This document discusses the anatomy, embryology, and management of L-TGA (transposition of the great arteries). Some key points: - In L-TGA, the ventricles are inverted such that the morphologic right ventricle is on the left and pumps blood to the lungs, while the morphologic left ventricle is on the right and pumps blood to the body. - Embryologically, abnormal leftward looping of the heart tube during development results in the inverted ventricles. The conduction system and coronary arteries also have abnormal anatomy. - Clinical features may include congenital heart block, progressive tricuspid regurgitation, pulmonary stenosis, and heart failure. Diagn

1. ANATOMY,EMBRYOLOGY
& MANAGEMENT OF L-TGA

2.  Isolated ventricular inversion
 Systemic veins to morph RA, connected
by a MV to an LV, connected to a PA which
is transposed
 Pulmonary veins to morph LA, connected
by a TV to an RV, connected to an Ao
which is transposed
 AV & VA discordance
Introduction

3.  0.03 per 1,000 live births
 0.05% of CHD
 risk in first-degree relatives =2%.

4.  ETIOPATHOGENESIS —
 Parental exposures to hair dye, smoking, & laboratory chemicals

5. EMBRYOLOGY
 22 days gestation …
primitive straight cardiac tube is formed
 Composed of 5 chambers with patterning regulated by homeobox
genes
- Truncus = aorta & PA
- Bulbis = outflow tracts & ventricle

6. • 23 days gestation … straight cardiac tube elongates
& bends forming cardiac loop.
– Cephalic portion bends ventrally, caudally, & right-ward.
– Caudal portion moves dorsally, cranially, & left-ward.
– rotational motion folding over of bulboventricular
portion bringing future ventricles side-by-side.
Embryology

7.  4th-7th weeks gestation … heart divides into 4 chambers via
formation of swellings (cushions) of tissue that exhibit
differential growth.
 Endocardial cushions divide AV canal forming mitral &
tricuspid valves.
 Conotruncal cushions form outflow tracts, aortic &
pulmonary roots.
Embryology

8. EMBRYOLOGY
 5th week gestation … conotruncal
cushions.
 Right superior truncal cushion grows
distally & left-ward.
 Left inferior truncal cushion grows
distally & right-ward.
 net effect is a twisting motion.
 truncal cushions fuse to form
truncal septum.
 Additional cushions develop in
conus which grow down & towards
each other until they fuse with
truncal septum to form RVOT &
LVOT.
 RVOT (anterolateral) & LVOT
(posteromedial)
subpulmonic conus elongates & subaortic conus resorbs, allowing
aorta to move posteriorly & connect with left ventricule

9.  Embryology
 instead of bending to right
 heart tube turns leftward.
 primitive ventricle moves to right
 bulbus cordis moves to left.

10. loop rule for ventricular localization
d-Ventricular looping =normal ventricular situs, with morphologic RV to right
& anterior & morphologic LV to left & posterior.
l-Ventricular looping -inverted ventricular situs

11.  such abnormal looping of ventricles is associated with
transposition of great arteries.

12.  aortic root- anterior & leftward of PA root (“L” transposed).
 Further twisting can result in a more superior-to-inferior relationship of RV
to LV .

13.  Morphology:
 95% situs solitus
 25% dextrocardia/mesocardia
 Dextrocardia & situs inversus -less
common variant of a CCTGA
 Ventricular Topology.
 Left hand ventricular looping (by Dr.
Anderson's palm)
Only Lt hand can fit
in RV with thumb in inlet, fingers
in outlet & palm on IVS
surface(morph RV on left, morph
LV on right)

14.  Atrial & Ventricular septa
 IVS tends to be more sagittal/horizontal--> malalignment of IAS & IVS
(seen often with AV discordance).
 IAS & IVS should meet at crux but IAS continues ant/rightward, , it will
deviate to a variable degree from IVS , creating a variable gap that in extreme
cases will go back as far as crux.
 malalignment of IAS & IVS determines size & extent of VSD, ventricular
outflows, & conduction system .

