Transposition of the Great Arteries — Orientation and Landmarks (3D Model)

Date
October 13, 2025
URL
https://x.com/WithAScalpel/status/1977705731198521448
Categories
TGACardiac Surgery

Transposition of the Great Arteries (TGA) — Orientation, Anatomy, and Surgical Implications

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Definition and segmental diagnosis

Transposition of the great arteries is a conotruncal malformation defined by ventriculo-arterial (VA) discordance: the aorta arises from the morphologic right ventricle (RV) and the pulmonary artery (PA) from the morphologic left ventricle (LV), typically with atrioventricular concordance. In d-TGA (S,D,D) the aorta lies anterior and rightward of the PA; in l-TGA (S,L,L, “cc-TGA”) both AV and VA connections are discordant, leaving a systemic RV despite series circulation [1]. In contemporary practice, the arterial switch operation (ASO) is the standard anatomic repair and >90% of patients now survive to adulthood [1]. PubMed+1

Spatial relationships you must visualize

  • Outflow tracts. The RV infundibulum gives rise to the ascending aorta, coursing anterior to the PA root; the LV outflow is short and non-infundibular, entering the posterior main PA.
  • Great-artery positions. In d-TGA the aorta is anterior/right, the main PA posterior/left, and the trunks run in parallel rather than crossing.
  • Branch PAs. The left PA runs leftward beneath/behind the anterior aorta pre-switch; after the Lecompte maneuver both branch PAs lie anterior to the neoaorta.
  • Coronary ostia. Coronaries originate from the aortic root committed to the RV. The usual pattern is Yacoub A / Leiden 1LCx-2R; variants—single coronary, intramural course, inverted origins, or circumflex from right sinus—drive technical risk during transfer [1,4]. PubMed

Circulatory physiology at birth

Parallel great arteries prevent outlet-level mixing. Survival depends on intercirculatory mixing:

  • Atrial level: patent foramen ovale or balloon atrial septostomy (BAS) if restrictive.
  • Ductal level: PDA maintained with prostaglandin E₁.
  • Ventricular level: VSD (~30–40%) augments mixing but may complicate repair.

    • Without adequate mixing, profound hypoxemia and metabolic acidosis appear early; postnatal fall in PVR can worsen desaturation unless ASD/VSD/PDA shunting is robust [3].

Epidemiology and burden

D-TGA accounts for ~5–7% of congenital heart defects and ~20–30 per 100,000 live births, with a male predominance [3]. PubMed+1

Morphologic associations and variants

  • VSD spectrum: perimembranous (most common), muscular, or malalignment (often with arch hypoplasia or coarctation).
  • LV outflow anatomy: typically unobstructed in “simple” TGA; subpulmonary stenosis suggests TGA/VSD/PS spectrum and may redirect strategy to Rastelli-type repairs rather than ASO.
  • Aortic arch anomalies: coarctation/arch hypoplasia require single-stage repair with the switch.
  • Coronary variants: the most consequential anatomic variable for ASO risk. Intramural or interarterial courses mandate unroofing and tailored transfer (button, trap-door, or hood). Late coronary stenosis/occlusion is reported in ~8–10% overall and clusters with certain patterns (e.g., Yacoub type D with a long retroaortic circumflex) [4,5]. PubMed+1

Imaging pearls

  • Echocardiography: defines segmental connections, great-artery relationship, coronary origins (high parasternal short-axis), mixing sites, and branch PA caliber.
  • CT angiography: complements ECHO when coronary anatomy is complex (e.g., intramural or high-takeoff courses) and is valuable in late surveillance [4,5].
  • Cardiac MRI: useful beyond infancy for PA geometry, neoaortic root dimensions, and ventricular–arterial coupling.

Operative strategy — Arterial Switch Operation (ASO)

Timing. Early neonatal repair (first 1–2 weeks) preserves LV preparedness for systemic work; late presenters may require LV retraining [1].

Core steps and anatomic logic.

