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D-TGA
Dr. Tahsin.N
TRANSPOSITION
• Abnormal origin of the Aorta and Pulmonary Artery from the
ventricular complex
• Atrioventricular concordance with ventriculo-arterial
discordance
• Abnormal spatial relationship of the great arteries
• Results in two circulations in parallel
Incidence & Prevalence
• 5% to 7% of all congenital cardiac malformations
• The incidence is reported to range from 20.1 to 30.5/100,000
live births
• strong (60%–70%) male preponderance
Embryology
Embryology
1. Spiral aortico-pulmonary septum forms but does not spiral or
twist during its partitioning of the truncus arteriosus
a. Aorta arises from right ventricle
b. Pulmonary trunk arises from the left ventricle
2. Result is two closed circuits
a. Systemic – unoxygenated – repeatedly re-circulated
b. Pulmonary - oxygenated - repeatedly re-circulated
Embryology
• The normal conus is subpulmonary, left-sided and anterior ; it
prevents fibrous continuity between the pulmonary and
tricuspid valve rings.
• In TGA, the infundibulum is usually subaortic, right-sided and
anterior; it prevents fibrous continuity between the aortic and
tricuspid valve rings and further results in abnormal
pulmonary to mitral valve ring fibrous continuity.
Anatomy
• The common clinical type - situs solitus of the atria,
concordant AV and discordant ventriculoarterial alignments complete TGA.
• TGA {S,D,D} - TGA with situs solitus (S) of the atria and viscera,
usual (D) looping of the ventricles and an anterior and
rightward (D) aorta.
Anatomy- Great artery relationship
• Situs solitus and intact ventricular septum - the aortic root is
directly anterior or anterior and to the right of the pulmonary
trunk in a slightly oblique relationship
• Less commonly, the aorta may be positioned anterior and to
the left or, rarely, posterior and to the right of the pulmonary
trunk.
Coronary Anatomy
• The two aortic sinuses of Valsalva adjacent to the
aorticopulmonary septum that “face” the pulmonary artery
contain the ostia of the coronary arteries in more than 99% of
cases
Coronary anatomy
• Usual-66.9
• CX from RCA-16.1
• Single RCA-3.9
• Single LCA-1.7
• Inverted-2.4
• Intramural LCA-2.1
• Other-1.6
SA node artery
• Origin and proximal course of artery may be variable; reaches
the sinus node by the interatrial groove on the anterior
surface of the heart, occasionally with an intramyocardial
course in the anterosuperior rim of the fossa ovalis.
• It can be damaged easily during balloon atrial septostomy,
during surgical septectomy or when this portion of the
septum is widely excised as in the Mustard or Senning atrial
switch operation.
Anatomy - Coexisting Anomalies
• Nearly half of the hearts have no other anomaly except a PFO
or a PDA.
• The VSD is the most frequent coexisting anomaly-40% to 45%.
- perimembranous (conoventricular 33%)
- AV canal (inlet septum 5%)
- muscular (27%)
- malalignment (30%)
- conal septal hypoplasia type (5%)
VSD
• The subaortic stenosis caused by the anterior malalignment of
the infundibular septum is frequently associated with aortic
arch hypoplasia, coarctation or even complete interruption of
the aortic arch
• Posterior (leftward) malalignment is associated with varying
degrees of LVOTO–subpulmonary stenosis, annular hypoplasia
or even pulmonary valvar atresia
Subpulmonary Stenosis 25% [5%]
• Fixed
-Circumferrential fibrous membrane /diaphragm
- Fibromuscular ridge
- Herniating tricuspid leaflet tissue
- Anomalous MV septal attachments
- Tissue tags from membranous septum
• Dynamic-associated with SAM
Subaortic Obstruction
• Rightward and anterior displacement of the infundibular
septum
• Associated aortic arch anomalies
- hypoplasia
- coarctation
- interruption
Asso. RV hypoplasia & tricuspid valve anomalies
TV anomalies
Nearly 31%
Functionally imp 4%
Ratio of tricuspid to mitral anulus circumference is less
than 1 in almost 50% of cases, whereas in normal hearts this
ratio is always greater than 1
TV anomalies
• Straddling/overriding of chordae
• Overriding of the tricuspid annulus
• Abnormal chordal atatchments
• Dysplasia
• Accessory tissue
• Double orifice
MV anomalies
Nearly 20%
Functionally imp 4%
– Cleft anterior mitral valve leaflet
– anomalous papillary muscles and chordae
– Straddling
– redundant tissue tags
Juxtaposition of atrial appendages
• Both appendages or left + part of right are adjacent
• 2-6%
• Left > right -6x
• Female preponderance
• often additionally associated with major cardiac pathology,
including dextrocardia, VSD, bilateral infundibulum, right
ventricular hypoplasia and tricuspid stenosis or atresia.
