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The Japanese Society of Pediatric Surgeons (JSPS)

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23

Surgery forPhysiologic,Transpositionand Technical

Tom R, KarL MD.', Andrew D.

of the Great ArteriesConsiderations

Cochrane,FRACS,

: Anatomic,

Christian PR. Brizard, MD.

" Victroian Paediatric Clardiac Surgicai Unit, Ro.val C7tiidren"s Hospital,

Melbourne, Austtulia

Abstract

The outcome of transposition surgery has been

revolutionized during the past two decades with the

arterial switch operation. Impertant contributions to

this strategy have come from Europe. the USA, Japan,

South America, and Australia. This paper will serve as

an update on some issues relating to the arterial

switch operation, including perioperative support,

pustoperative management, and surgical strategies for

various anatomic subgroups. In this review we analyse

indications, techniques, and outcome for various TGA

subsets, including patients with intact ventricular

septum beyond 21 days of age, intramural coronary

arteries, aortic arch obstruction, the Taussig Bing

anomaly, discordant (corrected) transposition, TGA

with LVOTO, and univentricular hearts with TGA and

SAS.

Abbreviations Used in This Manuscript

ASO l arterial switch operation

AV : atrioventricular

CPB :eardiopulmonarybypass

DORV : double outlet right ventricle

IMCA : intramurat coronary artery

IVS : intact ventricu!ar septum

LA :left atrium

' Adress reprinet requests to : Tom R. KarL M,D. Victorian

Paediatric Cardiac Surgical (Jnit, Royal Children's Hospital,

F]emington Road, Parkville. 3052, Melbourne, AtJSTRALIA,

( 43

LVLVOTOPARVSASTGATVUVHVSD

For the

speciattions,

but

physioLogy and the relative immatumty of the lungs

and the airway. Neonates are known to have a lower

tolerance for the side effects of CPB. There are also

some unique postoperative problems such as necrotiz-

ing enterocolitis and lntraventricular haemorrhage

which occur only rarely even in older infants.

There are a number of cardiac lesions that may

require neonatal repalr, and one of the most impor-

tant and interesting for the cardiac surgeon is TGA.

This lesion presents the surgeon with a unique oppor-

tunity to transform a lethal heart lesion into one with

an excellent long term prognosis. Furthermore this is

usually accomplished within the first week or two of

life. As such. transposition is now the prototype for

neonatal cardiac surgeons.

The ASO has evolved to become the treatment of

)

: left ventricle

: left ventricular outfiew traet obstruction

: pulmonary artery

: right ventricle

: subaortic stenosis

: transposition of the great arteries

: tricuspid valve

: univentricular heart

: ventricular septal defect

lntreduction

paediatric cardiac surgeon, neonates are a

group. This is due not just to size considera-

also to the presence of a dynamic foetal



The JapaneseSociety of Pediatric Surgeons {JSPS)

24

choice for most forms of TGA, and success with this

operation has become a standard by which paediatric

cardiac surgical units are judged. This is apprepriate,

since without expertise in neonatal anaesthetic

mangagement, perfusion, intensive care, cardiology,

and surgery, consistently good results are impessible

to achieve. Results of the arterial switch operation are

excellent in many centers werldwide these days. and

they surpass results achieved in the era of atrial

repair, especially for the more complex anatomic

subsets, StilL there are a number of anatomic subsets

that continue to present a challenge to the medical

and surgical team.

Surgical Anatomy of TGA

In the broad sense, thc term "TGA"

describes anyheart with a discordant VA connection (aorta fromRV, PA from LV). The anatomic diagnosis is further

defined by the intracardiac features. Most frequently,"TGA"

is used to describe the solituslconcordant/dis-

DORV

TaussigBing(sub-PAVSD)

TGA"Famity'

DtlheF.nL'i,-.. ig36ts1:- 2ooO{F2fi

cordant heart, A heart with an additional discordantAV connection is termed

"congenitally

eorrected" or

"discorclant"

TGA. The Taussig Bing anomaly is a

double outlet RV with subputmonic VSD. Strictly

speaking, a heart with a double outlet RV does net

have TGA, since one VA connection is concordant.

However, anatomically and physiologically, the

Taussig Bing anomaly closely resembles TGA with

VSD, and is appropriately included in this surgical

discussionii. "TGA'-

may also be applied to hearts

with a univentricular AV connection (e.g, double inletLV, tricuspid atresia) if an outlet chamber of RV

morphology gives rise to the aorta. The `'TGA

family"

is illustrated in Fig..].

Although the orientation of the great arteries varies

considerably in TGA, a nearLy constant feature is that

the coronaries arise from the aortic sinuses that face

the PA, which greatly facilitates the conduct of the

AS02). The extra aortic course of the coronaries is

variable (Fig. 2) , and the origin of one or both vessels

UlliventriculflrAV connection

Ao from 'RV'

{..,- SAS, AAO}

rDistordant

AV connection

ccTGA

ccTGA.IVS , ccTGA. L'SD

C+.,- LVOTO)

Fig. 1 The TGA "family",

which includes all hearts with a discordant ventriculo-arterial cenection,

as the Taussig Bing anomaly (DORV & subpulmonic VSD). See text for further explanation,

(44)

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Leiden lLCx-2R Leiden lL-2RCx . c. Leiden lCx-2LR