15. AV valves
 R sided AV valve
 Mitral valve- 2 pap muscles,
 no insertion onto IVS
 10% of MV's have significant abnormalities
 L sided AV valve
 Tricuspid valve
 Abnormal
 anterior positioning brings septal leaflet into gap created
by septal malalignment at membranous septum.
 This leaflet may thus form posterior wall of LVOT

16. LVOT obstruction
 LVOT is deeply wedged between Lt & Rt AV valves = readily subject to
obstruction.
 PV-fibrous continuity with mitral valve.

17.  RVOTO
 higher frequency -severe left AV valve regurgitation.
 Systemic outflow obstructions -functional and/or true aortic valve atresia /
obstructive anomalies of aortic arch.

18.  PATHOPHYSOILOGY
 mRV is not well suited to perform workload of systemic ventricle over a
normal lifespan.
 RV failure is a common late complication = unfavorable tripartite geometric
configuration that does not adapt to pressure or volume overload .

19. 1. Ventricle shape
Cylindric vs. crescent-shaped cavity
2. Contraction pattern
Concentric vs. bellow-like contraction
3. Pumping action
Pressure pump vs. low pressure-volume pump
4. Coronary artery supply
Two system vs. one system
5. Embryology
Primitive ventricle vs. bulbus cordis
6. Papillary muscles
Two papillary vs. small & numerous (septophylic)
Characteristics of Both Ventricles LV Vs RV

20. long-term systemic workload → TR → volume overload →
ventricular dysfunction & failure.
Increase vulnerability of this ventricle to ischemia, particularly
when hypertrophy is present

21.  Coronary Artery Anatomy
 coronary arteries originate from
posterior-facing sinuses of AV
 mirror-image distribution.

22.  right-sided coronary artery -epicardial
distribution of a morphologic LCA with
main right-sided coronary artery
bifurcating into LCX,LAD
 left-sided coronary artery runs in left
AV groove & gives rise to infundibular
& marginal branches.
crucial in era of double-switch surgical approaches

23. Variable pattern of coronary artery anomalies.
 persistent origin of sinus node artery off circumflex artery & its course
along medial side of RA wall.
 surgical risk of damaging artery during an atrial baffle procedure or
atriotomy repair.

24.  eccentric ostia.
 76% =normal pattern
 Single coronary
 main coronary branch coursing anterior to PT
 large coronary branch crossing RVOT = Rastelli
procedure

25. Specialized Conduction Tissues
 abnormal & potentially unstable.
 SA node -normal position
 AV conduction tissue- abnormal.
 two AV nodes
 normal posterior AV node - apex of
triangle of Koch but with no AV
bundle
 abnormal right anterior AV node -
penetrating AV bundle.

26.  right anterior AV node is located
anterosuperiorly in area lateral to
pulmonary/mitral valve continuity,
underneath opening of right
atrial appendage.
 If a VSD is present, anterior AV
bundle courses along its
anterosuperior margin.
 Development of an AV bundle from
normal AV node to summit of
IVS is anatomically hindered by
atrial & ventricular septal
malalignment

27.  degree of malalignment is related to size of LVOT & PT
 normal conduction system frequently are characterized by lesser degree
of atrial & ventricular septal malalignment.
 correlation is between size of LVOT, degree of septal malalignment,
& presence of normal AV conduction tissue.

28.  penetrating AV bundle descends for a long distance down septal
surface before branching.
 EP - multiple levels of conduction defects that include AV node,
penetrating bundle, & bundle branches.
 CHB at birth == discontinuity between anterior AV node & ventricular
septum.
 Ebstein’s anomaly of Lt AV valve with left-sided AP - preexcitation between
mLA & mRV.
 arrhythmogenic atrialized morphologic RV resides in left side of heart.

29.  Associated anomalies (95%)
 VSD
 PS
 Tricuspid valve anomalies
 Congenital CHB
 COA & IAA

30.  VSD
 80%.
 Perimembranous
 d/t atrial & ventricular septal
malalignment .
 subpulmonary location & in
approximation to septal leaflet of left-
sided tricuspid valve.
 large with anterior extension &
therefore suitable for intraventricular
tunneling.
 subarterial or muscular defect --
unusual.