• Imp in BAS
Bronchopulmonary Collateral Circulation
• Bronchopulmonary anastomotic channels > 30% of infants
with TGA under 2 years of age
• Persistence of a significant bronchopulmonary collateral
circulation after surgical repair - large enough left-to-right
shunt – CCF - warrant catheter embolization
PBF
• 50% of the patients - greater proportion of blood flow to the
right lung than normal due to rightward alignment of MPA
• associated with some degree of hypoplasia of the left
pulmonary arterial vessels and is further manifested in the
occasional reports of unilateral, always left-sided, pulmonary
vein stenosis or hypoplasia.
PBF
Postnatal Physiology of TGA
Determinants of effective gas exchange
• Effective ventilation
• Effective Pulmonary circulation
– Pulmonary blood flow
– Pulmonary vascular resistance
• Existence of a communication between pulmonary and
systemic circuits
– Persistent fetal channel – PFO or DA
– Abnormal channels – ASD, VSD
• Effective delivery of oxygenated blood to the tissues
Definition of shunts
• Anatomical shunts
– Left to Right: Blood flowing from left sided chambers to
the right sided chambers
– Right to Left: Blood flowing from right sided chambers to
the left sided chambers
Definition of shunts
• Physiological shunts
– Left to right: The volume of oxygenated pulmonary venous
return recirculated to pulmonary circulation (Qp – Qep)
– Right to left shunt: The volume of systemic venous return
that contributes to cardiac output (reentering the systemic
circulation) without having passed through the pulmonary
circulation (Qs – Qep)
Definition of shunts
• Effective pulmonary blood flow (Qep):
– The volume of systemic venous return that is effectively
oxygenated in the lungs
• Effective systemic blood flow (Qes):
– The volume of oxygenated pulmonary venous return that
enters the systemic circulation and perfuses the systemic
capillary bed
TGA: Atrial and Ventricular level shunts
• From LA to RA / LV to RV
– Anatomically left to
right
– Physiologically, this
volume of oxygenated
blood enters systemic
circulation. Hence,
they contribute to Qes
= Effective
Systemic
Blood Flow
TGA: Atrial and Ventricular level shunts
= Effective PBF
• From RA to LA/ RV
to LV
– Anatomically, right
to left shunt
– Physiologically, this
volume of systemic
venous blood enters
pulmonary
circulation. Hence
they contribute to
Qep
Recirculating
Oxy
Blood
Recirculating
systemic blood
TGA: Shunt at PDA level
• Aorta to PA flow:
– Anatomically it is left to right
– Here the deoxygenated systemic venous blood enters
pulmonary circulation. Hence, this volume contributes to
Qep
• PA to Aorta flow:
– Anatomically it is right to left
– Here the oxygenated blood enters systemic circulation.
