How is stenosis graded using coronary computed tomography angiography (CCTA)?

Updated: Dec 21, 2017
  • Author: Eugene C Lin, MD; Chief Editor: Eugene C Lin, MD  more...
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Answer

Answer

There are many different methods to grade the degree of stenosis, including visual assessment; manually determined diameter or cross-sectional area on multiplanar reformats perpendicular to the median centerline of the vessel ("end-on" view); diameter on maximum intensity projection (MIP) images parallel to the long axis of the vessel; and software calculation [8] of diameter or area. Dodd et al found that the cross-sectional area technique had the highest correlation with quantitative coronary angiography, and MIP technique had the smallest interobserver variability. [78] Grading is less accurate in calcified plaques and in distal coronary vessels. In one report the most common etiologies of diagreement between computed tomography angiography (CTA) and catheter angiography were motion-related degradation of image quality, calcification, smaller vessel diameter, left anterior descending (LAD) artery location, and bifurcation location. [79]

Maximum intensity projection (MIP): MIP image of a Maximum intensity projection (MIP): MIP image of a left anterior descending (LAD) artery stenosis secondary to calcified plaque. MIP images parallel to the long axis of the vessel can be used to assess the degree of stenosis.
"End-on" multiplanar reformat (MPR): "End-on" MPR "End-on" multiplanar reformat (MPR): "End-on" MPR view (perpendicular to the median centerline of the vessel) of a left anterior descending (LAD) artery stenosis secondary to calcified plaque. The degree of stenosis could be assessed on this view visually, or from manually or software-calculated diameter or cross-sectional area.

Cross-sectional images at the level of the most severe narrowing can be compared to a reference minimal lumen diameter averaging the segments proximal and distal to the stenosis. The diameter should be measured lumen to lumen rather than wall to wall. The distal reference vessel should not be distal to a bifurcation.

Because the spatial resolution is inadequate for precise grading, coronary stenoses are often graded with semiquantitative descriptors such as normal, mild (< 50%), moderate (50–70% stenosis), severe (>70% stenosis), and occluded.


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