ANATOMY,EMBRYOLOGY & MANAGEMENT OF L-TGA

• Overview• Introduction• Embryology• Anatomy• Specialised conduction system• Coronary aryety system• Associated abnormalities• Management• Follow up care

• Other names- Isolated ventricular inversion/double discordance/physiologically corrected transposition/L-TGA

• Systemic veins to morph RA, connected by a MV to an LV, connected to a PA which is transposed

• Pulmonary veins to morph LA, connected by a TV to an RV, connected to an Ao which is transposed

• --> AV & VA discordance• NET result- systemic venous blood

gets to lungs and pulmonary venous blood gets to body, so it appears good.

• However, even in the patient with no associated abnormalities, it is increasingly apparent that natural history and hemodynamics will be far from normal

Introduction

• Prevalence, Etiology, and Morphogenesis• Corrected transposition is an uncommon lesion. • Data from several sources suggest a prevalence of 0.03 per

1,000 live births accounting for approximately 0.05% of congenital heart malformations .

• Population-based studies continue to document the environmental factors in the etiology of this condition.

• Still, the familial occurrence and recent molecular biology investigations suggest the importance of genetic influence .

• It would seem wise therefore to continue to counsel a multifactorial etiology with a recurrence risk in first-degree relatives of approximately 2%.

• ETIOPATHOGENESIS —• A case-control study from the Baltimore Washington Infant

Study evaluated personal and occupational exposure data from 3495 live births between 1981 and 1989 including 36 infants with L-TGA .

• Over three-quarters of the cases of L-TGA occurred in two small contiguous regions of Maryland and Washington, DC.

• These two areas were characterized by release of toxic chemicals into the air and by hazardous waste sites.

• In addition, parental exposures to hair dye, smoking, and laboratory chemicals were more likely in infants with L-TGA than in the overall cohort.

• Two case series reported a risk of 2 to 5 percent of L-TGA in siblings of affected patients lending support to a genetic pathogenetic component

• Embryology:• If development proceeds in normal fashion, the primary

heart tube bends to the right during early development.• This leaves the atrioventricular canal connected primarily to

the part of the loop from which will develop the morphologically left ventricle.

• Expansion of the canal to the right then permits the right atrium to connect directly with the developing morphologically right ventricle, which itself is positioned rightward relative to the morphologically left ventricle.  

Embryology• 22 days gestation …

the primitive straight cardiac tube is formed• Composed of 5 chambers with patterning regulated by

homeobox genes- Truncus = aorta and pulmonary artery- Bulbis = outflow tracts and ventricle

• 23 days gestation … the straight cardiac tube elongates and bends forming the cardiac loop.– Cephalic portion bends ventrally, caudally, and

right-ward.– Caudal portion moves dorsally, cranially, and

left-ward.– The rotational motion folding over of the

bulboventricular portion bringing the future ventricles side-by-side.

Embryology

• Embryology• In certain circumstances, instead of bending to the right

during development, the heart tube turns leftward. • Such leftward looping places the outlet component of the

primary tube, from which will develop the morphologically right ventricle, to the left of the morphologically left ventricle.

• In this setting,so as to permit the atrioventricular canal to open directly to both ventricles, it must expand leftward rather than rightward, at the same time placing the developing morphologically left atrium in communication with the morphologically right ventricle, and leaving the morphologically right atrium connecting to the morphologically left ventricle.

• This process, therefore, produces discordant atrioventricular connections.

loop rule for ventricular localization as proposed by De la Cruz et al. as an explanation for corrected transposition of

the great arteries. d-Ventricular looping would result in normal ventricular

situs, with the morphologic right ventricle to the right and anterior and the morphologic left ventricle to the left and

posterior. l-Ventricular looping would result in inverted ventricular

situs

• The aortic root, arising from the RV, is anterior and leftward of the pulmonary artery root (“L” transposed).

• The inverted atrioventricular (AV) connections, combined with the reversed ventriculoarterial connections, “correct” the flow pattern such that deoxygenated systemic venous blood flows to the lungs, and oxygenated pulmonary venous blood is pumped to the systemic circulation.

• Further twisting can result in a more superior-to-inferior relationship of the right ventricle to the left ventricle .

• Morphology:• 95% situs solitus• 25%

dextrocardia/mesocardia• Ventricular Topology: • Left hand ventricular

looping (by Dr. Anderson's palm - only Lt hand can fit in RV with thumb in inlet, fingers in outlet and palm on IVS surface) ==>morph RV on left, morph LV on right

• LV & RV might be in a more sup-inf relationship because of further twisting during looping.

• Atrial & Ventricular septa • IVS tends to be more sagittal/horizontal--> malalignment of

atrial septum and ventricular septum (seen often with AV discordance).

• should meet at crux of heart, but the atrial septum continues ant/rightward, it will deviate from the ventric septum--> gap from malalignment of atrial septum==>implications in – VSD, and – variable outflow sizes and – conduction system placement.

• R sided AV valve (Penny et al)– Mitral valve- 2 pap muscles,– no insertion onto IVS– 10% of MV's have significant abnormalities

• L sided AV valve – Tricuspid valve- – often abnormal, – Its anterior positioning brings the septal leaflet into the

gap created by the septal malalignment at the membranous septum.

– This leaflet may thus form the posterior wall of the left ventricular outflow tract

• LVOT obstruction• Most frequently, AV discordance is associated with

transposition of the great arteries (TGA) and a leftward anterior position of the aortic valve relative to the pulmonary valve, though this is not absolute .