31.  .Pulmonary Outflow
Obstruction(LVOTO)
 30% to 50% of ccTGA & atrial situs
solitus.
 Usually with a large VSD.
 Cyanosis -presenting finding
 subvalvular
 aneurysm of IVS
 fibrous tissue tags
 discrete ring of subvalvular tissue
 Less frequently= valvar PS

32.  Lesions of Morphologic Tricuspid Valve
 Abnormalities of TV (systemic atrioventricular) -90% .
 impact - ventricular dysfunction & HF
 Pathology is dysplasia of valve, with or without displacement of
septal or posterior leaflets.
 Regurgitation is frequent & generally progressive

33.  Ebstein-like malformation of TV= 50%
 Symptoms = severity of defect.
 Both morphologic TV & on occasion MV can straddle ventricular
septum.

34.  Mitral valve abnormalities
 55 percent
 abnormal number of cusps,
 straddling chordal attachments of subvalvar apparatus creating LVOT
 mitral valve dysplasia.
 may not present with significant clinical findings

35.  Clinical features
 Isolated L-TGA(< 20 percent of L-TGA pts)
- present later in life with signs & symptoms related to either
arrhythmias or HF.
 CHB - MC arrhythmia
 Progressive fibrosis of conduction system with advancing age,
increases risk of CHB ( 2% per year ) & re-entrant tachyarrhythmias
including WPW syndrome.
 HF - adult patients with progressive dysfunction & increasing systemic
TR.

37. ELECTROCARDIOGRAPHIC FEATURES
 1, disturbances in conduction & rhythm;
 2. QRS & T wave patterns that reflect ventricular inversion;
 3. modifications of P wave, QRS, ST segment, & T wave caused by
coexisting CHD
 AV conduction - PR prolongation to CHB .
 > 75% of = varying degrees of AV block when all ages are included
 CHB == 30%.

38.  congenital & postsurgical complete heart block
 CHB -10% at initial presentation .
 risk of CHB rises over time with a 2 percent per year
increase in incidence

39. P-wave
 normal atrial situs who is free of significant intracardiac associated
malformations- direction of frontal P-wave axis is normal & .
 position of heart within thorax does not influence P-wave vector
or axis.

40. QRS
 normal heart = IVS from left to right .
 ccTGA= IVS has a more or less sagittal disposition & is oriented
from left posterior to right anterior.
 both its surfaces & ventricular bundle branches are inverted
 right to left & usually in a more superior & anterior direction.

41.  reversal of normal Q-wave pattern in precordial leads
 Q waves are present in right precordial leads but are absent in left
precordial leads.
 QS complexes in right precordial leads, large Q waves in leads III &
Avf
left axis deviation.

43. T WAVES
 CCTGA a nonrestrictive VSD, & a large left-to-right shunt.
 T waves are upright in all precordial leads but are taller in right precordial leads.
80% -T waves are positive in all six precordial leads== side-by-side relationship
of inverted ventricles
T waves are often taller in right precordial leads

44.  CXR
 25% -mesocardia or dextrocardia
 levocardia -leftward positioned aorta usually results in a prominence in
upper left border of mediastinum
Note levo-positioned aorta (arrows

45.  cardiomegaly with
increased pulmonary
vascular markings =VSD.
 RPA =high take-off
absent aortic shadow & is
also quite prominent

46. NONRESTRICTIVE VENTRICULAR SEPTAL DEFECT, & INCREASED PULMONARY BLOOD FLOW.
A SEPTAL NOTCH (UNMARKED ARROW, LOWER RIGHT) APPEARS JUST ABOVE LEFT HEMIDIAPHRAGM.
ASCENDING AORTA (AAO) IS CONVEX AT LEFT BASE,
DILATED POSTERIOR PULMONARY TRUNK CAUSES RIGHTWARD DISPLACEMENT OF SUPERIOR VENA
CAVA (SVC).

47. ECHOCARDIOGRAPHY
 Subcostal views
 examination of patient should begin with definition of situs, by cross-
sectional ultrasound examination of great vessels in abdomen.
 In situ inversus, aorta lies on right of spine, with IVC on left &
morphologic right atrium on left.
 Subcostal 4C views
-First clue to presence of AV discordance may be significant
malalignment between atrial & ventricular septae that occurs in this
condition
-look for features that define morphologic right versus morphologic
LV.

