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Transposition of the Great Arteries
Eric Osborn
January 27, 2010
Outline
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Definitions
Embryology
Epidemiology
Complete transposition (D-TGA)
Congenitally corrected transposition (L-TGA)
Echocardiography
Definitions
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The key anatomic characteristic of transposition
complexes is ventriculoarterial discordance.
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The aorta arises from the morphological RV
The PA arises from the morphological LV
Definitions
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Complete transposition (D-TGA)
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Atrioventricular concordance
Definitions
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Congenitally corrected transposition (L-TGA)
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Atrioventricular discordance
Embryology
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22 days gestation …
the primitive straight cardiac tube is formed
Embryology
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23 days gestation … the straight cardiac tube elongates
and bends forming the cardiac loop.
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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
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4th-7th weeks gestation … the heart divides into 4
chambers via formation of swellings (cushions) of
tissue that exhibit differential growth.
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Endocardial cushions divide the AV canal forming the mitral
and tricuspid valves.
Conotruncal cushions form the outflow tracts, aortic and
pulmonary roots.
Embryology
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5th week gestation … the conotruncal cushions.
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Right superior truncal cushion grows distally and left-ward.
Left inferior truncal cushion grows distally and right-ward.
The net effect is a twisting motion.
The truncal cushions fuse to form the truncal septum.
Additional cushions develop in the conus which grow down
and towards each other until they fuse with the truncal
septum to form the RVOT and LVOT.
Embryology
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Mechanism of great artery transposition
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Conotruncal cushion defect
Leads to failure of the conotruncal septum to spiral and
instead extends straight downward
Aorta fuses with the RV and PA with the LV
Epidemiology
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~0.8% of live births are complicated by a
cardiovascular malformation*.
>750,000 adult patients with congenital heart disease.
Transposition of the great arteries occurs in
approximately 1 per 5,000 live births.
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More common in males
Diagnosis possible in utero with fetal echocardiography
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Transvaginal ultrasound at 13-14 weeks (limited views)
Transabdominal ultrasound at 16 weeks
*not including bicuspid aortic valve and mitral valve prolapse
Complete transposition (D-TGA)
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Pulmonary and systemic circulations are in parallel
Lethal, if no mixing (ASD, PDA, VSD)
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¾ are simple with no major associated abnormalities
¼ are complex
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VSD (16%)
Pulmonary/subpulmonary stenosis (9%)
Coarctation of the aorta (4%)
Complete transposition (D-TGA)
Clinical Presentation and Outcomes
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Larger size and weight at birth
Dyspnea and cyanosis
Progressive hypoxemia
Congestive heart failure
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Without treatment, the outlook is dismal
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30% mortality within the 1st week
90% mortality within the 1st year
Complete transposition (D-TGA)
Management
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Prostaglandin E1 to maintain the PDA
Atrial septostomy (balloon or surgical)
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Palliative prior to corrective surgery
Repair within the first days to weeks of life
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2-4% mortality with 90% 1 year survival
Atrial switch
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Mustard or Senning
Arterial switch
Rastelli procedure
Complete transposition (D-TGA)
Atrial switch (Mustard/Senning)
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Developed in the 1950s
Baffle directs venous return to contralateral ventricle
Complete transposition (D-TGA)
Atrial switch (Mustard/Senning)
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Disadvantages
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RV functions as the systemic ventricle
Several significant long term complications
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Congestive heart failure
Arrhythmias
Baffle leaks and obstruction
Pulmonary hypertension
Paradoxial embolus
Endocarditis
Overall survival 75% at 25 years
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Senning may be better than Mustard [Moons et al, Heart 2004]
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340 patients (~⅔ Senning) compared
Less obstruction (1 vs. 15%) and better functional class with Senning
No significant mortality benefit
Complete transposition (D-TGA)
Atrial switch (Mustard/Senning)
Arrhythmias
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Palpitations, presyncope, and syncope are not uncommon
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Both brady and tachyarrythmias frequently seen
50% develop sinus node dysfunction
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Physical damage during surgery and baffle construction
Disruption of blood supply leading to ischemia
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20% develop atrial flutter
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Sensitive to nodal agents due to conduction system disease
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11% required pacemakers at 20 years [Gelatt et al, J Am Coll Cardiol 1997]
Pacemakers are difficult to place due to distorted anatomy
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Should be avoided if residual intracardiac communications due to risk of paradoxical
embolus and stroke
Complete transposition (D-TGA)
Atrial switch (Mustard/Senning)
Congestive heart failure
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Most adult patients develop congestive heart failure
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By 20 years most are NYHA Class I or II
RV filling compromised due to defects in baffle construction
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Baffle leaks (Mustard>Senning)
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Left-to-right shunts with pulmonary hypertension (7%)
Risk of paradoxical embolus and stroke
Indications for intervention include >1.5:1 left-to-right shunt or any right-to-left shunt
Baffle obstruction (5-15%, Mustard>Senning)
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SVC>IVC manifesting as SVC syndrome or hepatic congestion/cirrhosis
Often undetected due to collateral venous drainage (e.g. azygous vein)
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40% develop right ventricular dysfunction
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10-40% develop 2+ or greater tricuspid (systemic AV valve) regurgitation
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Annular dilatation from RV failure
Damage from surgery or endocarditis
Complete transposition (D-TGA)
Suggested Follow-up
Complete transposition (D-TGA)
Arterial switch
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Developed in the 1980s
Great arteries and coronaries are transected and reanastamosed
Complete transposition (D-TGA)
Arterial switch
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Advantages
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LV is the systemic pump
No disruption of atrial conduction (sinus rhythm)
Fewer long term complications compared to atrial switch
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Coronary ostial stenosis
Supravalvular pulmonary/aortic stenosis
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Intervention indicated for RVOT gradient >50 mmHg
Neoaortic regurgitation
Arrhythmias
Follow up with normal LV function and good exercise capacity
Complete transposition (D-TGA)
Rastelli procedure
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TGA with VSD and LVOT obstruction
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Outcomes
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RV-PA conduit obstruction
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Exercise intolerance/angina
RV failure
Intervention for RV-PA
gradient >50 mmHg
LV-Ao patch obstruction
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Dyspnea or syncope
Complete transposition (D-TGA)
RV Failure after Atrial Switch
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Standard heart failure therapies are unproven
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The two-stage arterial switch
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Stage 1 – the PA is banded to ‘re-train’ the LV to handle
systemic pressures
Stage 2 – the atrial baffles and pulmonary band are taken
down and an arterial switch is performed
50% survival at 8 years in early results
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Appears to be more successful in patients under 12
Congenitally corrected transposition (L-TGA)
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A rare disorder that may present in adulthood.