• The left ventricular outflow tract is deeply wedged between the left and right atrioventricular valves and is therefore more readily subject to obstruction.

• The pulmonary valve is most often in fibrous continuity with the mitral valve.

• RVOTO• The leftward anterior aorta is supported by a muscular

infundibulum and is not in fibrous continuity with either atrioventricular valve.

• Obstructive lesions of the right ventricular outflow tract and aorta are underemphasized.

• Several reports suggest the higher frequency of this problem in association with severe left AV valve regurgitation.

• Systemic outflow obstructions may take the form of functional and/or true aortic valve atresia as well as obstructive anomalies of the aortic arch.

• PATHOPHYSOILOGY• In patients with anatomically uncorrected L-TGA (ie,

persistent atrioventricular and ventriculoarterial discordance), the morphologic right ventricle (RV) is not well suited to perform the workload of the systemic ventricle over a normal lifespan.

• As a result, systemic ventricular failure (ie, systemic heart failure) is a common late complication in L-TGA patients including those without associated cardiac lesions.

• Right ventricular dysfunction is thought to be due to an unfavorable tripartite geometric configuration that does not adapt to pressure or volume overload .

1. Ventricle shape Cylindric vs. crescent-shaped cavity

2. Contraction pattern Concentric vs. bellow-like contraction

3. Pumping action Pressure pump vs. low pressure-volume pump 4. Coronary artery supply Two system vs. one system

5. Embryology Primitive ventricle vs. bulbus cordis

6. Papillary muscles Two papillary vs. small & numerous (septophylic)

Characteristics of Both Ventricles LV Vs RV

The long-term systemic workload results in progressive tricuspid regurgitation that increases volume overload and contributes to ventricular dysfunction and failure. Increase the vulnerability of this ventricle to ischemia,

particularly when hypertrophy is present

• Coronary Artery Anatomy• Changing approaches to the

surgical management of ccTGA have refocused attention on the coronary artery anatomy.

• In general, the coronary arteries originate from the posterior-facing sinuses of AV

• In patients with atrial situs solitus and ccTGA, the coronary arteries show a mirror-image distribution.

• The right-sided coronary artery has the epicardial distribution of a morphologic left coronary artery with the main right-sided coronary artery bifurcating into circumflex and anterior descending branches, whereas the left-sided coronary artery runs in the left AV groove and gives rise to infundibular and marginal branches.

• Several studies have demonstrated a variable pattern of coronary artery anomalies.

• A 14-specimen study by McKay et al. observed the persistent origin of the sinus node artery off the circumflex artery and speculated on its course along the medial side of the right atrial wall.

• They commented on the potential surgical risk of damaging the artery during an atrial baffle procedure or atriotomy repair.

• In that same paper, a correlation between commissural malalignment and eccentric coronary ostia was observed.

• Ismat et al. analyzed 20 specimens and found 7 specimens with eccentric ostia.

• Uemara et al. The largest specimen study (46 specimens) • They reported a 76% incidence of a relatively normal

pattern with the right and left coronaries off the left- and right-facing sinuses, respectively.

• Anomalies were found in 11 specimens.– Single coronary was the most common in four with two

off the right- and two off the left-facing sinuses. – A main coronary branch coursing anterior to the

pulmonary trunk was found in 96% of the specimens, and a large coronary branch crossing the right ventricular outflow tract was found in 61% of the specimens .

– The latter finding is of most importance when considering the Rastelli procedure

• Chiu et al. described a segmental approach to the coronary anatomy.

• From their study on 62 patients, they concluded that,• First , the proximal coronary pattern at the aortic sinus

depends on the aortopulmonary rotation, and • Second,the peripheral coronary pattern depends on the

atrial situs and apical position or the so-called apicocaval ipsilaterality, as well as the ventricular looping.

• A good understanding of the type and degree of variability of the coronary anatomy in patients with congenitally corrected transposition is crucial in the emerging era of double-switch surgical approaches to these patients.

• Specialized Conduction Tissues

• abnormal and potentially unstable.

• Anderson, Becker, Losekoot, et al. have elucidated conduction tissue.

• SA node lies in its normal position in relation to the atrial situs.

• AV conduction tissue, on the other hand, is abnormal.

• The classic description is that of two AV nodes, – a normal posterior AV

node located at the apex of the triangle of Koch but with no AV bundle, and

– an abnormal right anterior AV node giving rise to the penetrating AV bundle.

• The latter is located anterosuperiorly in the area lateral to the pulmonary/mitral valve continuity, underneath the opening of the right atrial appendage.

• Its AV bundle has a superficial course along the anterior aspect of the subpulmonary outflow tract and superior left ventricular wall, into the upper interventricular septum from which it descends and branches.

• If a VSD is present, the anterior AV bundle courses along its anterosuperior margin.

• The conduction tissue abnormality is not universal to all patients with ccTGA.

• The reason that certain patients had a normal AV node and AV bundle had remained elusive until Hosseinpour et al. elegantly elucidated this long-standing mystery.

• It is thought that the development of an AV bundle from the normal AV node to the summit of the interventricular septum is anatomically hindered by the atrial and ventricular septal malalignment

• The degree of malalignment is related to the size of the left ventricular outflow tract and the pulmonary trunk.

• Hosseinpour et al. showed that - normal conduction system frequently are characterized by the lesser degree of atrial and ventricular septal malalignment.

