In this lesson taken from our Cardiac CT Essentials course, you'll review normal coronary artery anatomy and learn a systematic approach to identify coronary anomalies and report them.
Want to learn how to perform and interpret your own cardiac CT scans? Our Cardiac CT Essentials course was designed and delivered by CT guru Dr Ronak Rajani–consultant cardiologist, lecturer at King's College London, and Director of the London Advanced Cardiac CT Academy. Dr Rajani will be your comprehensive guide to the ins and outs of cardiac CT application in a clinical environment. Don't miss out on your opportunity to supercharge your career.
[00:00:00] So, what are coronary artery anomalies? Coronary anomalies are congenital abnormalities in the coronary anatomy of the heart. They occur in less than 1% of the population and can be seen to occur concomitantly with other congenital heart defects. Let us now look at a few coronary anomalies. This is an example of the most common coronary anomaly. Can you identify what this is? We will allow this to play a few times to give you an opportunity to look at the images.
[00:00:30] The most common congenital coronary anomaly is known as muscle bridging or myocardial bridging, and this case
[00:01:00] demonstrates myocardial bridging. If you follow the course of the left anterior descending artery, this passes over the surface of the epicardium, in the midsegment of the LAD, then dives down into the myocardium and is of smaller vessel caliber. Before it emerges again to pass down the anterior interventricular groove, over the surface of the epicardium. This is a common finding and can be seen to occur in up to 60% of CT scans in some cardiac CT series.
[00:01:30] The finding of muscle bridging itself is usually incidental and is not usually clinically significant. Here is an example, of the muscle bridging, from this case. We can see that the coronary artery passes in the epicardial fat, over the surface of the epicardium, before diving down into the myocardium, and emerging out again. When evaluating muscle bridging, it is customary to not only measure the length of the muscle bridge but also the depth of the muscle bridge. Also note, that the caliber of the myocardial
[00:02:00] bridge segment is smaller than that of the normal unbridged segment, proximal to the muscle bridging. Before we look at some further examples of congenital coronary anomalies, let us first start by reviewing the normal coronary anatomy. Remember, that normally the left main stem should arise from the left coronary cusp, before bifurcating into the left anterior descending artery, and also the left circumflex artery. The right coronary artery, on the other hand, should normally arise from the right coronary cusp and pass
[00:02:30] anteriorly down the right-sided atrioventricular groove. Any deviations from this normal arrangement constitute a coronary anomaly. Here, is an example of normal coronary anatomy, so you can register the normal origins of the coronary artery. Pay attention to where the right coronary artery emerges, from the right coronary cusp and also where the left main stem emerges, from the left coronary cusp.
[00:03:00] Here, we can see the two origins—the left main stem, from the left coronary cusp and the right coronary artery, from the right coronary cusp. This is a normal anatomical arrangement of the coronary arteries. Let us now look at a coronary anomaly. And for this, what we would like you to do is to look at the origins of
[00:03:30] the coronary arteries. Are you able to spot the anomaly? Look closely, as to where the origins of the coronary arteries are. Does the right coronary artery emerge from the right coronary cusp? And does the left main step emerge from the left coronary cusp? Let us now review this case together. In this particular example, we can see that the left main stem arises from the non-coronary cusp. Can you see that this is the non-coronary cusp here and this is the left coronary cusp here? This is an example of an anomalous left main stem
[00:04:00] and this is depicted on the graphic on the right-hand side. Remember, that with normal coronary anatomy, the left main stem should arise from the left coronary cusp. And here's another opportunity to look at this case again. Here, is another coronary anomaly. Are you once again able to spot the anomaly on this scan, remembering,
[00:04:30] to look at the origins of the coronary arteries? Let us now look at this case together. Where is the left circumflex artery? Although we see that the right coronary artery emerges from the right coronary cusp
[00:05:00] and there is a left anterior descending artery emerging from the left coronary cusp, we see an additional small vessel, which constitutes the left circumflex artery. If you look closely on the scan, you can see that the left circumflex follows a retroaortic and infra-aortic course, below the aorta, before assuming its normal position and the left-sided atrioventricular groove. This is an example of an anomalous left circumflex artery. Here, we have used some multi-plane and reformatting imaging to show you the
[00:05:30] course of the left circumflex artery, as it emerges from the right coronary cusp. Can you see how it passes inferior to the aorta, before assuming its normal course on the left-sided atrioventricular groove? Let us look at it again, on the same image. Are you now able to see the anomalous left circumflex artery, as it arises from the right coronary cusp?
[00:06:00] Are you able to spot the anomaly on this scan? Look very closely, as to where the right coronary artery originates from.
[00:06:30] Were you able to spot the anomaly? When looking at anomalies, be careful to look at the origin of the vessel, look also at its course and evaluate the potential risk of a specific coronary anomaly. In this case, if you look very closely, just below the main pulmonary artery, as you scroll down, you can see the right coronary artery emerging from the left coronary cusp. This then follows an interarterial course and this particular variant is considered
[00:07:00] to represent a malignant coronary artery. As we can see on this particular graphic, this demonstrates the course of the anomalous right coronary artery. We can see that it arises from the left coronary cusp, before following an interarterial course. It is interarterial because it lies between the main pulmonary artery and the ascending aorta. For these type of coronary anomalies, it is important to evaluate whether or not they do pose a specific risk to the patient and risk can be defined, with
[00:07:30] these type of coronary anomalies, by using a number of anatomical parameters. Is there an acute angulation? Is there a slit-like orifice and does the vessel follow an intramural course? Here, we can see that this a true example of a malignant right coronary artery because it follows an intra-arterial course above the level of the pulmonary valve. Here's another opportunity to look at this case one further time.
[00:08:00] When evaluating coronary artery anomalies, always consider how the anomalies compare to normal. Ensure that you always review the course of the vessels, also look at the origins of the anomalous coronary arteries, and also assess their risk.