- 1. Complete Transposition of the Great Arteries (complete TGA).
- 2. Isolated ventricular inversion.
- 3. Congenitally-corrected TGA.
- 4. Double-outlet right ventricle (DORV).
- 5. Double-outlet left ventricle (DOLV).
- 6. Single ventricle.
Complete Transposition of the Great Arteries (complete TGA).
Complete Transposition of the Great Arteries (complete TGA) is defined as: origin of the aorta (AO) from the anatomical right ventricle (RV), and origin of the pulmonary trunk from the anatomical left ventricle (LV), i.e. there is Ventriculo-Arterial (VA) discordance.
The anatomical left atrium (LA) is connected to the anatomical LV and the anatomical right atrium (RA) is connected to the anatomical RV, i.e. Atrio-Ventricular (AV) concordance is preserved.
- Situs solitus of the atria: i.e. the anatomical RA lies to the right.
- Situs solitus of the viscera: i.e. liver to the right, stomach & spleen to the left, and Tri-lobed lung to the right.
- D-loop of the ventricles, i.e. anatomical RV to the right.
- Atrio-ventricular concordance, i.e. LA to LV and RA to RV.
- Ventriculo-Arterial discordance, i.e. AO from RV & PA from LV.
- D-position of the great arteries: i.e. aorta to the right (this anomaly is thus called D-transposition of the great arteries).
- Coronary arteries usually arise normally from the aorta.
One or more communication between the two sides of the circulation, i.e. mixing between the systemic & pulmonary circulation, is essential for survival, such as:
- Inter-atrial communication (Atrial septal defect or patent foramen ovale) in almost all patients.
- Patent ductus arteriosus: in two thirds of patients.
- Ventricular septal defect: in one third.
Pulmonary stenosis (PS) of various severity, is another essential feature of complete TGA, which occurs due to one of the following pathological changes:
- Mal-alignment of ventricular septum, which is pushed leftwards obstructing LV outflow tract, from which PA arises.
- Adhesion of ventricular septum to anterior mitral leaflet, also obstructing LV outflow tract.
- Ventricular septal aneurysm, again obstructing LV outflow tract.
- Membranous sub-valvular PS.
- Valvular PS.
Normally, the systemic venous return (drained into RA) is delivered to the pulmonary circulation via the PA system, while the pulmonary venous return (drained into LA) is delivered to the systemic circulation via the AO.
In complete TGA, on the other hand, the systemic venous return is delivered back to the systemic circulation, since the AO arises from RV, while the pulmonary venous return is delivered back to the pulmonary circulation, since the PA arises from LV.
If the systemic & pulmonary circulations are totally isolated, this would be incompatible with life.
For survival, therefore, some communication between them should exist, to allow mixing of the two circulations; at least part of the systemic venous return is allowed to access the pulmonary circulation for oxygenation, and part of the oxygenated pulmonary venous return is allowed to access the systemic circulation to deliver oxygen to the tissues.
For mixing to occur, the shunt through the communication should be bi-directional; this is allowed by the nearly equal pressures between the two sides of the circulation: RV is facing the systemic circulation via the AO, and LV is facing the pressure overload created by pulmonary stenosis (PS).
Depending on the severity of PS on one hand, and the size of communication; hence the amount of shunt on the other hand, the pulmonary blood flow is determined:
Pulmonary blood flow increases with milder PS & bigger shunt from RV to LV, while it decreases with severer PS & smaller shunt.
Increased pulmonary blood flow may precipitate CHF, while its decrease would result in cyanosis.
At birth TGA constitutes 4% of all congenital heart diseases.
In children with congenital heart disease: TGA constitutes 9% of cases.
Female: male ratio is 1:2.
It presents in variable degrees of cyanosis & CHF Depending on pulmonary blood flow (Qp), as already explained in Pathophysiology.
- With small QP:
- Similar to F4
- but oligemia is not that marked
- With large QP:
- Egg-on-side (egg-on-a string) appearance of cardiac shadow.
