Transposition of the Great Arteries (TGA), the second most common congenital cardiac defect appearing in early infancy, is caused due to abnormal development of the fetal heart during the first eight weeks of pregnancy. As a result of this abnormal development, the two major arteries, the aorta and pulmonary artery, are malpositioned or reversed. Thus, the aorta receives deoxygenated blood from the right ventricle and carries the same blood back into systemic circulation, without undergoing oxygenation. Similarly, the pulmonary arteries receive pure deoxygenated blood from the left ventricle, and carry it back into the lungs once again. Almost 90% of affected infants become cyanotic in the first day of life itself. Some may even show cyanosis within the first few hours. Cyanosis is more severe if other cardiac defects like patent ductus atreriosus are also present. Apart from cyanosis, other common symptoms of the condition include rapid and labored breathing, a rapid heart rate, lack of appetite, weight loss, and cold and clammy skin. About 5-7% of all congenital heart defects are TGA. Interestingly, the condition affects more boys than girls.
Chest X-rays, electrocardiograms, echocardiograms, and/or cardiac catheterization are used to diagnose this congenital defect in infants. Surgery is a must for effective management of the condition. Since the affected individuals are infants, initially, a temporary procedure connecting the two atria may be performed, in order to delay the actual surgical procedure. Surgery may be one of two kinds. The atrial or venous switch (also known as the Mustard or the Senning procedure), involves creating a tunnel between the atria to redirect the oxygenated blood to the right ventricle and the aorta, and the deoxygenated blood to the left ventricle and the pulmonary artery. The other procedure, known as the arterial switch procedure involves switching the two major arteries back to their correct position, connecting the aorta to the left ventricle, and the pulmonary artery to the right ventricle. Patients, however, need to be followed up their entire life for any complications, including decline in cardiac function, arrythmias, and/or endocarditis. Patients are recommended to be on medications for their entire life, and to limit their physical activity.