Congenital Heart Defects

Shunts & the "blue baby" · Septal defects · PDA · Tetralogy
A shunt is a hole or an extra pipe. It lets blood take a shortcut between the two sides of the heart. Pressure sets which way the blood flows, and that decides everything. Left → Right sends oxygen-rich blood back to the lungs, so the baby stays pink (non-cyanotic). Right → Left sends oxygen-poor blood out to the body, so the baby turns blue (cyanotic).

The defect & the shortcut

The left heart runs at a higher pressure than the right. So blood usually takes the shortcut left → right, unless something like Tetralogy forces it the other way.
Left → Right shunt · NON-cyanoticOxygen-rich blood recirculates to the lungs
Pick a defect on the right to see the shortcut.
Oxygen-rich (red) Oxygen-poor (blue) The hole / shunt

Is the baby blue?

Cyanosis means not enough oxygen is reaching the body. It happens only when oxygen-poor blood gets out to the body, which means a right → left shunt.
Pink & well-oxygenated
The body is still getting oxygen-rich blood, so there is no cyanosis.
Pick a defectFour classic congenital defects

👆 Pick a defect

This defect

The big picture

Every defect here is one of two kinds. The direction of flow tells you whether it is a blue baby.

◾ Left → Right · PINK

VSD, ASD, PDA
Oxygen-rich blood goes back through the lungs again. Extra work for the lungs and heart, but no cyanosis.

◾ Right → Left · BLUE

Tetralogy of Fallot
Oxygen-poor blood skips the lungs and goes to the body → cyanosis (a blue baby).
The one rule that ties it together: follow the blood at the hole. If red (oxygen-rich) blood is pushed to the right side, it just goes to the lungs → pink. If blue (oxygen-poor) blood crosses to the left side or the aorta, it goes to the body → blue.