Complete Transposition of the Great Arteries (D-TGA)
The aorta is positioned anterior and to the right of the pulmonary artery (instead of the normal right posterior relationship). The aorta is connected to the right ventricle and the pulmonary artery is connected to the left ventricle.
D-TGA is the most common cause of neonatal cyanosis. It is more common in male infants of diabetic mothers who are usually large for gestational age (happy chubby blue male infant).
The blood runs in two parallel circulations (rather than the normal series circulation). This situation is incompatible with life unless there is mixing between the two circulations. The mixing may occur at the atrial level (ASD or PFO), ventricular level (VSD) or at the ductal level (PDA).
The physical examination is usually benign except for severe cyanosis and a single loud S2 at the upper left sternal border.
Making the Diagnosis
- EKG usually shows right axis deviation and right ventricular hypertrophy (RVH).
- CXR may have the characteristic egg-shaped appearance (the great arteries are anterior posterior in relationship and the thymus is usually small).
- Echocardiogram is diagnostic of dTGA. Echo is also important for identifying sites of communications between the two circulations and in delineating the coronary artery anatomy which is important in surgical repair.
- Cardiac catheterization may be needed to perform atrial septostomy; this allows mixing at the atrial level.
Medical management includes starting PGE-1 to keep the ductus open and treatment of metabolic acidosis if present.
Surgical repair includes:
- Arterial switch (Jatene) the great arteries are switched back to the corresponding ventricle and the coronary arteries are re-implanted.
- Atrial switch (Senning or Mustard) involves redirecting the blood flow at the atrial level so the pulmonary venous blood is baffled to the right ventricle (systemic ventricle) and the systemic venous blood is directed to the left ventricle (pulmonary ventricle).