- Lung Plethora.
- Right aortic arch is present in 10 % of cases of complete TGA.
The heart is enlarged with a narrow "pedicle" giving the so called "egg on a string" appearance. The superior mediastinum appears narrow due to the anteroposterior relationship of the transposed great vessels and "radiological absence of the thymus"
X-ray showing characteristic finding in case of Transposition of the great vessels which is called egg on side sign.
- With small QP:
- Right atrial enlargement (RAE).
- Right ventricular hypertrophy (RVH).
- With large QP:
- Evidence of enlargement of the four chambers of the heart.
Echocardiographic diagnosis depends on segmental analysis to define:
- A-V connections.
- V-A connections.
- Ventricular outflow tracts.
- Communications between the 2 sides of circulation.
- O2 saturation in PA > AO.
- RV: Systemic pressure.
- LV: according to the degree of PS.
- Wide pressure gradient between RV & LV indicates intact ventricular septum.
- Wide pressure gradient between RA & LA indicates intact atrial septum.
- Absence of pressure gradient between atria or ventricles does not guarantee the presence of an adequate communication.
- RV & LV angiography will establish the diagnosis.
- Coronary angiography should also be done.
Balloon atrial septostomy:
Balloon atrial septostomy should be done at the time of cardiac catheterization, for the newborn with TGA, to increase blood mixing thus improving cyanosis.
Mortality by one month is 50 % and by one year is 90 %.
With intact ventricular septum: Worst prognosis.
With big VSD: prognosis is better.
With big VSD & appropriate degree of PS: the best prognosis.
Gradual narrowing or closure of ASD, VSD, or PDA may occur.
Gradual increase of PS may also occur.
Pulmonary vascular obstructive disease (PVOD) does not usually develop in 1st year.
Cerebrovascular accidents (CVA) may occur.
A. Infant presented during the first two weeks of life:
LV in the first two weeks of life is still sufficiently hypertrophied to function as the systemic ventricle.
1. First step: increase blood mixing through:
- Prostaglandin E1 infusion to keep the ductus open: this increases the pulmonary blood flow (Qp) and the pulmonary venous return to LA, thus increasing blood mixing at the atrial level.
- Balloon atrial septostomy is done during cardiac catheterization.
- If the systemic O2 SAT is still < 60 % or PO2 still < 30 mmHg: surgical atrial septectomy should be done; but this is rarely needed.
2. Second step: Surgical correction:
- Atrial redirection procedures (Atrial switch operations).
- Arterial switch operation of Jatene.
- Rastelli procedure.
Atrial redirection procedures (Atrial switch operations):
Atrial redirection procedures were developed in the 1950s and 1960s but were replaced by the arterial switch operation, which became widely adopted in the 1980s.
The most common surgical procedure in patients who are currently adults is the atrial switch operation. Patients will have had either a Mustard or a Senning procedure.
Blood is redirected at the atrial level using a baffle made of Dacron or pericardium (Mustard operation) or atrial flaps (Senning operation), achieving physiological correction.
Systemic venous return is diverted through the mitral valve into LV, and pulmonary venous return through the tricuspid valve into RV.
The most important drawback of these procedures is that the morphological right ventricle is kept to support the systemic circulation.
Physical examination after atrial switch operations:
If the procedure is uncomplicated, physical examination reveals:
- RV parasternal lift.
- Normal S1.
- Single S2 (P2 is not heard because of its posterior location).
- Pansystolic murmur from tricuspid regurgitation (TR) if present, but not increasing with inspiration.
- RV S3, when severe RV dysfunction is present.
Long-term follow-up after atrial switch operations:
- Most patients who reach adulthood are in NYHA functional Class I or II.
- Abnormal atrial pathway of blood adversely affects ventricular filling and patient's functional capacity.
- Symptoms of CHF in about 10% of patients .
- Echocardiographic evidence of moderate or severe RV dysfunction in about 40%, probably due to increased RV O2 demands.