Hence, this volume contributes to Qes
• Thus, the flow across the ductus is functionally opposite to
that of flow across ASD or VSD in TGA
Systemic
venous
Pulmonary
venous
return
return
Anat
R-L
RIGHT
Anat
L-R
LEFT
HEART
HEART
Physio
R-L
Physio
L-R
BODY
LUNGS
Unique feature
• Net inter-circulatory mixing volume is constant: net R-L, L-R,
Qep and Qes are equal to each other
• Any major difference in the volumes would result in depletion
of blood volume of one circulation at the expense of
overloading the other circulation
Precise factors controlling intercirculatory
exchange
SPECULATIVE, MULTIPLE
– LOCAL PRESSURE GRADIENTS
•
•
•
•
•
Compliance of the cardiac chambers
Phase of respiratory cycle
Vascular resistances
Heart rate
Volume of blood flow
Flow across the communications
“Rules of the Heart”
• With only ASD, the flow has to be bidirectional
• If the flow is only or predominantly left to right across the
ASD, it suggests presence of additional shunt (VSD or PDA)
• Unrestrictive VSD - flow is bidirectional
• Except in the initial few days, PDA flow is always left to right
(Ao to PA).
• Presence of right to left flow across ductus may suggest the
presence of coarctation of aorta
Right to Left Shunt
Systole
Left to Right Shunt
Diastole
• Initially, bidirectional flow across the ductus
• Later, once the PVR falls, the flow essentially becomes aorta
to PA
• The pulmonary circulation becomes overloaded fast,
especially if the PFO is restrictive
Factors influencing systemic saturation
• Extent of inter-circulatory mixing and Total pulmonary blood
flow
• High PBF results in increased oxygenated blood available in
the left sided chambers for mixing: higher systemic SO2 if
there is good mixing
• Reduced PBF will result in low systemic SO2 in spite of
adequate anatomic shunts
Factors influencing systemic saturation
• If there is delay in the fall of PVR (PPHN), hypoxemia will
persist despite adequate ASD
• Need ECMO or urgent ASO
• Hypoxemia provokes a fall in SVR and increase the
recirculating systemic volume
• Fall in SVR may deplete the pulmonary circulation further
Role of bronchopulmonary collaterals
• Systemic arterial hypoxemia may stimulate development of
bronchpulmonary collaterals
• Usually in TGA with solely a restrictive inter-atrial
communication
• Prolonged survival of such infants may be due to this extracardiac site of shunting/mixing
History
• M:F – 4:1;unless juxtaposition of atrial appendages
• Usually in multigravida-2X increase in > 3 pregnancies
• Familial recurrence-monogenic inheritance
Cyanosis
• As early as day 1 in pts with IVS(1st hr-56%;1st day-90%)
• More intense if associated PS/atresia
• Mild if associated non restrictive VSD
• PS often responsible for hypercyanotic spells-intense cyanosis,
tachypnea, extreme irritability and hypothermia
• Squatting is rare
• Reverse differrential cyanosis
CHF
• In patients with a large PDA
• Large VSD
Mortality
• 1st week-30%
• 1st month-50%
• 1st year-90%
• Depends on the degree of shunting
• Moderate PS improves survival
• Predilection for brain abscess but rare < 2 years
Appearance
• Birth weight greater than normal
• Reverse differential cyanosis
• Varicosities of scalp and arms
Arterial Pulse
• Bounding pulse
- due to large volume of highly unsaturated blood
- Not due to PDA-since only systolic shunt from aorta to
PA
• Diminished femoral pulses
- CoA
- Subaortic stenosis-anterior and rightward
displacement of septum
Palpation
• Nomal in neonates
• RV impulse in patients with CHF
• LV impulse – non restrictive VSD with low PVR
• Palpable S2 A2
Auscultation
• Loud A2
• LV S3-mildly cyanosed patients,increased PBF,LV failure
• RV S3-deeply cyanosed patients, increased systemic flow, RV
failure
Auscultation
• Ejection click-pulmonary;does not decrease with inspiration
• Aortic-subaortic stenosisdilated aortic root
• MSM-aortic:hypervolemic and hyperkinetic circulation
• Pulmonary: valvular- after few weeks of birth, progressively
