🫀 Understanding Abnormal 3VT Patterns

A Practical Approach to Fetal Cardiac Screening

The Three Vessel Trachea (3VT) view is not a diagnostic plane —

it is a screening plane that detects abnormal patterns.

When the 3VT view looks unusual,

the goal is not to jump to a diagnosis,

but to identify which pattern is abnormal.

✅ Step 1: Know the Normal Pattern

In a normal 3VT:

• Pulmonary artery (largest)
• Aorta (slightly smaller)
• Superior vena cava (smallest)

PA and Ao form a characteristic V-shape

to the left of the trachea.

If this V-pattern is disturbed,

something deserves further evaluation.

🚨 Step 2: Recognize the Abnormal Pattern

1️⃣ Ao Dominance (PA smaller than Ao)

Appearance: Asymmetric V-shape

Think about:

• Tetralogy of Fallot
• Severe pulmonary stenosis
• Pulmonary atresia

👉 Check RVOT flow carefully.

2️⃣ Very Small or Absent PA

Appearance: PA barely visible

Think about:

• Pulmonary atresia

👉 Look for ductal retrograde filling.

3️⃣ Parallel Great Vessels

Appearance: Loss of V-shape

Think about:

• DORV
• Transposition variants

👉 Confirm LVOT connection.

4️⃣ Single Large Vessel (2-vessel appearance)

Appearance: Only two vessels seen

Think about:

• Truncus arteriosus

👉 Trace both outflow tracts.

5️⃣ U-shape Around the Trachea

Appearance: Trachea between two vessels

Think about:

• Right aortic arch

👉 Check descending aorta position.

6️⃣ Complete Ring Appearance

Appearance: Trachea fully encircled

Think about:

• Double aortic arch

👉 Confirm in sagittal view.

🧠 Practical Algorithm

When 3VT looks abnormal, ask:

1. Is PA size normal?
2. Is the V-shape preserved?
3. Where is the trachea?
4. Is there antegrade RV→PA flow?
5. Are great vessels aligned normally?

🔥 Bottom Line

The 3VT view does not give a diagnosis.

It gives a direction.

Abnormal patterns guide the next step —

LVOT, RVOT, Doppler, and arch evaluation.