- Moderate-to-severe TR in about 25%.
- Arrhythmia (atrial flutter, sick sinus syndrome), due to surgical damage, causing palpitations and near-syncope/syncope.
- Short life expectancy: about 75% survival at 25 years.
- Sudden cardiac death in about 5%.
- Pulmonary vascular obstructive disease (PVOD) may develop.
- SVC or IVC baffle obstruction may occur, but collateral drainage through the azygos vein prevents systemic venous congestion.
- Pulmonary venous obstruction may also occur, with pulmonary congestive manifestations.
Arterial switch operation of Jatene:
- The second step nowadays after increasing blood mixing is the arterial switch operation of Jatene:
- AO is excised above the origin of the coronary arteries.
- Pulmonary trunk is excised a little above the pulmonary ring.
- AO is then anastomosed to the pulmonary trunk stump.
- Pulmonary trunk is anastomosed to the aortic stump.
- Coronaries are excised with a cuff of aortic wall & anastomosed to pulmonary trunk stump.
- The defects created in aortic stump after excision of coronary arteries are closed.
- The left-to-right shunt (VSD, ASD, PDA, foramen ovale) is closed.
Aorta & pulmonary trunk transected.
Aorta anastomsed to pulmonary stump and pulmonary trunk anastomsed to aortic stump, and coronary arteries transferred to the neo-aorta.
Advantages of Jatene operation:
- Restoration of the left ventricle as the systemic pump,
- Long-term maintenance of sinus rhythm.
Follow-up after arterial switch:
- Good left ventricular function and normal exercise capacity.
- Potential complications:
- Coronary occlusion.
- Supra- valvular pulmonary stenosis.
- Supra- valvular aortic stenosis and regurgitation.
- Satisfactory long-term patency and growth of the coronary arteries.
- Early systemic-to-pulmonary shunt, followed by:
- A corrective procedure:
- Extracardiac conduit between the right ventricle and the pulmonary trunk.
- Intracardiac baffle to direct LV blood to the aorta through the VSD.
Indications of Rastelli procedure:
Rastelli procedure is indicated in patients with complete TGA with VSD who have LVOFT obstruction causing marked diminution in pulmonary blood flow and critical cyanosis.
Physical examination after Rastelli procedure:
- No RV lift.
- An ejection systolic murmur from the conduit.
- Two components of the S2.
Long-term follow-up after Rastelli procedure:
- Angina, exercise intolerance, dyspnea and syncope may result from obstruction of the RV-to-PA conduit and/or the LV tunnel.
- Conduit replacement is inevitably required in surviving patients.
Electrocardiography after surgery:
- After atrial switch:
- Sinus bradycardia or junctional rhythm.
- No RA overload pattern.
- Marked RV hypertrophy.
- After arterial switch: ECG is normal.
- After Rastelli procedure: ECG shows RBBB.
Chest x-ray after surgery:
- After atrial switch:
- Egg on side appearance of TGA in PA view is preserved.
- The AO is filling the retrosternal space (due to its anterior position) on the lateral view.
- After arterial switch: normal mediastinal borders are present.
- After Rastelli procedure: CXR is normal, but may show a calcified conduit or a non-homograft prosthesis.
Echocardiography after surgery:
- After atrial switch:
- Parallel great arteries in parasternal long-axis view (running side by side) and in parasternal short-axis view (the aorta anterior and rightward).
- Assessment of RV function.
- Degree of TR.
- Presence or absence of subpulmonary LV obstruction.
- Baffle leak or obstruction.
- After arterial switch:
- Aortic valve regurgitation.
- Supravalvular pulmonary stenosis.
- Segmental wall motion abnormality due to coronary ostial stenosis.
- After Rastelli operation:
- LV-to-AO tunnel obstruction,
- RV-to-PA conduit degeneration with stenosis or regurgitation.
Cardiac catheterization after surgery:
Diagnostic cardiac catheterization may be required for assessing:
- Baffle obstruction or leak.