• Therefore, a correlation is made between the size of the LV outflow tract, the degree of septal malalignment, and the presence of normal AV conduction tissue.

• It is thought that the normal conduction tissue is in addition to rather than instead of the abnormal anterior conduction system.

• In patients with both conduction systems straddling the anterosuperior and inferoposterior margins of a VSD, there can exist a slinglike bundle located over the anterior margin of the VSD and connecting both AV bundles, as described by Monckeberg.

• Associated anomalies (95% of patients)• signs or symptoms are due to the pathophysiology of the

associated cardiac defects.

– VSD– Pulmonary stenosis– Tricuspid valve anomalies– Congenital complete heart block– Coarctation of the aorta and interruption of the aortic

arch are rare

• 1.Ventricular Septal Defect

• Approximatel y 80%. • Perimembranous and • A consequence of the atrial

and ventricular septal malalignment .

• In a subpulmonary location and in approximation to the septal leaflet of the left-sided tricuspid valve.

• The defects often are large with anterior extension and therefore suitable for intraventricular tunneling.

• Other defects such as the subarterial or muscular defect do occur but are unusual.

• 2.Pulmonary Outflow Obstruction(LVOTO)

• 30% to 50% of patients with ccTGA and atrial situs solitus.

• Usually is associated with a large VSD.

• Cyanosis is often a presenting finding in neonates due to major outflow tract obstruction and large VSD because of a significant Rt -Lt ventricular cardiac shunt

• commonly subvalvular and -due to an – aneurysm of the interventricular

septum, – fibrous tissue tags, or a– discrete ring of subvalvular tissue

– intimately related to the non branching atrioventricular

bundle. • Less frequently, valvar pulmonary

stenosis is the cause of LV outflow tract obstruction.

• The left ventricular outflow tract obstruction – may be muscular, reflecting wedging of the

subpulmonary outflow tract between the infundibular septum and the ventricular free wall, with contributions from the right-sided ventriculoinfundibular fold.

– Fibrous tissue derived from the membranous septum may participate in left ventricular outflow tract obstruction.

– Tissue tags derived from the tricuspid or mitral valve or – stenosis of the pulmonary valve itself may obstruct flow

into the pulmonary trunk. • Such tissue tags are likely the most common obstructive

lesion.

• Lesions of the Morphologic Tricuspid Valve• Abnormalities of TV (systemic atrioventricular) are intrinsic

to ccTGA. -90% .• A clinically apparent functional disturbance less often

manifested. • Since this valve is associated with the systemic ventricle,

tricuspid valve abnormalities have an important impact in the development of ventricular dysfunction and heart failure in older uncorrected patients.

• Pathology is dysplasia of the valve, with or without displacement of the septal or posterior leaflets of the tricuspid valve.

• Regurgitation is frequent and generally progressive

• Anderson et al. have described the features associated with the Ebstein anomaly of the left-sided tricuspid valve and these valves in general are a poor substrate for repair.

• An Ebstein-like malformation of the tricuspid valve, which is usually accompanied with right ventricular dysfunction and failure, has been reported in 20 to 53 percent of patients with L-TGA .

• Symptoms related to tricuspid valve abnormalities are dependent on the severity of the defect.

• Both the morphologic tricuspid valve and on occasion the mitral valve can straddle the ventricular septum. This anomaly is of course very important to recognize preoperatively

• Mitral valve abnormalities, although less frequent than tricuspid abnormalities, still occur in 55 percent of cases in autopsy series .

• These lesions include – abnormal number of cusps, – straddling chordal attachments of the subvalvar

apparatus creating pulmonary outflow tract obstruction, and

– mitral valve dysplasia. • This abnormality may not present with significant clinical

findings

• Clinical features • Isolated L-TGA — Less than 20 percent of L-TGA patients

have L-TGA as an isolated disorder and generally present later in life with signs and symptoms related to either arrhythmias or heart failure.

• Complete heart block is the most common arrhythmia in patients with L-TGA with signs and symptoms of bradycardia, fatigue, and poor exercise tolerance.

• Progressive fibrosis of conduction system with advancing age, which increases the risk of complete heart block (progressive incidence of 2 percent per year ) and re-entrant tachyarrhythmias including Wolff-Parkinson-White (WPW) syndrome.

• Symptoms of heart failure (eg, dyspnea, fatigue, fluid retention, and decreased exercise tolerance) typically occur in adult patients with progressive dysfunction of the morphologic right ventricle and increasing systemic tricuspid regurgitation .

• In one case series of 182 adult patients, two-thirds of patients with associated lesions and one-quarter of patients without additional cardiac defects had developed heart failure .

• Unoperated Natural History• Early natural history is significantly affected by the severity

of associated lesions and surgical management.• Although there have been repeated case reports of long-

term survival with ccTGA, this is likely unusual .• Beauchesne et al. followed 44 unoperated patients for 144

months and found that most (59%) had grade 3 or greater systemic atrioventricular valve regurgitation and that many of these demonstrated significant systemic RV dysfunction and were symptomatic.

• Presbitero et al. have followed 18 patients, again pointing to systemic atrioventricular valve regurgitation and ventricular dysfunction as major concerns.

• Graham et al. In a large multi-institutional study, found that, patients without associated lesions had a lower occurrence rate of heart failure and systemic ventricular dysfunction than those with associated lesions at a given age, these problems tended to increase in frequency with advancing age in both groups.

