A CAC score of 1 to 99 favors statin therapy, especially in those ≥55 years of age. For any patient, if the CAC score is ≥100 Agatston units or ≥75th percentile, statin therapy is indicated unless otherwise deferred by the outcome of clinician-patient risk discussion."
Valentin Fuster, MD, PHD, chief of cardiology of the Icahn School of Medicine at Mount Sinai in New York and editor of the Journal of the American College of Cardiology, interprets the new guideline for certain patient groups in this way: "The CAC score is important. If the calcium score is zero, forget about statins. If the score is more than 100, it's better to take them. But the critical issue is the [doctor's] discussion with the patient."
Patients with a high baseline CAC score are at considerable CHD and ASCVD risk (≈10% to 15% 10-year risk)
The current American College of Cardiology/American Heart Association 2013 Cholesterol Guidelines state that when the decision to initiate a statin remains unclear, a CAC score ≥300 may be used to inform decision making (ie, can be used to up-classify risk)
Several novel screening tests have been evaluated to improve ASCVD risk assessment; of these tests, coronary artery calcium (CAC) scanning has emerged as the top contender. High CAC scores are associated with a markedly increased risk of coronary heart disease (CHD) (4- to 10-fold higher) independent of other risk factors, and CAC has been shown to improve clinical reclassification of CHD and ASCVD risk. In addition, those with no CAC have a relatively good prognosis and may consider deferring preventive therapies such as statins.
CAC Score 1-100: In patients with CAC scores of 1 to 100 who elect to defer statin therapy or other preventive interventions, a case could be made for reassessment of CAC in concert with repeat global ASCVD risk assessment after an appropriate interval (ie, 5 years). Such a strategy should only be pursued after an informed discussion with the patient and only if the results would change management. Patients with CAC in this range are often younger, meaning the modest incremental cancer risk of repeat CAC scanning is greater than in older individuals, which should be incorporated in this discussion. More definitive data in this subgroup of patients are needed.
- 2018 AHA/ACC/AACVPR/AAPA/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA Guideline on the Management of Blood Cholesterol: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines
"Impact of Statins on Cardiovascular Outcomes Following Coronary Artery Calcium Scoring". JACC 2018.
Among this relatively lower-risk cohort, CAC >100 was consistently associated with a greater reduction in the hazard for MACE with statin therapy relative to CAC <100. In this large, long-term, retrospective analysis of the Walter Reed cohort, increasing severity of CAC was associated with increased benefit from statin treatment for the prevention of MACE, with greatest benefit in patients with CAC >100. In our primary, propensity-weighted analysis, patients with CAC 0 had no benefit from statin therapy in a mean follow-up of nearly 10 years. Calcium scoring, therefore, shows significant potential to help select patients most likely to benefit from statin therapy.
Patients with CAC who were prescribed a statin within 5 years of their CAC testing had a significantly lower risk of MACE (adjusted subhazard ratio [aSHR]: 0.76; 95% confidence interval [CI]: 0.60 to 0.95; p = 0.015), whereas patients without CAC had no MACE reduction with statin use (aSHR: 1.00; 95% CI: 0.79 to 1.27; p = 0.99) (Figure 1). The effect of statin use on MACE was significantly related to the severity of CAC (p for interaction <0.001) (Central Illustration, Table 2), with patients having CAC >100 associated with the most benefit. Using a 2-year cutoff for statin prescription in a sensitivity analysis yielded similar results (Online Appendix, Online Table 6).
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What To Expect ?
A coronary calcium scan is often done in a hospital or other medical imaging facility.
The test:
• Is fairly quick (it takes about 10-20 minutes to complete)
• Uses a low dose of radiation
• Doesn't require contrast - a special dye that is injected in your vein that is needed for some other imaging tests
• Often includes an electrocardiogram (ECG), too
Be sure to let your clinician know if you are or could be pregnant before having this test.
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What Increases Your Risk of Coronary Heart Disease?
It's important to talk with your clinicians about your risk for heart disease. This way you can decide together what you can do to lower that risk.
The main risk factors for blockages in the heart's arteries, called atherosclerotic cardiovascular disease or ASCVD include:
• Elevated LDL or total cholesterol
• High blood pressure
• Diabetes
• Cigarette smoking
• Being overweight or obese
• Not being physically active
• Family history of early heart disease, heart attacks or stroke
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