Accuracy of 64-slice multidetector computed tomography for classification and quantitation of coronary plaque: Comparison with integrated backscatter intravascular ultrasound

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Abstract

Background

Noninvasive assessment of coronary plaque is important for coronary risk stratification. Whereas integrated backscatter intravascular ultrasound (IB-IVUS) has proven effective for analysis of the tissue components of coronary plaque, plaque assessment by 64-slice multidetector computed tomography (MDCT) has not been established. We therefore evaluated the accuracy of MDCT compared with IB-IVUS for identification of coronary plaque components and determination of plaque volume.

Methods

Thirty-one sites in 17 coronary vessels (7 left anterior descending, 5 left circumflex, and 5 right coronary arteries) with substantial stenosis were visualized by both 64-slice MDCT and IB-IVUS. Coronary plaque was evaluated by MDCT and the findings were compared with those of IB-IVUS at the same sites and for the same vessel lengths. Plaque was classified as low-attenuated, fibrous, or calcified, and the volume of each plaque component and total plaque volume were calculated.

Results

Total plaque volume per vessel determined by MDCT was significantly correlated with that determined by IB-IVUS (r = 0.704, P < 0.05, n = 17). However, the volumes of individual plaque components determined by the two approaches were not correlated. The predominant plaque morphology as determined by the two approaches was consistent in 12 of the 17 vessels (70.6%), whereas calcified and low-attenuated plaques were overestimated by MDCT in the remaining vessels.

Conclusions

MDCT is a promising approach for noninvasive detection of different types of coronary plaque and may therefore contribute to coronary risk stratification. The ability of MDCT to determine the volume of individual plaque components, however, is limited.

Introduction

Noninvasive assessment of coronary plaque is important for risk stratification in coronary artery disease. Acute coronary syndrome (ACS) has been shown to be related to the rupture of plaques consisting of a thin fibrous cap overlying atheroma with a lipid core and local inflammation [1], [2], [3]. The identification of such plaques before disruption is an important clinical goal. Invasive coronary angiography, the present gold standard for assessment of coronary arteries, has limitations to detect coronary plaques. It can only reveal coronary stenosis in vessels, but does not provide information on plaque composition [4].

On the other hand, intravascular ultrasound (IVUS) allows cross-sectional imaging of coronary arteries and provides a more comprehensive assessment of coronary atherosclerotic plaques. Recently, integrated backscatter intravascular ultrasound (IB-IVUS), which provides two-dimensional color-coded maps for the tissue characterization of coronary plaques, has been developed [5]. It has been shown to be able to detect coronary plaque components and to measure the overall plaque burden [6], [7]. However, IB-IVUS is invasive and is not suited to routine application related to risk stratification.

Sixty four-slice multidetector computed tomography (MDCT) also provided diagnostic coronary images of sufficient quality for clinical decision making in the majority cases of suspected coronary artery disease [8]. Computed tomography (CT) angiography is a noninvasive imaging technique for assessing not only coronary artery stenosis, but also plaque characteristics [9]. Actually, CT angiography has been reported to be able to identify the components of coronary plaques [10] and those results correlate well with lesion echogenicity in gray scale IVUS [11], [12]. CT angiography has the potential for noninvasive assessment of risk stratification and this is likely to be the principal advantages of the technique. Despite this potential, however, the diagnostic value of CT angiography has not been compared with that of IB-IVUS. On the other hand, IB-IVUS has been widely evaluated for clinical use in Japan [13], [14], [15]. We present here an evaluation of the usefulness and accuracy of coronary angiography using 64-slice MDCT, in comparison with IB-IVUS data, for classification and quantification of coronary atherosclerotic plaques.

Section snippets

Methods

From November 2006 to December 2008, contrast-enhanced CT angiography was performed as part of a research protocol in 185 consecutive patients who attended Nagoya University Hospital for evaluation of chest discomfort suggestive of coronary artery disease. All patients had an abnormal electrocardiogram (ECG) but no evidence of ACS. If they were found to have obstructive stenosis or artifacts due to wall motion or couldn't be evaluated due to extensive calcification on examination by CT

Study population and characteristics

Clinical variables for the study population are shown in Table 1. Seven patients (41%) received an oral beta-blocker before MDCT. The mean heart rate during the scan was 58 ± 13 beats/min. Thirty-one sites in 17 coronary arteries with significant stenosis on conventional coronary angiography, including 5 right coronary arteries, 7 left anterior descending arteries, and 5 left circumflex arteries, were visualized by both contrast-enhanced 64-slice MDCT and IB-IVUS. No patients were excluded because

Discussion

This study was the first investigation to evaluate the accuracy of 64-slice MDCT angiography for quantification and classification of coronary atherosclerotic plaques using IB-IVUS images as gold standard. Several studies have already reported successful evaluation of coronary plaque characteristics using multi-slice CT and Virtual Histology (VH) IVUS [19], [20], [21], however Okubo et al. have reported that IB-IVUS has high diagnostic accuracy for coronary plaque tissue characterization, in

Conclusions

Coronary angiography by 64-slice MDCT is a useful approach for the noninvasive detection of total coronary plaque burden. Moreover, it provides high predictive accuracy about predominant coronary plaque morphology and may contribute to coronary risk stratification in patients with coronary atherosclerotic disease. However, the ability of MDCT to determine the volume of individual plaque components is limited.

Acknowledgement

The authors of this manuscript have certified that they comply with the Principles of Ethical Publishing in the International Journal of Cardiology [32].

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