• Electrocardiography —•  In L-TGA, the interventricular septum is depolarized in the

opposite direction of normal. • Q waves in the right precordial leads and an absence of Q

waves in the left-sided precordial leads • These electrocardiographic findings may be misinterpreted

as an inferior myocardial infarction • In addition, patients may also have varying degrees of AV

heart block due to abnormalities of the conduction system. • As noted above, the risk of CHB rises over time with a 2

percent per year increase in incidence

• Chest radiograph — • Twenty-five percent of patients with L-TGA will have

mesocardia (ie, location of the apex of the heart in the midline of the thorax) or dextrocardia (ie, the heart is on the right side of the chest and the apex points to the right)

• In those patients with levocardia (normal location), the leftward positioned aorta usually results in a prominence in the upper left border of the mediastinum

• PA chest radiograph shows cardiomegaly with increased pulmonary vascular markings secondary to aVSD.

• The right pulmonary artery appears to have a high take-off because of an absent aortic shadow and is also quite prominent indicating ventricular inversion, L-TGA.

congenitally corrected transposition of the great arteries, a nonrestrictive ventricular septal defect, and increased

pulmonary blood flow. A septal notch (unmarked arrow, lower right) appears just

above the left hemidiaphragm. The ascending aorta (AAo) is convex at the left base,

the dilated posterior pulmonary trunk causes rightward displacement of the superior vena cava (SVC).  

• ECHOCARDIOGRAPHY• Detailed sequential segmental

analysis is the pivotal investigation. This will show that the systemic veins drain to the morphologically right atrium, which is joined to the morphologically left ventricle.

• The connection of the morphologically left ventricle is then to the pulmonary trunk. The pulmonary veins will be identified joining the morphologically left atrium, which is connected to the morphologically right ventricle and thence to the aorta .

• The morphologic nature of the left ventricle is identified on the basis of its smooth walls, and the presence of paired papillary muscles supporting the morphologically mitral valve

• The morphologically right ventricle will be recognised on the basis of its coarse apical trabeculations, the presence of the moderator band, and attachments of the septal leaflet of the morphologically tricuspid valve directly to the septum.

• Associated lesions, such as ventricular septal defects,different types of obstruction within the outflow tract of the morphologically left ventricle such as tissue tags or fibrous shelve, and pulmonary valvar stenosis or atresia will clearly be seen.

• The morphology of the morphologically tricuspid valve must be studied with care.

• This can be markedly dysplastic, with displacement of the septal and inferior leaflets into the morphologically right ventricular cavity in those with associated Ebstein’s malformation .

• When there is marked dysplasia of the valvar leaflets, it is usual to see moderate-to-severe tricuspid valvar regurgitation on colour flow mapping.

• Straddling and overriding of either the right or left-sided atrioventricular valves should be identified if present, taking care to exclude hypoplasia of either ventricle sufficient to militate against biventricular surgical repair.

• Sequential segmental analysis will also serve to identify rarer combinations found in some patients with discordant atrioventricular connections, such as those with double outlet right or left ventricles, or concordant ventriculo-arterial connections.

• The latter combination is of particular significance, since although the patients present with the features of transposition, the segmental combinations mean that an atrial redirection procedure is the corrective procedure of choice, placing the morphologically left ventricle as the pump to the systemic circulation

• Catheterization• In the recent past, diagnostic right and left-sided heart cath-

eterization was performed prior to intracardiac repair, focusing on imaging the PA and coronary anatomy .

• Diagnostic catheterization remains important in the preoperative assess-ment of patients in whom – Pulmonary vascular resistance may be elevated (long-

standing VSD shunt, severe left-sided AV valve regurgitation) along with the response to pulmonary vasodilators,

– In patients with suspected aortopulmonary collaterals or unexplained cyanosis, and

– Less commonly in those with abnormal coronary artery anatomy that is not well-defined with noninvasive imaging.

– As a part of the assessment of left ventricular hemodynamics in patients undergoing left ventricular retraining prior to anatomic repair .

• Since ccTGA of the great vessels may occur with cardiac malposition, noting the catheter course in the abdomen to identify the course of the IVC or aorta aids in the diagnosis of the underlying situs and malposition.

• Observations about the course of the catheter may be important in recognizing the abnormal position of the great arteries in relation to the ventricles as well.

• Using anteroposterior and lateral fluoroscopy, their course can be determined.

• In patients with situs solitus and levocardia, the PA lies medially and posteriorly, with the venous catheter following a course close to the spine.

• The aorta lies anteriorly and along the left cardiac border.

• Because of the anterior position of the AV node and the intrinsically fragile conduction system, patients with ccTGA are at higher risk of developing heart block during catheter manipulation, especially, but not invariably, when attempt-ing access into the PA.

• Floating balloon catheter is preffered.• Thus, it is always important to have available a system for

emergent transvenous pacing during the procedure itself.

• ANGIOCARDIOGRAPHY• Assuming the usual position of the

ventricular septum, a frontal and lateral left ventriculogram, perhaps with 20 to 25 degrees of right anterior oblique (RAO), should profile the ventricular septum, the left ventricular outflow tract, and the mitral inflow

• A similar projection can be used for the injection in the morphologic RV.

• Obviously, if there are defects in other portions of the ventricular septum, the axial projections will have to be modified and expanded.

• The character of the subpulmonary obstruction is best imaged by selective injection of contrast into the morphologic left ventricle. In the setting of VSD, adding 20 to 25 of RAO will demonstrate to advantage both the VSD and the left ventricular outflow tract obstruction.

