Intramural versus septal course for anomalous interarterial coronary arteries

Imaging description Coronary artery anomalies are important to recognize due to their association with sudden cardiac death. Anomalous coronary arteries originating from the opposite aortic cusp with an interarterial course between the aorta and pulmonary artery are the highest risk, whereas septal, prepulmonic, and retroaortic courses are generally considered benign. Among patients with interarterial course, the presence of intramural coronary artery segments, in which the coronary artery courses within the wall of the aorta between layers of the media, is considered to further increase risk for sudden cardiac death. Intramural segments can be recognized by a slit-like orifice, acute angle of origin from the aorta, and an elliptical shape on sagittal oblique image (Figure 36.1). Interarterial course of the coronary arteries, with or without intramural segments, is important to distinguish from the septal course, which is generally accepted to be a lower-risk lesion. In the septal course, the left main coronary artery passes beneath the pulmonary valve, travels intramyocardially through the basilar interventricular septum, and exits in the anterior interventricular groove where it bifurcates into left anterior descending and circumflex coronary arteries (Figure 36.2). In this variant, the coronary artery main-tains a uniform round shape throughout its course, unlike the elliptical shape seen in intramural coronary artery segments. Importance The distinction of septal and interarterial courses of anomalous coronary arteries is important for patient management, given the elevated risk of sudden cardiac death associated with the latter. In patients with true interarterial course, characterization of intramural segments is important, not only because they confer greater risk, but also because they have a specific surgical management. Intramural segments can be managed through an unroofing procedure, in which the internal aortic wall is excised from the intramural segment, creating a neoostium and eliminating the intramural narrowing. Septal anomalies are often managed conservatively. Typical clinical scenario Coronary artery anomalies are rare, affecting less than 1% of the population; however, they are the second most common cause of sudden cardiac death in athletes after hypertrophic cardiomyopathy.