Interarterial course of the left coronary artery

Last revised by Dr Francis Fortin on 27 May 2020

An interarterial course of the left coronary artery is defined as 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.

The incidence of interarterial course of the left coronary artery is estimated at ~1.3% of coronary anomalies, and is feared most because of its association with myocardial ischemia and sudden death in young people.

In many cases of interarterial course of the left coronary artery, other associated anomalies such as slit-like orifice, stenotic ostium, a sharp, acute angle of takeoff, and an intramural aortic segment are also present.

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

  • 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 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, associated symptoms, evidence of myocardial ischemia, and surgeon preference.

Although 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, there are no recommendations for specific surgical technique 6. In practice, there is significant disagreement on the treatment of asymptomatic patients 6

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

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Cases and figures

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  • Case 2: 3D reformat
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  • Case 2: axial MIP
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