- Pulmonary hypertension.
- Coronary ostial stenosis.
- Tunnel or conduit obstruction.
B. Infant presented beyond two weeks of life:
- If LV pressure > 60 % of systemic: Jatene operation is done.
- If LV pressure < 60 % of systemic:
- LV preparation is needed before correction, in the form of:
- PA banding (to increase LV pressure),
- together with systemic-to-pulmonary (S-P) shunt (to maintain the pulmonary blood flow).
- Followed, 2weeks later, by Jatene operation, with removal of the PA band & closure of the S-P shunt.
Re-intervention after surgical correction of TGA:
Re-intervention after atrial switch:
- Severe symptomatic RV dysfunction may require a two-stage arterial switch procedure or cardiac transplantation.
- Severe TR rarely requires tricuspid valve replacement (TVR); if TR is due to a flail leaflet or cusp perforation providing RV function is adequate.
- A baffle leak resulting in a significant left-to-right shunt (>1.5/1), any right-to-left shunt, or attributable symptoms will require either surgical or trans-catheter closure.
- SVC or IVC pathway obstruction may require balloon dilation with or without stenting.
- Pulmonary venous obstruction will need re-operation, usually in childhood.
- Symptomatic bradycardia is managed by permanent pacemaker implantation.
- Tachyarrhythmias may require catheter ablation, an anti-tachycardia pacemaker device, or medical therapy.
Re-intervention after arterial switch:
- Significant RVOFT obstruction at any level (gradient >50 mmHg or RV/LV pressure ratio >0.6) may require surgical or catheter relief.
- Myocardial ischemia from coronary artery obstruction may require coronary bypass surgery.
- Significant AR may require aortic valve replacement (AVR).
Re-intervention after Rastelli procedure:
- Significant RV–PA conduit stenosis (>50 mmHg gradient) or significant regurgitation necessitates conduit replacement.
- Sub-aortic obstruction across the LV–AO tunnel necessitates LV–AO baffle reconstruction.
- A significant residual VSD (shunt >1.5/1) may require surgical closure.
Isolated Ventricular Inversion
Definition and pathology:
Isolated ventricular inversion refers to inversion of ventricles, so that LV is right-sided & RV is left sided. Atria are still in situs solitus (RA to the right), and origin of great arteries occurs normally from the correct ventricle. It is called isolated inversion because only the ventricles are inverted; there is no transposition of the great arteries and no change in atrial situs.
In this way; there is AV discordance (RA to LV and LA to RV), but with VA concordance (AO from LV, but on the right side, and PA from RV, but on the left side).
The systemic venous return drains to RA-LV-AO: i.e. it goes back to the systemic circulation.
The pulmonary venous return drains to LA-RV-PA, i.e. it goes back to the pulmonary circulation.
In this way, Pathophysiology is similar to that in complete TGA, inspite of different pathology.
Atrial redirection procedure.
Definition and pathology:
In Congenitally-corrected TGA, there is AV discordance (RA to LV & LA to RV), together with VA discordance, i.e. transposition of the great arteries (AO from RV & PA from LV).
Usually situs solitus of the atria (RA to the right) with l-loop of the ventricles (RV to the left) & l-position of great arteries (AO to the left).
In some cases there is situs inversus (RA to the left) with d-loop of the ventricles (RV to the right) & d-position of great vessels (AO to the right).
Congenitally-corrected TGA is rarely isolated, but usually associated with other anomalies, e.g.
- VSD: usually perimembranous.
- PS: usually infundibular.
- Tricuspid valve anomalies (on left side): Ebstein’s anomaly, clefts, dysplasia, straddling.
Systemic venous return drains into RA-LV-PA, thus delivered to the pulmonary circulation.
Pulmonary venous return drains into LA-RV-AO, thus delivered to the systemic circulation.
In this way the circulation is correct, though the anatomy is wrong.
If Congenitally-corrected TGA is not associated with other anomalies, the only problem will be that the anatomical RV is facing the systemic circulation and may fail with the passage of time.