YacoubA YacoubD

'

RCA

x

llS<D LAD LAD

B C

P

R

,

L

RCA RCA

LeidenlR-2LCx LeidenlLR-2Cx

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Fig. 2 The Leiden classification of eoronary anatomy in TGA. The right hand of an observer standing

in the non-corenary sinus (facing the coronary ostia) points to sinus 1, the left hand to sinus 2, The

most common pattern is ILCX, 2R. Corresponding Yacoub nomenclative in included where

appropnate.

may rarely be intramural and stenotic posing special

problems for the surgeon during AS03)`),

Diagnosis of TGA

The diagnosis of TGA colud be considered in any

cyanotic newborn, but ECG, CXR, and physical

examination are not diagnositc. 2D echocardiography

usually provides rapid and complete non-invasive

diagnosis, and in the neonate, cardiac catheterisation is

rarely necessary. A weak area in imaging is the

proximal coronary arteries, which may be difficult to

accurately describe with echocardiography or angiog-

(45

raphy`). Prenatal echo diagnosis of TGA is new

possible as well, although knowing what to do with the

information remains problematic5).

Physiolegy and Natural History

The central physielogic problem is arterial

haemoglobin desaturation. the severity of which varies

with the degree of communication between the

parallel systemic and pulmonary circulations. The

neonatal presentation varies from that of a healthy

appearing baby to complete cardiovascular collapse,

At the worst end of the clinical spectrum are those

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TheJapaneseSociety of Pediatric Surgeons {JSPS)

26

babies with a rest.rictive ASD and,'or aortic areh

obstruction, who are uften profoundly hypoxaemic und

acidotic.

The natural history of all forms of TGA is extremely

unfavourable, and without some form of palliative or

definitive surgery, most neonates would not survive

infancy. In nearly all cases, the initial resuscitation

efforts sheuld include balloon atrial septostomy.

irrespective of surgical plan.

Timing of operation is criticai. especially for babies

with TGA. IVS, In ext,rauterine life, the puln]onary

vascutar resistance drops from its foetal (systemic)

level to a nermal postnatal level within 2 weeks. This

decline will be accempanied by an involution of LV'

mass, unless a PDA. VSD, or LVOTO is present to

maintain the LV pressure at systemic levels. The

optimal time for ASO is therefore wihtin the first 2

weeks of life, if one is to avoid the preblem of a

"deconditioned" LV, "rhich may conLribute to low

cardiac output postoperativelyfi}. Infanrs wlth TGA and

arch obstructien (as weH as other PGE-1 dependent

patients) usuatly require operation within the first

few days of life7) In TGA. VSI). elective operation can

usually be carried out at 1-3 months of age, if the

clinical condition remains stable.

Surgery for TGA

The goal of transposition surgery is to restore a

series circulation with a feur chambered heart, using

the left ventricle and the systemic circuit in the right

ventricle and the pulmonary circuit. The left ventricle

is more suited for pressure work fer a number oi

reasons, The conus portion is minimal, and the left

ventricle is mostly sinus morphology. The left

ventricle was the original pump in evolution, and has a

dual coronary and conduction system and a more

compact myocardium than the right vcntricle. The

mitra] valve is a better design than the tricuspid valve

for high pressure work, since the papillary muscles

arise trom the free wall rather than the septum.

The ASO has emerged as the preeedure of choice

for most babies with TGA, The technical modification

employed at the RCH is a hybrid of techniques

proposed by Jatene, Lecompte, Quaegebeur, Mee, a]d

(

['IilxV"･ftStV･,'t,' ee36ts 1 ;]- LOoo# 2 H

others2)S)'iO). The proccdure is technically demanding,

but logical ancl reproducible. We briefly describe the

ASO technique herein.

With the heart arrested, the aorta and PA are

transected just above the commissures <Fig, 3). The

coronaries are excised with a large cuff of sinus tissue,

and medially based reetangular fiaps are cut into the

facing sinuses of the PA. The mobilised coronaries are

translecated and sutured in place with running 8,,'O

potypropylcne. We employ the Lecompte manoeuvre

in nearyl all cases, ineluding those with side by side

great vessetsD)]iL The neoaortic anastomosis is

completed by gathering tissue on the proximal side to

match the vessel sizes. At this point the VSD, if

present, is closed with pledgett.ed mat,tress sutures

A, v""

iK

Fig.

46 )

rkRCA

BPANeoaorta)

/

Neopulmenarya. .X#ila-

3 The ASO technique used at the RCH. We

employ medially based rectangular flaps in the

ncoaortic sinuses for coronary translocation. Theflaps decrease the are of rotation and prevent

tension on the anastomosis. Neopul-monary sinus

defects are repaired with large autulogous

pericardial patches, extended posteriorly.

'E /

/. ･At.ttT.-.'"r'l-.t't="t'.. t.'--

e.-'-..T=-t.''tt7?ttttt? ).'

/t ' i'NeoaorLa

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H4lib'Vkth ut36ts 1 ny- 2ooe4f zn

and a Dacron patch. The ASD is closed directly. and

the heart is deaired. With the aortic clamp efL the

neopulmonary sinus defects are repaired with

individual autologous pericardial patches. extended

posteriorly to lenghten the PA. The neopulmonary

anastomosis is completed, and the patient is warmed

to 37℃ , then separated from CPB. LA and PA lines

and a peritoneal dialysis catheter are used in most

cases.

