Acyanotic vs Cyanotic Heart Defects: Blood Flow Direction, Presentation, Surgical Timing
An infant with a VSD and an infant with Tetralogy of Fallot both have heart murmurs — but one turns blue during crying and the other develops heart failure from lung overcirculation. Picking the wrong shunt direction on the NCLEX flips every assessment finding and intervention priority.
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- L→R shunt: ↑ pulmonary blood flow
- Defects: VSD, ASD, PDA
- R→L shunt: blood bypasses lungs
- Defects: Tetralogy of Fallot, TGA
- SpO₂ normal
- No cyanosis at rest
- Tachypnea, diaphoresis with feeding
- Frequent respiratory infections
- ★Central cyanosis, worse with crying/feeding
- ↓ SpO₂
- Clubbing
- Tet spells (TOF)
- VSD: harsh holosystolic murmur at LLSB
- PDA: continuous "machinery" murmur
- TOF: systolic crescendo-decrescendo LUSB
- TGA: severe cyanosis, often no murmur
- Monitor for HF: tachypnea, poor feeding
- Give digoxin/diuretics as ordered
- ★Tet spell: knee-to-chest position
- Tet spell: give O₂, calm the infant
- Hydrate to prevent hyperviscosity
- ★PDA may close with indomethacin
- Small VSD/ASD often close on their own
- ★PGE1 keeps PDA open (TGA)
- Balloon atrial septostomy (TGA)
- TOF: complete repair in infancy
- Recognize HF signs
- Digoxin: check HR, never double a dose
- Manage tet spells: knee-to-chest
- Maintain hydration to prevent thrombosis
- Antibiotics before dental work
- Worsening heart failure signs
- Severe hypercyanotic (tet) spell
- Polycythemia: thrombosis/stroke risk
- Heart failure
- Pulmonary HTN (Eisenmenger)
- Chronic hypoxemia
- Thromboembolism
- Brain abscess
Acyanotic (L→R Shunt)
- L→R shunt: ↑ pulmonary blood flow
- Defects: VSD, ASD, PDA
Cyanotic (R→L Shunt)
- R→L shunt: blood bypasses lungs
- Defects: Tetralogy of Fallot, TGA
Acyanotic (L→R Shunt)
- SpO₂ normal
- No cyanosis at rest
- Tachypnea, diaphoresis with feeding
- Frequent respiratory infections
Cyanotic (R→L Shunt)
- ★Central cyanosis, worse with crying/feeding
- ↓ SpO₂
- Clubbing
- Tet spells (TOF)
Acyanotic (L→R Shunt)
- VSD: harsh holosystolic murmur at LLSB
- PDA: continuous "machinery" murmur
Cyanotic (R→L Shunt)
- TOF: systolic crescendo-decrescendo LUSB
- TGA: severe cyanosis, often no murmur
Acyanotic (L→R Shunt)
- Monitor for HF: tachypnea, poor feeding
- Give digoxin/diuretics as ordered
Cyanotic (R→L Shunt)
- ★Tet spell: knee-to-chest position
- Tet spell: give O₂, calm the infant
- Hydrate to prevent hyperviscosity
Acyanotic (L→R Shunt)
- ★PDA may close with indomethacin
- Small VSD/ASD often close on their own
Cyanotic (R→L Shunt)
- ★PGE1 keeps PDA open (TGA)
- Balloon atrial septostomy (TGA)
- TOF: complete repair in infancy
Acyanotic (L→R Shunt)
- Recognize HF signs
- Digoxin: check HR, never double a dose
Cyanotic (R→L Shunt)
- Manage tet spells: knee-to-chest
- Maintain hydration to prevent thrombosis
- Antibiotics before dental work
Acyanotic (L→R Shunt)
- Worsening heart failure signs
Cyanotic (R→L Shunt)
- Severe hypercyanotic (tet) spell
- Polycythemia: thrombosis/stroke risk
Acyanotic (L→R Shunt)
- Heart failure
- Pulmonary HTN (Eisenmenger)
Cyanotic (R→L Shunt)
- Chronic hypoxemia
- Thromboembolism
- Brain abscess
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Left-to-right shunt = extra lung blood, no blue; right-to-left shunt = blue baby, think TOF or TGA.
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