• The functional status of the left AV valve is perhaps best assessed by echocardiography and color Doppler, but rightventricular angiography will also add information .

• The character of subaortic stenosis, admittedly uncommon, may best be demonstrated by right ventricular angiography. Varying degrees of obliquity may be required to pro le the small left ventricle or the VA connection of double-outlet RV.

• The pulmonary arteries and their bifurcation are best imaged by a selective injection of contrast into the pulmonary arteries with craniocaudal angulation.

• A degree of right or left anterior obliquity will focus on the right or left PA, respectively.

• The aorta and the coronary arteries can be profiled by aortography, filmed in the frontal and lateral projections.

• The coronary arteries originate from the posterior-facing sinuses, and selective coronary angiography may be necessary to obtain adequate demonstration of the anatomy.

• When anatomical repair is planned, such as the double-switch,procedure, coronary angiography may be helpful in delineating the anatomy of the coronary arteries.

• When there has been prior construction of a systemic-to- pulmonary arterial shunt, or the pulmonary trunk has been banded to reduce the flow of blood to the lungs or to train the morphologically left ventricle haemodynamic and angiographic data is required to demonstrate the anatomy of the pulmonary arteries and to show whether the morphologically left ventricle has been adequately trained so that it can support the systemic circulation.

• Medical Management• Medical management involves the usual modalities for

cardiac failure, such as inhibition of angiotensin-converting enzymes, diuretics, and control of arrhythmias with pacing to raise the heart rate when necessary.

Operative Indications of CC-TGA

The presence of corrected TGA is not an indication for a reparative operation

WITHOUT ASSOCIATED DEFECTS Complete heart block -WITH ASSOCIATED DFECTS 1. Ventricular septal defect

2. VSD & Important PS 3. Left-sided tricuspid incompetence

• CHB• Dual chamber AV sequential pacemeker is

indicated in any symptomatic patient with AV block.

• CORRECTIVE SURGICAL MANAGEMENT • Overview — There has been a paradigm shift from • conventional repair/Physiological Repair of the

associated cardiac lesions while maintaining the congenitally corrected atrioventricular and ventriculoarterial discordance to an

• “anatomic” repair, which makes the morphologic left ventricle become the systemic pump and the morphologic right ventricle the pulmonary ventricle.

1. Ventricle shape Cylindric vs. crescent-shaped cavity

2. Contraction pattern Concentric vs. bellow-like contraction

3. Pumping action Pressure pump vs. low pressure-volume pump 4. Coronary artery supply Two system vs. one system

5. Embryology Primitive ventricle vs. bulbus cordis

6. Papillary muscles Two papillary vs. small & numerous (septophylic)

Characteristics of Both Ventricles LV Vs RV

The long-term systemic workload results in progressive tricuspid regurgitation that increases volume overload and contributes to ventricular dysfunction and failure. Increase the vulnerability of this ventricle to ischemia,

particularly when hypertrophy is present

• Isolated L-TGA –• the choice of anatomic repair is controversial.• complex procedures that require substantial time on

bypass .• In contrast, there are data that show adults with isolated L-

TGA without anatomic repair are at-risk for systemic heart failure, although the risk is lower than patients described above with associated lesions .

The final decision is individualized based on a review of the patient’s potential for heart failure without

anatomic correction versus the potential complications of the anatomic repair, and the

preference of the family.

• Suggested guide for deciding surgical approach • Pediatric patients with L-TGA and

– significant ventricular septal defect [VSD], – left ventricular (LV) outflow tract obstruction, and/or – Ebstein-like malformation of the tricuspid valve

• should be considered for anatomic repair as they are at greatest risk for developing systemic heart failure with conventional repair.

• Patients who are diagnosed with L-TGA beyond childhood eventually present with systemic ventricular dysfunction or failure, systemic tricuspid valve regurgitation, or arrhythmias.

• When systemic tricuspid regurgitation is present, these adults should be referred for systemic AV valve replacement before they have morphologic right ventricular failure or progressive dysfunction (systemic right ventricular EF less than 40 percent).

• PA banding has been found to improve systemic AV valve regurgitation in select patients.

• Cardiac transplantation or ventricular assist device placement should be considered in patients with persistent heart failure refractory to these measures and medical management.

• conventional repair/Physiological Repair • Associated cardiac anomalies can be repaired with this

approach, albeit that the morphologically right ventricle remains as the pump to the systemic circulation. – ventricular septal defects, if present, can be closed, – obstruction within the left ventricular outflow tract can

be relieved by either resection or placement of a valved conduit, and the

– tricuspid valve, if leaking, can be repaired or replaced.

• ventricular septal defect • Usually the VSD is perimembranous in position- • NO right ventriculuotomy and no damage to systemic av valve

- incision in the right atrium,, through the morphologically mitral valve either displacing septal leaflet or cutting the annulus .

• Some muscular outlet defects can be – closed via the pulmonary trunk and the pulmonary valve.

• The conduction system passes in anterocephalad fashion around the pulmonary outflow tract.

• To avoid damaging the conduction system, either continuous or interrupted sutures are placed on the morphologically right ventricular margin of the defect superiorly, and from the morphologically left ventricular side of the margin inferiorly

• PA banding to prevent pulomonary overcirculation and PAH –May help for anatomic repair in future.