Perioperative Support Systems

There are a number of problems related to cardiG

pulmonary bypass for ASO in neonates. They include

the prirning volume, the wide range of flows, the

extremes of temperature. duration of the procedure,

and dinthesis toward capillary leak syndreme and

bleeding,

For our CPB strategy we employ a fresh heparin-

ised blood prime, and a hollow fiber or membrane

oxygenator2). Citrate preseved blood (CPD) imposes a

pon-physiologic osmolar load due to glucose, and low

rnetabolism of citrate may occur due to hypothermia

and reduced hepatic perfusion and function, Newborns

are especially at risk due to altered calcium

'rnetabolism and a decreased capaeity to rnetabolise

'citrate, We therefore believe that fresh heparinized

blood is a superior physiologic solution for prirning the

CPB circuit. No citrate is added to the heparinized

unit, resulting in better in vivo preservatiun of 2, 3-

DPG, red cells, and labi!e coagulation factors.

AIpha stat pH strategy is fQllowed for ceeling to 26'

28℃, In most cases. full flow CPB (150 ml!kg) is used

for the entire operation, with aortic and bicaval 'cannulation, and left heart venting through the ASD.

We have employed cold crystalloid cardioplegia

solution and topical cold saline fpr myocardial

protection, although many units use sanguineous

cardioplegia with good resuLts. Various cardieplegia

solutions have been shown to have similar results in

neonatal cardiac surgery, However, equally important

to the content is the way in which it is delivered. For

antegrade cardioplegia in the arterial switch operation

it is critically important to maintain a physioiogic

aortic root pressure. in order to avoid poor distribution

(47

27

of cardioplegia(low pressure), or myocaridial oedema

(high pressure). Haemostasis is important in neonatal cardiac

surgery, especially for the ASO. We currently employ

aprotinin for all ASO. Aprotinin is a polyvalent

enzyme inhibitor and modulator of the coagulation and

infiammatory responses. It attenuates the release of

some pro infiammatory cytokines after bypass (TNF

a , interleuken 1, interleuken 6) . Aprotinin is known to

prevent coagulation, fibrinolysis, and platelet activation

during and/or after CPB, and haemostatic benefit has

been documented in numerous ctinical studies. The

disadvantage is that aprotinin is a basic polypeptide of

bovine origin with antigenic properties. Re-exposure

should therefore be avoided within 6 months of

uriginal exposure, to avoid the risk of anaphylaxis. Our

usual aprotinin dose is 10,OOO KIU!kg for loading, and

hourly during CPB. Higher doses of aprotinin (30,OOOKIUfkg) therefore may be associated with better

suppression ef the inflarnmatory response.

Control of fluid accumulation is a critical peint for

safe cenduct of the arterial switch operation. We

employ modified ultrafiltration following CPB as well

as peritoneal dialysis postoperatively. We also use

continuous AV haemofiltratien during CPB, Our

modified ultrafiltration circuit is shown in Fig. 4. 0ver

Ao cannulaM.

U, F, circuit for neonatesvenous

cannula

Fig. 4 Modified ultrafiltration circuit employed at the

Royal Children's Hospital. The priming volume

can usally be removed over a 20 minute period,

with predictable haemodynamic improvement.

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an average time of 20 minutes we are usuatly able to

remove the entire priming volume, resulting in signifi-

eant haernoconcentration. During this time we gener-

ally see improvement in systolic and diastolic function

which occurs more rapidly than would be expected

without the use of medified ultrafiltration, There may

also be a reduction in fluid retention, weight gain, and

transfusion requirements. Modified ultrafiltration has

been shown to attenuate the brain injury associated

with prolonged circulatory arrest times. There is a]so

a predictable reduction in pulmonary artery pressure

which takes place coneurrent to appearance of

endothelin 1 in the uttrafiltrate.

The peritoneal catheter is equally important for

neonatal cardiac surgery. This catheter is placed

routinely at the time of arterial switch operation, and

is left on free drainage for abdominal decompression.

For periods of reduced urine output or hypercal-

caemia, isotonic or hypertonic dialysate 10mLlkg (30minute exchange cycles) is used. We also employ cold

dia]ysis for core cooling for rhe treatment of postoper-

ative hypothermia, especially when associated with

arrhythmias.

The physiology of the capillary leak syndrome isnow reasonably well characterized, and is summarized

in Fig. 5. The initial common pathway is contact of

circulating blood with surfaces of the cardiopulmonary

Fig. 5 Pathogenesis of the capillary Leak syndrome

post CPB. The initial cemmon pathway is

contact of blood and the surfaces of the CPB circuit.

( 48

n,JiP"kE',l ac36ts 1 Fi 2oooff 2 N

bypass circuit.

Steroids are associated with reduced transcription of

RNA for pro-inflammatory cytokines, inducible nitric

oxide synthase, and various selectins, We are therefore

currently cenducting a study investigating the role of

steroids in reduction af the capillary leak syndrome

(Brizard et ai., 1998). In our prespective study in

neonates undergoing the ASO we are investigating

whether methylprednisolone pre CPB improves postCPB tung eompliance. Fi021Pa02 ratio, thoracic

bioimpedance, albuminuria, body weight, cardiac

function, and appearance of various biochemical

markers (IL6, IL8, ILIO. C5, B9, CRP. nitric oxide

metabolites).

