• physiological R → L shunt

Relevant Physiology

Etiology

• Long-standing L→ R shunts (non cyanotic conditions)
  • ASD
  • VSD
  • PDA
  • AVSD

Pathogenesis

• Prolonged PH - Pulmonary hypertension → RV pressure > LV pressure
• Resulting in R → L shunt (cyanotic)

Presentation

Signs and Symptoms

• Cyanosis
• Chronic cyanosis → Clubbing - Shamroth’s window

Investigation

• Cyanosis Hyperoxia Test (<150/>250)

CXR

• Dark lung field indicating hypoperfusion of lung