  1. Control pulmonary blood flow; institute CPB.
  2. Transect both great arteries above the sinotubular junctions.
  3. Transfer coronaries as buttons to the neoaortic root (prior PA root), tailoring button size/height and take-off angle to avoid tension, kinking, or ostial distortion; intramural segments require unroofing and separate buttons [1,4].
  4. Lecompte maneuver: bring the PA confluence anterior to the neoaorta to avoid compression.
  5. Reconstruct great arteries: neoaortic anastomosis (with STJ tailoring as needed); neopulmonary sinus reconstruction and main-PA anastomosis without torsion or caliber mismatch.
  6. Concomitant procedures as indicated: VSD closure, arch repair, relief of LVOT/RVOT obstruction.

Coronary transfer pitfalls.

  • Button too small → ostial stenosis; too large/low → sinus or leaflet injury.
  • Adverse take-off, twist, or tension → early ischemia/late kinking.
  • Intramural course → residual narrowing if unroofing is incomplete [4].

Early postoperative focus

  • Ischemia surveillance: continuous ECG, lactate kinetics, and echocardiography for regional wall-motion abnormalities.
  • PA pathway: evaluate for branch PA stenosis after Lecompte and check neopulmonary valve competence.
  • Neoaortic valve/root: mild early regurgitation is common; monitor for progressive root dilation over time.
  • Residual shunts/arch issues: confirm with echocardiography prior to discharge.

Outcomes and late considerations

Evidence across eras shows excellent survival after ASO. A 151-study meta-analysis (30,186 patients) reported 92% short-term, 90% medium-term (1–20 y), and 87% long-term (>20 y) survival [2]. Large single-center cohorts corroborate high survival with low rates of major cardiovascular events at 25 years, while highlighting coronary events, branch PA stenosis, and neoaortic dilation/regurgitation as leading late sequelae [5]. Branch PA stenosis is the most frequent cause for reintervention and is influenced by preoperative anatomy and post-Lecompte geometry [6,7]. Lifelong care in adult congenital heart disease (ACHD) programs is recommended; professional society guidance endorses at least one anatomic coronary assessment (CTA/MRA/catheter) in asymptomatic adults after ASO, with symptom-triggered reassessment thereafter [7]. PMC+3PubMed+3PubMed+3

Practical mental model for trainees

  1. Visualize the aorta anterior-right off the RV infundibulum and the PA posterior-left off the LV—two parallel trunks.
  2. Identify where mixing occurs (ASD/VSD/PDA) and whether it suffices.
  3. Map the coronaries first—their origins and paths determine ASO strategy and risk.
  4. After ASO, remember the new geometry: neopulmonary anterior, neoaorta posterior; ensure straight, non-angulated reconstructions.

References

[1] Villafañe J, Lantin-Hermoso MR, Bhatt AB, et al. D-transposition of the great arteries: the current era of the arterial switch operation. J Am Coll Cardiol. 2014;64(5):498-511.

[2] Morfaw F, Leenus A, Mbuagbaw L, et al. Outcomes after corrective surgery for congenital dextro-transposition of the arteries using the arterial switch technique: a scoping systematic review. Syst Rev. 2020;9(1):231.

[3] Martins P, Castela E. Transposition of the great arteries. Orphanet J Rare Dis. 2008;3:27.

[4] Ou P, Khraiche D, Celermajer DS, et al. Mechanisms of coronary complications after the arterial switch for transposition of the great arteries. J Thorac Cardiovasc Surg. 2013;145(5):1263-1269.

[5] Khairy P, Clair M, Fernandes SM, et al. Cardiovascular outcomes after the arterial switch operation for D-transposition of the great arteries. Circulation. 2013;127(3):331-339.

[6] Luo S, Yuan J, Liu C, et al. Branch pulmonary artery stenosis after arterial switch operation: effect of preoperative anatomic factors on reintervention. J Thorac Cardiovasc Surg. 2022;164(2):317-327.e8.

[7] Breinholt JP, Sabri M, Aziz PF, et al. Management of the adult with arterial switch. Methodist DeBakey Cardiovasc J. 2019;15(3):193-201.