How to grade the severity of coronary stenosis

Grading coronary stenosis severity can be performed in multiple ways, however, some techniques are much better than others. In this video, you'll discover which cardiac CT imaging techniques should (and should not) be used to grade stenosis severity.

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[00:00:00] How do we grade coronary stenosis severity? When grading stenosis severity, there are a number of techniques available. For the purpose of evaluating stenosis severity, it is recommended to use axial image, so in other words, the pure CT dataset, as it appears on your workstation and for you to scroll up and down. This can be seen on the left-hand imaging pane. Single oblique imaging is where the crosses are aligned with the plaque in one plane only, with the

[00:00:30] reader looking at all of the corresponding images thereafter. This is seen in the middle imaging pane. And my preferred technique is demonstrated on the right-hand image. This is called double oblique imaging. Double oblique imaging requires the crosses to be aligned in all three planes, simultaneously and for the reader to work their way down each vessel and its branches systematically. This technique is arguably the best for ensuring disease is not missed but also the most time-consuming. Many practitioners are also a fan of post-processing. This image shows a curved

[00:01:00] multi-plane and reformatted image. The CT workstation is able to extract the vessel of interest automatically or by one click of the mouse. Following this, the vessel can be swiveled and rotated around on its axis to look for plaque. For this technique, one must remember that it is a post-processed image and therefore, requires a good initial CT dataset acquisition or else artifacts may affect evaluation. The right-hand image shows a variation of this, the so-called straightened multi-plane and reformatted image, where the vessel is laid out

[00:01:30] straight by the computer. 3D volume rendered imaging should not be used for plaque stenosis assessment, since one cannot see inside the lumen. This technique is mainly used for demonstrating anatomy and also for making beautiful presentations. When grading plaque, it is important to remember to look at all of the data at your disposal. If we considered the above example, a plaque may not be seen in one plane but may be present in another. Therefore, it is important to align your crosshairs in two orthogonal planes

[00:02:00] and to interpret the plaque in the short-axis, to see the vessel lumen on FAST. In this example, the plaque would be graded mild in severity. Another important point to remember is to look at the length of the plaque and to determine stenosis severity at the point where the vessel lumen is compromised the most. If stenosis severity was graded at the left-hand image, this would be an example of minimal stenosis. The middle would be mild stenosis, and the right, moderate stenosis. This would have implications for the patient's

[00:02:30] subsequent treatment. Therefore, it is important to always report the most significant narrowing of the vessel lumen, when encountering a long plaque. A normal coronary artery is present when there is no plaque, at all, in any of the imaging planes. When you start to see plaque, I like to use my crosshairs to semi-quantify the plaque. In these images, we can see that the double oblique imaging has demonstrated a plaque in the lumen, that occupies less than 25% of the luminal surface or up to one quadrant made by the crosshairs.

[00:03:00] This is an example of minimal plaque. Using the same principle, a mild stenosis is one where the plaque occupies 24 to 49% of the lumen. You can see, in the on FAST image of the vessel, that the plaque is covering two quadrants. This is a mild stenosis. A moderate stenosis is where a plaque occupies 50% to 69% of the lumen or up to three quadrants. A severe stenosis is one that occupies 70% to 99% of the lumen

[00:03:30] or involves up to four quadrants. Vessel occlusion is where the entirety of the lumen is occupied by a plaque and there is no contrast to pacification seen at this point or immediately distal to the lesion. Using a systematic approach to grade plaque will improve reproducibility. Always report using standard recommended ranges and not isolated values.