increases
• Subvalvar dynamic obstruction-3rd LICS and radiates to the
right
Auscultation
• VSD: absentholosystolicshortensabolished
• PDA:
Systolic if large PDA since high PVR curtails diastolic flow
Continuous if restrictive PDA
• Continuous murmurs may arise in large systemic arterial
collaterals but rare
• MDM may be heard across AV valves
ECG
• Normal in first few days of life
• RAE-increased pressure(CHF)/volume (hypervolemic systemic
circulation)
• LAE-large ASD,increased PBF
• RAD-occurs when LV volume overload is curtailed by
pulmonary vascular disease or PS
ECG
• RVH - NR VSD +high PVR/PS
• BVH - NR VSD + low PVR
• Right precordial T waves not inverted but rather distinctly
taller than the left sided T waves
CXR
• Absent thymic shadow after 12 hours of life
• Narrow vascular pedicle bcoz - AP orientation of great vessels
• Right aoric arch -11-16%
• Egg on side appearance
• Juxtaposition-localised bulge along the mid left cardiac border
which represents contiguous mass of the 2 appendages together
• PBF & Heart size inversely proportional
ECHO
•
•
•
•
•
•
Diagnosis
Detection & quantitation of shunt
Detection of outfow obstructions
Asso anomalies
Coronary Anatomy
Post op Detection of Complications
Cardiac catheterization in
TGA
Fallacies in application of Fick’s Principle in
calculating shunts and flows in TGA
• Oxygen consumption is not normal, so assumed values are
unreliable
• Arteriovenous oxygen differences may be very small, so
magnitudes of errors in calculated values would be very large.
• Effect / contribution of Bronchopulmonary collaterals to PBF –
can result in overestimation.
TGA and PVOD
Changes in Pulmonary Vascular Resistance
• Accelerated PVD is common
• With unrestrictive VSD, Grade 3 or 4 changes seen in 20%
before 2 months and in 80% by 1 year
• Without VSD or PDA, it is seen in 6%, progression is slower
than with VSD
• The number of intra acinar pulmonary arteries are also shown
to be decreased
• In TGA/ASD, regression of PVR occurs as in simple ASD but
subsequently PVOD may develop rapidly.
• Reduced saturation
shear stress
Increased hematocrit
Increased
PVOD
• Bronchial artery collaterals bring poorly saturated blood to
pulmonary vessels
• Short MPA
Metabolism in TGA physiology
• Oxygen demands are high while delivery and uptake is poor –
at baseline
• Metabolic acidemia, lactic acidosis
• HYPOTHERMIA can KILL – EXAGGERATING TISSUE HYPOXIA
AND METABOLIC ACIDEMIA
• Hypoglycemia
• Hyperinsulinemia
Management
Definitive Repair
at three levels:
• the atrial level : Senning or Mustard Sx
• ventricular level : Rastelli operation
• great artery level : arterial switch operation or Jatene
operation
• Damus-Kaye-Stansel operation in conjunction with the Rastelli
operation can be used in patients with VSD and subaortic
stenosis
• Lecompte Operation-VSD+subpulmonary stenosis
Arterial switch operation (Jatene operation)
Advantages
• physiologic correction
• fewer long-term complications
– Arrhythmias
– RV dysfunction
– baffle stenosis
– tricuspid regurgitation (TR).
Arterial switch operation (or Jatene operation)
Pre requisite
• An LV that can support the systemic circulation after surgery
• The LV pressure should be near systemic levels at the time of
surgery, or the switch should be performed shortly after birth
(i.e., before 2 weeks of age).
• In patients whose LV pressure is low, it can be raised by PA
banding, either with or without a shunt, for 7 to 10 days (in
cases of a rapid, two-stage switch operation) or for 5 to 9
months before undertaking the switch operation.
• LV pressure >85% and LV posterior wall thickness >4.5 mm
appear to be satisfactory.
Pre-op
• Coronary artery pattern amenable to transfer to the neoaorta
without distortion or kinking.
• Risk is high when the left main or LAD coronary artery passes
anteriorly between the aorta and the PA.
Pre-op
• The left ventricular inflow and outflow tracts must be free of
significant structural abnormality.
