STEPTRACKERCARDIOVASCULAR | PATHOLOGY + EMBRYOLOGY | HIGH-YIELD REVIEW

Congenital Heart Disease — Cyanotic & Coarctation

Right-to-left shunts that make "blue babies" early, plus coarctation of the aorta — each with an image, an association and a first move.

FOCUS ON
Tetralogy of Fallot: pulmonary stenosis decides severity, squatting helps, boot-shaped heart. Transposition: parallel circuits, needs a mixing shunt, PGE1 at birth. Link each lesion to its syndrome (22q11, diabetic mother, lithium, Turner). Coarctation: arm HTN, weak femoral pulses, rib notching.
DEFECT
ANATOMY · EMBRYOLOGY
FINDINGS
CLUE · TREATMENT
Tetralogy of Fallot
most common cyanotic CHD overall
Anterosuperior shift of the infundibular septum → pulmonary stenosis, RVH, overriding aorta, VSD.
"Tet spells" relieved by squatting (↑ SVR → less R→L shunt); harsh SEM at LUSB
Boot-shaped heart; 22q11, Down · surgical repair
D-transposition of great arteries
most common at birth
Aorticopulmonary septum fails to spiral: aorta from RV, pulmonary artery from LV → parallel circuits.
Severe cyanosis in first hours, worse as ductus closes
"Egg on a string"; infant of diabetic mother · PGE1, balloon septostomy, arterial switch
Persistent truncus arteriosus
Truncus fails to divide → one great vessel over a VSD.
Cyanosis, HF
22q11 (DiGeorge)
Tricuspid atresia
No tricuspid valve, small RV; survival needs ASD + VSD.
Cyanosis
Left axis deviation on ECG
Total anomalous pulmonary venous return
Pulmonary veins drain into systemic veins/RA.
Needs ASD/PFO to reach left heart
"Snowman" heart (supracardiac type)
Ebstein anomaly
Tricuspid leaflets displaced toward the apex → "atrialized" RV, severe TR.
Cyanosis via ASD, right HF
Maternal lithium; WPW association; box-shaped heart
Hypoplastic left heart syndrome
Underdeveloped LV with mitral/aortic atresia.
Shock as the ductus closes (ductal-dependent systemic flow)
PGE1 → staged repair (Norwood)
Coarctation — postductal
adult type
Narrowing just beyond the left subclavian near the ligamentum arteriosum.
Arm HTN, weak/delayed femoral pulses, leg claudication; intercostal collaterals → rib notching, "3" sign
Bicuspid aortic valve, Turner, berry aneurysm · risks: HF, dissection, cerebral bleed
Coarctation — preductal
infantile
Narrowing before the ductus; lower body fed by PDA.
Lower-body cyanosis; shock when ductus closes
Turner syndrome · PGE1

Mechanism — why R→L shunts turn babies blue

Deoxygenated bloodBypasses lungs
→
Systemic hypoxemiaEarly cyanosis
→
CompensationPolycythemia, clubbing
→
RisksParadoxical emboli, brain abscess

In TGA the circuits run in parallel, so survival depends on mixing through a PDA, ASD or VSD — hence PGE1 and septostomy.

Images and associations

DEFECT
CLASSIC IMAGE
ASSOCIATION
Tetralogy of Fallot
Boot-shaped heart
22q11, Down
D-TGA
Egg on a string
Diabetic mother
Truncus arteriosus
Single great vessel
22q11 (DiGeorge)
Ebstein
Box-shaped heart
Lithium; WPW
TAPVR
Snowman
—
Coarctation
Rib notching, "3" sign
Turner, bicuspid aortic valve

How it's tested

COMMON CONFUSIONTGA is the most common cyanotic lesion in the first days of life. Tetralogy is the most common overall and often shows up later, with spells.
THE TRAPA cyanotic child squats after play. Squatting raises systemic vascular resistance, pushing more blood through the stenotic pulmonary valve instead of across the VSD.
YOUR APPROACHTiming of cyanosis + CXR shape + maternal/genetic clue → lesion → PGE1 if ductal-dependent.

If you see… think…

Child squats after exertion, cyanotic spells, boot-shaped heart → tetralogy of Fallot
Cyanosis at birth worsening as the ductus closes, egg on a string → D-TGA — PGE1
Cyanotic newborn of a diabetic mother → transposition
DiGeorge features + single great vessel → truncus arteriosus
Mother on lithium; newborn with severe TR → Ebstein anomaly
Arm hypertension, weak femoral pulses, rib notching → coarctation of the aorta
Turner syndrome + hypertension in the arms → coarctation (± bicuspid valve)
Newborn in shock as the ductus closes → HLHS or critical coarctation — PGE1
Cyanotic CHD patient with fever, headache, focal signs → brain abscess