Coronary anomalies

The systematic approach

Ask five questions every time

1. Where is the ostium? Name the sinus, height, relation to commissures, and whether origins are separate or shared.
2. What is the proximal morphology? Take-off angle, ostial shape, narrowing, calibre, and intramural length.
3. What course does the vessel take? Interarterial, retroaortic, prepulmonic, intraseptal/subpulmonic, or another defined route.
4. Where does it terminate? Normal myocardial bed, chamber, coronary sinus, pulmonary artery, or another vessel.
5. What is the consequence? Ischaemia, infarct, ventricular dysfunction, dilation/aneurysm, shunt, collateralisation, or no secondary effect.

Why CCTA excels

CT turns a two-dimensional mystery into a three-dimensional relationship

Invasive angiography shows the lumen superbly but can struggle to locate an ectopic ostium and to prove how a vessel relates to the aorta, pulmonary trunk, and septum. CCTA displays ostial morphology, vessel wall, great-vessel relationships, intramural length, distal course, and extracardiac anatomy.

CT anatomy is one part of risk assessment. Symptoms, age, exertional association, arrhythmia, ventricular function, and appropriately chosen physiological/ischaemia testing also matter.

Organise before memorising

Origin, course, termination, and intrinsic anatomy

Not every variant is dangerous. Risk follows the actual morphology and physiological consequence, not the mere presence of unusual anatomy.

Anomalies of origin

High take-off, separate ostia, and single coronary artery

• High take-off: ostium above the sinotubular junction. Record vessel, height, angle, and any proximal narrowing; it matters for catheterisation and aortic surgery.
• Multiple ostia: separate LAD/LCx, conus, or nodal origins can be benign variants. Map each before declaring a branch absent.
• Single coronary artery: the entire coronary tree arises from one ostium. Prognosis depends on the route of the branch supplying the opposite territory—not on “single” alone.
• Commissural origin: note proximity to an aortic commissure and whether a shared wall/intramural segment is present.
• Ostial atresia: absence/obliteration of the expected ostium with collateral-dependent filling; distinguish from technical nonvisualisation or chronic occlusion.

Measure ostial height and proximal calibre in double-oblique planes aligned with the root. A VRT can orient the reader, but source and MPR images must establish the diagnosis.

Name the route precisely

The four classic proximal courses

Use anatomy, not “malignant/benign,” as the primary language. Those binary labels can conceal important features and do not substitute for individual risk assessment.

Anomalous aortic origin

Opposite-sinus origin: the vessel and course both matter

AAOCA includes an RCA arising from the left sinus (R-AAOCA) or a left coronary/LAD arising from the right sinus (L-AAOCA), among other configurations. The anomalous left coronary supplying a large myocardial territory is generally of greater concern, but anatomy, symptoms, age, and ischaemia all influence risk.

• State whether the ostia are separate, adjacent, or share a common ostium.
• Name the precise sinus and relation to the commissures.
• Identify every course component; a vessel can have both intramural and interarterial segments.
• Measure the length of intramural/interarterial course and the narrowest proximal calibre.
• Assess ostial shape, take-off angle, proximal ellipticity, and any systolic narrowing if multiphase data exist.

The crucial distinction

Intramural is within the aortic wall; interarterial is between great arteries

An intramural coronary shares the aortic wall for a distance before exiting into mediastinal fat. An interarterial coronary runs in the space between the aorta and pulmonary trunk/RVOT. They frequently coexist but are not synonymous; an intramural segment can exist without an interarterial course.

The 2026 international nomenclature initiative reserves “IM” specifically for the shared aortic-wall segment and allows multiple applicable course descriptors. Clear prose should accompany any abbreviation.

Risk morphology

High-risk features are a constellation

• Interarterial course, particularly involving the left coronary system.
• Intramural aortic-wall course and longer intramural length.
• Slit-like/fish-mouth ostium or ostial stenosis.
• Acute take-off angle and tangential origin.
• Proximal narrowing, elliptic compression, or hypoplasia.
• Dynamic systolic compression on multiphase imaging.
• Exertional syncope/chest pain, documented ventricular arrhythmia, ischaemia, or prior aborted sudden death.

Mechanisms may include a restricted ostium, compression of an intramural segment, dynamic deformation with aortic expansion, and limited coronary flow reserve. External “squeezing between two great vessels” alone is an incomplete explanation.

Wrong great vessel

ALCAPA and ARCAPA

In ALCAPA, the left coronary arises from the pulmonary artery; in ARCAPA, the RCA does. After pulmonary pressure falls, coronary steal and collateral-dependent retrograde flow can produce ischaemia, infarction, mitral regurgitation, ventricular dysfunction, or sudden death.

• Show the pulmonary ostium and exact sinus/segment of origin.
• Map enlarged tortuous donor coronary and intercoronary collaterals.
• Look for dilated recipient vessel, retrograde route, LV dysfunction, infarct/fat/calcification, and papillary-muscle consequences.
• Distinguish true pulmonary origin from a coronary-to-pulmonary artery fistula.

Anomalous termination

Coronary artery fistula: trace from donor to drainage

A fistula bypasses the myocardial capillary bed and connects a coronary artery to a chamber or vessel. Drainage to a low-pressure right-sided structure is common. The donor may become dilated and tortuous; complications include steal, volume overload, aneurysm, thrombosis, endocarditis, and rupture.

1. Name every feeding coronary artery and ostial origin.
2. Trace the full tortuous course in thin images—do not stop at the largest aneurysmal segment.
3. Measure maximal calibre and any aneurysm; note thrombus/calcification.
4. Identify the exact drainage site and number of exit points.
5. Assess chamber enlargement, pulmonary artery dilation, and other shunt effects.
6. Provide images that show relationships relevant to catheter or surgical closure.

