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PubMed This is a summary of 15 peer-reviewed journal articles Updated
Pediatric Cardiology

The Anatomy of Transposition: D-TGA, L-TGA, and Associated Defects

At a Glance

Transposition of the Great Arteries (TGA) is a congenital heart defect where the two main arteries leaving the heart are swapped. D-TGA creates separate blood loops requiring prompt surgery, where success largely depends on carefully transferring the heart's tiny coronary arteries.

To understand Transposition of the Great Arteries (TGA), it helps to think of the heart as a house with two separate plumbing systems.

The Normal Heart: Normally, the strong left lower chamber (Left Ventricle) pumps red, oxygen-rich blood out through the aorta to the body. The right lower chamber (Right Ventricle) pumps blue, oxygen-poor blood out through the pulmonary artery to the lungs to get more oxygen.

In TGA, the pipes are connected to the wrong “pumps,” which changes how oxygen moves through the body [1].

The Two Types: D-TGA vs. L-TGA

While both involve “swapped” arteries, they affect the body in very different ways.

D-TGA (Dextro-transposition):
In this form, the two main “pipes” leaving the heart—the aorta and the pulmonary artery—are swapped [2]. This creates two separate loops that never meet. The blue blood just keeps circling from the body to the heart and back to the body, never picking up oxygen. Meanwhile, the red blood just circles between the heart and the lungs [3]. This is why D-TGA is a medical emergency at birth; the body cannot survive without a way for these two loops to mix.

L-TGA (Levo-transposition):
(Note: If your baby has D-TGA, you can skip this section, as L-TGA is a completely different, much rarer condition.)
Also known as Congenitally Corrected TGA, this is a “double swap.” Not only are the arteries swapped, but the heart’s lower chambers (ventricles) are also swapped [4][5]. Because of this double error, the blood actually ends up going to the right places [5]. However, the chamber now pumping blood to the whole body is the right ventricle, which is naturally thinner and designed only to pump blood a short distance to the lungs [6]. Over time, this “wrong pump” can become tired and fail [7].

Associated Heart Defects

TGA rarely happens in isolation. Most babies will have other structural differences that doctors must account for:

  • Ventricular Septal Defect (VSD): This is a hole in the wall (septum) between the heart’s two lower chambers. In D-TGA, a VSD can actually be helpful initially because it allows the “red” and “blue” blood loops to mix, providing the body with some oxygen [2]. However, it must still be repaired during surgery.
  • Pulmonary Stenosis (PS): This is a narrowing of the exit to the lungs. If a baby has both a VSD and PS, it can significantly change the type of surgery they need [2][8].

The Critical Role of Coronary Arteries

The most complex part of TGA surgery isn’t swapping the big pipes; it’s moving the tiny “fuel lines” that feed the heart muscle itself—the coronary arteries [9].

About 33% of babies with TGA have unusual coronary artery patterns [10]. For the Arterial Switch Operation (ASO) to be successful, the surgeon must carefully detach these tiny vessels and re-attach them to the new aorta [11]. If these arteries are pinched, twisted, or in an unusual spot (like an intramural course where the artery travels inside the heart wall), it increases the complexity of the surgery [12][13]. This is why doctors use detailed “mapping,” often via echocardiogram or CT scan, to plan the surgery with extreme precision [14][15].

Common questions in this guide

What is the difference between D-TGA and L-TGA?
In D-TGA, the two main arteries leaving the heart are swapped, creating two separate blood loops that do not mix. In L-TGA, both the arteries and the lower heart chambers are swapped, allowing blood to flow to the correct places but putting long-term strain on the right ventricle.
Why is a Ventricular Septal Defect (VSD) sometimes helpful in D-TGA?
A VSD is a hole between the lower heart chambers. In babies born with D-TGA, this hole actually allows oxygen-rich and oxygen-poor blood to mix, which provides the body with some needed oxygen before surgery.
Why are coronary arteries so important in TGA surgery?
Coronary arteries are tiny blood vessels that supply oxygen directly to the heart muscle. During the Arterial Switch Operation, surgeons must carefully detach and move these arteries to the new aorta, which can be complex if they have unusual branching patterns.
What does it mean if my baby has an intramural coronary artery?
An intramural coronary artery is one that travels inside the wall of the heart rather than on the surface. This unusual pathway makes moving the arteries during surgery more complex and requires precise planning by the surgical team using advanced imaging.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Based on the imaging, what is the exact branching pattern of my baby's coronary arteries?
  2. 2.Is there an 'intramural' coronary artery, and how does that change the surgery?
  3. 3.Does my baby have a Ventricular Septal Defect (VSD), and is it large enough to affect how blood mixes before surgery?

Questions For You

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References

References (15)
  1. 1

    A unique indication for the senning procedure: Atrioventricular discordance with ventriculoarterial concordance.

    Hermsen JL, Okorie UC, Srinivasan S, et al.

