Complete transposition of the great arteries refers to the reversal of the positions of the aorta and pulmonary artery. The aortic valve, instead of being located to the right and posterior of the pulmonary valve as in normal anatomy, is positioned to the right and anterior, connecting to the right ventricle. Meanwhile, the pulmonary valve is located to the left and posterior of the aortic valve, connecting to the left ventricle. The positions of the atria and ventricles, as well as the relationship between the atria and ventricles, remain unchanged. Deoxygenated blood returns to the right atrium and right ventricle, then exits through the aorta to the systemic circulation, while oxygenated blood returns from the pulmonary veins to the left atrium and left ventricle, still exiting through the pulmonary artery to the lungs. This causes the systemic and pulmonary circulations to operate independently, violating the physiological principle of circulatory interaction. For the infant to survive temporarily, there must be an exchange of blood flow through an atrial septal defect, ventricular septal defect, or patent ductus arteriosus.

bubble_chart Diagnosis

(1) Symptoms Most symptoms manifest during the neonatal period and can be broadly categorized as follows: 1. Hypoxia and acidosis (55%) Due to insufficient blood exchange between the two circulations, the infant exhibits rapid breathing, an enlarged heart, and progressively worsening cyanosis and acidosis. 2. Often accompanied by ventricular septal defect (VSD) (40%) With greater blood exchange, symptoms may appear later, primarily including dyspnea, congestive heart failure, and cyanosis, typically emerging within two to three months. The condition deteriorates over time, and cyanosis worsens further after the onset of pulmonary edema or lung infection. 3. Presence of stenosis at the left ventricular outlet to the pulmonary artery, combined with a large VSD leading to reduced pulmonary blood flow (5%). Symptoms appear later than in the second group, often without heart failure, and cyanosis is less severe. The clinical presentation resembles tetralogy of Fallot.

(3) X-ray Examination Anteroposterior films show three key features: narrowing of the great vessels at the heart base, an oval-shaped cardiac silhouette, and increased pulmonary blood flow. The size of the cardiac shadow is directly related to the amount of pulmonary blood flow.

(4) Echocardiography M-mode can simultaneously display the anterior and posterior alignment of the great arteries (aorta and pulmonary artery). In the two-dimensional short-axis view, the anterior-right structure is the aorta, while the posterior-left is the pulmonary artery. The size ratio of the two can also indicate the presence and severity of pulmonary artery stenosis.

(5) Cardiac Catheterization The objectives are threefold: 1. Confirm the diagnosis; 2. Identify associated anomalies such as VSD, pulmonary artery stenosis, patent ductus arteriosus, and aortic coarctation; 3. Perform balloon catheter dilation.

(6) Cardiac Angiography Right ventricular angiography reveals a right ventricle with prominent trabeculae in its normal position, topped by a conus that is positioned higher than usual and anterior-right to the aortic valve. If a VSD is present, contrast may rush into the pulmonary artery. Right ventricular angiography can also detect stenosis in the left ventricular outflow to the pulmonary artery.

bubble_chart Treatment Measures

﹝Treatment﹞

Medical treatment includes oxygen therapy, Rehmannia, diuretics, and iron supplements. Active preparation for cardiac catheterization and angiography should be made, along with performing balloon catheter atrial septostomy (Rashkind procedure). Two-dimensional ultrasound can be used to monitor the operation. In recent years, the Huslard atrial septal reconstruction technique has been applied, which involves excising the atrial septum and using a pericardial membrane to create a baffle. This directs the systemic venous return to the mitral valve and into the left ventricle to the pulmonary artery, while the pulmonary venous blood flows outside the baffle to the tricuspid valve and into the right ventricle to the aorta, thereby achieving physiological correction of blood flow direction.