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JAMA Diagnostic Test Interpretation |

Coronary Artery Calcium Score FREE QUIZ

Tamar S. Polonsky, MD, MSCI1; Roger S. Blumenthal, MD2; Philip Greenland, MD3,4
[+] Author Affiliations
1University of Chicago, Department of Medicine, Chicago, Illinois
2Ciccarone Preventive Cardiology Center, Johns Hopkins University School of Medicine, Baltimore, Maryland
3Department of Preventive Medicine, Northwestern University, Chicago, Illinois
4Senior Editor, JAMA
JAMA. 2014;312(8):837-838. doi:10.1001/jama.2014.1948.
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Published online

A 58-year-old woman presents to a cardiologist’s office to discuss her cardiovascular disease (CVD) risk. She is asymptomatic and has never smoked. She has a history of hypothyroidism and swims 4 times a week for 30 minutes. Her brother experienced a myocardial infarction (MI) at age 59. Prior to his MI, her brother was a vegetarian and an avid runner without hypertension or dyslipidemia. His 10-year atherosclerotic cardiovascular disease (ASCVD) risk was 7% (calculated based on traditional risk factors). Her father was a smoker and had an MI at age 66. The patient’s blood pressure is less than 120/80 mm Hg without medication. Her body mass index is 21.3. Her estimated 10-year ASCVD risk is 2% based on traditional risk factors. However, her low-density lipoprotein cholesterol (LDL-C) level has increased. Her most recent lipid panel showed a total cholesterol level of 286 mg/dL, triglycerides of 75 mg/dL, HDL-C level of 106 mg/dL, and LDL-C of 165 mg/dL. Because of her family history and increasing LDL-C, she underwent a cardiac computed tomography (CT) scan to measure her coronary artery calcium (CAC) score. Her CAC score is 88 (normal value = 0 Agatston units) (Table).

Table Graphic Jump LocationTable.  Excerpt From the Patient’s Cardiac Computed Tomography Reporta

Box Section Ref ID

How do you interpret these test results?
  • The patient’s CVD risk is not elevated because her CAC score is <300.

  • The patient has atherosclerosis and should undergo a stress test.

  • The patient has atherosclerosis and should undergo a coronary angiogram.

  • The patient should continue aggressive lifestyle changes and consider statin therapy.

Figures in this Article

D. The patient should continue aggressive lifestyle changes and consider statin therapy.

CAC is estimated from noncontrast CT images obtained from a multidetector row scanner. Calcium appears white on the CT image (Figure) and the intensity of the calcium signal is assigned a value ranging from 1 to 4, with 4 being the densest. The area of each plaque is measured and multiplied by the intensity index, yielding a number known as the Agatston unit. The resulting numbers are summed for each coronary artery plaque, producing a CAC score. Usually coronary arteries do not have plaques or calcium and the normal score is 0. A CAC score of 300 or higher or 75th percentile or higher for age, sex, and ethnicity is considered high risk.1,2

Place holder to copy figure label and caption
Figure.

Sample images from the cardiac computed tomography of the patient. A, Calcified lesion (arrowhead) appears in the left anterior descending artery. B, Calcified lesion appears in the right coronary artery (arrowhead).

Graphic Jump Location

The CAC score is strongly correlated with the overall atherosclerotic burden and has highly reproducible results.3 CAC measurement improves CVD risk classification over traditional risk factors substantially more than does inclusion of ankle-brachial index or high-sensitivity C-reactive protein in risk classification schemes.4,5

Limitations include that a CAC-guided treatment strategy has not been studied in a randomized trial powered for clinical events. CAC testing may be associated with incidental findings (eg, pulmonary nodules) in about 5% to 10% of adults.6 Medicare does not cover CAC testing to screen for subclinical CVD. Out-of-pocket cost—including imaging and interpretation—ranges from $75 to $400 (http://www.cms.gov/Medicare/Medicare-Fee-for-Service-Payment/ClinicalLabFeeSched/clinlab.html).

