D-Transposition of Great Arteries
- D-TGA exists when the aorta arises from the morphologic right ventricle and is found anterior and rightward of the pulmonary artery. The pulmonary artery arises from the morphologic left ventricle and is found leftward and posterior with respect to the aorta.
- This is the second most common congenital heart defect found in early infancy with a relatively prevalence rate of approximately 0.24 per 1,000 live births (ch. 37, Keane)
- Ventricular septal defects are commonly associated with D-transposition of the great arteries and present in approximately 35% of cases (Keane) at birth.
- Transposition of the great arteries results in two parallel circulations in which systemic venous (deoxygenated) blood passing through the right heart to aorta and back to the systemic circulation. Highly oxygenated blood pass from the lungs to the pulmonary veins to the left ventricle, pulmonary artery, and back to the lungs. Since survival requires mixing of these parallel circulations, a communication exists in the form of an Atrial Septal Defect or Persistent Ductus Arteriosus. In either case, the amount of blood flowing into and out of the pulmonary circulation must be equal or greater than that in the systemic circulation.
- Clinical manifestations of D-transposition of the great arteries depend, in part, on whether the ventricular septum is intact. Infants born with an intact ventricular septum may show cyanosis within hours of birth, while those with a ventricular septal defect may show little to no cyanosis at all. Tachypnea is generally present and varies in timing of onset and severity depending on the degree of pulmonary resistance or stenosis. Additional complications in these individuals commonly include: respiratory distress and congestive heart failure, which may also develop within days of birth.
- Management of the transposition patient includes medication and/or surgical intervention. For example, prostaglandin E is given to maintain a Persistent Ductus Arteriosus and allow left-to-right shunting when a ventricular septal defect is not present. An Arterial Switch Operation (ASO) (Jetene Procedure) is routinely conducted to correct this defect. The ASO requires translocation of the great arterial and relocation of the coronary arteries. It is recommended that closure of ventricular septal defects occurs as early as possible after the atrial switch to prevent complications and improve survival rates. Without a surgical correction, infants with an intact ventricular septum, typically do not survive past one year: i.e., they usually die during early infancy. Patients with ventricular septal defects or patent ductus arteriosus may survive beyond the first year, but almost always develop pulmonary vascular obstructive disease, limiting their long-term survival.