Congenital heart defects (prenatal)

Definition

• Congenital heart defects are structural malformations of the heart and great vessels and the most common form of birth defects.

Classification

• Conotruncal anomalies include transposition of the great arteries, tetralogy of Fallot, double-outlet right ventricle and truncus arteriosus.
• Other examples are ventricular septal defect, atrioventricular septal defect and coarctation of the aorta.

Occurrence & epidemiology

Epidemiology

• They affect about 8 to 10 per 1,000 live-born term infants (0.8 to 1%); in preterm infants the rate is up to ten times higher.

Aetiopathogenesis

Aetiology and associations

• Chromosomal anomalies are frequently associated; with a prenatally detected ventricular septal defect the rate is about 10 to 30% depending on type and size, and atrioventricular septal defect is often linked to trisomy 21.
• Increased nuchal translucency is associated with fetal heart defects; apparently isolated findings may reflect an underlying heart defect.

Clinical features

• Atrioventricular septal defect is usually tolerated in utero; a few fetuses develop heart failure with non-immune hydrops due to severe AV valve regurgitation or complete heart block.

Diagnosis

• Normally two thirds of the heart lie on the left and the cardiac axis is about 45 ± 20 degrees; an abnormal axis is associated with chromosomal anomalies and heart defects.
• The four-chamber view alone misses many conotruncal anomalies; adding the outflow tracts raised sensitivity from about 30% to 69 to 83%, and the three-vessel and three-vessel-trachea views are added.
• An absent or hypoplastic thymus in the three-vessel view points to a 22q11.2 deletion.

Keep learning in the app

Further reading (selection)

1. Indian Heart Journal 2018: Prenatal diagnosis of congenital heart disease: A review of current knowledge (PubMed Central)
2. Diagnostics (Basel) 2022: A Pain in the Neck – Genetic Testing in Fetuses with Nuchal Fluid Collections (PMC, open access)

Cross-references