D-TGA

DR.VINOD.G.V

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

Trunco conal malseptation Hypothesis

Normally related great arteries result from spiral downgrowth of the truncoconal septum, whereas TGA results from straight downgrowth of the trunco conal septum.

The embryonic Aortic switch procedure

During development of the conotruncal region, the pulmonary artery is related

to the left conus and the aorta to the right conus

normal movement of the pulmonary valve proceeds from posterior to anterior on the left side in the interval between 30 and 34 days of age and is related to normal development of the subpulmonary infundibulum

During this same interval, the aortic valve remains stationary, apparently because of the normal lack of development (or absorption) of the subaortic infundibulum

abnormal growth and development of the subaortic infundibulum and the absence of growth of the subpulmonary infundibulum.

The aortic valve is protruded superiorly and anteriorly by the development of the subaortic infundibulum, placing it above the anterior right ventricle .

Failure of development of the subpulmonary infundibulum prevents the normal morphogenetic movement of the pulmonary valve from posterior to anterior 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.

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.

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.

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 (33%)

- inlet septum( 5%)

- muscular (27%)

- malalignment (30%)

- conal septal hypoplasia type (5%)

Malalignment VSD

anterior malalignment of the infundibular septum

is frequently associated with sub aortic stenosis,

aortic arch hypoplasia, coarctation ,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%)

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

Straddling/overriding of chordae

Overriding of the tricuspid annulus

Abnormal chordal attatchments

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.

HAEMODYNAMICS

Fetal and Post natal physiology

Fetal circulation

Fetal circulation in TGA

TGA with VSD in Fetus

TGA +VSD+PS IN FETUS

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

Systemic venous

return

Pulmonary venous return

Anat R-L

Anat L-R

Physio R-L

Physio L-R

BODY LUNGS

RIGHT

HEART

LEFT

HEART

Right to Left Shunt

Systole

Left to Right Shunt

Diastole

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

TGA: Shunt at PDA level Aorta to PA flow:

Anatomically it is left to rightHere the deoxygenated systemic venous blood enters

pulmonary circulation. Hence, this volume contributes to Qep

PA to Aorta flow:Anatomically it is right to leftHere 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

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

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

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

CLINICAL MANIFESTATIONS

TGA PHYSIOLOGIC CLINICAL CLASSIFICATION

1. TGA (IVS OR SMALL VSD) with increased PBF and small ICS

2. TGA (VSD large) with increased PBF and large ICS

3. TGA(VSD and LVOTO), with restricted PBF

4. TGA(VSD and PVOD),with restricted PBF

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 – CHF develops within 1-3 wks

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

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

Normal in neonates

RV impulse 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

Subvalvular dynamic obstruction-3rd LICS and

radiates to the right

Auscultation

VSD: holosystolicshortensabolished

PDA:

Systolic if large PDA since high PVR curtails

diastolic flow

Continuous if restrictive PDA

MDM may be heard across AV valves

ECG

Normal in first few days of life

RAE-increased pressure(CHF) or volume (hypervolemic

systemic circulation)

LAE-large ASD,increased PBF

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 - 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

D-TGA with VSD

ECHO

Diagnosis Detection of shunt Detection of outflow obstructions Associated anomalies Coronary Anatomy

Parasternal long axis view showing the 2 great vessels parallel to each other.  In a normal heart, the 2 great vessels should not appear together in any plane as they cross each other in their proximal course.  The aorta here is anterior, not posterior as it normally should be.

Parasternal short axis view showing the aortic valve anterior to the pulmonary valve. .

Parasternal long axis with a tilt of the probe to show the entire length of the abnormally situated anterior aorta.  The posteriorly situated pulmonary artery can be seen to bifurcate, a clue that the posterior vessel is not an aorta.

Subcostal view showing the pulmonary artery coming from the left ventricle and bifurcating as it travels distally.

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 WITH NO ASSOCIATED DEFECTS IN NEWBORN

TGA WITH LARGE VSD IN NEWBORN

Management

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.

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

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

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.

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.

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

THANK U

MCQ

1.In a neonate with TGA false statement

a.Ductal closure can precipitate severe desaturation

b.The pulmonary and systemic circulations are arranged in series

c.It may be necessary to create an ASD

d.Immediate complete surgical repair is usually indicated

2.Most common coronary anomaly in TGA

a.Single LAD

b.Single RCA

c.LCX from RCA

d.Intramural LAD

3.Reverse differential cyanosis

a.TGA with PDA+ high PVR

b.PDA with reversal

c.L TGA with reversal

d.TGA+VSD+PS+PDA

4.Wrong statement in TGA

a.TGA babies are predominantly males

b.Maternal diabetes may be associated

c.Birth weight are normal

d.Extracardiac anomalies are frequent

5.Surgical procedure of choice for a neonate with complete TGA

a.Atrial switch surgery

b.Arterial switch surgery

c.Rastelli operation

d.Fontan operation

6.In TGA true statement

a.A2 loud

b.Arterial switch is the best option in the presence of pulmonary obstruction

c.Cardiac catheterisation is the investigation of choice

d.Egg on side in X ray always present

7.RVH in TGA at birth is defined by

a.Monomorphic R wave in V1

b.T upright after 1week in V1

c.RS ratio <1 in V6

d.Incomplete RBBB

8. Effective pulmonary blood flow(Qep)

a.0.9L/Min/m2

b.1.2L/Min/m2

c.1.5L/Min/m2

d.0.5L/Min/m2

9.Anatomical right to left shunt

a.0.9L/Min/m2

b.0.6L/Min/m2

c.1.5L/Min/m2

d.2L/Min/m2

10.Physiological right to left shunt equals to

a.11.1L/Min/m2

b.15L/Min/m2

c.20L/Min/m2

d.7L/Min/m2