1. Transposition of the Great Arteries
Francesca N. Delling, MD
January 11, 2009

2. Cardiac Tube
At the end of the third week of development one is left with a 5 chamber cardiac tube
1. Sinus Venosus – absorbed into the RA and contributes to formation of sinus node
anterior cardinal veins become the IVC
posterior cardinal veins become the SVC and coronary sinus
2. Atrial canal – develops into the atria
3. Ventricular canal – develops into the left venticle
4. Bulbis Cordis – develops into the RV and LV outflow tract (subpulmonic muscular conus and subaortic muscular conus. The subpulmonic conus elongates and the subaortic conus resorbs, allowing the aorta to move posteriorly and connect with the left ventricule: resorption of the subpulmonic instead of the subaortic conus may be central to transposition of the great arteries.
Then ends of the tube are fixed – as the tube grows it is forced to bulge and twist.
Looping of the heart tube changes it into a more complex structure consisting of two atria and two ventricles – the key is looping to the right

3. Heart is the 1st structure to demonstrate L-R asymmetry
1. Looping of the primitive heart tube ventrally and to the right to form the d-loop
2. D-loop places the bulbus cordis (future RV) to the right and the primitive ventricle to the left (future LV)
3. The postlooped heart then rotates slightly to place the RV in front of the left. The AV canal is devided by the endocardial cushions into the tricuspid and mitral orifices

4. Complete Transposition of the Great Arteries
Ventriculoarterial discordance
Also known as d-TGA
(d = dextroposition of the
bulboventricular loop)
Aorta on the right and anterior
1. Aorta arises from the morphological RV
2. Pulmonary artery arises from the LV

5. Complete Transposition of the Great Arteries
Systemic and pulmonary circulation
run in parallel  need for a
communication between the two -
ASD, VSD (most common), or
PDA to support life
One of the most common cyanotic
defects in the newborns
If circulatory mixing via
PDA, its physiological closure
 abrupt cyanosis and
deterioration  need for Rashkind
atrial balloon septostomy until
definite surgery
When the ventricular septum (or atrial septum) is intact D-TGA is cyanotic in the first day of life (due to circulatory mixing via PDA).

6. Atrial switch procedures
Senning (1958):
atrial baffle from autologous tissue to direct the venous return to the contralateral AV valve and ventricle
Deoxygenated blood from the vena cava is directed to the MV and LV, PA, and PV blood is directed into the morphological RV and aorta

7. Atrial switch procedures
Mustard: atrial septum is excised, baffle is created with synthetic material
Deoxygenated blood from the vena cava is directed to the MV and LV, PA, and PV blood is directed into the morphological RV and aorta. Both procedures provide excellent midterm results but are associated with long term complications

8. Late complications of atrial switch procedures:
Arrhythmias
Late development of both brady and tachyarrhythmias
Sinus node dysfunction common in adults
Series of 534 children by Gelatt et al (J Am Coll Cardiol.1997;29: )
- NSR in 77% at 5 years, 40% at 20 years
- 11% needed PPM
- 14% had atrial flutter
- 16% had a late death (due to arrhythmias and myocardial
failure)
Ventricular arrhythmias uncommon in the absence of severe
ventricular dysfunction

9. Late complications of atrial switch procedures:
Systemic Ventricular dysfunction and TR
RV is the systemic ventricle
TR secondary to annular dilatation (TVR not indicated) or
damage at the time of VSD repair or endocarditis (TVR
warranted)
Treatment of systemic ventricular dysfunction is challenging:
- No convincing data of utility of ACE-inhibitors
- Caution with the use of beta-blockers (AVB, bradycardia)
- Two-stage repair surgery (pulmonary artery banding
to “retrain” the LV, followed by baffle take-down and
arterial switch) is extensive and LV failure occurs after
pulmonary banding

10. Late complications of atrial switch procedures:
Atrial baffle obstruction and leaks
Obstruction of SVC (with “SVC syndrome”) more common
than IVC (hepatic congestion or cirrhosis).
If significant stenosis, may need percutaneous balloon
and stenting or even surgery
Pulmonary vein stenosis much less common but may
cause PHTN

11. Late complications of atrial switch procedures: Pulmonary hypertension
Occurs in 7% of those who survive to adulthood
Cause unclear (in some cases: PV baffle obstruction)
Risk factors: age > 2, shunts at ventricular or great artery
level before repair (Newfeld EA et al. Am J Cardiol.1974;34: )

