Congenital Heart Disease
Late-cyanosis shunts, the 5 T's, and the syndromes that flag each lesion
Shunt direction and the timing of cyanosis
Left-to-right shunts. VSD, ASD, and PDA (in that order of frequency) return oxygenated blood to the lungs. They are acyanotic at first and cause late cyanosis only if pulmonary hypertension eventually reverses the shunt.
Right-to-left shunts. The 5 T's route deoxygenated blood into the systemic circulation, bypassing the lungs, so cyanosis is present at or soon after birth.
Left-to-right shunts
Ventricular septal defect. The most common congenital heart defect overall; the membranous septum is the most common site. It produces a harsh holosystolic murmur at the left lower sternal border. Smaller defects are louder (a high-velocity jet) and often close spontaneously; large ones cause pulmonary overcirculation and heart failure in infancy.
Atrial septal defect. Ostium secundum is the most common type; ostium primum defects belong to the endocardial cushion spectrum seen in Down syndrome. Extra flow through the right heart delays pulmonic valve closure regardless of respiration, giving wide, fixed splitting of S2, plus a systolic ejection murmur from increased pulmonic flow. An ASD permits paradoxical emboli: a venous clot crosses to the systemic circulation.
Patent ductus arteriosus. The ductus connects the aorta to the pulmonary artery and gives a continuous machine-like murmur. It normally closes after birth as oxygen rises and prostaglandins fall, leaving the ligamentum arteriosum; persistence is common in premature infants and with congenital rubella.
Indomethacin, an NSAID that lowers prostaglandins, closes a PDA; prostaglandin E1 (alprostadil) holds it open for duct-dependent lesions.
| Lesion | Auscultation | Key points | Association |
|---|---|---|---|
| VSD | Harsh holosystolic murmur, left lower sternal border | Most common defect; membranous type; small ones louder and often close | Down syndrome (with AV septal defects), fetal alcohol |
| ASD | Wide, fixed split S2; systolic ejection murmur | Secundum most common; paradoxical emboli | Down syndrome (primum) |
| PDA | Continuous machine-like murmur | Indomethacin closes, PGE1 keeps open | Congenital rubella, prematurity |
Eisenmenger syndrome
- Left-to-right shuntAn uncorrected VSD, ASD, or PDA overloads the pulmonary circulation.
- Pulmonary hypertensionChronic overcirculation remodels pulmonary arterioles; the RV hypertrophies.
- Shunt reversalWhen pulmonary pressure exceeds systemic pressure, flow becomes right-to-left.
- Late cyanosisClubbing and secondary polycythemia follow.
Too late to close. Once the pulmonary vascular disease is fixed, closing the defect no longer helps; cyanosis and clubbing are the warning signs. With a PDA, reversed flow enters the aorta beyond the arch vessels, so the legs are cyanotic and clubbed while the arms stay pink (differential cyanosis).
Cyanotic lesions: the 5 T's
| Lesion | Anatomy | Survival need or clue | Association |
|---|---|---|---|
| 1 Truncus arteriosus | Single great vessel overriding a VSD | Mixing at the VSD | DiGeorge (22q11) |
| 2 Transposition (D-TGA) | Aorta from RV, pulmonary artery from LV | PDA, ASD, or VSD to mix; egg-on-a-string X-ray | Maternal diabetes |
| 3 Tricuspid atresia | Absent tricuspid valve, hypoplastic RV | Both an ASD and a VSD | — |
| 4 Tetralogy of Fallot | Four features (PROVe) | Boot-shaped heart; most common cyanotic lesion | DiGeorge (22q11) |
| 5 TAPVR (five letters) | Pulmonary veins drain into the right heart | ASD needed; snowman sign | — |
Tetralogy of Fallot. Pulmonary (RV outflow) stenosis, RV hypertrophy, Overriding aorta, and VSD, all from anterosuperior displacement of the infundibular septum. The degree of pulmonary stenosis sets how much blood shunts right-to-left and therefore how cyanotic the child is. Hypercyanotic tet spells are relieved by squatting, which raises systemic vascular resistance, reduces the right-to-left shunt, and pushes more blood through the stenotic outflow.
D-transposition. Failure of the aorticopulmonary septum to spiral leaves the aorta on the RV and the pulmonary artery on the LV, creating two parallel circulations that are incompatible with life unless blood mixes through a PDA, ASD, or VSD. Give prostaglandin to keep the duct open, then perform an arterial switch.
Truncus, tricuspid atresia, TAPVR. In truncus arteriosus the outflow tract never divides, so one vessel overrides a VSD. Tricuspid atresia leaves no inflow to a hypoplastic RV, so survival requires both an ASD and a VSD. In TAPVR, pulmonary venous blood returns to the right heart and reaches the left side only through an ASD.
Coarctation and duct-dependent circulation
Coarctation of the aorta. A narrowing near the ductus produces hypertension in the upper extremities, weak and delayed femoral pulses (brachial-femoral delay), lower-limb claudication, and rib notching from enlarged collateral intercostal arteries. It is classically associated with Turner syndrome and bicuspid aortic valve. Complications include heart failure, aortic rupture or dissection, endocarditis, and hemorrhage from cerebral berry aneurysms.
Duct-dependent lesions. Transposition, tricuspid atresia, and severe coarctation depend on the ductus arteriosus for survival; keep it open with prostaglandin E1 (alprostadil) until surgery.
This is the opposite of routine PDA management, in which indomethacin is used to close the duct.
Syndrome associations
| Condition | Classic cardiac lesion |
|---|---|
| Down syndrome | Complete AV septal (endocardial cushion) defect |
| DiGeorge (22q11 deletion) | Conotruncal defects: truncus arteriosus, tetralogy of Fallot |
| Congenital rubella | PDA, pulmonary artery stenosis |
| Turner syndrome | Coarctation, bicuspid aortic valve |
| Maternal diabetes | Transposition of the great arteries |
| Marfan syndrome | Aortic root dilation and dissection, mitral valve prolapse |
| Williams syndrome | Supravalvular aortic stenosis |
| Maternal lithium | Ebstein anomaly |