We have also looked at surface modification of the

CPB cireuit and its effect on the inflammatory

responseiZ). Our findings were that the use of heparin

bonded circuits or albumin coating pre CPB did not

attenuate release of interleuken 6 or interleuken 8

within the first 24 hours. This would suggest to us･

that if these strategies, reduce the inflamrnatory

response, it is not mediated through a decreased

release of the cytokines measured.

Nitric oxide has been an important development in

neonatal cardiac surgery, perhaps the most useful

drug to appear since prostaglandin Ei, Nitric oxide is a

selective and effective pulmonary vasodilator. There

are some potential problems, including early develop-

rnent of nitric oxide dependence due to inhibition of

exogenous nitric oxide production, clienculties for use

long term in non-ventilated children, respense

variabMty, and concerns about the build up of toxic

metabelites, including N02 and rnethemoglobin (rare

in clinical practise at doses<30 ppm).

There are parallet pathways, possibly synergistic,

for effecting arterial smooth muscle relaxation (Fig, 6) .

For pulmonary vasodilatation in nitric oxide non-re-

sponders, inhaled PGIz may be suitable therapy. PGI2

can be given by uttrasonic nebulizer, added to the

inspiratory limb of the ventilator circuit, 10 to

40 ngfkg/'min. We are initiating a clinical trial in

postoperative cardiac patients to evaluate this

modality (CochraneetaL 1998).

Another area of research pertinent to neonates

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L-arginine

arachidonic acid

Fig.

1 ll

.8

.6

.4

2

o

o NO ocGMP

(lliiiiil})

O PG-12 =>cAM

6 Parallel pathways for relaxation of arterioLar

smooth muscle, both relevant for control of PHT

in neonates post CPB. There may be a therapeutic

role for both nitric oxide and prostaeyelin (PG I2).

29

Table 1 Parameters studied for prediction of major

adverse events post CPB. Only MAP index and serum

lactative hact signifi-cant predictive value. From i

Duke T, Butt W, South M, Karl TR. Early markers of

major adverse events in children after cardiac

operations, J Thorac Cardiovasc Surg, l14:1042-

1052, 1997.

Predicting major adverse events (admission to ICU)

Variable Event NocventOdds ratiop

Prebability {log-iikelihood)

MAP index

Hean rate

CtD02SV02Base

deficit

Lactate(mmolU)

GastricpHi

DC027be-core

temp

109

98

3.45619,4

48.9-2.4

3

Z26 15.4

3.f

12S104

4.22470

61.7-O.4

2,2

7,31 12.9

3.2

O.96O.97e.7O.96O.95O.841.36O,64e,96O,98O.03O.12O.25O,09O,12O.J4O.03O.2O.3e.

84

e 2 4 6 8 10 Lactate in mmoVl

Fig. 7 Probability of a major adverse event following

open heart surgery, based on serum lactate levels

in the ICU. Serum lactate at 4 hours had

singificant predictive value for adverse events.

From1Duke T, Butt W, South M, Karl TR. Eary

markers of major adverse events in children after

cardiac operations. J Thorac Cardiovasc Surg.

114 : 1042-1052, 1997.

undergeing the ASO is prediciton of major adverse

events after cardiac operationsi3). Such events include

cardiac arrest, need for emergency chest opening.

sepsis, multiorgan failure and death, We know that

hypotension may be a late and unre!iable sign, and

that measurement of cardiac output is invasive,

dithcult, expensive and unreliable in neonates, Table 1

summarizes the parameters examined in predicting

major adverse everits in our patients during their ICU

stay, Figure 7 shows a predicted probability of major

adverse events following cardiac surgery based on the

serum lactate level at 4 h. There is a strong cerrela-

(49

tion, which was not found with the other parameters

examined. The unanswered question is whether

treatment of elevated lactate in isolation can prevent

the development of a major adverse event,

Special Problems

A number of anatomic and physiologic TGA subsets

require special consideration, and are discussed

herein :

1 . The older baby with TGA. IVS

Beyond 2 weeks of age, LV involution has usually

begun, and concerns are therefore raised regarding

postoperative centractility. An early ASO study using

pooled CHHS data suggested that the risk of ASO

increased beyond 7 days of agei4}, This result !ed many

centres to adopt a 2 stage approach for children

beyond 2'3 weeks of age. especialLy those with

subnormal calculated LV mass or wali thicknessiS)', We

know that post-natal myocardial growth is character-

ized by an early hyperplastic phase of myocytes and

capillaries, followed by myocyte hypertrophy only.

Pressure overload induces hypoplasia, hypertrophy

and angiogenesis in neonates but only rnyocyte hyper-

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30

trophy tater on. Therefore the capacity and rapidity of

LV hypertrophy may decrease dramatlcally with

increasing age of the patient. Rapid LV hypertrophy

has been doeumented in the early postoperative

period6). We have therefore taken the appreach of

offering a primary ASO to all children up to 8 weeks

of age, <and selectively to older children us we]1)

irrespective gf LV pressure, geemetry or massE),

Infants with TGA.IVS presenting between 8 weeks

and 6 mont,hs of age are best treated with a two stage

Aso strategy6)i5)i6). The capacity of the LV to respond

to a pressure load with hypertrephy in this age group

makes rapid retraining (<2 weeks) possible, The

first stage is transsternal PA band placement,

accompanled by a 4 rrim PTFE innominate to right PA

sh'u'ht to maintain oxygenation, Tennporary low cardiac

output follewing this procedure is common, but within

7'10 days the LV pressure and mass will usually be

adequate to allow ASO without severe low cardiac

output postoperatively. Within this time frame,

adhesions are generally llot too troublesome at

resternotomy, and ASO (with simple debanding and

shunt.division) can be performed as described above.