• LVOTO• Mostly subvalvular posteriorly located overlied by RV anteriorly.• Conduction system runs on left ventricular side of septum- any

tension on septum can damage it. • Incisions placed across the attachments of the pulmonary

valvar leaflets• the ventriculotomy is placed towards the apex of the ventricle

– careful resection of accessory tissue, or – open pulmonary valvotomy, but in general – a valved conduit is placed from the morphologically left

ventricle to the pulmonary arteries so as to relieve the obstruction.

• Valved conduits will not last forever, and most will need to be changed.

• It is wise, therefore, to close the pericardium with a membrane to protect the heart during sternal re-entry at reoperations.

• Morphologically tricuspid valve abnormalities• Repair or replacement of the morphologically tricuspid

valve sometimes has to be done as part of physiological repairs when there is severe tricuspid valvar regurgitation.

• with problems of continuing cardiac failure, since often the morphologically right ventricle is failing by the time such surgery is entertained.

• In addition, particularly in younger patients where there is marked dysplasia of the valvar leaflets, repair can be extremely difficult, if not impossible.

• Under these circumstances, replacement may well be necessary.

• Difficulties are Similar to ebstein anamoly

Classic Operation of CC-TGA 1. Repair of ventricular septal defect 2. Repair of coexisting VSD & PS · Extracardiac conduit · Without extracardiac conduit 3. Correction of incompetent tricuspid valve · Repair ( annuloplasty ) · Replacement 4. Fontan-type repair Straddling, A-V canal , hypoplastic ventricle

• Outcome and complications — • Although the early mortality is low, • long-term outcome is poor --progressive systemic RV

dysfunction and heart failure. • In a case series from a single center of 123 patients with L-

TGA that underwent conventional repair, postoperative survival rates at 1, 5, 10, and 15 years were 84, 75, 68, and 61 percent, respectively .

• Risk factors associated with a poorer outcome included – tricuspid valve replacement, – preoperative poor RV function, – complete heart block after surgery, – subvalvular pulmonary stenosis, and – Ebstein-like malformation of the tricuspid valve.

• Anatomic repair — 

• Associated lesions remains the major determinant

regarding surgical repair.

• The poor late outcome results associated with conventional

repair of L-TGA has led to anatomic correction to make the

morphologic LV the systemic pump and the morphologic RV

the pulmonary ventricle.

1. Morphologic LV that is prepared (ie, sufficiently hypertrophied or “trained”) to take over the workload of the systemic ventricle, thereby minimizing the likelihood of postoperative LV failure.

2. Current LV/RV pressure ratio greater than 0.7

3. Unobstructed LV-PA & RV-Ao connections

4. Balanced ventricular & AV valve sizes

5. Septatable heart, without AV valve straddling

6. Translocatable coronary arteries

7. Competent mitral valve with good LV function

(Karl TR, et al. ATS 1997)

Proposed Patient Selection Criteria

• Anatomical Correction• The current choice of surgical intervention for anatomic

correction of the ventricles is largely dependent on the – presence of subpulmonary obstruction and the – anatomy of the VSD:

• morphologically left ventricle is restored to pumping the systemic circulation by – double-switch operation-combining atrial and arterial

switch procedures, or – atrial switch along with ventricular rerouting.

• Double -switch operation– Where competent and non-stenotic valves.

• Atrial switch along with ventricular rerouting/ Senning-Rastelli procedure.– Where there is pulmonary stenosis or atresia, usually in

association with a large ventricular septal defect, the atrial switch is combined with tunnelling of the morphologically left ventricle to the aorta.

– A valved conduit is then placed from the morphologically right ventricle to the pulmonary arteries.

• Pulmonary artery banding or left ventricular “training” — 

• Not needed in significant PS/pulmonaryhypertension/unrestrictive VSD.

• In these patients, the LV is already functioning at pressure levels consistent with what will be required as the systemic ventricle.

• However, in other patients in whom the LV is not initially ready to become the systemic ventricle, PA banding is used to “train” the LV.

• Pulmonary artery banding or left ventricular “training” — 

• In L-TGA patients with a LV that is not ready to function as the systemic ventricle, placement of a band on the pulmonary artery (PA) is used to increase the afterload of the morphologic LV.

• This exposure to near systemic pressure increases the LV posterior wall thickness (ie, left ventricular “training”).

• Altering the left and right ventricular pressure ratio may also reduce the right ventricular sphericity and improve the geometry of the right ventricle prior to anatomic correction .

• Although pediatric cardiac surgical centers use varying measurements to determine if a morphologic LV is adequately prepared for the systemic circulation, most published reports suggest a morphologic LV pressure of 66 to 80 percent of systemic pressure is sufficient.

• In addition, others recommend that normal LV mass and thickness for systemic function using echocardiography and/or magnetic resonance imaging be required prior to anatomic correction .

• Risk factors for failure of PA band retraining include – mild LV dysfunction before banding, – development of significant LV dilation and dysfunction,

and – postoperative development of tricuspid regurgitation .

• In several case series, the median time from PA banding to the double switch procedure ranged from 2 to 14.5 months .

• Typically, PA banding appears to be more successful in patients less than 13 years of age, and the younger the patient, the shorter interval required for training.

• Patients older than 16 years of age appear to be unlikely to achieve sufficient LV function to proceed to anatomic correction.

• Pulmonary artery banding  for Large ventricular septal defect — 

• In infants with a large unrestrictive VSD, an increase in pulmonary blood flow may result in heart failure in the first few weeks of life as the pulmonary vascular resistance falls.

• The placement of a PA band can be considered in patients who are refractory to medical management.

