**5.3.4 Preaortic course without intramural segment (type D)**

As mentioned before, a preaortic course without intramural segment is possible, for example an ectopic vessel with an orthogonal take-off from the contralateral or a high origin from the aorta. The ectopic course is juxtamural with the aorta. Making a distinction between preaortic course without intramural segment and preaortic course with intramural course is essential, while the latter has a recognized higher risk of life-threatening symptoms.

### **5.3.5 Retroaortic course (type E)**

The retroaortic course, the most commonly encountered ectopic course, is also the easier to diagnose. This course involves, almost without exception, the LCA. Unlike other coronary arteries, the CX coronary artery is associated, to the exclusion of uncommon patterns, with the same ectopic course, i.e. a retroaortic course. The ectopic vessel courses first behind or more precisely below the aorta, then crosses between the aortic root and the left atrium with a juxtamural course, and finally emerges into the left atrioventricular groove between the left atrial appendage and the left atrium (figure 12).

Fig. 11. Volume-rendered computed tomography images of an ectopic right coronary artery

As mentioned before, a preaortic course without intramural segment is possible, for example an ectopic vessel with an orthogonal take-off from the contralateral or a high origin from the aorta. The ectopic course is juxtamural with the aorta. Making a distinction between preaortic course without intramural segment and preaortic course with intramural course is essential, while the latter has a recognized higher risk of life-threatening

The retroaortic course, the most commonly encountered ectopic course, is also the easier to diagnose. This course involves, almost without exception, the LCA. Unlike other coronary arteries, the CX coronary artery is associated, to the exclusion of uncommon patterns, with the same ectopic course, i.e. a retroaortic course. The ectopic vessel courses first behind or more precisely below the aorta, then crosses between the aortic root and the left atrium with a juxtamural course, and finally emerges into the left atrioventricular groove between the

(arrow) arising from the left sinus with a preaortic course tangential to the aorta.

**5.3.4 Preaortic course without intramural segment (type D)** 

symptoms.

**5.3.5 Retroaortic course (type E)** 

left atrial appendage and the left atrium (figure 12).

Fig. 12. Computed tomography imaging of anomalous connection of the left main coronary artery (arrow) with the right sinus close to the right coronary artery (arrowhead). LA : left atrium.
