An anomalous coronary artery arising from the opposite sinus usually takes four common courses:
- interarterial
- retroaortic
- prepulmonic
- septal (subpulmonic)
In the case above, the course of the LAD is septal (subpulmonic). This can be difficult to differentiate from a malignant interarterial course, but a septal LAD has a more inferior position. Also a septal LAD is usually surrounded by myocardium compared to the interarterial course where it is surrounded by epicardial fat. A septal LAD also has a downwards course giving the 'hammock sign', and usually does not have an oblong or slit-like orifice, unlike the inter-arterial variant.