Congenital heart disease can present with subtle but important differences on fetal ultrasound.
Two commonly discussed conditions are Tetralogy of Fallot (TOF) and Double Outlet Right Ventricle (DORV).
Although they may appear similar at first glance,
understanding their key differences is essential for accurate diagnosis.
What is Tetralogy of Fallot (TOF)?
Tetralogy of Fallot is characterized by four classic features:
- Ventricular septal defect (VSD)
- Overriding aorta
- Right ventricular outflow tract obstruction
- Right ventricular hypertrophy
๐ On fetal ultrasound, the most noticeable finding is the overriding aorta.
What is Double Outlet Right Ventricle (DORV)?
In DORV, both the aorta and pulmonary artery arise from the right ventricle.
This leads to:
- Abnormal great vessel connection
- Variable positioning of the VSD
- More complex anatomy compared to TOF
Key Differences on Ultrasound
TOF vs DORV comparison on fetal ultrasound highlighting subaortic VSD in TOF and variable VSD location in DORV, along with differences in great vessel origin and alignment.
1. Great Vessel Origin
- TOF: Aorta overrides the ventricular septum
- DORV: Both great vessels originate from the right ventricle
๐ This is the most important distinction
2. Vessel Alignment
- TOF: Partial alignment abnormality
- DORV: More severe misalignment
๐ DORV tends to look more โdisorganizedโ
3. 3VT View Findings
- TOF:
- Aorta appears enlarged
- Pulmonary artery may be small
- DORV:
- Abnormal vessel arrangement
- Loss of normal left-to-right alignment
4. Overall Pattern
- TOF: Recognizable pattern with overriding aorta
- DORV: More variable and complex appearance
Why This Matters
Distinguishing TOF from DORV is important because:
- Prognosis may differ
- Surgical planning is different
- Follow-up strategies vary
Early detection improves clinical outcomes.
Clinical Tip
Always evaluate:
- 4-chamber view
- Outflow tracts
- 3VT view
๐ No single view is sufficient for diagnosis
Conclusion
While TOF and DORV may share overlapping features,
their key differences lie in vessel origin, alignment, and 3VT appearance.
Careful evaluation of these factors allows more accurate diagnosis in fetal ultrasound.