CAC testing results in approxmiately 0.9 to 1.1 mSv of radiation.3 In comparison, a digital mammogram transmits about 0.44 mSv.4

The patient’s score is at the 99th percentile for her age and sex. Therapeutic lifestyle changes, including regular exercise and a healthy diet, are essential. Because a high CAC score signifies a substantially elevated CVD risk, recent guidelines recommend initiating a moderate-dose statin, such as atorvastatin at 10 to 20 mg/d.1 A meta-analysis of statin trials suggested a similar relative reduction in vascular and all-cause mortality with statin therapy in high-risk vs low-risk adults.7 Because this patient is asymptomatic, a stress test and coronary angiogram are not indicated.

The arterial age calculator may be used to help communicate CAC results to patients.8 The arterial age is the age at which the estimated coronary risk is the same as that for the observed CAC score. This patient’s chronological age is 58 years, but her arterial age is 72. The arterial age can be used to revise the estimated 10-year coronary risk. Her estimated 10-year coronary risk was 2% based on chronological age and traditional risk factors, but 11% when substituting her arterial age.

For many low-risk adults CAC testing would not be needed. However, according to recent guidelines, CAC testing can be considered if treatment decisions are uncertain after quantitative risk assessment.1 This patient has 2 characteristics that would make additional testing reasonable: an LDL level higher than 160 mg/dL and a high lifetime ASCVD risk (hers is 33%). A downloadable spreadsheet enabling estimation of 10-year and lifetime ASCVD risk is available at http://my.americanheart.org/cvriskcalculator. Furthermore, adults with a family history of premature CVD (age 55-60 years in men and <65 years in women) have a higher prevalence of CAC.9

This patient started atorvastatin at 20 mg/d. She continued exercising and maintained a diet high in fruits, vegetables, whole grains, low-fat dairy, fish, nuts, and vegetable oils, while limiting sweets, sugar-sweetened beverages, and red meat. Because the patient was asymptomatic she did not undergo any further cardiac testing.

Box Section Ref ID

Clinical Bottom Line: CAC Score

• According to recent ACC/AHA guidelines, CAC testing is most appropriate among adults with an estimated 10-year ASCVD risk <7.5%, in whom questions remain about whether statin therapy is indicated.1

• A CAC score ≥300 or ≥75th percentile for age, sex, and ethnicity is considered higher risk and would justify revising a patient's risk upward.

• CAC is rare among men <45 years and women <55 years

Corresponding Author: Tamar S. Polonsky, MD, MSCI, 5841 S Maryland Ave, MC6080, Chicago, IL 60637 (tpolonsky@medicine.bsd.uchicago.edu).

Conflict of Interest Disclosures: The authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported.

Disclaimer: Dr Greenland, senior editor for JAMA, was not involved in the editorial review of or decision to publish this article.

Additional Contributions: We thank the patient whose medical care was described in this article for granting permission to publish this information.

