coronary artery calcium score (CACS)

Last edited 10/2021 and last reviewed 01/2023

  • non-contrast cardiac computed tomography (CT) has become an established diagnostic tool in clinical practice

    • main purpose of these coronary calcium scans is to obtain the coronary artery calcium score (CACS)

      • CACS is associated with a graded increased risk of future coronary events, heart failure and mortality (1,2)

      • a negative or zero CACS denotes a mid- to long-term risk of coronary events that is close to zero (3,4)

      • evaluation of coronary artery calcium scoring via CT offers a fast, reproducible modality to determine the extent and presence of coronary calcification

      • presence of coronary calcium is associated with plaque burden - however, it is not a marker of plaque vulnerability
        • despite this limitation the CACS gives an insight to the patient's level of cardiovascular disease risk and is helpful for guiding interventions or prevent coronary artery disease (5,6)

      • ACC/AHA guidelines on assessment of cardiovascular risk state that assessment of CACS may be considered based on a large number of observational studies:
        • with a CACS of >=300 Agatston units (or >=75th percentile for age, sex and ethnicity) supporting an upward revision in risk assessment (7)

    • formally evaluated using dedicated non-contrast ECG-gated cardiac CT (8)
      • cardiac gating or ECG gated angiography in CT is an acquisition technique that triggers a scan during a specific portion of the cardiac cycle. Often this technique is conveyed to obtain high-quality scans void of pulsation artefact.
      • performed with 3 mm contiguous slices and a tube voltage of 120 kVp
      • Agatston scoring system
        • is the most widely used method to assess CAC, although alternatives such as the mass and volume scores are available
        • is performed using semi-automated software to identify areas of calcification (above 130 Hounsfield units), which are then weighted based on the maximum attenuation density and summed
        • patients may then be classified into risk groups, with CAC score
          • 0 Agatston units (AU) (very low risk),
          • 1-99 AU (low risk),
          • 100-299 AU (moderate risk),
          • >= 300 AU (high risk)
          • asymptomatic patients with an Agatston score >300 AU have a sevenfold increase in the risk of myocardial infarction or coronary heart disease death compared to patients with no CAC

    • absence of CAC on gated cardiac CT scans identifies a patient population that has a low risk for subsequent cardiovascular events in many different subsets of patients, including patients presenting with cardiac symptoms, as well as asymptomatic patients (9)

    • coronary artery calcification on non-gated thoracic CT
      • CAC can be identified on non-gated thoracic CT with an excellent diagnostic accuracy compared to gated CT
        • however, CAC is frequently not reported on non-gated thoracic CT
      • for non-gated thoracic CT in routine clinical practice
        • recommend a simple visual ordinal score performed on a whole patient basis. CAC is scored as None, Mild, Moderate or Severe on a whole patient basis, aiming to summarise the cumulative findings in all the coronary arteries (8)
          • can be applied to both non-contrast and contrast-enhanced images
          • if patients are symptomatic with suspected coronary artery disease. they should be managed as per standard guidelines (e.g. NICE CG95 2016 revision or SIGN 151)
            • if they are asymptomatic, we recommend the referrer or general practitioner review and consider modifiable cardiovascular risk factors and manage these as per standard guidelines (e.g. NICE CG 181)
            • for asymptomatic patients, there is no current evidence to support further imaging (ischaemia testing, CT coronary angiography or invasive coronary angiography)
        • suggested reporting example (8):
          • “Mild/Moderate/Severe coronary artery calcification, indicating the presence of coronary artery disease. If the patient has associated symptoms recommend management as per chest pain guidelines (e.g. NICE CG95, SIGN 151). If the patient is asymptomatic consider reviewing modifiable cardiovascular risk factors and managing as per guidelines for primary prevention (e.g. NICE CG 181).”

  • coronary artery calcium (CAC) score is a CVD risk tool which may be used to target therapy and encourage patients and physicians to improve risk factor control (9)
    • study evidence showed that CAC-guided statin treatment protocol in asymptomatic, statin naive participants with a family history of premature CAD led to a 18% relative risk reduction in the pooled cohort equation (PCE) score-based predicted 10-year risk, compared to usual care

Reference:

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