Blalock-Taussig shunt, Norwood and Fontan surgery

Have always bee confused how do these all work up here i hope to simplify them

BTS
- Simply to connect left pulmonary artery and left subclavian artery
- Reason : there is limited pulmonary blood flow as in TOF or to become another source of pulmonary circulation ( as in Norwood procedure )

Bottom line
- We use BTS if there is not enough blood in pulmonary circulation
- Without blood going through lung, there will be no oxygenation of the blood and the kid will be in cyanosis ( as the circulating blood is deoxygenated blood )

Norwood
- BTS + Atrial septectomy + Anastomosis between MPA and aortic arch
- Reason to do this - only RV is working
- Distal MPA is transected and proximal MPA is anastomosed to aortic arch -> so now all blood is delivered to systemic circulation by RV
- Now the problem arises : from where pulmonary circulation gets the blood ? As MPA has already been transected....We use a BTS !!!
- To make sure the blood from LA gets to RV, atrial septectomy is done for shunting to right chambers to occur

Bottom line
- Norwood is done if we want temporary RV function to pump blood to systemic circulation

Fontan
- 2 stages - 1st stage - redirect all SVC blood to pulmonary circulation; 2nd stage, redirect IVC blood to pulmonary circulation BYPASSING RV
- Purpose - when ONLY one ventricle is working
- Done after Norwood
- By shunting all venous blood to pulmonary circulation, we spare RV

Now then RV is either not working ( Tricuspid atresia ) so the atrial septectomy done in Norwood can be used to shunt the blood to LV
If LV is not working, blood is shunted to right and RV is used to pump blood to systemic circulation

Note that
In Norwood, the blood in RV is mixed
In Fontan, RV is separated from vena cava by a tube - so ALL the blood in RV/LV is OXYGENATED blood