Transposition of the great vessels is a condition in which the anatomical inversion of the aorta and the pulmonary artery occurs and is one of the most common forms of cyanotic congenital heart disease.
In neonates with pure transposition of the great vessels, respiratory distress and cyanosis are main clinical signs, usually appearing in the first few days of life, but symptoms may occur as early as several hours after birth . If concomitant ASD, VSD or PDA is present, some oxygenated blood reaches the right heart and is eventually pumped into the aorta, which could delays the onset of symptoms up to 4-8 weeks, with minimal cyanosis . In such cases, signs of heart failure such as tachypnea or tachycardia could be the presenting features .
Transposition of great vessels can be detected during prenatal assessment and use of fetal echocardiography , but the diagnosis may be difficult to make, as great experience is necessary to distinct the vessels arising from the left and right heart, respectively . If the diagnosis is made postnatally, arterial blood gas analysis and a complete blood count are vital in assessing the severity of hypoxemia and hemoglobin/hematocrit values . Electrocardiography and chest X-rays are useful, but they may show normal findings .
Initial management of hypoxemia, acidosis and hypoglycemia should be immediate through supplementation with oxygen, sodium bicarbonate and dextrose solution, respectively . Administration of prostaglandin E1 (PGE1) is frequently recommended to keep the ductus arteriosus open and thus allow left-to-right shunting of oxygenated blood. The cornerstone of the treatment is surgical repair as early as possible . Two procedures are recommended :
The prognosis is generally poor without appropriate therapy, which emphasizes the importance of an early diagnosis. Successful surgical treatment, however, carries a normal life expectancy with minimal impairment in 70-75% of patients, while the remaining 20-25% require reoperation or develop sequelae after the procedure . Overall mortality rates are around 5% .
The cause of discordant connection between the ventricles and their respective vessels that develops during embryogenesis is yet to be determined .
Transposition of the great vessels constitutes approximately 5% of all CHDs and 10% of all neonatal cyanotic CHDs, with incidence rates estimated at 1 in 3,500-5,000 live births  . For still unknown reasons, a significant predilection toward male gender is observed (male-to-female ration of 1.5-3.2:1) . Although risk factors are currently not established, gestational diabetes, maternal use of antiepileptics and exposure to rodenticides and herbicides have been associated with this disorder .
Transposition of the great vessels results in a situation where deoxygenated blood enters systemic circulation, while oxygenated blood flows in a closed loop comprised of the lungs and the left heart . This mechanism leads to profound and life-threatening cyanosis. The concomitant presence of atrial septal defect (ASD), ventricular septal defect (VSD) or patent ductus arteriosus (PDA) enables mixing of oxygenated and deoxygenated blood and is thus critical for the initial survival after the birth.
A prenatal diagnosis that allows early treatment can minimize mortality rates, making fetal echocardiography one of the main preventive strategies for transposition of the great vessels, but for all CHDs as well.
Transposition of the great vessels is a rare form of congenital heart disease (CHD) characterized by anatomical discordance of the aorta and the pulmonary artery . The aorta arises from the right ventricle and the pulmonary artery starts from the left ventricle. Additional defects may be present, most common being ventricular septal defect (VSD) and left ventricular outflow tract obstruction , and symptoms also depend on their existence. Cyanosis within the first few days or weeks of life and congestive heart failure during a neonatal period and infancy are main clinical signs . The diagnosis can be made by echocardiography either prenatally or postnatally. Early recognition of the disease may provide sufficient time to decide on optimal therapy  . Supportive care, infusion of prostaglandin E1 and surgical repair in early life are main treatment options  .
Transposition of the great vessels is a rare congenital heart disease distinguished by complete inversion of the two main vessels coming out of the heart - the aorta and the pulmonary artery. Normally, the aorta arises from the left ventricle and transfer oxygenated blood from the lungs throughout the body, while pulmonary artery stems from the right ventricle and transfers deoxygenated blood from the venous system into the lungs. When transposition occurs, the aorta carries deoxygenated blood into systemic circulation, causing profound bluish discoloration of the skin (cyanosis) as early as several hours after birth. The diagnosis can be made by performing an ultrasound of the heart during a prenatal assessment, but the diagnosis can be missed, in which case signs and symptoms seen shortly after birth must raise suspicion toward transposition of the great vessels, but also to other forms of congenital heart disease. Echocardiography is then used for confirmation and treatment consists of supportive measures and immediate surgical treatment to correct the anomaly. With early recognition and successful surgical repair, the prognosis is very good, Transposition of the great vessels may be fatal if not diagnosed on time.