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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Comparison
- L→R shunt then pulmonary overcirculation
- Defects: VSD, ASD, PDA
- R→L shunt bypasses lungs then hypoxemia
- 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 in TOF
- VSD: harsh holosystolic murmur at LLSB
- PDA: continuous "machinery" murmur
- TOF: systolic crescendo-decrescendo LUSB
- TGA: cyanosis without murmur — red flag
- Monitor for HF: poor feeding, tachypnea, sweat
- Give digoxin/diuretics as ordered
- ★Tet spell then knee-to-chest position
- O₂, calm
- hydrate to prevent polycythemia
- ★PDA may close with indomethacin
- Elective surgical repair by 6–12 mo
- ★PGE1 keeps PDA open
- balloon septostomy (TGA)
- TOF surgical repair
- Recognize HF signs
- give meds correctly
- Infection prevention
- dental prophylaxis
- Manage tet spells: knee-to-chest
- Maintain hydration to prevent thrombosis
- Progresses to biventricular heart failure
- Severe hypercyanotic (tet) spell
- Polycythemia then thrombosis/stroke
- Heart failure
- pulmonary HTN (Eisenmenger)
- Chronic hypoxemia
- thromboembolism
- brain abscess
Acyanotic (L→R Shunt)
- L→R shunt then pulmonary overcirculation
- Defects: VSD, ASD, PDA
Cyanotic (R→L Shunt)
- R→L shunt bypasses lungs then hypoxemia
- 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 in 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: cyanosis without murmur — red flag
Acyanotic (L→R Shunt)
- Monitor for HF: poor feeding, tachypnea, sweat
- Give digoxin/diuretics as ordered
Cyanotic (R→L Shunt)
- ★Tet spell then knee-to-chest position
- O₂, calm
- hydrate to prevent polycythemia
Acyanotic (L→R Shunt)
- ★PDA may close with indomethacin
- Elective surgical repair by 6–12 mo
Cyanotic (R→L Shunt)
- ★PGE1 keeps PDA open
- balloon septostomy (TGA)
- TOF surgical repair
Acyanotic (L→R Shunt)
- Recognize HF signs
- give meds correctly
- Infection prevention
- dental prophylaxis
Cyanotic (R→L Shunt)
- Manage tet spells: knee-to-chest
- Maintain hydration to prevent thrombosis
Acyanotic (L→R Shunt)
- Progresses to biventricular heart failure
Cyanotic (R→L Shunt)
- Severe hypercyanotic (tet) spell
- Polycythemia then thrombosis/stroke
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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