Basics
Description
Abnormal anatomic relationship between the great arteries and the ventricles in which the aorta arises from the anatomic right ventricle and the pulmonary artery arises from the anatomic left ventricle
Incidence
Incidence is 20 " 30 per 100,000 live births, with a 60 " 70% male predilection.
Prevalence
Transposition of the great arteries represents up to 7% of all cases of congenital heart disease.
Pathophysiology
- Systemic and pulmonary circulations are separated and function in parallel.
- Desaturated systemic venous blood is ejected from the right heart to the aorta, whereas the oxygenated pulmonary venous blood is ejected from the left ventricle into the lungs.
- Degree of hypoxemia depends on amount of intercirculatory mixing (patent ductus arteriosus [PDA], patent foramen ovale [PFO], ventricular septal defect [VSD]).
- Degree of left-to-right shunting is the effective systemic blood flow, whereas right-to-left shunting determines effective pulmonary flow.
Commonly Associated Conditions
- PDA and PFO with intact ventricular septum (50%)
- VSD (40%)
- Posterior malalignment VSD with left ventricular outflow tract obstruction (e.g., subpulmonic stenosis, pulmonary stenosis, pulmonary atresia) (10%)
- Anterior malalignment VSD with right ventricular outflow tract obstruction (e.g., subaortic stenosis, aortic stenosis, coarctation of the aorta or interruption of the aortic arch) (10%)
- Leftward juxtaposition of the atrial appendages (5%)
- Straddling of the atrioventricular valve
Diagnosis
History
- Infants are of normal birth weight or sometimes large for gestational age.
- Cyanosis
- Tachypnea often without retractions
- Poor feeding
Physical Exam
- General
- Moderate to severe cyanosis
- Cardiovascular
- Heart sounds: Single loud S2, but no heart murmur is heard in infants with intact ventricular septum; soft systolic murmur in those infants with a VSD and a systolic ejection murmur of valvar or subvalvar aortic or pulmonic stenosis may be heard.
- Respiratory
- Generally, dyspnea and tachypnea present without retractions in a neonate without a VSD; with a large VSD and congestive heart failure (CHF), retractions may be present.
- Abdomen
- Hepatomegaly may occur with a large VSD and CHF.
Diagnostic Tests & Interpretation
Lab
Arterial blood gas
- Hypoxemia (Po2 often in low 30s) unchanged in 100% FiO2. Infants with inadequate mixing have Po2 <25 torr with metabolic acidosis.
Imaging
- Chest radiograph
- Mild cardiomegaly with an egg-shaped heart with narrow superior mediastinum (so-called egg on a string) and increased pulmonary vascular markings
- ECG
- Initially normal, progressing to right ventricular hypertrophy and right axis deviation
- Echocardiogram
- 2D ECHO and color-flow Doppler studies usually provide all anatomic and functional information required for management of infants with D-transposition of the great arteries (D-TGA). The study should focus on the alignment of the great arteries and other associated anomalies, specifically defects that promote intercirculatory mixing, the presence of left or right ventricular outflow tract obstruction, and the coronary anatomy.
Pathologic Findings
- In D-TGA, the aorta is oriented anteriorly and rightward from the pulmonary artery and originates from the right ventricle, carrying desaturated blood to the body. The pulmonary artery originates posteriorly from the left ventricle and carries oxygenated blood to the lungs. There is fibrous continuity between the pulmonary and mitral valves; subaortic conus (infundibulum) is present. In the normal heart, the aorta arises posteriorly from the left ventricle and carries oxygenated blood to the body, there is fibrous continuity between the aortic and mitral valves, and subpulmonary conus is present.
- TGA types
- The most common type of TGA, known as D-TGA, has transposed great arteries with cardiac segments S, D, and D: situs solitus of the atria and viscera (S), dextroventricular segment situs (D), aortic valve annulus to the right of the pulmonary artery (D). There is atrioventricular concordance and ventriculoarterial discordance.
- L-TGA, or "corrected transposition, " has transposed great arteries with cardiac segments S, L, and L: situs solitus of the atria and viscera (S), levoventricular segment situs (L), and the aortic valve annulus is to the left of the pulmonary artery (L). There is atrioventricular discordance and ventriculoarterial discordance.
- Abnormal coronary artery (CA) branching occurs in 33%.
