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This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.
Key points
- Most common CHD overall: VSD (~30%). Most common cyanotic CHD: Tetralogy of Fallot
- Acyanotic (left-to-right shunts): VSD, ASD, PDA — cause volume overload, pulmonary overcirculation, eventually Eisenmenger if uncorrected
- Cyanotic (right-to-left shunts): 5 T's — Tetralogy of Fallot, Transposition (TGA), Truncus arteriosus, Tricuspid atresia, Total anomalous pulmonary venous return
- Tet spells (TOF): hypercyanotic episodes in infants — knee-to-chest position (increases SVR, reduces R-to-L shunt). Treat with O2, morphine, phenylephrine, propranolol
- Adults with CHD (ACHD): growing population, need lifelong follow-up at specialized centers
Overview
Congenital heart disease encompasses structural defects of the heart and great vessels present from birth, affecting ~1% of live births (~40,000/year in the US). With advances in surgical and interventional techniques, >90% now survive to adulthood, creating a large and growing adult CHD (ACHD) population. Classification is based on the presence or absence of cyanosis. Acyanotic lesions have left-to-right shunting (oxygenated blood recirculates through the lungs) or obstructive lesions (coarctation, pulmonic stenosis). Cyanotic lesions have right-to-left shunting (deoxygenated blood enters systemic circulation).
Clinical Features
Symptoms
Acyanotic (VSD, ASD, PDA): often asymptomatic if small. Large shunts: failure to thrive, recurrent respiratory infections, dyspnea, diaphoresis with feeding
Cyanotic (TOF, TGA): cyanosis from birth or infancy (depending on degree of shunting), poor feeding, poor growth
TOF tet spells: episodic cyanosis with crying/feeding in infancy — life-threatening
Coarctation of aorta: upper extremity HTN, lower extremity claudication, headaches in older children/adults
Signs
VSD: harsh holosystolic murmur at LLSB, thrill. Small (restrictive) VSD = loud murmur. Large VSD = soft murmur + signs of HF
ASD: fixed split S2 (does not vary with respiration) + systolic flow murmur at LUSB (increased pulmonic flow, not the shunt itself)
PDA: continuous "machinery" murmur at left infraclavicular area, bounding pulses, wide pulse pressure
Coarctation: BP differential (upper > lower extremity), radio-femoral delay, rib notching on CXR, "3 sign" on CXR (pre-stenotic aortic knob + post-stenotic dilation)
TOF: cyanosis, clubbing (if longstanding), RV heave, single S2 (absent P2), systolic ejection murmur (RVOT obstruction)
Eisenmenger syndrome: cyanosis, clubbing, polycythemia — shunt has reversed (L-to-R becomes R-to-L from pulmonary HTN). Closure is CONTRAINDICATED
Investigations
First-line
EchocardiogramDiagnostic for most CHD: identifies defects, shunt direction, gradients, chamber sizes, associated anomalies. Doppler quantifies shunt (Qp:Qs ratio — >1.5:1 generally indicates significant shunt warranting closure)
Pulse oximetryPre-ductal (right arm) and post-ductal (foot) in neonates. Differential cyanosis (post-ductal SpO2 lower) = PDA with R-to-L flow or coarctation with PDA. Universal newborn screening: SpO2 <95% or >3% difference = positive screen
CXRCardiomegaly, increased pulmonary vascular markings (L-to-R shunt), decreased markings (R-to-L shunt). Boot-shaped heart (TOF — upturned apex from RVH), egg-on-a-string (TGA), rib notching (coarctation), snowman sign (TAPVR type I)
ECGRVH (TOF, ASD, pulmonary HTN), LVH (VSD, coarctation, PDA), superior axis (AV canal defect)
Second-line
Cardiac MRIGold standard for anatomy of complex CHD, quantification of shunts and ventricular volumes. Essential for ACHD follow-up
Cardiac catheterizationHemodynamic assessment, shunt quantification (Qp:Qs by Fick method), interventional procedures (device closure of ASD/PDA, balloon valvuloplasty)
1
Acyanotic lesions
- VSD: small/restrictive VSDs often close spontaneously in infancy. Surgical/device closure if large with HF, Qp:Qs >1.5:1, or pulmonary HTN
- ASD (secundum): percutaneous device closure (Amplatzer) if adequate rims. Surgical for primum or sinus venosus type. Closure indicated if Qp:Qs >1.5:1 or RV dilation
- PDA: indomethacin or ibuprofen in premature neonates (prostaglandin inhibition closes ductus). Surgical ligation or percutaneous device closure if persistent
- Coarctation: balloon angioplasty + stenting or surgical repair. Lifelong HTN monitoring (may persist post-repair)
2
Cyanotic lesions
- TOF: surgical repair (VSD closure + RVOT reconstruction) typically at 3-6 months. Tet spells acutely: knee-to-chest position (increases SVR), O2, morphine (calming), IV phenylephrine (increases SVR), propranolol (relaxes RVOT spasm)
- TGA: prostaglandin E1 (alprostadil) to maintain PDA (mixing). Balloon atrial septostomy (Rashkind) for emergent mixing. Definitive: arterial switch operation (Jatene) in first 2 weeks of life
- Prostaglandin E1 (alprostadil): given to any duct-dependent cyanotic lesion to keep PDA open until surgical repair. Side effects: apnea (monitor), hypotension, fever
3
ACHD — lifelong management
- Follow-up at specialized ACHD centers
- Endocarditis prophylaxis: only for prosthetic valves, unrepaired cyanotic CHD, repaired CHD with residual defects, or within 6 months of repair
- Pregnancy counseling: contraindicated in Eisenmenger, severe pulmonary HTN, severe aortic obstruction
- Arrhythmia monitoring: atrial arrhythmias common post-Fontan and post-atrial repair (Mustard/Senning)
- Exercise: individualized; most can exercise with guidance. Avoid competitive sports in certain conditions (Eisenmenger, severe aortic obstruction)
USMLE Step 2 CK Exam Tips
- 1Most common CHD: VSD. Most common cyanotic CHD: Tetralogy of Fallot
- 2Fixed split S2 = ASD. Widely split S2 that varies with respiration = normal or RBBB. Paradoxical splitting = LBBB or severe AS
- 3Continuous machinery murmur = PDA. Indomethacin closes PDA; prostaglandin E1 (alprostadil) keeps it open
- 4Tet spell (TOF): knee-to-chest (increases SVR, pushes blood through lungs). Treat with O2 + morphine + phenylephrine + propranolol
- 5Coarctation: upper limb HTN > lower limb, radio-femoral delay, rib notching on CXR. Associated with Turner syndrome and bicuspid aortic valve
- 6Eisenmenger: irreversible pulmonary HTN from long-standing L-to-R shunt now reversed. Closure is CONTRAINDICATED — would cause RV failure
- 7Down syndrome is associated with AV canal defect (endocardial cushion defect). Turner syndrome with coarctation. DiGeorge (22q11) with truncus arteriosus and interrupted aortic arch
- 8Cyanotic newborn not improving with O2: think CHD (hyperoxia test negative = cardiac cause)
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