12. Comparison between atrial switch procedures
Senning better than Mustard
340 pts (124 Mustard vs. 215 Senning) Heart, 2004; 90:
Mortality
82 deaths (24%)
Senning showed trend to better mortality but not statistically significant
Baffle Obstruction
15% - Mustard
1% - Senning
Senning patients had better functional status

13. Atrial switch procedures and pregnancy
Pregnancy poses a significant volume load that may increase
RV dimensions and is sometimes irreversible
Poses a definite risk of deterioration of functional class, even
if pt is asymptomatic
Risk of congenital heart disease in the offspring, in the absence
of a family history, is probably < 5% (Clarkson PM et al. J Am
Coll Cardiol.1994;24: )

14. Arterial switch procedure
Jatene 1976
Usually performed in the first month of life
Involves: transection of the great arteries, detachment of the coronary arteries with a “button” from the aortic wall
Complications: coronary stenoses with sudden death or MI, RV outflow tract distortion, dilatation of neo-aortic root with AI

15. Rastelli procedure
Used when d-TGA + large subaortic VSD and pulmonary stenosis
A patch directs blood from the LV through the VSD to the aorta (1)
PV is oversewn and a valved conduit is inserted from the RV to the PA to bypass the pulmonary stenosis (2)

16. Rastelli procedure (continued)
Advantages: LV functions as systemic ventricle
Disadvantages:
- Conduit degeneration and stenosis, necessitating reoperation
- Atrial and ventricular arrhythmias with sudden death
- Possible RV and LV failure

17. Echo: parasternal long-axis
Posterior pulmonary artery and anterior aorta aligned rather than in the usual crossing arrangement

18. Parasternal short-axis
Aorta is anterior and on the right

20. Parasternal short-axis base

21. 4-chamber view

22. CMR: 4-chamber

25. LVOT

26. RV 2-chamber

27. Short axis

28. Congenitally corrected Transposition
RA enters the morphological LV  PA, and left atrium communicates
with morphological RV  aorta

29. Congenitally corrected Transposition (continued)
Left-handed looping of the heart tube  morphologic RV in levo-position  AV discordance
Aortopulmonary septum fails to rotate 180  ventriculoarterial discordance (although blood flows in the normal directions, it passes through the “wrong” chamber)
Aorta anterior and to the left, great arteries may be side to side

30. Congenitally corrected Transposition (continued)
Because the TV always enters a morphological RV
it too is on the left side in the systemic circulation and is termed
systemic AV valve
The crux anatomy facilitates recognition of AV morphology because the TV is always lower than the MV and always enters a morphological RV (more difficult to identify, trabeculations are not always easy to see!)
AV concordance
AV discordance

31. Congenitally corrected Transposition:
Associated anomalies
VSD (70%): if large (LR flow), pts present in infancy
or childhood with congestive heart failure. Reversal of flow
R L leads to desaturation
Pulmonary stenosis (40%), commonly subvalvular. Associated
valvular PS also occurs
Abnormalities of the systemic (tricuspid) AV valve (90%)
 Ebstein’s anomaly:
- apical displacement of valve BUT no “saillike” anterior
leaflet

32. Congenitally corrected Transposition:
Conduction anomalies
AV node and His have unusual position
Many have dual AV nodes
Conduction system is vulnerable to fibrosis  2% per
year incidence of CHB

33. Congenitally corrected Transposition:
CXR
Levocardia or dextrocardia: vascular pedicle abnormally straight because ascending aorta is not visible on the R, and the convexities from desc aortic knob and PA are absent on the left; ventricular border is more straight.
Dextrocardia: should be suspected when there is abdominal situs solitus (gastric bubble on the left)
Levocardia
Dextrocardia

34. Congenitally corrected Transposition:
EKG
Ventriculuar excitation begins at the septal endocardium of the right sided LV results in septal vector directed from r to L and posterior
(inversion of the q waves)
Ventriculuar excitation begins at the septal endocardium of the right sided LV

35. Congenitally corrected Transposition:
Echocardiography
Hypertrophied RV on the left
Moderator Band
Apical attachment of the TV

36. Congenitally corrected Transposition:
Echocardiography
Overriding great vessels
a. Aorta arises anteriorly and comes off the RV
b. PA arises posteriorly from the LV