• Creating increased resistance to the pulmonary circuit will reduce pulmonary blood flow, improve the symptoms of heart failure, and promote weight gain.

• Promotion of growth is desired as anatomic surgical correction is easier to perform in a larger infant.

• Double switch operation — 

• The double switch (DS) operation consists of an atrial switch procedure that creates an intra-atrial baffle (Mustard or Senning procedure) and an arterial switch operation (ASO).

• The intra-atrial baffle diverts the deoxygenated systemic venous return into the subpulmonary ventricle and oxygenated pulmonary venous return to the subsystemic ventricle.

• The ASO involves transection of both great arteries, and then translocation of the vessels to the opposite root similar to the ASO procedure performed for D-TGA requiring coronary artery transfer.

• Relocation of the pulmonary trunk may be achieved by transposing the pulmonary arteries anterior to the reconstructed aorta, or they may be left in posterior position.

• In general, if the aorta is more or less anterior to the pulmonary trunk, then the pulmonary arteries are relocated anteriorly.

• If the arterial trunks are more side-by-side, then we leave the pulmonary arteries behind the newly reconstructed aorta.

• At the end of the procedure, it is important to check on the reconstruction using transoesphageal or epicardial echocardiography, confirming the patency of the venous and arterial pathways as well as ensuring adequate ventricular function

• After a DS procedure, normal concordance is established with systemic deoxygenated blood baffled across the tricuspid valve into the morphologic right ventricle and flow into the pulmonary artery.

• In addition, the oxygenated pulmonary venous return is baffled from the left atrium across the mitral valve into the morphologic left ventricle and then pumped across the neo-aorta to the systemic circulation

• This operation is a technically difficult and challenging procedure with a long cardiopulmonary bypass time.

• Therefore, identifying the ideal surgical timing is a complex issue.

• Various centers report a median age at the time of surgery that ranges from 7 months to 3.2 years and a median weight of 9.6 to 14.7 kg.

• Early hospital mortality is reported to range from 0 to 7.4 percent, and reported event-free survival rates are between 70 to 85 percent at 10 years .

• In addition, coronary artery transfer is required. As a result, in patients undergoing this surgical intervention, delineating the coronary anatomy is mandatory.

• Senning-Rastelli procedure — • In patients with L-TGA that have a VSD and LV outflow tract

obstruction, the Senning-Rastelli (SR) procedure is typically used. • In this intervention, the intra-atrial baffle (Senning tunnel) is

created and a baffle is placed in VSD so that the blood from the LV is directed into the aorta, and a conduit is placed between the right ventricle and pulmonary artery (Rastelli procedure).

• The Rastelli procedure requires a sizable and appropriately located VSD so that the baffle can be placed to redirect blood flow into the aorta.

• The intermediate-term results show improved survival of this group compared with the patients undergoing a double switch operation same used for D-TGA, VSD, and LV outflow tract obstruction.

• Long-term, conduits become stenotic as they do not grow as the child grows. As a result, patients who undergo a Senning-Rastelli procedure require serial conduit replacements.

• Ventricular Rerouting Combined with Atrial Redirection

• The atrial switch is performed in the same manor as for the double-switch procedure

• An incision is made in the morphologically right ventricle, permitting creation of an intraventricular tunnel between the ventricular septal defect and the aorta.

• In creating this tunnel, care has to be taken to avoid any subaortic stenosis.

• The repair is completed by placing a valved conduit from the right ventriculotomy to the pulmonary arteries.

• Outcome and complications — Because these procedures were initially introduced in the 1990s, there are limited long-term outcome data. Nevertheless, several case series have provided information regarding mortality and morbidity.

• Mortality — • The following case series demonstrate comparable

mortality rates to that seen with conventional repair. It remains to be seen if long-term survival improves

• In a large case series of 113 patients from an English pediatric cardiac surgical center of patients undergoing anatomic repair from 1991 to 2011, actuarial survivals at 1, 5, and 10 years were 88, 84, and 84 percent in the DS group (n = 68), and 92, 92, and 77 percent in the SR group (n = 45), respectively .

• Early deaths occurred in five patients in the DS group, and no patients in the SR group

• Morbidity — • The complications associated with anatomic correction in

patients with L-TGA are primarily due to conduction abnormalities (ie, complete heart block and arrhythmias), left ventricular dysfunction, and neo-aortic regurgitation.

• In addition, some of the baffle-associated complications seen in patients with D-TGA who undergo ASO repair may also occur in patients with L-TGA who undergo DS operation.

• Conduction abnormalities — • New onset complete heart block and atrial arrhythmias are

common complications postoperatively .• In the previously mentioned English case series of 113

patients.• After anatomic correction, pacemaker insertion was

required in 10 of the 68 patients who underwent DS and in 5 of the 45 patients with SR procedure. In this cohort, tachyarrhythmias were observed in four patients preoperatively and developed in four patients postoperatively (three in the DS group and one in the SR group).

• Left ventricular dysfunction — .  • Morphologic LV dysfunction -reported in 14 to 18 percent of

patients .• Due to the small numbers of patients, it is currently difficult

to determine with certainty the underlying cause or risk factors of postoperative LV dysfunction.

• In the previously mentioned English case series, 16 of the 113 patients (14 percent) developed LV dysfunction postoperatively, all of whom were in the DS group .

• Neo-aortic regurgitation — • Patients who have undergone DS appear to be at greater

risk for neo-aortic regurgitation than patients who have undergone SR procedure.