In older patients, a more pro]onged period of LV

conditioning is usually requiredii). Fortunately, sueh

patients are unusual in today's practise.

1)he left ventricular assist device provides

postoperative support for rapid retraining of the LV in

patients with borderline function after the ASO due to

preoperative deconditioning. Looking at 53 infants and

children who required ventricular assist device

support in our unit (alg diagnostic groups), those

with TGA or ALCAPA syndrome had the best overall

survival probability of 0.91 (CL O.59J1.0).

2. Coronary artery abnormalities

We would consider virtually all coronary artery

variations to be potentially suitable for ASO, although

some are more problematic than others from n

technical point of veiw. In ()ur experience with over

400 ASO, only 1 patient was considered unsuitable by

virtue of coronary anatomy (a premature infant with

bilateral intramural branching of a single coronary,

coursing between Ao and PA). IMCA was noted in

(50

H,]sptftas bl36tsle 2000ny2H

Fig. 8 Intramural left coronary artery shown in cross

sectional echocardiogram. The proximal left

coronary courses within the aortic walL The ostium

is eccentrically placed and frequently stenotie. This

pattern is seen in about 5% of cases of TGA, and

creates technical problems for excision,

(a) (b) (1c1)

(d) (e>

Fig. 9 Teehnique mobi!ization and translecation of an

IMCA. The posterior aortic commissure is

detached (a)to provide sinus tissue for eoronary

excision {b). The ostium is cutback to enlarge

and move it laterally (c), The commissure is

resuspended from the pericardial patch <d e),

5% of infants undergoing ASO in our institute <Fig.

8). The natural history of IMCA in TGA is unknown,

but there is an association of this type of coronary

anatorny with sudden death in concordant hearts.

In tnfants with IMCA, the arterial switch technique

must be modified4). Following aortic transection, an

IMCA should be suspeeted if there is an eccentrically

)

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nilhSSkts ee36msle 2000ijt- 2n

placed, small, or apparently single ostium er a vessel

arising atop a valve commissure. To mobilise and

translocate this type of vessel safely, the posterior

aortic valve commissure must be detached (Fig. 9).

The ostium is then cut back to enlarge it and move it

laterally. The coronaries are excised as a large cuff

which can be divided and translocated as described

above. This technique leaves a single large defect in

the neopulmonary artery which can be repaired with

one pericardial patch, The commissure can then be

resuspended to the patch with interrupted sutures to

reconstruct the neopulmonary valve. The operation

may then be completed as described above.

3 . TGA with LVOTO

LVOTO is found in 20% of infants with TGA, and is

often considered a contraindication to ASO, In such

patients, alternate strategies can be employed, but the

longterm results may be less satisfactory than those of

the ASO. A minority of patients may have a

resectable type of LVOTO, such as accessory AV

valve or endocardial cushion tissue, fibrous subvalvar

membranes, and anornaldus rnuscle bundlesi8}. The

final decision regarding resectability must often be

made intraoperatively. Resection is performed via the

transected PA, combined with exposure through the

tricuspid valve if necessary. Structures at risk during

resection include the ,neoaortic valve, coronary

branches, and the cenduction tissue. Sustained relief of

obstrvction can be expected in preperly selected

cases.

4 . TGA with aortic arch ob$truction

Aortic arch obstruction. rare in TGA.IVS,

complicates 7'10% of cases of TGA.VSD and Taussig

Bing anomalyii). The obstruction is mest commonly a

discrete coarctation with a hypoplastic transverse arch

and isthmusi9)20), A compLete interruption is more likely

to occur in the UVH with TGA and SASMZi'. For all

types of TGA with arch obstruction, closure of the

ductus can precipitate profound cardiovascular

collapse in the neonate. The risk of necrotising

enterocolitis and intraventricular haemorrhage is also

increased as compared to other forms of TGA. Most

(51

31

patients with TGA and arch obstruction should have a

one stage neonatal repair via median sternotomy7)2b,

For arch repair, two arterial periusion cannulas are

placed, one in the ascending aorta .and the ether in the

ductus, which is proximally ligated. The patient is

cooled to 18℃. the circulation is arrested, and snares

are placed to occlude the head vessels, Selective

myocardial perfusion has been employed in some

patients, The descending aorta is transected justbeyond the duct insertion and anastomosed to the

ascending aorta at the base of the innominate artery.

The arterial switch is then cpmpleted as described

above.

5. TheTaussig Bing Anomaty

Defining this entity has created more problems for

the anatomist than for the surgeon. Certainly there is

some overlap between DORV with uncomitted VSD,

Taussig Bing anomaly, and TGA with VSD. For

surgical purposes, however. the key question in DORV

is whether or not the LV can be directly connected te

the aorta via an intraventricular tunnel, or whether

the LV can be more directly connected to the PA.