Section Editor: Mary McGrae McDermott, MD, Senior Editor.
Goff  DC  Jr, Lloyd-Jones  DM, Bennett  G,  et al.  2013 ACC/AHA Guideline on the Assessment of Cardiovascular Risk: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. Circulation.
PubMed
Greenland  P, Alpert  JS, Beller  GA,  et al.  2010 ACCF/AHA guideline for assessment of cardiovascular risk in asymptomatic adults: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines. Circulation. 2010;122(25):e584-e636.
PubMed   |  Link to Article
Detrano  RC, Anderson  M, Nelson  J,  et al.  Coronary calcium measurements: effect of CT scanner type and calcium measure on rescan reproducibility—MESA study. Radiology. 2005;236(2):477-484.
PubMed   |  Link to Article
Yeboah  J, McClelland  RL, Polonsky  TS,  et al.  Comparison of novel risk markers for improvement in cardiovascular risk assessment in intermediate-risk individuals. JAMA. 2012;308(8):788-795.
PubMed   |  Link to Article
Polonsky  TS, McClelland  RL, Jorgensen  NW,  et al.  Coronary artery calcium score and risk classification for coronary heart disease prediction. JAMA. 2010;303(16):1610-1616.
PubMed   |  Link to Article
Horton  KM, Post  WS, Blumenthal  RS, Fishman  EK.  Prevalence of significant noncardiac findings on electron-beam computed tomography coronary artery calcium screening examinations. Circulation. 2002;106(5):532-534.
PubMed   |  Link to Article
Mihaylova  B, Emberson  J, Blackwell  L,  et al.  The effects of lowering LDL cholesterol with statin therapy in people at low risk of vascular disease: meta-analysis of individual data from 27 randomised trials. Lancet. 2012;380(9841):581-590.
PubMed   |  Link to Article
Arterial age calculator. http://www.mesa-nhlbi.org/Calcium/ArterialAge.aspx. Accessed September 10, 2013.
Nasir  K, Michos  ED, Rumberger  JA,  et al.  Coronary artery calcification and family history of premature coronary heart disease. Circulation. 2004;110(15):2150-2156.
PubMed   |  Link to Article
Hendrick  RE.  Radiation doses and cancer risks from breast imaging studies. Radiology. 2010;257(1):246-253.
PubMed   |  Link to Article

Figures

Place holder to copy figure label and caption
Figure.

Sample images from the cardiac computed tomography of the patient. A, Calcified lesion (arrowhead) appears in the left anterior descending artery. B, Calcified lesion appears in the right coronary artery (arrowhead).

Graphic Jump Location

Tables

Table Graphic Jump LocationTable.  Excerpt From the Patient’s Cardiac Computed Tomography Reporta

References

Goff  DC  Jr, Lloyd-Jones  DM, Bennett  G,  et al.  2013 ACC/AHA Guideline on the Assessment of Cardiovascular Risk: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. Circulation.
PubMed
Greenland  P, Alpert  JS, Beller  GA,  et al.  2010 ACCF/AHA guideline for assessment of cardiovascular risk in asymptomatic adults: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines. Circulation. 2010;122(25):e584-e636.
PubMed   |  Link to Article
Detrano  RC, Anderson  M, Nelson  J,  et al.  Coronary calcium measurements: effect of CT scanner type and calcium measure on rescan reproducibility—MESA study. Radiology. 2005;236(2):477-484.
PubMed   |  Link to Article
Yeboah  J, McClelland  RL, Polonsky  TS,  et al.  Comparison of novel risk markers for improvement in cardiovascular risk assessment in intermediate-risk individuals. JAMA. 2012;308(8):788-795.
PubMed   |  Link to Article
Polonsky  TS, McClelland  RL, Jorgensen  NW,  et al.  Coronary artery calcium score and risk classification for coronary heart disease prediction. JAMA. 2010;303(16):1610-1616.
PubMed   |  Link to Article
Horton  KM, Post  WS, Blumenthal  RS, Fishman  EK.  Prevalence of significant noncardiac findings on electron-beam computed tomography coronary artery calcium screening examinations. Circulation. 2002;106(5):532-534.
PubMed   |  Link to Article
Mihaylova  B, Emberson  J, Blackwell  L,  et al.  The effects of lowering LDL cholesterol with statin therapy in people at low risk of vascular disease: meta-analysis of individual data from 27 randomised trials. Lancet. 2012;380(9841):581-590.
PubMed   |  Link to Article
Arterial age calculator. http://www.mesa-nhlbi.org/Calcium/ArterialAge.aspx. Accessed September 10, 2013.
Nasir  K, Michos  ED, Rumberger  JA,  et al.  Coronary artery calcification and family history of premature coronary heart disease. Circulation. 2004;110(15):2150-2156.
PubMed   |  Link to Article
Hendrick  RE.  Radiation doses and cancer risks from breast imaging studies. Radiology. 2010;257(1):246-253.
PubMed   |  Link to Article
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