48.  Sub costal Four-chamber view (A)

50. PLAX view
 Note posterior PA
 Subpulmonary stenosis with accessory atrioventricular tissue from both right & left
atrioventricular valves. Ao, aorta.
PLAX views
Two great arteries are seen to arise in parallel
outflow tract obstruction to either aorta or PA

51.  PSAX views
 aorta with its coronary arteries usually is demonstrated in
an l-position (ltward & anterior)
PSAX-view of anterior levo-positioned aorta with posterior PA bifurcation..

52.  VSD,different types of obstruction
within outflow tract of
morphologically LV such as tissue
tags or fibrous shelve, &
pulmonary valvar stenosis or
atresia

53.  Tricuspid valve
 markedly dysplastic
 displacement of septal & inferior
leaflets into morphologically RV
cavity =Ebstein’s malformation .
 moderate-to-severe TR
 Straddling & overriding of either
right or left-sided atrioventricular
valves

54.  A4C- atrioventricular valve
anatomy with particular reference to
Ebstein malformation
 quantitate AV valve regurgitation.
 perimembranous inlet VSD.
A4C view in CCTGA
Dilated LA from TR & Ebstein's-like
displacement of septal leaflet.

55.  Catheterization
 imaging PA & coronary anatomy .
 Elevated PVR (long-standing VSD shunt, severe left-sided AV valve
regurgitation) along with response to pulmonary vasodilators,
 suspected aortopulmonary collaterals or unexplained cyanosis
 Abnormal coronary artery anatomy that is not well-defined with
noninvasive imaging.
 LV hemodynamics in patients undergoing LV retraining prior to anatomic
repair .

56.  Catheter course in abdomen =course of IVC or aorta aids in situs &
malposition.
 AP & lateral fluoroscopy= position of great arteries can
 situs solitus & levocardia= PA lies medially & posteriorly, with venous
catheter following a course close to spine.
 aorta lies anteriorly & along left cardiac border.

57.  Because of anterior position of AV node & intrinsically fragile
conduction system, = higher risk of developing heart block during
catheter manipulation, especially, when attempting access into PA.
 Floating balloon catheter is preffered.

58.  ANGIOCARDIOGRAPHY
 frontal & lateral left ventriculogram, with
20 to 25 degrees of RAO, profile IVS,
LVOT, & mitral inflow
 A similar projection can be used for
injection in morphologic RV.
 character of subpulmonary obstruction
=selective injection of contrast into
morphologic LV.
 VSD= adding 20 to 25 of RAO will
demonstrate to advantage both VSD &
LVOTO.

59.  character of subaortic
stenosis=RV angiography.
 Varying degrees of obliquity
may be required to profile
small LV or VA connection of
double-outlet RV.

60.  pulmonary arteries & their bifurcation =selective injection of contrast
into pulmonary arteries with craniocaudal angulation.
 degree of right or left anterior obliquity will focus on right or left PA,
respectively.
 aorta & coronary arteries =aortography in frontal & lateral
projections.
 Selective coronary angiography

61. MANAGEMENT

62. Medical Management
 usual modalities for cardiac failure

63. CORRECTIVE SURGICAL MANAGEMENT
 1. Classic repair /Physiological Repair
• leaves anatomic RV as systemic ventricle.
• Competent tricuspid valve (or left AV valve) & good RV function are
required.
• Even after repair, progressive TR & RV failure may develop.
 a. In patients with VSD,
VSD is closed through an atrial approach.
 b. In patients with VSD & PS ( LVOTO),
 VSD is closed & an LV-to- PA conduit is placed.

64. Anatomic repair
 anatomic LV systemic ventricle= reduce likelihood of TR & RV failure.
 combination of Senning procedure (atrial switch operation; ) + arterial
switch == “double switch” operation,
 Performed in VSD.
 PA banding =to delay procedure until after 1 year of age.
 Closure of a VSD=through RA.

65.  VSD & PS (or LVOT obstruction),
 Senning operation + Rastelli operation
 VSD right ventriculotomy to connect VSD to aorta.
 Enlargement of VSD is often necessary.
 RV-to-PA continuity =extracardiac valved conduit.

