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Feb 23, 2012

Complete Transposition of Great Arteries (D-TGA)



  • In normal heart aorta is connected to left ventricle and pulmonary artery is connected to right ventricle
  • In normal heart aorta lies  posterior and right of pulmonary artery 
  • In transposition of great arteries aorta is connected to right ventricle and pulmonary artery is connected to left ventricle. Aorta is anterior and right of pulmonary artery
  • As aorta is right of pulmonary artery this condition is termed as D –TGA
1.      prevalence of D-TGA is  0.2 per 1000 live birth, male to female ratio 2:1
2.      In D-TGA  is normal atrial and ventricle relation is present, and ventricle and great vessel discordance is present this is called single discordance 
3.      Oxygenated blood coming to left atrium is pumped to pulmonary artery  because left ventricle is connected pulmonary artery and unoxygenated blood coming to right atrium is pumped to aorta as right ventricle is connected  aorta
4.      With this type of circulation, systemic blood never gets oxygenated this not compatible with life. For survival with this type of circulation there is a need of mixing of  blood either at atrial or ventricle or at dutus arterious level.
  • In L-TGA (congenital corrected transposition of great arteries)
1.      Aorta is left and anterior of pulmonary artery.so name L-TGA
2.      Here there is a double discordance i.e. Left atrium is connected to right ventricle and right atrium is connected to left ventricle. Aorta is connected to right ventricle and pulmonary artery is connected to aorta.(ventricle inversion is present)
3.      Circulation is normal expect that right ventricle has to pump for systemic circulation and left ventricle has to pump for pulmonary circulation
4.      Although circulation arraignment is normal these patient have associated anomalies.
  • Anomalies associated with D-TGA
1.      Instead of a aorta mitral continuity of normal heart in D-TGA there is mitral and pulmonary continuity (pulmonary artery is posterior and mitral valve of Left ventricle is posterior to it)
2.   Shunt lesion  mandatory for survival are
·         All most babies have inter atrial communication more than half has patent foraman ovale
·         Next shunt commonly seen is PDA  i.e. two third of patients have this
·         Next common is VSD one third patients have this
·         If mixing of blood is not adequate then patient will present with severe cyanosis soon after birth. Such babies need Prostaglandin infusion followed by either emergence atrial septostomy (creating a hole inter atrial septum) or stenting the ductus arteriosus so blood mixing is adequate. This is has to followed by corrective surgery.
·         5% of patients have LVOT obstruction (subpulmonary), of these dynamic obstruction of LVOT occurs in 20% due bowing of interventricular septum to left ventricle leading obstruction and decreased pulmonary flow.
·         VSD with LVOT obstruction occurs in 10%. These babies have associated defects like CoA, interrupted aortic arch, pulmonary atresia, straddling AV valve.

History and clinical features
  • As two third to three forth of D-TGA have intact IVS , so these are cyanotic since birth
  • Large male new born, with cyanosis, tachypneic without chest retractions unless CHF is present
  • Feeding difficulties, dyspnea hepatomegly may develop which suggest CHF supervening
  • Hypoglycemia and hypocalcaemia may be present
ECG
  • Right axis deviation with RVH
  • Biventricular hypertrophy suggest large VSD and PDA
Chest X-ray cardiomegly and egg on side

Echocardiography
1.      PLAX  great arteries run parallel to each other  pulmonary artery which bifurcates take posterior turn and is continues with mitral valve
2.      PSA aorta is anterior and normal cup and sausage appearance is lost, one may see owl eye appearance
3.      Apical view pulmonary artery i.e. artery which bifurcates arise from LV, aorta arises from RV
4.      ASD, VSD, LVOT obstruction, CoA may be present
Coronary artery
From Anderson Textbook

1.      LMCA arises usually from anterior sinus of aorta i.e sinus 2  and RCA from posterior sinus of aorta sinus 1 ( 60%)
2.      LCX from RCA 22%
3.      Single RCA 9.5%
4.      Single LCA 3%
5.      LMCA from posterior sinus and RCA from anterior sinus in 3%
Natural history
1.      Babies with heart failure and hypoxia 90% of infants dye with in 6months of life
2.      Babies with IVS intact and cyanosis, after atrial septostomy (Raskind procedure) do well
3.      Babies with VSD and PDA  are least cyanotic but have CHF, may develop pulmonary vascular obstructive disease with in three to for months of life, so corrective surgery has to done before this
4.      VSD with PS has longer survival in D-TGA
Treatment
1.      Medical and pre surgical workup
§  Hypoglycemia and hypocalcaemia and metabolic acidosis has to be treated
§  Cyanosis needs prostaglandin infusion and followed by atrial septostomy
§  oxygen therapy to prevent pulmonary vascular obstructive disease
§  heart failure needs to treated with diuretic and digoxin
2.      Definitive surgical procedure
§  These are done at level of atrial, ventricular and arterial level. Now a days most commonly and preferred approach atrial switch operations
§  Arterial switch surgeries
·         Like in normal heart in this surgery both the great arteries are transferred to their respective ventricle that is aorta to left ventricle along with coronaries and pulmonary artery to right ventricle. Mortality is less than 5%. VSD if present is closed.
·         LV pressure should be more than 80% of RV pressure to do this procedure
·         If surgery delayed more than 3 weeks than LV pressure may drop so early surgery is advised
·         For those babies whose LV pressure is less than 80% of RV pressure, PA banding is done. After 8 days arterial switch operation is done.
§  Atrial repair  surgery (Senning and Mustard)
·         In these surgeries systemic blood coming to RA is diverted to mitral valve to LV than to PA and pulmonary venous blood coming to LA is shunted to tricuspid valve and RV than to aorta
·         Mustard operation uses pericardial or prosthetic baffle. Senning uses atrial septal flap
·         RV has to support systemic circulation in this surgery.
·         Complication SVC obstruction less than 5%, baffle leak less than 20%, absence of sinus rhythm more than 50%
·         This surgery is less preferred now a days
§  Ventricle level surgery (Rastelli)
·         For babies with large malaligned VSD with LVOT obstruction Rastelli procedure is done
·         LV is tunneled through VSD and connected to aorta, pulmonary artery is divided and connected to RV
·         This procedure is done beyond infancy