Cardiac Catheterisation and Oxygen Saturation Levels

Key points

• Basics: deoxygenated blood returns via SVC/IVC at ~70% · RA, RV and PA normally ~70% · lungs oxygenate to 98-100% · LA, LV and aorta should be 98-100%
• ASD: step-up from the RA onwards (e.g. RA 85% · RV 85% · PA 85% · left side 100%)
• VSD: step-up from the RV onwards, RA remains deoxygenated (RA 70% · RV 85% · PA 85% · left side 100%)
• PDA: only the PA is intermediate (RA 70% · RV 70% · PA 85% · left side 100%) — a PDA connects the higher-pressure aorta with the lower-pressure PA
• With Eisenmenger's (shunt reversal): VSD → LV/aorta 85% (LA 100%) · PDA → only aorta 85% · ASD → LA/LV/aorta all 85%

Decision points in this pathway

• Step-up from the RA onwards (RA, RV and PA all intermediate)?
• RA remains ~70% with a step-up at the RV or beyond?

The full step-by-step algorithm, including what to do at each branch, opens in the app for approved members.