How does transposition of the great arteries (TGA) result in systemic circulation of deoxygenated blood?

From the Guidelines

Transposition of the great vessels results in systemic circulation of deoxygenated blood due to an abnormal anatomical arrangement where the aorta arises from the right ventricle and the pulmonary artery from the left ventricle, creating two separate circulatory loops. In normal cardiac anatomy, deoxygenated blood returns to the right side of the heart and is pumped to the lungs for oxygenation, while oxygenated blood returns to the left side and is pumped to the body. In transposition, this pathway is disrupted. The right ventricle, which receives deoxygenated blood from the body, connects directly to the aorta, sending this oxygen-poor blood back to the systemic circulation without being oxygenated first. Meanwhile, oxygenated blood returning from the lungs enters the left ventricle but is recirculated back to the lungs through the pulmonary artery. This creates a critical situation where tissues and organs receive insufficient oxygen, leading to cyanosis and potential organ damage. Survival depends on mixing between the two circulations, typically through atrial or ventricular septal defects or a patent ductus arteriosus, which allows some oxygenated blood to enter the systemic circulation, as noted in a study published in the Journal of the American College of Cardiology 1.

Some key points to consider:

• The most common types of surgery performed for D-TGA are the atrial switch procedures (Mustard and Senning procedures) and the arterial switch procedures (Jatene procedure) 1.
• The atrial baffle procedure for D-TGA has characteristic late long-term problems, including baffle obstruction, baffle leaks, pulmonary venous obstruction, and systemic right ventricular dysfunction 1.
• The 20-year survival rate after atrial switch for D-TGA is approximately 80% to 85%, with nearly equal survival after the Senning and Mustard procedures 1.
• Adults with congenitally corrected transposition of the great arteries (CCTGA) have a high likelihood of developing systemic ventricular dysfunction and heart failure, with approximately 18% to 22% of adults developing systemic ventricular dysfunction and up to 65% of adults over 45 years old developing symptomatic heart failure 1.

Overall, the management of transposition of the great vessels requires careful consideration of the underlying anatomy and physiology, as well as the potential long-term complications of surgical repair, as discussed in the guidelines for the management of adults with congenital heart disease 1.

From the Research

Transposition of the Great Vessels and Systemic Circulation

• Transposition of the great vessels is a congenital heart defect where the two main arteries that carry blood out of the heart are reversed 2.
• In a normal heart, the aorta arises from the left ventricle and carries oxygenated blood to the body, while the pulmonary artery arises from the right ventricle and carries deoxygenated blood to the lungs.
• In transposition of the great vessels, the aorta arises from the right ventricle and carries deoxygenated blood to the body, while the pulmonary artery arises from the left ventricle and carries oxygenated blood to the lungs.
• This results in the systemic circulation of deoxygenated blood, which can lead to hypoxia and other complications 2.

Effects on the Heart

• Patients with transposition of the great vessels often undergo surgical procedures, such as the atrial switch procedure (Mustard or Senning operation), to correct the defect 2.
• However, these procedures can lead to long-term problems, such as RV failure, tricuspid regurgitation, and atrial arrhythmias 2.
• Patients with congenitally corrected transposition also have a morphological right ventricle and delicate tricuspid valve in the systemic circulation, which can lead to progressive tricuspid regurgitation and deterioration of RV function 2.

Relevance of Other Studies

• The other studies provided 3, 4 do not appear to be directly relevant to the topic of transposition of the great vessels and its effects on systemic circulation.
• These studies discuss topics such as phospholipid antigens and acute hepatitis, which are not related to the cardiovascular system or congenital heart defects 3, 4.