Classification of Anomalous Coronary Arteries:
Anomalies can be classified as hemodynamically or non-hemodynamically significant. The hemodynamically significant anomalies include coronary atresia, origin from the pulmonary artery, and interarterial course, or a congenital fistula. Non-hemodynamically insignificant variants include origin from a different coronary cusp, high or anomalous origin from the aorta, and a pre-pulmonic, transseptal, or retroaortic course. There have been documented cases of the coronary arteries arising from almost any vascular structure in the mediastinum. This presentation is limited to the most common anomalies arising from cardiac structures.
Hemodynamically significant anomalies:
Interarterial course:
The interarterial course of the left coronary artery has been shown to predispose patients with an increased risk for sudden cardiac death. Theories as to etiology are still highly debated, but the most agreed-upon theory is an angulated or slit-like origin, raising the risk of occlusion.
The anomaly is most often discovered incidentally on autopsy of otherwise healthy military recruits or marathon participants who experience unexplained sudden cardiac death.
Fig. 1: Sagittal CT image shows the four potential anomalous locations through the myocardium. The intraatrial course is highlighted in red.
Fig. 2: White arrow – LMA/Left anterior descending artery (LAD). Ao = aorta
Fig. 3: Anomalous vessel is in yellow. See the course through the interarterial groove.
Origin from the Pulmonary Artery:
Coronary arteries arising from the pulmonary artery (PA) carry significant cardiac sequelae. The left main coronary artery (LMCA) is most commonly affected. It was described in 1956 and is covered by the eponym Bland-Garland-White syndrome. More commonly, the process is referred to as anomalous origin of the left coronary artery from the pulmonary artery, abbreviated ALCAPA.
ALCAPA has been noted to occur in 0.25-0.5% of cases of congenital heart disease. This anomaly usually results in myocardial steal syndrome, where oxygenated blood flows from the right coronary artery (RCA), through coronary-coronary collaterals to the LMCA and into the low-pressure pulmonary artery circulation. This starves the myocardium of oxygen-rich blood, quickly leading to myocardial ischemia. Enlarged coronary collateral vessels are sometimes noted on coronary CT.
Fig. 4: White arrow indicates PA origin of the right coronary artery (RCA) in this pediatric patient. Ao = aorta, PA = pulmonary artery
Fig. 5: Yellow artery demonstrates the PA origin. White arrow = anomalous LMCA. Chevron = filling collaterals.
Atresia:
Extremely rare, coronary artery atresia is usually described in relation to the LMCA. In this case, the LMCA origin is atretic or absent, relying on collateral arteries to provide blood flow to the left coronary circulation.
Fig. 6: The asterisk (*) shows atresia of the LMCA origin, Chevron = smaller yellow collateral arteries filling the main LAD (white arrow).
Very few radiologic correlates have been found for this anomaly.
Congenital Fistula:
A coronary artery fistula is normally a tortuous, anomalous vessel or vessel branch that terminates in a low-pressure vascular structure. This commonly involves anomalous termination into the right atrium or ventricles, but can involve the main pulmonary artery, pulmonary veins, or the coronary venous system. If blood is being re-routed to a low-pressure system and away from the myocardium, a coronary steal syndrome can occur, similar to origin of a vessel from the pulmonary artery.
Fig. 7: Congenital fistula of the LAD (chevron) with the pulmonary artery (white arrow).
Fig. 8: Yellow artery demonstrating the congenital fistula (white arrow) with the LMCA (chevron).
Non-Hemodynamically Significant Anomalies:
Unlike the previous anomalies, which can carry significant risk for sudden cardiac death, these anomalies are often found incidentally on imaging performed for another cause. They are often asymptomatic and do not require repair. They can, however, interfere with standard surgical procedure when they occur in the setting of another disease process.
High Origin:
Typically, high origin is defined as an origin of any coronary vessel from approximately 1 cm above the sinotubular junction. There is no hemodynamic significance to this anomaly, but traditional cardiac angiography may not visualize this vessel, and it can be difficult to preferentially catheterize a high origin vessel. Identifying this anomaly is critical for pre-surgical planning involving aortic root or aortic valve replacement. Inducing cardioplegia may be unsuccessful if a high origin vessel is not identified. The RCA is most commonly affected, with the anomaly arising more frequently in those with a bicuspid aortic valve.
Fig. 9: Volumetric rendering showing high origin of the RCA.
References: Pictorial essay: Coronary artery variants and anomalies - Scientific Figure on ResearchGate. Available from: https://www.researchgate.net/figure/High-origin-of-the-RCA-VRT-image-shows-the-RCA-RC-arising-from-the-root-of-the-aorta_fig9_26831393
Fig. 10: Clay model with yellow artery demonstrating high origin of the RCA (white arrow).
Pre-pulmonic, Transseptal, or Retroaortic course:
Most commonly, a retroaortic artery arises from the contralateral coronary cusp and supplies the LMCA or left circumflex artery. While there is no hemodynamically significant consequence of this anomaly, this artery can complicate aortic valve replacement. Pre-pulmonic or transseptal courses may also complicate surgery, but are generally incidentally noted on pre-surgical imaging.
Fig. 11: CT images of the anomalous LMCA (arrowhead) arising from the right coronary cusp. Arrow = LAD. B = transseptal course, c= retroaortic course, d = prepulmonic course.
References: Prepulmonic Case courtesy of Dr. Yune Kwong, Radiopaedia.org, rID: 29253
Fig. 12: CT images of the anomalous LMCA (arrowhead) arising from the right coronary cusp. Arrow = LAD. B = transseptal course, c= retroaortic course, d = prepulmonic course.
References: Prepulmonic Case courtesy of Dr. Yune Kwong, Radiopaedia.org, rID: 29253
Fig. 13: CT images of the anomalous LMCA (arrowhead) arising from the right coronary cusp. Arrow = LAD. B = transseptal course, c= retroaortic course, d = prepulmonic course.
References: Prepulmonic Case courtesy of Dr. Yune Kwong, Radiopaedia.org, rID: 29253
Fig. 14: Clay models demonstrating the different courses. Anomalous vessels are portrayed in yellow - transseptal course
Fig. 15: Clay models demonstrating the different courses. Anomalous vessels are portrayed in yellow - retroaortic course.
Fig. 16: Clay models demonstrating the different courses. Anomalous vessels are portrayed in yellow - prepulmonic course.