My husband is a very healthy 53-year-old lifelong distance runner who jogs not only to stay in shape but to avoid needing antihypertensive medication from which he was successfully weaned over a decade ago. In addition to his personal history of high blood pressure, he has a family history of hypercholesterolemia. At his last annual check-up his triglycerides were 49 mg/dL (normal is below 150 mg/dL), total cholesterol was 179 mg/dL (desired is less than 200 mg/dL), his low density lipoprotein (LDL) was 105 mg/dL (optimal is less than 100 mg/dL), high density lipoprotein (HDL) was 60 mg/dL (desired is greater than or equal to 60 mg/dL); and his total cholesterol to HDL-C ratio was 3 (less than 5 is normal; less than 3.5 is highly desirable). While these results were generally very good, with an elevated LDL his primary care provider recommended a coronary artery calcium (CAC) test to help determine whether he should be prescribed a statin (cholesterol-lowering drug). My husband promptly scheduled the test and upon receiving the results very proudly reported “I have the coronaries of a 30-year-old!” Thankfully a statin would not be needed at this time and with his blood pressure under control, my husband will have many more years of running ahead. While I was elated with this news, I had never heard of a CAC score and wondered “Should I have this test done too?”

Coronary Artery Calcium (CAC) Score

A CAC score measures the presence of coronary artery calcification in the heart. CAC begins as microscopic flecks that grow into large plaque deposits, typically in the intimal layer of the coronary artery. The CAC score signifies the extent of atherosclerotic cardiovascular disease (ASCVD), and results can assist in selecting treatments such as statin therapy and lifestyle modification (Kramer & Villines, 2022). The CAC score has been found to be a stronger predictor of cardiac risk than most other serum biomarkers.

A CAC (also known as CT-calcium) score is obtained by computed tomography (CT) scan and is commonly measured using the Agatston method which calculates the area and density of calcified plaque. CAC scores are reported both as a total score for the patient, and as scores for each individual coronary artery (Orringer, 2020). We’ll focus on the total CAC score which can be broken down as follows (Kramer & Villines, 2022):

• 0 Agatston units = No identifiable disease
• 1 to 99 Agatston units = Mild disease
• 100 to 399 Agatston units = Moderate disease
• 400 or more Agatston units = Severe disease

The score is then compared to results from patients of similar age, sex, and ethnicity to produce a percentile. This is achieved using the Multiethnic Study of Atherosclerosis (MESA) calculator applied to individuals aged 45 to 84 years who don’t have diabetes or known cardiovascular disease (CVD). The absolute CAC score reports short term (5- to 10- year ASCVD) risk, while the CAC percentile score provides the best approximation of relative risk and lifetime treatment benefit (Orringer, 2020).
 
CAC screening is beneficial in the following individuals (Kramer & Villines, 2022):

• Asymptomatic adults over 40 years of age at intermediate to high risk (7.5 to less than 20 percent 10-year ASCVD risk) as assessed by the American College of Cardiology/American Heart Association (ACC/AHA) risk calculators
  •  Among asymptomatic patients, the CAC score assists in predicting ASCVD and mortality particularly for those with borderline and intermediate risk (5 to 20 percent 10-year ASCVD risk).

• Patients with borderline elevated ASCVD risk (5 to 7.4 percent 10-year ASCVD risk) who have a family history of premature ASCVD

CAC tests aren’t helpful in the following patients (Oringer, 2020):

• Individuals with a low (less than 5 percent 10-year risk) or very high (20 percent or greater 10-year risk) ASCVD risk, as the results likely won’t change the treatment strategy
• Individuals with clinical ASCVD including acute coronary syndrome, history of acute myocardial infarction, stable or unstable angina or coronary or other arterial revascularization, stroke, transient ischemic attack, or peripheral artery disease, including aortic aneurysm
• As a primary diagnostic tool in individuals with symptoms of myocardial ischemia (angina or dyspnea) as CAC alone is less predictive of coronary artery disease
  •  However, CAC may be obtained along with CT angiography to provide additional information.

Advantages of  CAC Tests (Orringer et al., 2020)

There are several advantages of CAC imaging compared to invasive coronary angiography.

• Minimal to no patient preparation is required. Patients do not need an intravenous (IV) catheter, intra-arterial line, beta blockers, or nitroglycerin.
• Iodinated contrast isn’t used.
• The patient doesn’t need to fast or hold medications prior to the procedure.
• Quick and efficient, CAC can be obtained on any CT scanner that can perform ECG gating, where data is acquired during a specific phase of the cardiac cycle.
• There is a low radiation dose; CAC scans use a radiation dose comparable to a screening mammogram.

Management (Kramer & Villines, 2022)

In general, all patients are advised to make lifestyle changes such as eating a healthy diet, ceasing smoking, and exercising regularly. Repeat CAC scanning isn’t recommended to assess effectiveness of lifestyle changes.

• CAC score greater than or equal to 100 (or 75% for age, sex, and race): statin is recommended if the low-density lipoprotein cholesterol (LDL-C) is between 100 and 190 mg/dL.
• CAC score 1 to 99 (or less than 75^th percentile for age, sex, and race): providers should discuss statin therapy with the patient. Benefit of statins may be small for these patients.
• CAC score of 0 and no other risk factors: patients have a low 10-year ASCVD risk, therefore statin or aspirin therapy isn’t recommended. Repeat risk stratification should be performed at five years. A CAC score of 0 is the strongest “negative risk marker” for ASCVD.

Summary of CAC Score (Campbell et al., 2024)

CAC Scoring
CAC	Disease Stage	Treatment
0	No disease	No indication for statin
1- 99	Mild disease	Starting a statin may be indicated
100-399	Moderate disease	Statin and low-dose aspirin (if low risk for bleeding) is indicated
400 or higher	Severe disease	High-intensity statin and low-dose aspirin (if low risk for bleeding) is indicated

It is important to note that CAC scans may not be covered by insurance. However, it serves as an additional tool that provides valuable information regarding ASCVD risk and helps providers and their patients make important decisions about risk reduction and treatment strategies. I will discuss CAC testing with my primary care provider at my next annual visit and I now feel better informed to talk about this type of screening with my patients, family, and friends.
 
What is your experience with CAC testing? Please share in the comments below.
 

References
 
Campbell, K., Harber, A., Jennings, J., & Smiley, L. (2024). CT calcium score testing for early detection of coronary artery disease. The Nurse practitioner, 49(2), 6–9. https://doi.org/10.1097/01.NPR.0000000000000140
 
Kramer, C.M. & Villines, T.C. (2022). Coronary artery calcium scoring (CAC): Overview and clinical utilization. UpToDate. https://www.uptodate.com/contents/coronary-artery-calcium-scoring-cac-overview-and-clinical-utilization

Orringer, C. E., Blaha, M. J., Blankstein, R., Budoff, M. J., Goldberg, R. B., Gill, E. A., Maki, K. C., Mehta, L., & Jacobson, T. A. (2021). The National Lipid Association scientific statement on coronary artery calcium scoring to guide preventive strategies for ASCVD risk reduction. Journal of clinical lipidology, 15(1), 33–60. https://doi.org/10.1016/j.jacl.2020.12.005

 

More Resources
GUIDELINE SUMMARY	POCKET CARD	PRACTICE SPECIALTY
Assessment of Cardiac Risk	Cardiovascular Assessment	Cardiac Specialty