Interarterial course of the left coronary artery

Last revised by Liz Silverstone on 7 Aug 2023

An interarterial course of the left coronary artery is defined as the origination of the left main or left anterior descending coronary artery from the right coronary sinus of Valsalva, with a course between the ascending aorta and the pulmonary artery trunk. 

An interarterial course is sometimes referred to as a "malignant" coronary arterial course, due to the increased risk of myocardial ischemia or sudden cardiac death in young adults 8,9, particularly during strenuous exercise.

The incidence of interarterial course of the left coronary artery is estimated at ~1.3% of coronary anomalies, however the increasing use of non-invasive imaging is likely to increase the detection rate.

Anatomic and dynamic features on stress imaging may help direct treatment. In many cases of interarterial course of the left coronary artery, associated anomalies such as slit-like orifice, stenotic ostium, a sharp, acute angle of takeoff, and an intramural aortic segment are also present and have been linked to increased risk 7.

Different theories have been postulated as a cause of sudden death in these patients:

  • the most accepted theory is the higher incidence of occlusion of the ostium secondary to a more slit-like orifice

  • occlusion during physical activity due to compression between the major arteries

An intramural segment and its length and angle within the aortic wall (not to be confused with myocardial bridging) further increases the risk of sudden death.

Management of an aberrant left coronary artery with interarterial course is complex and depends on factors which include patient age, the presence of coronary artery disease, associated symptoms, evidence of myocardial ischemia, and surgeon preference.

Although the 2008 American College of Cardiology and American Heart Association guidelines for congenital heart disease generally recommend surgical revascularization of any left main coronary artery lesion with interarterial coarse 5, the evidence base is poor and there are few recommendations for specific surgical technique 6. In practice, there is significant disagreement on the treatment of asymptomatic patients 6 or older patients with co-existing coronary artery disease. Functional imaging can help to define perfusion deficits and determine the relevance of imaging findings. Selected older patients may be managed conservatively with sport-restriction and beta-blockers 7.

Possible interventions include 5:

  • transcatheter coronary artery stented (uncommon)

  • coronary artery bypass grafting

  • coronary artery marsupialization or "unroofing" - opening the intramural portion of the anomalous artery to better communicate with the aortic lumen

  • neo-ostium

  • ostioplasty

  • reimplantation

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