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Coronary artery calcium scores are of most use in those patients at intermediate risk for cardiovascular disease, where the result will either lower or raise the risk profile and provide a change in management.
Those at low risk (such as an asymptomatic 35 year old male non-smoker who exercises and has no significant family history) and those at high risk (such as a 60 year old obese male long-term smoker with chest pain on exertion) would not benefit from the study.
In general, coronary artery calcium score CT scans are most useful in women between 35 and 70 years and in men between 40 and 60 years.
There is a place for scans outside these ranges. For example, finding a score of zero in an elderly man will indicate a very low risk of a cardiac event; however, this result is very unusual in the general population.
The test is valid for main ethnic groups; however, the result is most accurate in patients of Caucasian origin. coronary artery calcium scoring in patients on dialysis and with established long-term diabetes is not recommended, due to the high likelihood of a high score and the current scientific uncertainty over the interpretation of the result.
It must be stressed that there is potential for a technically false result. A score of zero does not exclude the possibility of myocardial infarction in the future.
Any contraindication to X-ray exposure, of which pregnancy is the most common.
The very young and very old will get no benefit from a calcium score.
Any patient with high risk of coronary event and symptoms should have appropriate investigation and treatment urgently.
Anyone who has already had a myocardial infarction or coronary re-vascularisation will not have any benefit with the information from a calcium score study.
All scanners have physical limitations due to table weight limits and the diameter of the scanner aperture. Older scanners are able to scan patients up to 150kg. Newer scanners can in some cases accommodate patient weights of 220 – 250kg. Some obese patients have large abdominal girths. Most scanners have a gantry diameter of about 68cm with newer scanners up to 78cm. If you are concerned that your patient may exceed any of these limits, it is best to contact the hospital or practice to find out whether this may preclude scanning.
Radiation risks are discussed in detail in another information item on InsideRadiology (see radiation risk of medical imaging in adults and children).
Alternative strategies exist to assess the personal risk of a cardiovascular event. Risk stratification techniques to assess a ten–year individual risk of a cardiovascular event include:
These are in wide usage but tend to have a heavy weighting to patient’s age and may not adequately take into account lifestyle factors such as smoking, diet, exercise, and body mass index.
Alternative methods of imaging or testing to better stratify the individual’s risk include:
References: These major review articles may be helpful in adding detail and depth to the information given:
Last saved on 6 October 2016.
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