Intrinsic course variant

Myocardial bridging: an intramyocardial coronary segment

A bridged segment—most commonly mid LAD—dives beneath myocardium and returns to the epicardial surface. “Myocardial bridge” should not be called an intramural aortic course; these are anatomically different.

• Report artery/segment, length, and depth when clinically relevant.
• Describe systolic compression only if multiphase images demonstrate it; CTCA acquired in one phase may not assess dynamic severity.
• Review proximal plaque, since altered shear may be associated with atherosclerosis before the bridge.
• Most bridges are incidental; symptoms and physiology determine significance.

Branching anomalies

Dual LAD and coronary duplication

Dual LAD consists of a short LAD and a long LAD reaching the distal anterior interventricular groove by different routes. Multiple subtypes exist, including long LAD origin from the opposite sinus. The practical task is to identify both channels and their origins/courses.

A short LAD should not be mistaken for a mid-LAD occlusion when a long LAD supplies the distal groove. This distinction matters in bypass planning and prevents accidental ligation. Similarly, duplicated RCA/PDA or split branches should be described anatomically rather than forced into a familiar tree.

Workstation sequence

How to prove an anomaly

1. Use axial images to find all ostia and exclude motion/partial-volume error.
2. Create double-oblique root views to define sinus, commissure, ostial angle, and shape.
3. Trace the entire vessel with curved MPR; keep source images linked.
4. Use short-axis cross-sections to assess ellipticity and narrowing.
5. Map relation to aorta, pulmonary trunk/RVOT, and septum in orthogonal planes.
6. Review all available phases for dynamic change when relevant and diagnostic.
7. Use VRT only after the anatomy is proven; label aorta, pulmonary artery, ostium, and course.
8. Search deliberately for secondary effects and coexisting atherosclerosis.

A surgeon-useful handoff

Structured anomaly report

Example: “RCA arises from the left coronary sinus immediately adjacent to the left main ostium, with an acute take-off and slit-like ostium. The proximal 12 mm has an intramural aortic-wall course followed by a 9 mm interarterial course between the aortic root and pulmonary trunk, with moderate proximal elliptic narrowing. Distal RCA anatomy is otherwise conventional and right dominant.”

Anatomy informs; it does not decide alone

Connect CT to symptoms and physiology

Current adult congenital guidance recommends anatomic definition plus evaluation for physiological/ischaemic consequences when opposite-sinus origin is suspected. Management depends on the specific artery, high-risk morphology, symptoms, documented ischaemia/arrhythmia, age, comorbidity, and expert multidisciplinary assessment.

• Do not promise safety from a negative pharmacological test when dynamic exertional compression remains plausible.
• Do not recommend surgery solely from an imprecise “interarterial” label; provide the features needed for risk stratification.
• After repair, define the intervention and evaluate the relevant complications—residual ostial narrowing, kinking, graft patency, neo-ostium, or recurrent fistula.

Apply the five questions

Worked anomaly cases

Case A · LCx from right sinus, behind the aorta

Anomalous LCx with retroaortic course—usually not a high-risk ischaemic route, but important before aortic/mitral surgery. State origin, course, and any compression/plaque.

Case B · RCA from left sinus, between great arteries

Do not stop at interarterial. Assess separate/common ostium, acute angle, slit-like opening, intramural segment/length, proximal narrowing, and symptoms/ischaemia.

Case C · Left coronary from right sinus, through septum

Prove intraseptal/subpulmonic course in orthogonal images and distinguish it from an interarterial route. Describe any intramural aortic-wall component separately.

Case D · Giant tortuous RCA draining to coronary sinus

Coronary fistula. Map feeding ostium, maximum diameter/aneurysm, thrombus, full route, exact drainage site, and right-sided volume/shunt effects.

Case E · Short LAD seems to end, but another vessel enters distal groove

Consider dual LAD. Trace the long LAD to its origin and define its course; do not diagnose chronic LAD occlusion from the short channel alone.

Active recall

Self-test: answer before opening

Printable quick revision

One-page coronary anomaly card

• AAOCA: origin ≠ course ≠ intramurality—report each.
• High-risk anatomy: slit ostium, acute angle, intramural length, proximal ellipticity/narrowing, dynamic compression.
• Courses: behind aorta = retroaortic; before PA = prepulmonic; through septum = intraseptal; between great arteries = interarterial.
• Fistula: feeder → full route → aneurysm → drainage → shunt effect.
• ALCAPA/ARCAPA: prove pulmonary origin and collateral/ventricular consequences.
• Bridge: artery, segment, length, depth, dynamic compression if available.
• Dual LAD: find short and long channels before calling occlusion.
• Final rule: VRT shows the map; axial/MPR proves the anatomy.

Provenance

Sources and scope

This chapter follows the Webinar 3 coronary anomaly talk, approximately 18:37–46:39. Automated captions contain transcription errors; terminology and risk framing were checked against current guidance.

1. 2025 ACC/AHA multisociety guideline for adults with congenital heart disease — current AAOCA anatomic/physiological assessment and management context.
2. 2026 international standardized nomenclature for anomalous aortic origin — precise origin and course terminology, including intramural definition.
3. SCCT Interpretation and Reporting of CCTA: 2026 Update — systematic coronary review and mandatory anomaly reporting.
4. SCCT congenital cardiac CT expert consensus — ostial anatomy, angulation, proximal course, intramurality, and dominance.

Educational material only. Clinical significance and management require patient-specific specialist assessment. Nomenclature continues to evolve; accompany abbreviations with clear anatomical prose. External references require internet; this chapter works offline.