• The right ventricular outflow tract should be free of significant
stenosis.
Anatomic variants that may impact operative mortality include
–
–
–
–
–
–
–
An intramural course of a coronary artery
A retropulmonary course of the left coronary artery
Multiple VSDs
Coexisting abnormalities of the aortic
Straddling AV valves
Longer duration of global myocardial ischemic (cross-clamp)
prolonged circulatory arrest times
Complications
• PA stenosis at the site of reconstruction - 5% to 10%
• complete heart block - 5% to 10%.
• Aortic regurgitation (AR)
– late complication > 20% of patients especially PA banding
– An important cause of AR may be unequal size of the pulmonary cusps
that leads to eccentric coaptation
• Coronary artery obstruction
– myocardial ischemia, infarction, and even death.
Atrial level Surgery
Mustard operation: This oldest surgical technique redirects the
pulmonary and systemic venous return at the atrial level by
using either a pericardial or a prosthetic baffle.
• Senning operation: This is a modification of the Mustard
operation. It uses the atrial septal flap and the RA free wall to
redirect the pulmonary and systemic venous return
Complications
a.Obstruction to the pulmonary venous return (<5% of all cases)
b.Obstruction to the systemic venous return (<5% of all cases)
c.Residual intra-atrial baffle shunt (=20% of all cases)
d.Tricuspid valve regurgitation (rare)
e.Absence of sinus rhythm (>50% of all cases) and frequent supraventricular
arrhythmias
f.Depressed RV (i.e., systemic ventricular) function during exercise
g.Sudden death attributable to arrhythmias (3% of survivors)
h.Pulmonary vascular obstructive disease
Rastelli operation
• In patients with VSD and severe PS
• The LV is directed to the aorta by creating an intraventricular
tunnel between the VSD and the aortic valve.
• A conduit is placed between the RV and the PA
Rastelli operation
Complications
• conduit obstruction (especially in those containing porcine
heterograft valves)
• complete heart block (rarely occurs).
• This conduit needs to be replaced as the child grows.
Medical
• Prostaglandin E1 infusion should be started to improve
arterial oxygen saturation by reopening the ductus. This
should be continued throughout the cardiac catheterization
and until the time of surgery.
• Oxygen should be administered for severe hypoxia. Oxygen
may help lower pulmonary vascular resistance and increase
PBF, resulting in increased systemic arterial oxygen saturation.
Role of PGE1 in TGA
• Considerable benefit in first few days till PVR is elevated,
especially if PFO is small
• Enables bidirectional shunting, improves mixing
• If valve of FO is competent, it would result in increased LA
pressure and pulmonary edema
Atrial Septostomy
• Before surgery, cardiac catheterization and a balloon atrial
septostomy (i.e., the Rashkind procedure) are often carried
out to have some flexibility in planning surgery.
• a balloon-tipped catheter is advanced into the left atrium (LA)
through the PFO. The balloon is inflated with diluted
radiopaque dye and abruptly with-drawn to the right atrium
(RA) under fluoroscopic or echo monitoring.
Atrial Septostomy
• For older infants and those for whom the initial balloon atrial
septostomy was only temporarily successful, blade atrial
septostomy may be performed.
• Following this, the balloon procedure can be repeated for a
better result.
Pulmonary Artery Banding
Transposition associated with large VSD without LVOTO
To prevent
Heart failure
Pulmonary vascular disease
Present Indications
Presence of complex/multiple VSDs
Coexisting medical conditions that cause a delay in surgery
To train LV before switch in TGA/IVS
Systemic-Pulmonary Anastomosis
TGA/VSD and severe LVOTO
Operative mortality - as low as 5%.
Reassessment of pulmonary vascular resistance
• D-TGA (Complete Transposition of • Severe cyanosis in a large
great arteries)
newborn
• Male preponderance (3:1)
• Single S2
• Signs of CHF (±)
• Usually no heart murmur
• “Egg-shaped” heart with narrow
waist (on x-ray film)
• ECG: Normal or RVH
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