Associated anomalies (95% of patients)
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VSD (75%, commonly perimembranous)
Pulmonary stenosis (75%, commonly subvalvular)
Tricuspid valve anomalies (>75%)
Congenital complete heart block (5%)
Congenitally corrected transposition (L-TGA)
Outcomes
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Arrhythmias
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Abnormal AV node and His positions
Dual AV nodes
2% per year incidence of complete heart block
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Susceptible to fibrosis of conduction system
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Median survival 40 years
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Mortality from progressive RV failure or arrhythmias
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Tricuspid regurgitation is major predictor
Congenitally corrected transposition (L-TGA)
Double Switch Procedure
Echocardiography
Segmental approach to congenital heart disease
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Position of the apex
Situs of the atria
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Morphological atria based on anatomic appearance of their appendages
75% concordance with abdominal situs (aorta and IVC positions)
Atrioventricular relationship
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Differentiate the morphological RV from LV:
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Trabeculated apex
Moderator band
Septal attachment of the tricuspid valve
Lower (apical) insertion of the tricuspid valve
Ventriculoarterial relationship
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Pulmonary artery is distinguished by its early branching pattern
Curved contour of the aortic arch with three major branches
Echocardiography
Complete Transposition with Atrial Switch
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Hallmark is parallel great arteries (parasternal long axis)
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Aorta is anterior to PA
Echocardiography
Complete Transposition with Atrial Switch
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Systemic hypertrophied RV septum bows into LV
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May impact TR and enhance subpulmonary stenosis
Echocardiography
Complete Transposition with Atrial Switch
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Aortic and pulmonic valves lie in the same plane
Aorta is anterior and to the right (parasternal short axis)
Echocardiography
Congenitally Corrected Transposition
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Hallmark is reversed offsetting of the AV valves
Aorta is anterior and to the left (parasternal short axis)
Echocardiography
Special Considerations
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Atrial switch
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RV function
Tricuspid regurgitation
Subpulmonary obstruction
Baffle leak or obstruction (color Doppler)
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Arterial switch
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Normal baffle flow is phasic with peak velocity <1 m/sec
Neoaortic valve regurgitation
Supraneopulmonary valve stenosis
Wall motion abnormalities due to coronary artery ostial stenosis
Rastelli procedure
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LV-Ao tunnel patch obstruction
RV-PA conduit degeneration (stenosis/regurgitation)
Endocarditis Prophylaxis
ACC/AHA 2008 Guidelines state that antibiotic
prophylaxis is reasonable to consider for patients at the
highest risk of adverse outcomes (Class IIa)
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Prosthetic valves
Prior endocarditis
Congenital heart disease
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Unrepaired cyanotic, including palliative shunts and conduits
Completely repaired with prosthetic material or device (6 months)
Repaired with defects at or near a prosthetic device
Post-cardiac transplant with valvular disease
Endocarditis Prophylaxis
References
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Webb et al., Congenital Heart Disease in Braunwald’s Heart Disease, 8th ed., Chapter 61, 1561-1624.
Sadler, Cardiovascular System in Langman’s Medical Embryology, 8th ed., Chapter 11, 208-259.
Otto, The Adult with Congenital Heart Disease in Clinical Echocardiography, 4th ed., Chapter 17,
418-447.
Warnes, Transposition of the Great Arteries, Circulation 2006 114:2699-2709.
Love et al., Evaluation and Management of the Adult Patient with Transposition of the Great
Arteries Follow Atrial-level (Senning or Mustard) Repair, Nature Clinical Practice Cardiovasc Med
2008 5:454-67.
Verhuegt et al., Long-term Prognosis of Congenital Heart Defects: A Systematic Review, Int J
Cardiol 2008 131:25-32.
Skinner et al., Transposition of the Great Arteries: from Fetus to Adult, Heart 2008 94:1227-35
ACC/AHA Guidelines for the Management of Adults with Congenital Heart Disease, J Am Coll
Cardiol 2008 52:e1-121.