There are a nurnber of operatiens which have been

employed for this latter situation. including atrial level

and intraventricular repairs wlthout ASO. Our strong

preference, however, is ASO, performed within the

first three months ef Lifei2). The surgeon should be

aware that Taussig Bi4g hearts are more Likely to

have atypical coronary anatomy, side by side great

vessels, and aortic arch obstruction than are other

TGA variants. ASO is performed as for TGA,VSD,

with a transatrial approach for placement of a LV-PA

baffle, Exposure through the tricuspid valve ls usually

quite adequate. and pledgetted individual sutures can

be placed around the subpulmonic conus and through

the septal TV leaflet. A large Dacron patch is used for

septation, in order to achieve an unobstructed

pathway to the neoaorta, which has a biventricular

origin, overriding the VSD. The neopulmonary artery

anastomesis can be constructed on a branch PA,

closing a portion of distal main PA. to compensate for

a side by side vessel position. In an occasional patient

PA reeonstruction may be performed better without

)

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32

the use of the Lecompte manoeuver]2).

6. DiscordantTGA

"Classical"

repairs (i.e. simple septation ± LXr to PA

conduit) of discordant (corrected TGA) leave a

discordant AV ancl VA connection (Fig. 10). Thelongterm outlook is suboptirnai due to progressive TI

and RV dysfunction in a significant proportion of

patientsL'3L As an alternative, patients with ccTGA can

be considered for Senning plus ASO if they meet the

follewing criteria.

1 . Unobstructed LV to pulmonary artery and RV

te aortic connections (with or without surgical

revision)

2 . Balanced ventricular and AV valve sizes

3 . Septatable heart, without majer AV valve

straddling

4 . Transiocatable coronary arteries

5 . Current <or recent) LVfRIv' pressure ratio of>

O,7

6 . Competent mitral valve with good LV' function

The majority of chidren with diseordant TGA will

thereiore be excluded frem the Senning and ASO

strategy by virtue of LVOTO, and they are best

treated with a Senning plus Rastelli operation, or a

Fontan procedure24). Newborns without LVOTO coutd

¢

ooegl

･ oo

Y

(a) (b)

Fig.10 Repair strategies for discordant (eorrected) TGA. (a)

"Classical" septation of a heart with

discordant TGA, leaving the RXJ and TV in the

systemic circuit, (b) Senning+ASO restores

concordant AV and VA connections, aveiding tate

problems attributable to an RV in the systemic

circuit.

(52

HJJx･ptkE't[ ca36ts1 ny- 2000f2H

justifiabty be palliated with a pulmonary artery band,

deferring this eomplex and somewhat lengthy

eperation to about 1 year of age.

The operation proceeds as fbr ASO in TGA,IVS, up

to the point of ASD repair. The VSD is closed via the

mitral valve, placing sutures en the RV side of the

septum to avoid heart block. the atrium is then

septat,ed according te the Senning technique25}.

7. ASOforUniventricularAnatomy

Infants with double inlet LV or tricuspid atresia can

be considered to have TGA if the aorta arises from an

outlet chamber of RV morphology. Such infants have

their systemic blood flow regulated by a muscular VSD

(or bulboventricular foramen), which has a strong

tendency toward spontaneous elosure. The resulting

SAS may evolve spontaneously, or more rapidly

following PA banding. In newborns with arch obstruc-

t,ion, SAS is very like]y to be established2i). LV

hypertrophy consequent to SAS may preclude a later

Fontan operation in some of these patients, Preserva-

tion of an unobstructed LV' outlet and regulation of

pulmonary blood flow should be primary goals in the

treatment of this type of UVH. One way to achieve

these goals is to perform a "palliative"

ASO. Ieaving

pulmonary btood flow under control of the restrictive

VSD, with an unobstructed LV outlet to neoaortaL'i). As

most patients will also have arch obstruction, an arch

repair is perforrned concurrently. The operation is

technically identical to that described above for TGA

with arch obstruction, except that an atrial septec-

tomy is performed rather than ASD closure. Post CPB

saturations should run in the 70'80% range. Some

patients will need augmentation ef pulmonary blood

flew with a modified Blalock-Taussig shunt as the

VSD centinues to close in the postoperative period

(weeks to rnonths). Early conversion to bidireetiunal

cavopulmonary shunt is advisable either as a definitive

procedure or a step toward Fontan operation in

suitabre candidates.

Results of ASO

The RCII results of ASO for the various anatomic

subsets described above is surnmarised in TabLe 2.

)

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u,]wlftde ng36-g1e 2ooorp2H

The lowest risk group consists of babies with TGA.

IVS operated upon within the first 3 weeks of life. The

risk of primary ASO for infants in the 3'8 week age

range compares favourably to that of a two stage

approach with PAB prus shunt (Table 3), although

we don't have a large experience with the latter

strategy in our own unit. This risk also compares

favourably with that of many other open heart

procedures, especially those performed in neonates.

The risk has been higher for the mere compLex TGA

subset7)i2)2V. Intramural coronary artery has not been

an independent risk factor for operative mortallty,

whether considered against non-IMCA patients as a

group, or within the various anatomic subsets (Table4a, b) 4)en).