66. Fontan-type operation.
 complex intracardiac anatomies, including hypoplasia of one
ventricle, straddling AV valves, or multiple VSDs

67. Other Procedures.
 Valve replacement=significant TR
 Pacemaker implantation = spontaneous or postoperative
CHB
 Cardiac transplantation=complex L-TGA

68.  Conventional repair/Physiological Repair
 Morphologically RV remains as pump to systemic circulation.
 VSD - closed,
 LVOTO- resection or placement of a valved conduit
 TR- -repaired or replaced.

69.  VSD
 NO right ventriculuotomy & no damage to systemic av
- incision in RA,, through morphologically mitral valve either
displacing septal leaflet or cutting annulus .
- conduction system passes in anterocephalad fashion around
pulmonary outflow tract.
 either continuous or interrupted sutures are placed on
morphologically RV margin of defect superiorly, & from
morphologically LV side of margin inferiorly

70.  PA banding–May help for anatomic repair in future.
 CHB -post surgery in 15% to 30%
 mortality -5% to 10% ( higher than simple VSD )

71. LVOTO
 Mostly subvalvular posteriorly located overlied by RV anteriorly.
 Conduction system runs on LV side of septum- any tension on
septum can damage it.
 ventriculotomy is placed towards apex of ventricle
 resection of accessory tissue, or
 pulmonary valvotomy, /valved conduit from LV to PA
 surgical mortality rate =10% to 15%

72. Morphologically tricuspid valve abnormalities
 Repair or replacement
 younger patients where there is marked dysplasia o- repair can be
extremely difficult.

73. Outcome & complications —
 early mortality is low,
 long-term outcome is poor --progressive systemic RV dysfunction &
heart failure.
 postoperative survival rates at 1, 5, 10, & 15 years were 84, 75, 68, &
61 percent
 poorer outcome
 tricuspid valve replacement,
 preoperative poor RV function,
 CHB after surgery,
 subvalvular PS
 Ebstein-like malformation .

74. Anatomic repair
 Associated lesions remains major determinant regarding surgical repair.


75. 1. Morphologic LV that is prepared (ie, sufficiently hypertrophied or
“trained”) to take over workload of systemic ventricle
2. Current LV/RV pressure ratio greater than 0.7
3. Unobstructed LV-PA & RV-Ao connections
4. Balanced ventricular & AV valve sizes
5. Septatable heart, without AV valve straddling
6. Translocatable coronary arteries
7. Competent mitral valve with good LV function
(Karl TR, et al. ATS 1997)
Proposed Patient Selection Criteria

76.  Anatomical Correction
 dependent on
 presence of subpulmonary obstruction
 anatomy of VSD:
double-switch /atrial switch along with ventricular rerouting.

77.  PA banding
 Not needed in significant PS/ pulmPAH /unrestrictive VSD.
 LV is already functioning at pressure levels

78.  Placement of a band on PA -increases LV posterior wall thickness (ie,
left ventricular “training”).
 Altering LV & RV pressure ratio reduce RV sphericity & improve
geometry of RV prior to anatomic correction .

79.  morphologic LV pressure of 66 to 80 percent of systemic pressure is
sufficient.
 Risk factors for failure of PA band -
 mild LV dysfunction before banding,
 significant LV dilation & dysfunction.
 postoperative development of TR .

80.  median time from PA banding to double switch procedure = 2 to 14.5
months .
 PA banding =more successful in patients less than 13 years of age
 younger patient= shorter interval required for training.
 Patients >16 years of age =unlikely to achieve sufficient LV function to
proceed to anatomic correction.

81. PA banding for Large VSD
 large unrestrictive VSD=n increase in PBF may result in HF in first few
weeks of life
 placement of a PA band =refractory to medical management.
 Promotion of growth is desired as anatomic surgical correction is easier to
perform in a larger infant.

82. Double switch operation —
 atrial switch (Mustard or Senning
procedure) & ASO
 intra-atrial baffle diverts
deoxygenated systemic venous return
into subpulmonary ventricle &
oxygenated pulmonary venous return
to subsystemic ventricle.
 ASO involves transection of both
great arteries, & then translocation of
vessels to opposite root similar

83.  Relocation of pulmonary trunk achieved by transposing PAs
anterior to reconstructed aorta
 If arterial trunks are more side-by-side, then we leave PA behind
newly reconstructed aorta.


