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Min et al. (1) present important information on a large database of individuals undergoing coronary computed tomography angiography (CCTA) with regard to the significance of coronary stenosis as a predictor of future mortality. This study demonstrates the prognostic significance of coronary stenosis as assessed by CCTA in predicting future mortality.
There is another important question that this data set has the potential to answer. Does the number of vessels with significant coronary stenosis present have prognostic significance in terms of mortality beyond a simple measure of total coronary artery plaque as assessed by coronary artery calcium screening computed tomography (CT)?
A key question for any diagnostic tool to be added to the armamentarium of available tests for the purpose of assessing mortality is whether the new test performs better than less expensive test modalities, particularly if there is a less expensive diagnostic test with slightly less risk.
Coronary calcium CT is much less expensive and uses approximately one-tenth of the radiation of CCTA (2). It is important therefore to demonstrate an improvement over this less-costly modality, which imparts considerably less radiation, when the goal is to predict prognosis regarding mortality.
Would the authors re-examine their data for stratification of these same patients according to coronary calcium results with regard to mortality prognosis? Because CCTA, in many cases, is performed with a coronary calcium CT at the onset of the test, this information is potentially available.
In the dataset of the paper, 42.5% of the patients were normal, 34.0% were found to have nonobstructive coronary artery disease (CAD), 13.1% had 1-vessel CAD, and 10.4% were found to have either 2- or 3-vessel CAD when assessed by using CCTA.
Using scores from the screening coronary calcium CT scan, the patients can similarly be divided into the 10% with the highest absolute coronary calcium scores, the 13% of the patients with the next highest scores, followed by the next 34% of the patients, and finally the remaining approximately 43% of patients with no calcium present (or very low calcium scores).
The same Kaplan-Meier analysis can then be applied to these groups separated on the basis of their absolute coronary calcium score (assuming that score is available). If these groups, when separated on the basis of the calcium scores, stratify mortality outcomes as well as the CCTA results for the number of vessels with coronary stenosis, this would be useful information.
A much less expensive test that imparts considerably less radiation can then be used to help assess future mortality. In addition, regardless of the result, this would represent additional information regarding how much coronary artery stenosis plays a role in mortality prognosis beyond total coronary plaque burden.
- American College of Cardiology Foundation