systemic venous return re-enters systemic circulation directly
most prominent feature is cyanosis (O2 sat <75%)
hyperoxic test differentiates between cardiac and other causes of cyanosis
obtain preductal, right radial ABG in room air, then repeat after the child inspires 100% O2
if PaO2 improves to greater than 150 mmHg, cyanosis less likely cardiac in origin
Cyanotic heart diseases - shunt from right → left
коарктация аорты → ↑ BP → Eisenmenger syndrome
Tetralogy - pulmonary stenosis → RVH → shunt R to L → cyosis;