    Journal of cardiac surgery 2020; (35(2)):444-446 doi:10.1111/jocs.14342.

    PMID: 31793037
  2. 2

    Pathogenesis and Surgical Treatment of Dextro-Transposition of the Great Arteries (D-TGA): Part II.

    Zubrzycki M, Schramm R, Costard-Jäckle A, et al.

    Journal of clinical medicine 2024; (13(16)) doi:10.3390/jcm13164823.

    PMID: 39200964
  3. 3

    Mechanisms for heart failure in systemic right ventricle.

    Andrade L, Carazo M, Wu F, et al.

    Heart failure reviews 2020; (25(4)):599-607 doi:10.1007/s10741-019-09902-1.

    PMID: 31853794
  4. 4

    Cardiac Conduction System in Congenitally Corrected Transposition of the Great Arteries and Its Clinical Relevance.

    Baruteau AE, Abrams DJ, Ho SY, et al.

    Journal of the American Heart Association 2017; (6(12)) doi:10.1161/JAHA.117.007759.

    PMID: 29269355
  5. 5

    Incidental congenitally corrected transposition of the great arteries (ccTGA) in an adult with suspected coronary artery disease: review on radiological features and pathophysiology.

    Sayuti KA, Azizi MYSB

    BMJ case reports 2020; (13(4)) doi:10.1136/bcr-2019-234225.

    PMID: 32327461
  6. 6

    Congenitally corrected transposition of the great arteries (CCTGA).

    Grech N, Borg A, Sammut MA, Caruana M

    BMJ case reports 2021; (14(6)) doi:10.1136/bcr-2021-242069.

    PMID: 34108155
  7. 7

    Prognostic Implications of Progressive Systemic Ventricular Dysfunction in Congenitally Corrected Transposition of Great Arteries.

    Egbe AC, Miranda WR, Jain CC, Connolly HM

    JACC. Cardiovascular imaging 2022; (15(4)):566-574 doi:10.1016/j.jcmg.2021.09.016.

    PMID: 34801447
  8. 8

    Contemporary management and outcomes in congenitally corrected transposition of the great arteries.

    Kutty S, Danford DA, Diller GP, Tutarel O

    Heart (British Cardiac Society) 2018; (104(14)):1148-1155 doi:10.1136/heartjnl-2016-311032.

    PMID: 29326110
  9. 9

    The influence of coronary artery anatomy on mortality after the arterial switch operation.

    Fricke TA, Bell D, Daley M, et al.

    The Journal of thoracic and cardiovascular surgery 2020; (160(1)):191-199.e1 doi:10.1016/j.jtcvs.2019.11.146.

    PMID: 32222408
  10. 10

    Coronary Artery Anomalies in Patients With Transposition of the Great Arteries and Their Impact on Postoperative Outcomes.

    Moll M, Michalak KW, Sobczak-Budlewska K, et al.

    The Annals of thoracic surgery 2017; (104(5)):1620-1628 doi:10.1016/j.athoracsur.2017.03.078.

    PMID: 28648541
  11. 11

    Corridor technique for coronary arteries from a single arterial sinus.

    Agematsu K, Nagashima M, Nishimura Y, Higaki T

    Asian cardiovascular & thoracic annals 2020; (28(6)):333-335 doi:10.1177/0218492320937506.

    PMID: 32551840
  12. 12

    Mid-Term Outcomes of Primary Arterial Switch Operation for Taussig-Bing Anomaly.

    Gu M, Hu J, Dong W, et al.

    Seminars in thoracic and cardiovascular surgery 2023; (35(3)):562-571 doi:10.1053/j.semtcvs.2022.06.001.

    PMID: 35691468
  13. 13

    Coronary artery augmentation with the right subclavian artery for single coronary artery variants of dextro transposition of the great arteries treated by an arterial switch operation.

    Issa HMN, Lalani S, Drake RE, Gandhi SK

    JTCVS techniques 2022; (13()):139-143 doi:10.1016/j.xjtc.2022.02.030.

    PMID: 35711182
  14. 14

    Identification of coronary artery anatomy on dual-source cardiac computed tomography before arterial switch operation in newborns and young infants: comparison with transthoracic echocardiography.

    Goo HW

    Pediatric radiology 2018; (48(2)):176-185 doi:10.1007/s00247-017-4004-9.

    PMID: 29032431
  15. 15

    Can we predict potentially dangerous coronary patterns in patients with transposition of the great arteries after an arterial switch operation?

    Michalak KW, Sobczak-Budlewska K, Moll JJ, et al.

    Cardiology in the young 2019; (29(11)):1350-1355 doi:10.1017/S104795111900204X.

    PMID: 31507258

This page explains TGA heart anatomy for educational purposes. Your pediatric cardiologist and cardiothoracic surgeon are the best sources for understanding your baby's specific heart structure and surgical plan.

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