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Coronary artery disease (CAD) is still a leading cause of morbidity and mortality in Europe. There has been much interest in developing screening methods to identify those at risk of having a primary cardiac event.
What is coronary artery calcium (CAC)?
The presence of calcium in coronary arteries is almost always indicative of atherosclerotic plaque (but bears no relationship to plaque stability or instability). Cardiac risk factors and insulin resistance lead to progression of coronary artery calcification.
How do we measure the coronary artery calcium score (CACS)?
CACS is determined by CT scanning which is non-invasive and can be of two types:
- Electron beam CT scan (EBCT).
- Multidetector CT scan (MDCT).
EBCT is the most common technology currently used to measure CACS.
Coronary artery calcium score results
The amount of calcium detected in the coronary arteries is converted to a calcium score which correlates with the severity of the atherosclerosis.
|Coronary Artery Calcium Score (CACS)|
method of reporting results and their interpretation
|Negative test - ie significant obstructive luminal disease highly unlikely|
|High calcium score - ie above-average risk of a cardiac event in the following five years|
|Very high calcium score - ie high risk of a cardiac event|
Coronary artery calcium scanning is not useful in those at very low or very high risk, or in those with known coronary artery disease (CAD). It is unclear at present as to who should be offered coronary artery calcium (CAC) scanning but the following are possibilities:
- Screening asymptomatic patients.
- Screening those with intermediate risk of coronary artery disease (ie Framingham risk score of 10-20% over 10 years).
- Presence of just one risk factor, eg mild hypertension. Note that diabetic patients and those with chronic kidney disease (CKD) will probably have high calcium scores which may not necessarily represent significant clinical coronary atherosclerosis.
- Presence of a strong family history of premature CAD.
The main disadvantages of CACS are its lack of information regarding a patient's functional capacity (which could be inferred from an exercise tolerance test (ETT)) and lack of data in ethnic groups. It has been argued that a CACS over 100 indicates the presence of atherosclerosis and, unless there is a clinical indication, the treatment is lifestyle modification.
The main benefit of CACS is its high negative predictive value, reported as high as 98% in some studies.
What does the evidence tell us about the coronary artery calcium score?
Some evidence suggests that increased CACS predicts subsequent development of heart disease. However, prospective studies are lacking and there are also some data suggesting that CACS does not add anything over and above other scoring systems.
Further evidence and guidance is required to determine how to use CAC scans effectively and the role they play amongst other cardiac investigations.
Further reading & references
- European guidelines on cardiovascular disease prevention in clinical practice, European Society of Cardiology (2007)
- Kittleson MM, Nasir K and Blumenthal RS, Coronary artery calcification measurements: developments, recommendations - EBCT and MDCT each offer unique advantages; both are useful for noninvasive screening of those at risk, Today in Cardiology, (2004)
- Boyar A, EBT Coronary Calcium Scoring Guide (2004), Advanced Body Scan of Newport
- Grayburn PA; Interpreting the coronary-artery calcium score. N Engl J Med. 2012 Jan 26;366(4):294-6.
- Pletcher MJ, Tice JA, Pignone M, et al; Using the coronary artery calcium score to predict coronary heart disease events: a systematic review and meta-analysis. Arch Intern Med. 2004 Jun 28;164(12):1285-92.
- Taylor AJ, Bindeman J, Feuerstein I, et al; Coronary calcium independently predicts incident premature coronary heart disease over measured cardiovascular risk factors: mean three-year outcomes in the Prospective Army Coronary Calcium (PACC) project. J Am Coll Cardiol. 2005 Sep 6;46(5):807-14.
- Church TS, Levine BD, McGuire DK, et al; Coronary artery calcium score, risk factors, and incident coronary heart disease events. Atherosclerosis. 2007 Jan;190(1):224-31. Epub 2006 Mar 15.
Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.
Dr Gurvinder Rull
Dr Gurvinder Rull
Dr Adrian Bonsall