Long term follow up of our own TGA patiellts (>

Table 2 RCH results of the ASO for various anatomic

groups. The highest risk group comprised infants with

uni-ventricular anatemy. Arterial Switch Outcome in

413 Cases (to December 1997)

95 % confidenceHospitalmortality intervals

33

1000 patient years) has shown that most children

have experieneed normal growth and development

with a good quality of life following ASO, We have

hand no late deaths in patients undergoing ASO for

TGA. IVS or TGA. VSD,

The operative risk of ASO for 27 infants with Taus-

sig Bing anomaly was 7% (CL=1-23%) and, in our

exprience, not increased for patients requiring cencur-

rent aortic arch obstruction (p := 1.0)i2). Actuarial survial

and freedom from reoperation at 72 months were

likewise similar (p>O.05). All survivors are in NYHA

classIata rnean jla time of 54 (+1-36) months, and

all are in sinus rhythmi2]. The risk of ASO for Taussig

Bing anomaly also compares very favourably to

alternate surgical strategies used for similar patients.

The experience with Senning+ASO for discordant

TGA is limited. Fourteen patients have had the

operation performed since July, 198922). Age and

Operation type

TGA,IVS

TGA,VSD

TaussigBing

Double switch

DILV-SASConversion

2r222 ( O.9%)5X121 ( 4,1%)21 30 (6.6 %)lt 14 (7 %)31 12 <25 %)

2t !9 (le.5%)

O- 3%1-

9%1-22

%O-34 %S-S7 %1-33%

Table 4a,b Outcome of ASO in the presence of IMCA.

(a) The risk of ASO stratified according to coronary

anatomy, There was no signMcant risk increment for

[MCA vs ILCX-RR. the most cornmon (and

technically most straightforward) variant. (b) ASO

risk stratified by coronary anatomy within anatemic

subgroups. Once again, we could not demonstrate a

risk increment fbr IMCA.

(a) Risk ofASO Stratified by Coronaiy Anatomy

Coronary type n Risk (95%CL) p

Table 3 Outcome for babies with TGA and intact ventri-

cular septum operated after day 21. Although the risk is

higher in older babies with intact septum, primary ASO

compares favourably to a 2 stage approach up to 8

weeks of age.

ASO after day 21 1 Outcome

iLdr2RIL2RCxSingleintramurat

ILR2CxInvertedOther

Group

21969332e

17

17

7

swI9 (2.3%, 1- 5%)lt 69 (1.5 %, O- 8%)

31 33 (9 %,2-24 %)

cr 20( O-17 %)

Of 17( O-19 %)lf l7 (5,8%,O-29 %)Ol 7( O-41 %)

LJ

1

Mortalityrisk 95%CL p

T6A.IVS

(<21 days)

TGA.IVS

(>21 days)>21 days, low pLV>21 days, high pLV

O/191 O- 2%

21 24 (8.3%) 1-27% O.Ol

U19 (5,2%) O-26% O.09

IX 5 <20 %) 1-72% O.02

<b) ASO Risk Stratified by Coronary & Intracardiac

Anatomy

Anatomy non-IMCA IMCA p

IVS 1 % <O-3%) Ot14 (O-23 %) 1

VSDtDORV 4.8%(2-10%) O16(O-46%) 1

Total 2.6% (1-5%) Of20 (O-17%) 1

(53)




34

weight medians were 12 months (O.5-120) and 8.2 kg

(3.2J3.4). AII but one patient had a left ventricular te

right ventricular pressure ratio>O,7, due to a large

ventricular septal defect (+!-previous PA band),

severe congestive heart failure frorn RV dysfunction

and tricuspid insufficiency, or pulmonary artery band

for left ventricular retraining. At Ieast 10 patients had

strong contraindications to laclassical"

repair, including

right ventricular hypoplasia (n=2) moderate to

severe RV dysfunction, (n=5) and/or moderate to

severe tricuspid insufficiency (n=9). There was one

hospital death, occurring in a neonate (7%, CL=O-

34%). Actuarial survival beyond 10 months is 81%

(CL=42-95%), currently with 389 patient months

total fellow-up time. The median grade of tricuspid

insufficieficy fell from 3,/4 preoperatively to 1,i4 post-

operatively (p=.O03), Right ventricutar function is

normal in 1IA2 current survivors, a!t but one of whom

are in NYHA calss 1 or 2. 0ne child required revision

of the Senning baffle.

26 of our first 413 ASO paticnts had some form of

anatomic LVOTO, due to uccessory endocardial

cushion,!AV valve tissue, iibromuscular subpulmonic

obstruction, or anomalous muscle bands]S). Actuarial

survival at 5 and 10 years following ASO and LVOTO

resection was similar C97 vs 92%p>O.05) to the rnain

ASO cohort, but there was a higher probability of

reoperation (p<O.O05). The preoperative LV-PA

gradient was not a good predictor of resectabilityi8).

