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

= Effective Systemic

Blood Flow

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

TGA: Atrial and Ventricular level shunts

• 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

= Effective PBF

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

return

Pulmonary venous return

Anat R-L

Anat L-R

Physio R-L

Physio L-R

BODY LUNGS

RIGHT

HEART

LEFT

HEART

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 extra-

cardiac 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 stenosisdilated 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: absentholosystolicshortensabolished

• 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 Increased hematocrit Increased

shear stress 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 SurgeryMustard 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 great arteries)

• Severe cyanosis in a large 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

THANK U