Does coronary artery calcification scoring still have a role in practice?
ITS ROLE IS MORE CONTROVERSIAL IN SYMPTOMATIC PATIENTS
Perhaps a less established and more controversial use of coronary artery calcification scoring is in patients who are having coronary symptoms. In patients at high cardiovascular risk, this test by itself may miss an unacceptable number of those who truly have significant stenoses.9 However, when the appropriate population is selected, there is substantial evidence that it can be an important means of risk stratification.
In patients at low to intermediate risk, the absence of calcification indicates a very low likelihood of significant coronary artery stenosis, as demonstrated in the Coronary CT Angiography Evaluation for Clinical Outcomes: An International Multicenter (CONFIRM) registry.10 In the 10,037 symptomatic patients evaluated, a score of 0 had a 99% negative predictive value for excluding stenosis greater than 70% and was associated with a 2-year event rate less than 1%. These data were supported by a meta-analysis of nearly 1,000 symptomatic patients with a score of 0, in whom the 2-year event rate was less than 2%.4
Taken together, these data suggest that the absence of coronary calcification in people at low to intermediate risk indicates a very low likelihood of significant stenotic coronary artery disease and foretells an excellent prognosis.
These data have already been incorporated into the British National Institute for Health and Clinical Excellence (NICE) guidelines, in which calcification scoring is an integral part of the management algorithm in patients with chest pain who are at low risk.
WHY NOT JUST DO CT ANGIOGRAPHY?
But why bother with coronary artery calcification scoring when we can do CT angiography instead? The angiography scanners we have today can cover the entire heart in a single gantry rotation. Dual-source scanners provide temporal resolution as low as 75 ms, and sequential, prospective electrocardiographic gating and iterative reconstruction can routinely achieve scans with doses of radiation as low as 3 mSv that provide coronary artery images of exquisite quality.
On the other hand, calcification scoring is fast and easy to perform and poses less potential harm to the patient, since it uses lower doses of radiation and no contrast agents. In addition, the quantification is semi-automated, so the results can be interpreted quickly and are reproducible.
In the CONFIRM trial, prediction by CT angiography was no better than calcification scoring in asymptomatic patients, so it is not recommended in this population.2 In symptomatic patients, the CONFIRM trial data suggest that almost 1,000 additional CT angiography procedures would need to be done to identify one myocardial infarction and more than 1,500 procedures to identify one patient at risk of death missed by calcification scoring of 0 in patients at low to intermediate risk.11
Chauffe and Winchester nicely summarize the limitations of calcification scoring. However, we would emphasize the potential implications of the above findings. Appropriately utilized, calcification scoring is safe, reproducible, and inexpensive and helps individualize treatment in asymptomatic patients at low to intermediate risk, thereby avoiding under- and overtreatment and potentially reducing downstream costs while improving compliance.
In patients at low to intermediate risk who present with chest pain, documenting the absence of calcification can rationalize downstream testing and reliably, quickly, and safely permit patient discharge from emergency departments. In a time of increasing costs and patient demands and finite resources, clinicians should remain cognizant of the usefulness of evaluating coronary artery calcification.