84. Results
 median age at time of surgery -7 months to 3.2 yr
median weight of 9.6 to 14.7 kg
Early hospital mortality =0 to 7.4 percent,
event-free survival rates =70 to 85 percent at 10 years .
-CHB =0% to 23%.

85. Senning-Rastelli procedure —
 L-TGA that have a VSD & LVOTO- Senning-Rastelli (SR)
 intra-atrial baffle (Senning tunnel) is created & a baffle is placed in
VSD so that blood from LV is directed into aorta, & a conduit is
placed between RV & PA (Rastelli procedure).
 requires a sizable & appropriately located VSD
 Conduits become stenotic in long-term as they do not grow as child
grows.
 require serial conduit replacements.

86.  Ventricular Rerouting Combined
with Atrial Redirection
 incision is made in morphologically
RV, permitting creation of an
intraventricular tunnel between
VSD & aorta.
 repair is completed by placing a
valved conduit from RV to PAs.

87.  Outcome & complications — .
 Mortality —
 actuarial survivals at 1, 5, & 10 years
88, 84, & 84 percent in DS group (n = 68),
92, 92, & 77 percent in SR group (n = 45)
 Early deaths
5 patients in DS group,
no patients in SR group

88.  Morbidity —
 -conduction abnormalities (ie, CHB & arrhythmias),
- LV dysfunction
- neo-aortic regurgitation.
- baffle-associated complications in patients who undergo
DS operation.

89. Conduction abnormalities —
 New onset CHB & atrial arrhythmias =postoperatively .
- tachyarrhythmias =4 patients

90.  Left ventricular dysfunction — .
 14 percent=postoperatively
 Neo-aortic regurgitation —
 DS
 70 percent = at least mild AI
 six patients with severe AI
 neo-aortic root dilation =previous pulmonary arterial banding & ASO
performed in a later era

91.  Coronary artery stenosis or insufficiency
 89 percent occurring in first 3 months following ASO = “kinking” or
other anatomic obstructions to coronary perfusion.
 Unexplained ventricular dysfunction or poor hemodynamics =early
evaluation of coronaries in postoperative setting.
 Risk factors for coronary events include
1) type of coronary anatomy (presence of a single coronary orifice )
2) occurrence of a major intraoperative event
-coronary translocation difficulty,
- LV dysfunction,
- cardiac arrest, or
- temporary mechanical support at end of intervention

92. Baffle-associated complications —
 Obstruction at RA & SVC junction -Mustard procedure.
chylothorax, upper extremity edema, or facial plethora.
 Pulmonary venous obstruction more -Senning procedure.
 Progressive obstruction =reactive airway disease.

93.  Reintervention
 In SR group - right ventricular-PA conduit changes or ballooning.
 In DS group - aortic valve replacements.

94.  History —:
 syncope or palpitations -arrhythmia or CHB
 Increasing exercise intolerance- declining systemic ventricular function
or increasing PA obstruction
 Exertional chest pain - coronary artery insufficiency.
 Edema of face & upper extremities - SVC obstruction due to a baffle
complication seen in Senning procedure
 Dyspnea -systemic AV regurgitation or systemic ventricular dysfunction
in adult patient that is unoperated

95.  Endocarditis prophylaxis —
 surgical repairs that include use of prosthetic material (eg,
heart valve), prior episode of endocarditis, & those with high-
risk lesions for endocarditis (eg, unrepaired cyanotic heart
disease or with a residual defect such as a patch margin
VSD).

96.  PREGNANCY —
 systemic ventricular ejection fraction that <40
percent and/or have a New York Heart functional class III & IV
=against pregnancy

97.  Conclusion
 LTGA- is an unusual congenital heart defect characterized by AV &
VA discordance.
 clinical picture is dominated by pathophysiology of associated
cardiac anomalies.
 Long-term follow-up of conventional surgical approaches is
disappointing & has led to novel surgical approaches aimed at
restoring normal AV & VA connections.
 Early results are promising, but final assessment of evidence requires
further long-term follow-up.