- Circumflex artery off the right CA (16%), single right CA (4%), single left CA (2%)
Differential Diagnosis
The differential diagnosis for the neonate with TGA is that for the cyanotic neonate.
- Cardiac
- Lesions with ductal-dependent pulmonary blood flow
- Tricuspid atresia with normally related great arteries
- Tetralogy of Fallot
- Tetralogy of Fallot with pulmonic atresia
- Critical pulmonic stenosis
- Pulmonary atresia with intact ventricular septum
- Ebstein anomaly
- Heterotaxy (most forms)
- Ductal-independent mixing lesions
- Total anomalous pulmonary venous connection without obstruction
- Truncus arteriosus
- Lesions with ductal-dependent systemic blood flow
- Hypoplastic left heart syndrome
- Interrupted aortic arch
- Critical coarctation of the aorta
- Critical aortic stenosis
- Pulmonary
- Primary lung disease
- Airway obstruction
- Extrinsic compression of the lungs
- Neurologic
- CNS dysfunction
- Respiratory neuromuscular dysfunction
- Hematologic
- Methemoglobinemia
- Polycythemia
Treatment
Medication
- Correction of metabolic acidosis, hypoglycemia, and hypocalcemia improves myocardial function.
- Prostaglandin E1 (PGE1) is used for severe cyanosis to promote left (aorta) to right (pulmonary artery) shunting at the ductus arteriosus, thereby increasing pulmonary blood flow, distention of the left atrium, and improved mixing at the atrial level. Side effects of PGE1 include apnea, fever, and hypotension.
Surgery/Other Procedures
- Interventional catheterization
- Balloon atrial septostomy (Rashkind procedure) is used in the severely hypoxemic infant with an intact or restrictive atrial septum to promote intercirculatory mixing at the atrial level and stabilize the neonate before definitive or palliative surgery.
- Definitive surgery for D-TGA includes procedures that redirect the pulmonary and systemic venous return at the atrial, ventricular, and great artery levels.
- Atrial inversion: Atrial inversion procedures involve baffling the pulmonary venous blood flow to the tricuspid valve (systemic circulation) and the systemic venous blood flow to the mitral valve (pulmonary circulation). The 2 atrial inversion operations include the Mustard procedure, in which prosthetic or pericardial baffles are used to redirect the blood, and the Senning procedure, in which the baffles are composed of an atrial septal flap and the right atrial free wall. The Senning or Mustard procedures may be used in the following infants:
- Infants with D-TGA with intact ventricular septum who have not had surgical repair within the 1st month of life
- Neonates with D-TGA with intact ventricular septum and severe pulmonic stenosis. Most centers would perform a Rastelli procedure for this anatomic variant (see subsequent list items).
- Neonates with D-TGA with "unswitchable coronaries " (<1% of cases)
- Ventricular inversion
- D-TGA with a VSD and severe pulmonic stenosis: The Rastelli operation may be used to redirect blood flow at the ventricular level. In this operation, the proximal main pulmonary artery is divided and oversewn, and the left ventricular blood flow is baffled to the aorta by creating an intraventricular tunnel between the VSD and the aortic valve. A conduit is placed from the right ventricle to the pulmonary artery to redirect the right ventricular blood flow.
- Arterial switch
- D-TGA with intact ventricular septum and "switchable " coronaries: The arterial switch operation (ASO) is performed in which the great arteries are transected above their respective semilunar valves and switched with reimplantation of the CAs into the neoaortic root (native pulmonary valve root).
- D-TGA with anterior malalignment VSD with severe aortic stenosis: ASO with VSD patch closure and transannular patch of the right ventricular outflow tract
Ongoing Care
Prognosis
- Without treatment, mortality is 30% within the 1st week of life, 50% within the 1st month, 70% within the first 6 months, and 90% within the 1st year.
- In most centers, the mortality rate after ASO for D-TGA with intact ventricular septum or D-TGA with a VSD is <3%. Factors that have been shown to increase the mortality risk include an intramural course of the left CA, retropulmonary course of the left CA, complex arch abnormalities, right ventricular hypoplasia, multiple VSDs, and straddling atrioventricular valves.
