Rationale and Objectives
Coronary computed tomographic (CT) angiography has been shown to detect noncalcified coronary artery plaque. Depending on tissue composition, noncalcified plaque differs in CT attenuation from blood and epicardial fat. The aim of this study was to determine whether noncalcified plaque can be visually detected on non-contrast-enhanced CT calcium scoring studies.
Materials and Methods
A total of 106 patients (40 women; mean age, 59 years) who underwent coronary calcium scoring, coronary CT angiography, and quantitative catheter angiography were prospectively investigated. Two blinded observers independently reviewed calcium scoring studies for positive vascular remodeling and hypoattenuation within the vessel wall, suggestive of noncalcified plaque. Findings on calcium scoring studies were compared with those on coronary CT angiography and quantitative catheter angiography.
Results
The mean Agatston score was 515.8 ± 826.8. Overall interobserver agreement for the identification of noncalcified lesions was substantial (κ = 0.69). Observer 1 and observer 2 identified 21 and 17 patients, respectively, with 38 and 35 lesions suggestive of noncalcified plaque. Coronary CT angiography confirmed noncalcified plaque in 33 of 38 (86.8%; observer 1) and 31 of 35 (88.6%; observer 2) lesions. Thus, the overall positive predictive value for correct identification of noncalcified plaque on calcium scoring studies was 0.88, although overall sensitivity was low at 0.39.
Conclusions
Noncalcified plaque can be visually detected on calcium scoring studies. Review of calcium scoring studies for features of noncalcified plaque may enhance the identification of patients with more active disease and higher cardiovascular risk.
Computed tomographic (CT) coronary calcium scoring has been proposed to provide incremental prognostic information in addition to conventional risk factor assessment for predicting cardiac events in intermediate-risk populations . Although there is no good relationship between the degree of coronary artery calcification and stenotic coronary artery disease (CAD) , the amount of coronary artery calcium is thought to reflect the overall coronary atherosclerotic plaque burden , albeit in an imperfect manner .
There is increasing evidence that the acute coronary syndrome (unstable angina, ST-segment elevation and non–ST-segment elevation myocardial infarction, sudden cardiac death) frequently has its surrogate in the sudden rupture of noncalcified or mixed (ie, containing both calcified and noncalcified components) coronary artery plaques . Therefore, efforts in primary disease prevention increasingly focus on the prospective identification of patients with such “vulnerable” lesions .
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Materials and methods
Patients
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Table 1
Characteristics of the Study Population
Variable Value Age (y) 59 ± 12 (27–79) Men/women 66 (62%)/40 (38%) Body mass index (kg/m2) 31 ± 7 <25 20 (18.9%) 25–30 32 (30.2%) >30 54 (50.9%) Hypertension 85 (80.2%) Hyperlipidemia 29 (27.4%) Current or former smoker 54 (50.9%) Diabetes mellitus 21 (19.8%) Family history of CAD 60 (56.6%)
Data are expressed as mean ± standard deviation (range) or as number (percentage).
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CT Procedures
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QCA
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Data Analysis
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Statistical Analysis
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Results
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Table 2
Interobserver Agreement for Detecting Noncalcified Coronary Artery Plaque on Non-contrast-enhanced Calcium Scoring Studies by Vessel and Overall
Vessel Observer 1 Observer 2 Interobserver Agreement (κ) LM 4 5 0.86 LAD 21 17 ∗ CX 5 4 0.58 RCA 8 9 0.51 Total 38 35 0.69
CX, circumflex coronary artery; LAD, left anterior descending coronary artery; LM, left main coronary artery; RCA, right coronary artery.
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Table 3
Performance Indices for Detecting Noncalcified Coronary Artery Plaque on Non-contrast-enhanced Calcium Scoring Studies
Performance Index LM LAD CX RCA Total Observer 1 Observer 2 Observer 1 Observer 2 Observer 1 Observer 2 Observer 1 Observer 2 Observer 1 Observer 2 Sensitivity 0.27 0.33 0.49 0.48 0.40 0.38 0.30 0.28 0.39 0.38 Specificity 1.00 1.00 0.96 0.99 0.99 0.99 0.99 0.98 0.99 0.99 PPV 1.00 1.00 0.86 0.94 0.80 0.75 0.88 0.78 0.88 0.89 NPV 0.89 0.90 0.80 0.82 0.94 0.95 0.84 0.84 0.87 0.88
CX, circumflex coronary artery; LAD, left anterior descending coronary artery; LM, left main coronary artery; NPV, negative predictive value; PPV, positive predictive value; RCA, right coronary artery.
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Discussion
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Conclusions
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