37. Congenitally corrected Transposition:
Echocardiography
anterior and leftward aorta

39. Congenitally corrected Transposition:
Cardiac cath:
hemodynamic assessment of associated anomalies
evaluation of systemic AV valve regurgitation and ventricular
function
MRI: Defines ventricular function and volumes

40. Systemic ventricular failure and AV valve regurgitation
? Cause
Inherent vulnerability to failure
- concordant coronary anatomy: morphological RV perfused
by single right coronary artery with limitations of perfusion
Acar et al. Heart 1999: 20 pts with L-TGA and ETT MIBI 
all 20 had perfusion defects at rest, 17 worsened with exercise
Controversy exists as to which comes first: AV valve
regurgitation or ventricular failure

41. Systemic ventricular failure and AV valve regurgitation
PM implantation may precipitate deterioration in systemic
ventricular function and worsening of AV valve regurgitation
EF 40% prior to PM implantation, mod regurg. 18 months later EF 15% severe regurg

42. Congenitally corrected Transposition:
Surgical repair
Two schools of thought:
Classic approach – fix only the defects associated with the condition (VSD, systemic AV valve regurgitation)
Newer approach is to restore the LV as the systemic ventricle (anatomical repair)
Major advantage is drastically reduces risk of TR which is associated with RV failure and late sudden death

43. Congenitally corrected Transposition:
Classical repair
118 pt classical repair J Thorac Cardiovasc Surg 117 (1999), pp. 1190–1203
15 % operative mortality
56% underwent reoperation within 20 yrs
48% survival rate at 20 years – CHF > 70%

44. Congenitally corrected Transposition: Double switch operation
Venous Switch via Mustard or Senning
Great vessel Switch
Closure of VSD

45. Congenitally corrected Transposition
And VSD
A patch can be inserted to tunnel the LV flow into the aorta, and the morphological RV is connected to the pulmonary artery via
conduit “Rastelli technique”

46. Before anatomic repair (either double switch or Rastelli) LV needs to be prepared to function as a systemic ventricle  pulmonary banding

47. Congenitally corrected Transposition:
Anatomic repair
54 pt restoration of LV – J Thorac CV Surg. 2003;125:
Early mortality 5.6 % (3 pts)
Long term mortality:
1 year – 94% survival
4 year – 90% survival
9 year – 90% Survival vs. Classic 60 – 83% (10 years)

48. Congenitally corrected Transposition:
Anatomic repair
Early mortality of 5% encouraging, but:
- 7 pts with Rastelli needed repeat conduit, aortic valve replacement
or transplantation.
Balloon angioplasty of baffle obstruction or pulmonary stenosis
also needed
Need for re-intervention post anatomic repair confirmed by
more recent paper by Sharma et al (J Thorac Cardiovasc Surg Feb;137)
68 patients (31 Rastelli/atrial switch; 37 arterial switch/atrial rerouting)
early deaths, late re-operations, late deaths (LV dysfunction, tachyarrhytmias
observed in both groups

49. Pregnancy and C-TGA
Women with systemic EF <40% or significant systemic AV
valve regurgitation should be counseled against pregnancy
Series of Connolly et al ( J Am Coll Cardiol.1999;33:1962)
60 pregnancies 22 ♀ resulting in 50 live births (83%)
none of the offspring had congenital heart disease
no pregnancy related deaths
1 woman with significant AV valve regurgitation
1 had CHF
45 pregnancies 19 ♀ (Am J. Card. 1999;84:820-24)
27 live births; 12 miscarriages; 6 elective term
1 child with a congenital heart defect
Mothers with 6 CV events
3 episodes of CHF
2 Episodes of increasing cyanosis, one CVA

50. Antibiotic prophylaxis
Prophylaxis is reasonable in patients with CHD with the highest risk for adverse outcome from infective endocarditis
patients with prosthetic valves
previous endocarditis
unrepaired and palliated CHD
repaired CHD within 6 months after the procedure
repaired CHD with residual defects at or adjacent to the site of a prosthetic patch or prosthetic device that inhibits endothelization ACC/AHA guidelines for the management of adults with congenital heart disease. J Am Coll Cardiol Dec 2;52(23):e1-121

51. References
Carole A. Warnes. Transposition of the great arteries. Circulation 2006;114:
Yale University School of Medicine. Congenital Heart Disease Echo Atlas.

52. Thank you