Congenital Heart Disease
A board-focused walkthrough of congenital heart disease: acyanotic left-to-right shunts, the cyanotic \"5 T's,\" ductus-dependent lesions and PGE1, with the classic vignette buzzwords, imaging clues, the failed hyperoxia test, syndrome associations, and next-best-step management.
Overview: Shunts & Ductal Dependence
Congenital heart disease is divided by whether the child is cyanotic.
Acyanotic lesions are left-to-right shunts (VSD, ASD, PDA) or obstructive lesions (coarctation). Oxygenated blood recirculates through the lungs, causing volume overload and, over years, pulmonary hypertension.
Cyanotic lesions are right-to-left shunts (the 5 T's) that dump deoxygenated blood directly into the systemic circulation. Cyanosis appears early — often in the newborn period — and characteristically does not correct with supplemental oxygen (a failed hyperoxia test points to a cardiac shunt rather than lung disease). Timing varies: TGA and obstructed TAPVR present in the first hours–days, whereas tetralogy of Fallot often declares itself over the first months with tet spells.
Many neonatal cyanotic — and left-sided obstructive — lesions are ductus-dependent: survival requires mixing or systemic flow across a patent ductus arteriosus. Prostaglandin E1 (alprostadil, PGE1) keeps the ductus open; indomethacin (a prostaglandin-synthesis inhibitor) closes it.
Chronic uncorrected L→R shunts can raise pulmonary pressures until flow reverses to R→L — Eisenmenger syndrome — producing late cyanosis, clubbing, and polycythemia. Once Eisenmenger physiology develops, the defect is no longer surgically correctable.
- VSD is the most common congenital heart defect (bicuspid aortic valve is more common overall but is usually counted separately).
- Tetralogy of Fallot = most common cyanotic CHD overall; TGA = most common cyanotic lesion presenting at birth (first day of life).
- 5 T's (cyanotic, R→L): Truncus arteriosus, Transposition, Tricuspid atresia, Tetralogy of Fallot, TAPVR.
- Cyanotic lesions fail the hyperoxia test — PaO₂ stays low despite 100% O₂.
- PGE1 keeps the PDA open; indomethacin closes it.
- Squatting / knee-to-chest relieves a tet spell (↑ SVR → ↓ right-to-left shunt).
- ASD → wide, fixed split S2; PDA → continuous machine-like murmur.
- Coarctation → upper-extremity hypertension, radio-femoral delay, rib notching.
- Uncorrected L→R shunt → Eisenmenger syndrome (shunt reversal, late cyanosis).
Acyanotic (Left-to-Right) Lesions
| Lesion | Classic murmur / finding | Association | Management |
|---|---|---|---|
| VSD | Harsh holosystolic murmur, LLSB (smaller defect = louder) | Down syndrome; many close spontaneously | Observe; close if large/symptomatic |
| ASD (ostium secundum) | Wide, fixed split S2 + systolic flow murmur | Paradoxical emboli; ostium primum → Down | Close if significant shunt/symptoms |
| PDA | Continuous machine-like murmur | Congenital rubella, prematurity | Indomethacin closes; catheter/surgery if persistent |
| Coarctation | Systolic murmur, radio-femoral delay, rib notching | Turner, bicuspid aortic valve | Surgical or balloon/stent repair |
Cyanotic (Right-to-Left) Lesions — the 5 T's
| Lesion | Key feature | Imaging / ECG clue |
|---|---|---|
| Tetralogy of Fallot | PROVe: pulmonary stenosis, RVH, overriding aorta, VSD | Boot-shaped heart |
| Transposition (D-TGA) | Aorta off RV, PA off LV; needs a shunt (PDA/ASD/VSD) | Egg on a string |
| Truncus arteriosus | Single arterial trunk overriding a VSD | Single great vessel |
| TAPVR | Pulmonary veins drain to systemic venous system; needs ASD | Snowman / figure-of-8 |
| Tricuspid atresia | Absent tricuspid valve, hypoplastic RV; needs ASD and VSD | Left-axis deviation, small RV |
The 5 T's of cyanotic CHD (the number is the memory hook):
- Truncus arteriosus — 1 vessel
- Transposition — 2 arteries switched
- Tricuspid atresia — 3
- Tetralogy of Fallot — 4 features
- TAPVR — 5 words (Total Anomalous Pulmonary Venous Return)
PROVe — Tetralogy of Fallot:
- Pulmonary stenosis (determines severity of cyanosis)
- Right ventricular hypertrophy
- Overriding aorta
- VEntricular septal defect
Vignette: A 6-month-old has episodes of turning blue while crying and squats during play to feel better. Exam: harsh systolic ejection murmur at the left upper sternal border. CXR shows a boot-shaped heart with decreased pulmonary markings.
Diagnosis: Tetralogy of Fallot. The blue spells are "tet spells" — dynamic RVOT obstruction acutely increases the right-to-left shunt. The murmur comes from pulmonary stenosis, not the VSD (a louder murmur means more flow across the RVOT and a less severe spell).
Next best steps (acute tet spell):
- Knee-to-chest positioning (↑ SVR, mimics squatting)
- Oxygen
- Morphine (calms, reduces hyperpnea)
- IV fluids; β-blocker (propranolol) and phenylephrine (↑ SVR) if refractory
Definitive treatment is surgical repair. Classic association: DiGeorge / 22q11 syndrome.
Vignette: A newborn of a diabetic mother becomes severely cyanotic within hours of birth. Cyanosis does not improve with oxygen. CXR shows an "egg on a string" (narrow mediastinum).
Diagnosis: D-Transposition of the great arteries — the aorta arises from the RV and the pulmonary artery from the LV, creating two parallel circuits. Survival depends on mixing through a PDA, ASD, or VSD.
Next best steps:
- PGE1 (alprostadil) infusion to keep the ductus arteriosus open and maintain mixing
- Balloon atrial septostomy (Rashkind) if mixing is inadequate
- Definitive: arterial switch operation
Pitfall: do not rely on oxygen alone or give indomethacin — closing the ductus here is fatal.
Vignette: A 15-year-old girl with short stature and a webbed neck has hypertension in both arms but weak, delayed femoral pulses and low leg blood pressure. CXR shows rib notching and a "3 sign."
Diagnosis: Coarctation of the aorta, associated with Turner syndrome and bicuspid aortic valve. The arm–leg pressure gradient and radio-femoral delay are classic; rib notching reflects collateral flow through dilated intercostal arteries (develops over years, so it is seen in older children/adults, not neonates).
Next best step: Confirm with echocardiography (CT/MR angiography defines the anatomy); check four-extremity blood pressures. Treat with surgical or balloon/stent repair.
Key distinction: neonatal (critical, preductal) coarctation is ductus-dependent — start PGE1 to maintain systemic perfusion until repair.
Syndrome & Exposure Associations
| Syndrome / exposure | Classic cardiac defect(s) |
|---|---|
| Down (trisomy 21) | Complete AV septal (endocardial cushion) defect, ostium primum ASD, VSD |
| DiGeorge (22q11) | Tetralogy of Fallot, truncus arteriosus, interrupted aortic arch |
| Turner (45,X) | Coarctation, bicuspid aortic valve |
| Congenital rubella | PDA, pulmonary artery stenosis |
| Maternal diabetes | Transposition (TGA), VSD (and transient septal hypertrophy) |
| Williams | Supravalvular aortic stenosis |
| Lithium (in utero) | Ebstein anomaly |
| Marfan | Aortic root dilation, mitral valve prolapse |
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