Three-Part Segmental Notation for Congenital Heart Disease

A practical radiology review of Three-Part Segmental Notation for Congenital Heart Disease, focused on imaging findings, differential diagnosis, reporting points, and high-yield teaching pearls.

Concept Overview

• Systematic way to describe congenital heart anatomy
• Uses Van Praagh 3-part notation → {,, }

1. Visceroatrial situs (atrial sidedness & organ position)

2. Ventricular loop orientation (embryologic folding)

3. Great vessel position & relation

• Radiologists use this to structure cardiac interpretation (Echo, CT, MRI) and communicate precisely.

The Three-Part Code Explained

• Example: {S, D, S} = Normal
• Situs solitus (S): RA + liver right, LA + stomach + spleen left
• D-loop (D): morphologic RV right of LV
• S (normal vessels): aorta posterior & right of MPA

Step 1 – Visceroatrial Situs {S / I / A}

• S (Solitus): Normal layout → liver/RA right, stomach/LA left
• I (Inversus): Mirror image
• A (Ambiguus): Heterotaxy (asplenia/polysplenia)
• Bronchial anatomy clues: Right bronchus = eparterial; left = hyparterial Helps identify morphologic RA

Step 2 – Ventricular Loop Orientation {D / L / X}

• D-loop (normal) → RV on right, LV on left
• L-loop → RV on left (CCTGA pattern)
• X → indeterminate
• Morphologic RV: Moderator band Coarse trabeculae, Tricuspid valve, Papillary muscles attach to septum + free wall
• Morphologic LV: Smooth septum, Fine trabeculae, Mitral valve, Papillary muscles attach to free wall only
• Step 3 – Great Vessel Relation {S / I / d-TGV / l-TGV / d-MGV / l-MGV}
• S: Normal → Ao posterior & right of MPA
• I: Inverted → Ao posterior & left of MPA
• d-TGV: Ao anterior & right (D-TGA)
• l-TGV: Ao anterior & left (CCTGA)
• d-MGV / l-MGV: Ao right/left of MPA (malposition, not transposed)
• Putting It Together
• Examples ⬇
• {S, D, S} → Normal
• {S, D, d-TGV} → D-transposition
• {S, L, l-TGV} → Congenitally corrected TGA
• {A, L, I} → Situs ambiguus + L-loop + inverted vessels

Radiology Resident Tips

• Always start with atria → ventricles → vessels
• Identify morphologic (not positional) chambers
• Use bronchial & IVC drainage clues for atrial situs
• Look for moderator band to find morphologic RV
• Note aortic vs pulmonary position at valve level