Definition:

Transposition of the great arteries (TGA) is the most common cyanotic congenital heart defect.  Normally, the pulmonary artery comes off the right ventricle to pump DEOXYGENATED (less oxygen content) blood to lungs to get oxygen, while the aorta comes off the left ventricle to pump OXYGENATED from the lungs to the rest of the body.  In TGA, the aorta comes off the right ventricle to pump DEOXYGENATED blood to the body while the pulmonary artery comes off the left ventricle to pump DEOXYGENATED/OXYGENATED blood to the lungs.  To survive without intervention, there has to be an additional defect that will allow the right and left side of the heart to communicate so that blood can mix, and this defect can either be an atrial septal defect, ventricular septal defect, or a patent ductus arteriosus.  It has a male predominance with a 90% mortality rate within first year of life if not treated.

Symptoms:

• Infants born at term with cyanosis (bluish discoloration) within few hours of life, then dependent on type of additional defects
  • TGA with no defect - severe cyanosis within 24hrs of life
  • TGA with large VSD - mild cyanosis when crying, tachypnea (increased breathing rate), tachycardia (increased heart rate), sweating, and failure to gain weight over first 6 weeks of life
  • TGA with VSD and obstruction in left ventricle - extreme cyanosis at birth
  • TGA with VSD and pulmonary artery obstruction - progressive cyanosis from birth

Diagnosis:

• Physical exam findings
• Hyperoxia test - to see oxygen saturation in blood
• Echocardiography - show show TGA , may also see other defects in heart
• Cardiac catheterization - usually done for infants whose echocardiogram does not anatomy

Treatment:

• IV Prostaglandin E1 if patient has patent ductus arteriosus to make it stay open
• Balloon septostomy - increases hole size between right and left atria to allow for more mixing
• Arterial Switch Surgery - divide off pulmonary artery and aorta from wrong ventricles and attach them to right ventricles; also transfer coronary arteries also to allow heart to receive proper blood flow