The Three Vessel Trachea (3VT) view is a crucial plane in fetal cardiac assessment.
When Tetralogy of Fallot (TOF) or Double Outlet Right Ventricle (DORV) is suspected,
3VT can provide important clues — but it does not always give a complete answer.
So what should we look for?
1️⃣ Normal 3VT Pattern
In a normal heart:
- Pulmonary artery (largest, most anterior)
- Aorta (slightly smaller)
- Superior vena cava (smallest)
They form a characteristic V-shape, converging toward the descending aorta.
Loss of this pattern raises suspicion.
2️⃣ 3VT in TOF
In Tetralogy of Fallot:
✔ Pulmonary artery is small (due to pulmonary stenosis)
✔ Aorta appears relatively larger
✔ The V-shape becomes asymmetric
✔ Sometimes the pulmonary artery is barely visible
However:
👉 The aorta still follows its normal anatomical course
👉 It connects to the left ventricle (despite override)
Key clue:
Pulmonary artery hypoplasia is the dominant feature.
3️⃣ 3VT in DORV
In Double Outlet Right Ventricle:
✔ Great vessel relationship may appear parallel or abnormal
✔ Both great arteries arise predominantly from RV
✔ V-shape may be distorted or absent
Unlike TOF:
👉 The problem is not just pulmonary narrowing
👉 The origin of both vessels is abnormal
The aorta may not show the expected leftward course from LV.
4️⃣ Practical Differentiation Strategy
On 3VT alone, differentiation can be difficult.
So combine with:
✔ LVOT view — Does LV connect directly to the aorta?
✔ RVOT view — Degree of pulmonary stenosis?
✔ 4-chamber + septal alignment
If pulmonary artery is small but LV–aorta connection exists → think TOF.
If both great vessels seem to arise from RV and LV lacks direct aortic connection → think DORV.
5️⃣ Important Reminder
3VT is a screening plane.
Definitive differentiation requires:
- Multi-plane imaging
- Careful tracing of outflow tracts
- Assessment of override degree
Bottom Line
On 3VT:
- TOF → asymmetric V-shape with small pulmonary artery
- DORV → abnormal vessel origin and distorted pattern
The critical question remains:
👉 Is the aorta directly connected to the left ventricle?
“3VT alone suggests size and alignment abnormalities, but definitive differentiation requires LVOT assessment.”
