Congenital heart disease: overview
- Topic
About one baby in a hundred is born with a heart defect. Most come from errors in weeks three to eight of development, some from known genes or syndromes.
What it is
Congenital heart disease is the commonest birth defect, affecting roughly one in a hundred live births when moderate and severe lesions are counted. Most defects arise between the third and eighth weeks of gestation, when the heart tube loops and septates. Causes include chromosomal syndromes, single-gene mutations in cardiac transcription factors and signalling pathways, and environmental factors (maternal diabetes, rubella, alcohol, some drugs). Defects fall into left-to-right shunts, right-to-left shunts and obstructions. Long-standing left-to-right shunts can reverse (Eisenmenger syndrome).
Step by step
- A left-to-right shunt (ASD, VSD, PDA) sends extra blood through the lungs.
- The pulmonary arteries respond with medial hypertrophy and intimal thickening.
- Pulmonary vascular resistance rises toward systemic levels.
- The right ventricle hypertrophies to push against it.
- Once right pressures exceed left, the shunt reverses and unoxygenated blood enters the systemic circulation.
- Late cyanosis, clubbing, polycythemia and paradoxical emboli appear: the defect is now inoperable.
Syndromes and the heart defects they bring
| Syndrome | Typical defects |
|---|---|
| Down syndrome (trisomy 21) | Atrioventricular septal (endocardial cushion) defect, VSD |
| 22q11.2 deletion (DiGeorge) | Conotruncal defects: tetralogy of Fallot, truncus arteriosus, interrupted aortic arch |
| Turner syndrome (45,X) | Coarctation of the aorta, bicuspid aortic valve |
| Williams syndrome (elastin deletion) | Supravalvular aortic stenosis, pulmonary artery stenosis |
| Noonan syndrome | Pulmonary valve stenosis, hypertrophic cardiomyopathy |
| Marfan syndrome | Aortic root dilation, mitral valve prolapse |
Clinical notes
- Many small VSDs and ASDs close by themselves; others need repair before irreversible pulmonary vascular disease.
- Adults with repaired congenital heart disease are a growing population with arrhythmias and heart failure.
Test yourself
Think of the answer, then tap the question to see it.
What is Eisenmenger syndrome?
Reversal of a long-standing left-to-right shunt to right-to-left after pulmonary vascular disease raises right-sided pressures, with late cyanosis.
Which heart defect is classic for Down syndrome?
The atrioventricular septal (endocardial cushion) defect.
Which defects belong to the 22q11.2 deletion syndrome?
Conotruncal defects such as tetralogy of Fallot, persistent truncus arteriosus and interrupted aortic arch.
Elsewhere in DurgiPedia
- Embryonic heart structures and their adult derivatives (the table to know)
- Heart tube: formation and looping
- 22q11.2 deletion (DiGeorge): the third and fourth pouches
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Congenital Heart Disease | Congenital Heart Defects | MedlinePlus (MedlinePlus, US National Library of Medicine, 2025); Congenital heart disease: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2025).
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Representative model, for educational purposes only.