Understanding Transposition of the Great Arteries

WHAT IS IT?

In a normal heart, the pulmonary artery carries deoxygenated blood to the lungs. Oxygenated blood returns to the left side of the heart and the aorta then pumps the oxygenated blood to the rest of the body. In Transposition of the Great Arteries (TGA), the pulmonary artery and aorta have changed places (i.e., they are transposed). Therefore:

• The pulmonary artery, which usually arises from the right side of the heart and carries deoxygenated blood to the lungs, will now connect to the left side of the heart and send oxygenated blood back to the lungs
• The aorta, which usually arises from the left (oxygenated) side of the heart, is now exiting the right side and therefore will carry deoxygenated blood to the rest of the body, bypassing the lungs
• 5 out of 10,000 babies are born with TGA
• TGA is referred to as a ‘cyanotic’ (lacking oxygen) defect leading to babies with bluish discoloration and shortness of breath, with symptoms dependent on whether there is any ability for the deoxygenated and oxygenated blood to mix and be delivered to the rest of the body
• Surgery is often necessary shortly after birth, especially in the case of complete TGA (also known as d-TGA referring to ‘dextroposition’) which is considered a ‘critical congenital heart defect’

Image credit: Centers for Disease Control and Prevention, National Center on Birth Defects and Developmental Disabilities

KEY POINTS:

• While TGA can be diagnosed prenatally on ultrasound, it may not always be detected
• In the majority of cases, a cause is not readily apparent
• In some cases, TGA can be associated with genetic abnormalities and therefore, if a prenatal diagnosis is made or suspected, referral for genetic counseling is recommended, in addition to high risk obstetrical services, neonatology and pediatric cardiology
• TGA is sometimes referred to as Transposition of the Great Vessels (TGV)

Learn More – Primary Sources:

CDC: Facts about dextro-Transposition of the Great Arteries (d-TGA)

Circulation-AHA journal: Transposition of the Great Arteries

CDC: About Critical Congenital Heart Defects

Current diagnosis and treatments for critical congenital heart defects

Fetal Growth and Neurodevelopmental Outcome in Congenital Heart Disease

Locate a Genetic Counselor or Genetics Services:

Genetic Services Locator-ACMG

Genetic Services Locator-NSGC

Genetic Services Locator-CAGC

Locate a Maternal Fetal Medicine Specialist:

Maternal Fetal Medicine Specialist Locator-SMFM