Complications
- Complications of intra-atrial surgeries include absence of sinus rhythm (>50% of cases), supraventricular arrhythmias (50%), moderately to severely depressed right ventricular function (20%), residual intra-atrial baffle shunt (20% of cases), tricuspid regurgitation (5 " 10% of cases), obstruction of systemic venous return (5% of cases), and obstruction of pulmonary venous return (<2% of cases). Follow-up observation is recommended every 12 months to detect arrhythmias, tricuspid regurgitation, or depressed right ventricular function that generally occurs years after surgery. Arrhythmias include sinus node dysfunction (e.g., marked sinus bradycardia, ectopic atrial rhythm, junctional rhythm, or junctional bradycardia) and supraventricular tachycardia, especially atrial flutter.
- Complications after the Rastelli operation include left ventricular outflow tract obstruction, conduit obstruction, and complete heart block. Follow-up observation is recommended every 12 months to monitor for conduit obstruction, left ventricular outflow tract obstruction, and heart block.
- The most common complication after the ASO is neoaortic root dilation with or without neoaortic insufficiency. Other rarer complications include supravalvar pulmonary stenosis at the anastomotic site (5% of cases), supravalvar aortic stenosis at the anastomotic site (5% of cases), and CA obstruction, which may lead to ischemia and infarction. These complications are uncommon and usually hemodynamically insignificant. Mortality varies depending on the period of time being assessed:
- Early mortality is usually related to kinking or obstruction of the CAs during transfer to the neoaorta, an "unprepared " left ventricle, or hemorrhage from the multiple suture lines.
- Late mortality (i.e., 1 " 2%) usually results from myocardial ischemia, pulmonary vascular obstructive disease, or during reoperation for supravalvar stenosis.
- Follow-up observation is recommended every 12 months to monitor for neoaortic root dilation, neoaortic valve insufficiency, supravalvar aortic or pulmonic stenosis, and CA ischemia.
Additional Reading
- Bellinger DC, Wypij D, Du Plessis AJ, et al. Neurodevelopmental status at eight years in children with dextro-transposition of the great arteries: the Boston Circulatory Arrest Trial. J Thorac Cardiovasc Surg. 2003;126(5):1385 " 1396. [View Abstract]
- Culbert EL, Ashburn DA, Cullen-Dean G, et al. Congenital Heart Surgeons Society. Quality of life of children after repair of transposition of the great arteries. Circulation. 2003;108(7):857 " 862. [View Abstract]
- Formigari R, Toscano A, Giardini A, et al. Prevalence and predictors of neoaortic regurgitation after arterial switch operation for transposition of the great arteries. J Thorac Cardiovasc Surg. 2003;126(6):1753 " 1759. [View Abstract]
- Langley SM, Winlaw DS, Stumper O, et al. Midterm results after restoration of the morphologically left ventricle to the systemic circulation in patients with congenitally corrected transposition of the great arteries. J Thorac Cardiovasc Surg. 2003;125(6):1229 " 1241. [View Abstract]
- Marino BS, Wernovsky G, McElhinney D, et al. Neo-aortic valvar function after the arterial switch. Cardiol Young. 2006;16(5):481 " 489. [View Abstract]
- Mavroudis C, Backer CL. Physiologic versus anatomic repair of congenitally corrected transposition of the great arteries. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu. 2003;6:16 " 26. [View Abstract]
- Pasquali SK, Hasselblad V, Li JS, et al. Coronary artery pattern and outcome of arterial switch operation for transposition of the great arteries: a meta-analysis. Circulation. 2002;106(20):2575 " 2580. [View Abstract]
- Warnes CA. Transposition of the great arteries. Circulation. 2006;114(24);2699 " 2709. [View Abstract]
- Williams WG, McCrindle BW, Ashburn DA, et al; Congenital Heart Surgeon 's Society. Outcomes of 829 neonates with complete transposition of the great arteries 12 " 17 years after repair. Eur J Cardiothorac Surg. 2003;24(1):1 " 9. [View Abstract]
Codes
ICD09
- 745.10 Complete transposition of great vessels
- 745.12 Corrected transposition of great vessels
ICD10
- Q20.3 Discordant ventriculoarterial connection
- Q20.5 Discordant atrioventricular connection
ICD10
- 26146002 Complete transposition of great vessels (disorder)
- 83799000 Corrected transposition of great vessels
- 399216004 D - transposition of the great vessels
- 399046008 L - transposition of the great vessels