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
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)
Atrial Septal Defect (ASD) – Summary and Implications
WHAT IS IT?
Atrial septal defects can be generally classified into 3 subtypes:
Ostium secundum ASD: defect of the atrial septum that involved the region of the fossa ovalis
More common in females (65-75%)
While endocardial cushion defects are more commonly associated with Down syndrome, secundum ASDs have also been associated with Down syndrome
Ostium primum ASD: actually an atrioventricular (AV) septal defect, sometimes referred to as an AV canal defect or endocardial cushion defect
Associated with Down syndrome (15 to 20%) but may also be associated with other chromosomal abnormalities such as DiGeorge syndrome (22q11 deletion syndrome)
Sinus venosus ASD: occurs at the junction of the right atrium and superior vena cava and is almost always associated with partial anomalous pulmonary venous return
May be associated with arrhythmias
Other uncommon subtypes do exist
Image credit – National Heart Lung and Blood Institute (NIH)
ASD is typically sporadic, however may occur as an isolated finding in families or as part of various genetic syndromes including but not limited to Down syndrome, DiGeorge syndrome and Holt-Oram syndrome which involves variable radial ray anomalies.
Can range from small isolated finding that will close on its own, to complex congenital heart defect (CHD) requiring surgical repair and interdisciplinary team management
Consider genetic consultation to identify potential cause as may influence management
ACOG guidance recommends offering invasive testing using microarray in the setting of fetal structural anomalies seen on prenatal ultrasound
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