For infants with UV'H, TGA, and SAS, ASO as

palliative treatment has carried an operative risk

which is high but competitive with other treatment

strategies (e.g. Norwood operation, PA band+/rV'SD

enlargement, cardiac transplantation)2[). Although ASO

has been highly effective for permanent relief of SAS

In our patients, ultimate suitability for further

operations has been limited ln some cases by I'A

distortion related to the use of the Lecompte

manoeuvre. Of 12 neonates so treat.ed, 7 of 8 Iong-term

survivors have had a bidirectional cavopulmonary

shunt and 5 of these have progressed to a Fontan

operation (over 400 patient months follow up), The

best treatment strategy for this difficult TGA subset

remains undecided although the Damus connection

(54

il4ieFftax ca36#1･e 2000qi2H

Cwith MBTS) is currently our favoured approach,

reserving the technically more complex ASO for

selected patients,

The ASO in biventricular hearts with TGA comes

very close to being both a complete anatomic and

physiologic correction. The mujority of patients (>

95%) after ASO, at teast those with the less eomplex

variants, have normal resting LV function. Segmental

perfusion abnormalities may occasionally be seeen on

Tc 99 scuns at rest but they tend to improve with

exercise. These defects are not predicted by ECG or

echo. LV end systolic wall stress/fibre shortening

vetocity has been relative]y normaL suggesting that

contractility is not impaired. Importantly, these results

are significantly better than the best published data

concerning atrial level repairs!'7)'35). The presence of an

IDvTCA at operation has not been associated with late

death, or with ischaemic features on ECG or echocar-

diography`)ZO), Routine angiographic surveillance of

postoperative ASO patients in our own institution has

failed to reveal any coronary anastomotic problems

{irrespective of coronary anatomy and translocation

technique). We are initiating a study to assess the

ability of MRI to image coronary post ASO (Karl et al.,

1999).

The most frequent indication for reoperation has

been supravalvar putmonary stenosis (8 patients in our

series). but this complication has been nearly eliminated

by the use ol our current PA recenstruction techniques

(see technique section) .

Following ASO, there has been a tendency for great

vessel (anastomotic) diameter to be smaller than that

of controls, and for the neoaortic root to be larger.

Reported risk factors for neoaortic root enlargement

include the presence of neoaortic insufficiency, a

previous PAB, and switch conversion followirig atrial ttt tt /tttrepalr.

Concerns have been raised about a6rLic insufficiency,

which develops in abeut 10% ef patients following the

ASO. This has been at,tributed to progressive dilation

of the neopulmonary annulus, a phenomenon that has

aLso been reported in other conditions in which the

pulmonary valve is used in the systemic circulatlon.

We lookcd at our own patients at a mean follow up of

)

NII-Electronic Mbrary



TheJapanese Society of Pediatric Surgeons {JSPS)

H ,JiSF ft:-S S36g 1 t 2000f 2 fi

105 months. calculating the echocardiographic diam-

eter of the ･neoaortic annulus and neopulmonary

annulus (Fig, 11). We found that the neoaortic

annulus was significantly Larger than predicted (meanZ score 2,59 ± 2.7). However if the regression was

performed against a normal pulmonary annulus, the

mean Z score fell to O.87± 1.35. This difference was

highly significant (p=O,OOOI). In a multivariate

analysis neither age at operation, weight at operation,

follow up interval, nor type of intracardiac anatomy

were predictive of the Z score, The median grade of

aortic insufficiency in these patients was O (range O-2)

and was not related to the annular Z score using

either the aorta or the pulmonary artery as a controL

These data suggest that the neoaorta does not dilate

abnormally but rather grows as a normal pulmonary

valve. The mechanism of the insufficiency may lie

elsewhere.

Although ASO results are now exceilent in most

large centres when only operative mortality is

considered, concerns have been-raised regarding long-

term neurodevelopmental outcome36)37}, There are a

number of CPB strategies available for the ASO. We

have preferred full fiow with moderate hypothermia

for most operations. Circulatory arrest is unnecessary

for most ASO. and has been associated with some sub-

Neoaortic diameter following ASO

62 patients, 105 (84-180) months flu

Z SCORE {annulus diameter) 8

6

4

2

o-2-4

p-,Oop1

Fig. tl Neoaortic diameter a'fter ASO. Regression

against normal aortic controls suggests 'dilation,

but using normal PA control values the mean Z

score is significantly lower.

( 55

35

optimal correlates of neurological outcome. Children

who have been subjected to circulatory arrest for ASO

were found to have developmental index scores that

were lower (at 1 year) than children operated with

low flow CPB36)3ny. Whether or not the use of full flow

CPB affords more neurological protection remains to

be demonstrated and is currently under investigatient tmour own unlt.

'･

We are evaluating a cohort of 220 survivors of ASO

for TGA with intact ventricular septum. Five year

actuarial survival in this group is 99%. All of these

patients had operation according to a similar flow and

temperature stragtegy whicli consisited primarily of

full flow bypass at 150 ml!kgfmin. These patients

have been reviewed and compared to "best

friend"

controls, Using a battery of standard neurodevelop-

mental outcome tests, as well as clinical examination

and neurologic testing. our results to date suggest that

the switch patients cannot be 'distinguished from the

best friend controls, based on a total impairment seore

which takes into account a number of growth and

manual skill factors. Likewise vision, hearing,

neurological exam abnormalities, and learning

disabilities were similar in the two greups. '

Conclusion

The ASO has emerged as the treatment of choice

for most TGA variants. The results compare favor-abiy to what was achieved in the era of atrial level

repairs. The promise of an improved outlook has been

fulfi11ed at 15 year follow-up, Unresolved issues center

on the Iongterm fate of the coronaries and neoaortic

valve as survivors or neonatal ASO reach their adult

years.

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