• In the case series from England, 70 percent of patients after DS repair had at least mild aortic insufficiency (AI) at follow-up, including six patients with severe AI requing AVR.

• Risk factors for neo-aortic root dilation were previous pulmonary arterial banding and ASO performed in a later era

• A change in surgical technique is a likely explanation for the association between surgery in a more recent era with neo-aortic root dilation, possibly related to the increased size of the coronary “buttons” taken for the translocation.

• In this current era, pulmonary arterial banding is very rare as complete repairs are typically performed in the first week of life, thereby reducing the frequency neo-aortic regurgitation.

• Coronary artery stenosis or insufficiency  • The incidence of coronary events continues to be bimodal

with the majority of events (89 percent) occurring in the first three months following the ASO .

• These tend to be related to “kinking” or other anatomic obstructions to coronary perfusion. Unexplained ventricular dysfunction or poor hemodynamics should prompt early evaluation of the coronaries in the postoperative setting.

• Risk factors for the development of coronary events include type of coronary anatomy (presence of a single coronary orifice ) and the occurrence of a major intraoperative event (coronary translocation difficulty, left ventricular dysfunction, cardiac arrest, or temporary mechanical support at the end of the intervention).

• Baffle-associated complications — • Although there are limited reports of baffle-associated

complications in patients with L-TGA undergoing anatomic repair, they have been reported frequently in adult patients undergoing D-TGA surgical repair

• Obstruction at the right atrial and superior vena caval junction is a recognized complication of the Mustard procedure. The clinical presentation may include chylothorax, upper extremity edema, or facial plethora.

• Pulmonary venous obstruction is a complication more commonly associated with the Senning procedure. Pulmonary venous congestion may be an early manifestation. Progressive obstruction may be seen later and may present with symptoms of reactive airway disease.

• Reintervention — • Surgical reintervention is common in patients who undergo

either a SR procedure or DS operation as illustrated by the following findings from the previously mentioned English case series :

• In the SR group (n = 45), 34 reinterventions were performed in 16 patients including 14 right ventricular-pulmonary artery conduit changes or ballooning.

• In the DS group (n = 68), 41 reinterventions were performed in 13 patients including six aortic valve replacements, and surgical and catheter reinterventions of the Senning pathway in 14 patients.

• FOLLOW-UP CARE —•  Longitudinal follow-up care is required in all patients with

levo- or left-transposition of the great arteries (L-TGA) by a cardiologist with expertise in congenital heart disease.

• Clinicians need to know the potential complications following the various surgical repairs and in unoperated patients.

• Follow-up routine care includes focused history, physical examination, and detailed imaging study by echocardiography and/or magnetic resonance imaging (MRI).

• History —:• Episodes of syncope or palpitations that may suggest an

underlying arrhythmia or complete heart block• Increasing exercise intolerance suggestive of declining

systemic ventricular function or increasing pulmonary artery obstruction

• Exertional chest pain may suggest coronary artery insufficiency.

• Edema of the face and upper extremities suggest superior venal caval obstruction due to a baffle complication seen in the Senning procedure

• Dyspnea may suggest systemic atrioventricular (AV) valve regurgitation or systemic ventricular dysfunction in the adult patient that is unoperated

• Physical examination — • Vital signs, particularly the pulse, to determine any

irregularity that suggests an underlying arrhythmia• Cardiac auscultation to detect any murmur (eg, pulmonary

stenosis, aortic or tricuspid insufficiency) or gallop (eg, failure)

• Examination for signs of cardiac failure including pulmonary congestion, peripheral edema, and hepatomegaly

• Tests — Routine testing includes electrocardiography and echocardiography.

• Electrocardiography (ECG) is performed yearly to detect and diagnose arrhythmias. ECG is essential to look for complete heart block as there is a 2 percent annual risk for the development of complete heart block

• Holter or event recorder monitoring may be useful in patients with a history suggestive of arrhythmia.

• Routine echocardiography is used to assess ventricular function, detect pulmonary artery stenosis, and evaluate competency of the neo-aortic valve. Evaluation of the systemic and pulmonary venous baffles can also be performed with echocardiography.

• Angiography remains the preferred modality to diagnose coronary artery occlusions in patients who undergo the arterial switch operation

• Cardiac magnetic resonance imaging is an excellent tool to quantify ventricular function.

• It should be used when evaluating adults who have not undergone repair, and can be used to accurately assess left ventricular thickness and function in those patients who have undergone PA banding.

• This diagnostic modality is also helpful in identifying fibrosis and scar formation.

• Endocarditis prophylaxis —•  Prophylactic antibiotics for endocarditis are recommended

for patients who have surgical repairs that include the use of prosthetic material (eg, heart valve), prior episode of endocarditis, and those with high-risk lesions for endocarditis (eg, unrepaired cyanotic heart disease or with a residual defect such as a patch margin VSD).

• PREGNANCY —•  In general, women with a systemic ventricular ejection fraction

that is less than 40 percent and/or have a New York Heart functional class III and IV should be counseled against pregnancy as the added volume load of pregnancy is typically not well tolerated.

• In a one study of 22 women with L-TGA, 50 of the 60 pregnancies resulted in live births including one preterm birth at 29 weeks gestation. None of the infants had congenital heart disease.

• There were no pregnancy-related deaths but one woman developed heart failure due to worsening systemic atrioventricular valve regurgitation.

• In addition, one woman with 12 pregnancies resulting in 10 live births subsequently developed endocarditis and heart failure