A transseptal, intraseptal or subpulmonic course refers to a coronary artery passing anteriorly and inferiorly to the aortic valve in a subpulmonic route through the interventricular septal myocardium and is mostly described as a ‘benign anomalous course’ without hemodynamic significance.
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Epidemiology
Associations
Clinical conditions associated with a transseptal course of a coronary artery include 1-3:
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other congenital coronary artery anomalies
ectopic origin of the left anterior descending artery
ectopic origin of the left main coronary artery
other forms of congenital heart disease
Clinical presentation
Similar to a retroaortic course a transseptal course is often not of increased hemodynamic risk especially if subpulmonic and might be found incidentally on invasive coronary angiography (ICA), cardiac CT or cardiac MRI. Other conceivable symptoms include angina or arrhythmia 4.
Radiographic features
A transseptal or intraseptal course is usually associated with an ectopic origin of either the left anterior descending artery, left main coronary artery or right coronary artery. It can be depicted in coronary CTA or coronary MRA or invasive coronary angiography (ICA) as a major coronary artery coursing through the interventricular septum 1-4.
Features indicating a transeptal course versus an interarterial course include the following 1:
artery surrounded by the myocardium of the interventricular septum
a downward course below the crista supraventricularis (hammock sign)
no slitlike or oblong orifice
Radiology report
The radiology report should include a description of the following features:
right coronary artery origin, course, segments
left main coronary artery origin and variant anatomy
left anterior descending artery with course branches and segments
circumflex artery with course, branches and segments
coronary artery disease and stenoses with location based on the AHA coronary artery segment model
any associated congenital cardiovascular anomalies
Treatment and prognosis
A retroaortic course is considered benign and not of hemodynamic importance. Management will entirely depend on symptoms and associated findings. However, it can complicate aortic valve surgery 1.
Differential diagnosis
A condition that can mimic the radiological appearance of a transseptal course is an interarterial course, the latter is associated with an increased risk of sudden cardiac death 1,2.
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