Understanding Coronary Artery Calcium (CAC) Scoring

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.

“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

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.

A test by many names — CAC scoring may also be called:

  • Calcium Scan of the Heart
  • Coronary Calcium Score
  • Cardiac Scoring
  • Cardiac CT for Calcium Scoring
  • Calcium Scan Test

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.

CAC Scoring is Helpful If You Are at Intermediate Risk

Low Risk Intermediate Risk High Risk
  • Few risk factors
  • Low calculated risk of heart disease or stroke
  • No symptoms
  • No existing heart disease
  • May have several risk factors, but there is uncertainty about whether a statin should be started
  • Multiple risk factors
     


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. 

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.

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 

Questions to Ask Your Care Team

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?

High Cholesterol Home

Published: November 2018
Medical Reviewers: Martha Gulati, MD, MS, FACC, FAHA, FASPC; Salim S. Virani, MD, FACC

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