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Identifying Coronary Artery Calcification on Non-gated Computed Tomography Scans
Published on: August 28, 2018
Obstructive coronary artery disease: reverse attenuation gradient sign at CT indicates distal retrograde flow--a
Minghua Li1, Jiayin Zhang, Jingwei Pan
1Department of Radiology, Shanghai No. 6 People's Hospital, School of Medicine, Shanghai Jiaotong University, 600 Yishan Rd, Shanghai, China 200233.
Insights
The reverse attenuation gradient (RAG) sign on coronary CT angiography is a key indicator of chronic total occlusions (CTOs). This imaging finding helps differentiate CTOs from subtotal occlusions, improving diagnostic accuracy.
Area of Science:
- Cardiovascular Imaging
- Radiology
- Interventional Cardiology
Background:
- Coronary artery disease (CAD) diagnosis relies on accurate assessment of lesion severity.
- Differentiating chronic total occlusions (CTOs) from subtotal occlusions (SOs) is crucial for treatment planning.
- Coronary computed tomographic (CT) angiography is a valuable non-invasive tool for evaluating CAD.
Purpose of the Study:
- To evaluate the clinical significance of the reverse attenuation gradient (RAG) sign in patients with occlusive coronary artery disease.
- To determine the RAG sign's utility in distinguishing between CTOs and SOs using coronary CT angiography.
Main Methods:
- Prospective enrollment of 80 consecutive patients with occlusive coronary artery disease.
- Coronary CT angiography was performed to assess the RAG sign, lesion length, and collateral vessels.
- The RAG sign was defined as a reverse intraluminal opacification gradient distal to occlusive lesions.
- Statistical analysis included Mann-Whitney Wilcoxon and Fisher exact tests.
Main Results:
- The RAG sign was significantly more frequent in CTOs (65%) compared to SOs (7%) (P < .001).
- Significant differences were observed in attenuation gradient measurements and lesion length between CTO and SO groups.
- The RAG sign accurately identified retrograde collateral flow in CTO segments.
- Combined parameters achieved 90% sensitivity and 93% specificity for CTO diagnosis.
Conclusions:
- The RAG sign on coronary CT angiography reflects retrograde collateral flow distal to occlusive lesions.
- This sign is highly specific for CTOs.
- The RAG sign aids in differentiating CTOs from SOs, enhancing diagnostic capabilities.
Purpose:
To study the clinical importance of the reverse attenuation gradient (RAG) sign in patients with occlusive coronary artery disease observed with coronary computed tomographic (CT) angiography.
Materials And Methods:
All patients provided written informed consent, and the institutional review board committee approved the study protocol. Eighty consecutive patients (mean age, 67.1 years ± 12.1 [standard deviation]; range, 35-87 years; 62 men [mean age, 65.8 years ± 12.5; range, 35-86 years] and 18 women [mean age, 71.7 years ± 9.3; range, 58-87 years]) were enrolled prospectively in this study. The RAG sign was defined as the reverse intraluminal opacification gradient of vessels distal to the occlusive lesions, which has lower attenuation in the proximal segment and gradually increased attenuation along the vessel. Other parameters, such as lesion length and bridging collateral vessels visible at coronary CT angiography, were recorded. Mann-Whitney Wilcoxon and Fisher exact tests were used for comparison.
Results:
There were 94 occlusive lesions. Invasive coronary angiography was used to confirm 49 chronic total occlusions (CTOs) and 45 subtotal occlusions (SOs). The CTO group had the RAG sign significantly more frequently than did the SO group (65% [32 of 49] vs 7% [three of 45]; P < .001). Similarly, significant difference of measurements of the attenuation gradient (5.1 HU/10 mm ± 13.4 vs -13.4 HU/10 mm ± 8.7; P < .001) and lesion length (23.6 mm ± 22.7 vs 6 mm ± 3; P < .001) was noted between the groups. Bridging collateral vessels were present in only four cases of CTO at coronary CT angiography. All segments with RAG at coronary CT angiography were shown by means of invasive coronary angiography to be supplied by retrograde collateral vessels. When a combination of all those parameters was used for diagnosis of CTO, sensitivity and specificity were 90% (44 of 49) and 93% (42 of 45), respectively.
Conclusion:
The RAG sign represents the retrograde collateral flow distal to an occlusive lesion. This sign is highly specific for CTO and helps to differentiate CTO from SO.
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