Transposition of the Great Arteries

18 Transposition of the Great Arteries



Rima S. Bader, James C. Huhta



I. CASE


A 23-year-old white woman, gravida 4, para 0+3, was referred at 23 weeks’ gestation by the obstetrician for an abnormal scan and a previous baby with ventricular septal defect (VSD).



A. Fetal echocardiography findings




1. The fetal echo reveals situs solitus of the atria, levocardia, left aortic arch, and heart rate of 142 bpm.


2. The four-chamber view is normal, with equal-sized ventricles and a normal cardiac axis, position, and size (cardiothoracic ratio = 0.3).


3. The outflow assessment reveals transposition of the great arteries (TGA) (aorta anterior and to the right of the pulmonary artery), with mild asymmetry. Aorta–to–pulmonary artery diameter ratio is 1:0.7 (Fig. 18-1).


4. The pulmonary valve is bicuspid and domes mildly in systole. There is moderate flow acceleration through it by Doppler (1.5 m/s).


5. There are good-sized branch pulmonary arteries. The right pulmonary artery is 2.2 mm and the left pulmonary artery is 2.2 mm.


6. The aortic annulus is of normal size and there is normal Doppler velocity through it.


7. The aortic arch is leftward and the ductal and aortic arches are of similar size. Both arches have antegrade flow.


8. There is a large subpulmonary perimembranous VSD.


9. Flow through the foramen ovale is unrestricted, with a bidirectional shunt.


10. The pulmonary venous flow pattern is normal.


11. The RV and LV Tei indices (myocardial performance index) are normal.


image

Fig. 18-1 Parallel great arteries in the outflow tract view in the fetus. The right ventricle (RV)connects to the aorta (Ao) and the left ventricle (LV) connects to the pulmonary artery (PA).



B. Cardiovascular profile score




1. The cardiovascular profile score is 10/10.


2. The venous and arterial flow patterns are normal.


3. There are no signs of heart failure.



C. Associated syndromes and extracardiac anomalies


None.



D. Fetal management and counseling




1. Amniocentesis was not offered. The risks from amniocentesis are probably higher than the risk of abnormal karyotype in simple transposition.


2. Follow-up includes serial antenatal studies at 4- to 6-week intervals.


a. The size of the ventricles should be compared. RV hypoplasia is a rare finding but one that can alter the surgical management to a single-ventricle repair.


b. Pulmonary outflow should be monitored for progressive pulmonary outflow tract obstruction as well as progressive main and branch pulmonary arteries and change in direction of ductus arteriosus flow.


c. Progressive foramen ovale restriction can occur (Maeno et al, 1999).


d. Progressive ductus arteriosus constriction can occur (Maeno et al, 1999).


e. The VSD can close spontaneously.



E. Delivery




1. In TGA with pulmonary stenosis, delivery should be at term or as close as possible to term in a tertiary care center given the risk of foramen ovale restriction and ductus arteriosus constriction.


2. In addition, the true degree of pulmonary stenosis after birth and after ductus arteriosus closure may be difficult to fully predict.



F. Neonatal management




1. Medical.


a. Prostaglandin E1 (PGE1) infusion to keep the ductus open to increase pulmonary blood flow and raise arterial oxygen saturation.


b. Administration of oxygen can increase oxygen saturation by decreasing the pulmonary vascular resistance and increasing blood flow.


c. Therapeutic balloon atrial septostomy may be performed if the infant is very cyanotic, particularly with metabolic acidosis (a PaO2 level of 25 mm Hg and a pH of less than 7.15).


d. At times, volume and inotropic support may be indicated to improve ventricular function and atrial-level mixing.


2. Surgical.


a. Palliative.


    (1) If the pulmonary stenosis is moderate and the foramen ovale is restrictive or not allowing enough interatrial mixing, the baby could have a balloon atrial septostomy and then be sent home as long as the pulse oximeter saturations are sufficient (75%).

    (2) If the saturations are not sufficient despite therapeutic balloon atrial septostomy or if the pulmonary stenosis is severe, the patient will have an initial aortopulmonary shunt in the first week of life.

    (3) Surgical mortality is about 5%.

b. Corrective.


    (1) Rastelli operation.

       (a) Used for moderate or severe pulmonary stenosis.

       (b) Surgery is performed at the age of 6 months to 2 years at the atrial level for patients with TGA plus VSD plus severe valvar or subvalvar pulmonary stenosis.

       (c) When patients have critical pulmonary stenosis at birth, some centers elect to perform the Rastelli operation at that time.

       (d) Surgical mortality is 10% to 15%.

    (2) Arterial switch operation.

       (a) Used for mild pulmonary stenosis, simple TGA, TGA with a small VSD, TGA with coarctation of the aorta, TGA with resectable subpulmonary stenosis, or TGA with mild valvar pulmonary stenosis.

       (b) The technique consists of switching the right- and left-sided structures at the great artery level.

       (c) It is the procedure of choice in most centers.

       (d) It is usually performed at 1 to 2 weeks of life.

       (e) Surgical mortality is 5%. In patients with closure of VSD or arch repair performed at the time of the arterial switch, the mortality is higher.

c. Timing of surgery varies by institution.



G. Follow-up




1. Subacute bacterial endocarditis (SBE) prophylaxis is required for life.


2. If there are residual hemodynamic abnormalities, anticongestive medications and some restriction of activities may be required.


3. The patient should have one or two yearly outpatient follow-up visits with 12-lead electrocardiogram (ECG) and echocardiogram.


4. If there is any history of unexplained palpitations or abnormal heart rhythm, a metabolic stress test with 24-hour Holter monitoring is recommended.


5. Possible complications.


a. Rastelli operation.


    (1) Conduit stenosis and the risk of reoperation (surgical mortality for reoperation is 1%-2%) and accompanying morbidity.

    (2) Risk of subaortic stenosis.

    (3) Rhythm disturbance.

b. Arterial switch operation.


    (1) Stenosis at the anastomosis site at the pulmonary trunk or peripheral pulmonary artery stenosis.

    (2) Aortic regurgitation, aortic stenosis (less common than regurgitation), subaortic stenosis.

    (3) Idiopathic neoaortic root dilation.

    (4) Late complications of coronary artery obstruction, resulting in myocardial ischemia or infarction and sometimes sudden death.

    (5) Long-term assessment of myocardial perfusion with and without exercise may be necessary to exclude coronary issues.

    (6) LV dysfunction.

    (7) Arrhythmias.


H. Risk of recurrence


Because there is a previous sibling with VSD, the recurrence risk is 3% to 5%.



I. Outcome of this case




1. The baby was born at term with good Apgar scores and good weight.


2. Moderate cyanosis was noted at birth. Pulse oximeter reading was 77%.


3. Postnatal echocardiography confirmed the diagnosis with large subpulmonary VSD with posterior deviation of the outlet septum causing valvar and subvalvar pulmonary stenosis.


4. The pulmonary arteries were of good size, with a transpulmonary Doppler velocity of 4.5 m/s.


5. The foramen ovale and ductus arteriosus were good sized and patent, with bidirectional shunting. PGE1 infusion was started.


6. The baby had a palliative aortopulmonary shunt at 1 week of age followed by a successful Rastelli operation at 12 months of life.

Related posts:

  1. Tetralogy of Fallot with Absent Pulmonary Valve Syndrome
  2. Ventricular Septal Defect
  3. Pulmonary Atresia and Intact Ventricular Septum
  4. Suggested Views for Fetal Heart Imaging

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Jun 18, 2016 | Posted by in CARDIOLOGY | Comments Off on Transposition of the Great Arteries

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