The presence of associated anomalies in most cases, however, complicates matters, and results in cyanosis and/or CHF in various combinations, similar to other transposition & malposition complexes.
Most patients have PS & VSD and present with variable degrees of cyanosis & CHF, similar to complete TGA.
Rarely no associated conditions occur and the circulation is normal.
Slow irregular HR in 30 % due to heart blocks: 10 % of cases of congenital complete heart block (congenital CHB) are due to anatomically-corrected TGA.
Accentuated second heart sound at the upper left sternal border is common due to anterior displacement of the aorta: i.e. it is A2 not P2.
Murmurs of TR, PS, and VSD may be present
The ascending aorta is seen on the left side.
- Deep Q & S waves (QS pattern) in leads V1-3.
- Small r with deep S waves (rS pattern) in leads V4-6, I, & aVL.
- Heart blocks in 30 %.
- Identifies the pathology through segmental analysis.
- Identifies associated anomalies, particularly VSD & PS.
- Right-sided catheter passes from RA to LV and usually via VSD to AO in the position normally occupied by PA.
- PA entry may be difficult due to posterior and medial displacement.
- Angiography demonstrates the pathology: ventricular septum is seen lying in the sagittal rather than the coronal plane.
Survival to adulthood is possible
The most common cause of death is CHF, often during the first year; RV, connected to the systemic circulation, cannot usually sustain adequate cardiac output over a normal life span.
Two approaches are available:
- Keeping RV as the systemic ventricle, with correction of defects as necessary and as possible.
- Switching the circulation, if possible, so that the anatomical LV becomes the systemic ventricle.
RV is the systemic ventricle:
Surgery depends on anatomical & physiological details;
- PA banding, if pulmonary blood flow (Qp) is large.
- Systemic-Pulmonary shunt, if Qp is small.
- Tricuspid valve replacement if needed.
- Closure of VSD.
- Relief of PS, if possible.
- LV-PA valved conduit if PS cannot be relieved.
LV is the systemic ventricle:
- Double switch procedure:
- Mustard operation: to divert LA blood to LV & RA blood to RV plus;
- Jatene operation: to switch AO to LV & PA to RV.
- Mustard operation, plus Rastelli procedure:
- Routing LV to AO via a prosthetic baffle through VSD, and
- Placing a conduit from RV to PA bifurcation.
Double-Outlet Right Ventricle (DORV)
Definition and pathology:
Double-Outlet Right Ventricle (DORV) refers to origin of more than 50 % of the orifices of both semilunar valves from the morphologic RV.
It is characteristic that AO & PA lie side by side, with the two semilunar valves at the same level.
In most cases there is D-position of the great arteries (AO to the right).
No fibrous continuity exists between the mitral valve and any of the semi-lunar valves. This is pathognomonic of DORV and differentiates it from TOF, pulmonary atresia with VSD, and PTA, as detailed under TOF.
In all cases there is VSD:
- Sub-aortic VSD in 70 %
- Sub-pulmonary VSD in 20 % (a condition called: Tausig-Bing heart).
- Doubly committed in 3 %.
- Remote from both valves in 7 %.
Uncommonly there is l-position of great arteries (AO to the left), or aortic origin is directly anterior.
- Pulmonary stenosis (PS) in 50 %.
- Aortic stenosis (AS).
- Coarctation of the aorta.
- Atrial septal defect (ASD).
- Mitral stenosis (MS) or straddling mitral valve.
- Hypoplastic left ventricle.
It is a rare anomaly, found in 0.5 % of patients with congenital HD.
Its importance arises from its clinical resemblance to other more common anomalies from which it should be differentiated:
- DORV with sub-aortic VSD & no PS: Similar to isolated large VSD.
- DORV with sub-aortic VSD & PS: Similar to TOF.
- DORV with sub-pulmonary VSD & no PS: Like TGA without PS.
- DORV with sub-aortic VSD & no PS: Similar to Isolated large VSD.
- DORV with sub-aortic VSD & PS: Similar to TOF.
- DORV with sub-pulmonary VSD & no PS: Similar to TGA without PS, but PA is seen dilated & lying side by side, rather than posterior to AO.
- Right axis deviation,
- RA enlargement, and
- RV enlargement.
Echocardiography can establish the diagnosis & identify associated defects.
Differentiation between TOF, DORV & pulmonary atresia with VSD is mentioned under TOF.
- O2 saturation:
- RV: High O2 saturation.
- PA: Higher than A0, in cases with Sub-pulmonary VSD, and lower than A0, in cases with sub-aortic VSD.
- Pressures: LV > RV if VSD is small.
- Selective angiography of LV, RV & AO will establish the diagnosis.
Without PS: patients either die in infancy from CHF or develop PVOD.
Spontaneous narrowing or closure of VSD will cause progressive LVH and dyspnea & can be life threatening.
With PS, progressive cyanosis occurs, with its complications.
Treatment of CHF in those without PS.
Prevention & treatment of the complications of cyanosis, in those with PS.
- With sub-aortic VSD: Placement of a patch to close the communication between LV & RV, but directing LV blood through VSD into the AO.
- With sub-pulmonary VSD, or when the great arteries are transposed: Arterial switch operation, directing LV blood to the neo-aorta & closing VSD.
- With complex anomalies, e.g. in the presence of ventricular hypoplasia, valvular anomalies …… etc. palliation may be the only option, accordingly, e.g.
- PA banding.
- Systemic-to-pulmonary shunts.
- Fontan's operation.
Double-Outlet Left Ventricle (DOLV):
Both great arteries arise from the morphological LV.
It is a very rare anomaly, and is usually associated with VSD & PS (Valvular or sub-valvular).
Clinically, it presents like other transposition & malposition complexes with cyanosis and/or CHF according to pulmonary blood flow.
Correction is by closure of VSD and placement of an RV-PA conduit.
Single ventricle (SV) or uni-ventricular heart is characterized by flow of both systemic & pulmonary venous returns into a common ventricular chamber.
- In 70 % of cases there is a dominant ventricle with LV characteristics, communicating with a rudimentary RV, through an opening called the bulbo-ventricular foramen.
- In 20 %: dominant RV & rudimentary LV.
- In 10 %: neither ventricular feature can be identified.
The great arteries:
- These may be concordant (Normal).
- Discordant (Transposition).
- Double-outlet: both AO & PA arising from the dominant ventricle (either anatomical LV or RV).
- Or Single-outlet: one of the great arteries is atretic.
- PS or pulmonary atresia.
- Sub-valvular AS .
Variable degrees of cyanosis and/or CHF, according to the degree of PS and pulmonary blood flow.
- With severe PS:
- Normal heart size.
- Pulmonary oligemia.
- With no PS:
- Marked cardiomegaly.
- Pulmonary plethora
Either LVH or RVH according to the dominant ventricle.
Can identify the pathology and assess the severity of PS or AS.
- O2 saturation: Various degrees of systemic arterial destruction, according to the magnitude of pulmonary blood flow.
- Pressures: To asses the 4 valves.
- Angiography: To visualize Pathology.
According to pulmonary blood flow, patients may die either from CHF or cyanosis.
Sub-aortic obstruction may develop.
Atrioventricular valve regurgitation may also occur.
Infective endocarditis is a threat.
Progressive deterioration of ventricular function is particularly liable when the dominant ventricle is of RV type.
Treatment and prevention of cyanosis, CHF, anemia, Polycythemia…etc.
Prostaglandin E1 may be needed in neonates who have severe PS, and pulmonary flow is dependent on the ductus arteriosus from AO.
Any of the following procedures may be required:
- Systemic-to-pulmonary arterial shunt.
- PA banding.
- Fontan's operation (Anastomosis of RA to PA).
- Glenn’s operation (Anastomosis of SVC to PA).