Question
Which of the following measures has the least role in correcting the underlying pathophysiology of Tetralogy of Fallot (TOF)?
| A. |
Systemic-to-pulmonary artery shunt
|
| B. |
Modified Blalock–Taussig shunt
|
| C. |
Administration of 100% oxygen
|
| D. |
Complete intracardiac repair
|
Show Answer
|
Correct Answer » C
Explanation
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|
Tetralogy of Fallot (TOF) is characterized by:
- Ventricular Septal Defect (VSD)
- Right ventricular outflow tract (RVOT) obstruction (pulmonary stenosis)
- Overriding aorta
- Right ventricular hypertrophy
The primary hemodynamic abnormality is RVOT obstruction, resulting in a right-to-left shunt across the VSD and reduced pulmonary blood flow.
Administration of 100% oxygen has only a limited role because it does not relieve the RVOT obstruction or eliminate the right-to-left shunt. Although oxygen is routinely administered during hypercyanotic (Tet) spells as supportive therapy, it does not correct the underlying anatomical defect or significantly improve pulmonary blood flow.
Therefore, among the given options, it has the least role in correcting the underlying pathophysiology.
Why the Other Options Are Incorrect
A. Systemic-to-pulmonary artery shunt
- Correct intervention.
- Increases pulmonary blood flow by creating a communication between the systemic and pulmonary circulations.
- Used as a palliative procedure before definitive repair.
B. Modified Blalock–Taussig shunt
- Correct intervention.
- The commonest palliative shunt for TOF.
- Connects the subclavian artery to the pulmonary artery using a Gore-Tex graft, thereby increasing pulmonary blood flow.
D. Complete intracardiac repair
- Correct intervention.
- Definitive treatment for TOF.
- Involves closure of the VSD and relief of RVOT obstruction, thereby correcting the underlying hemodynamic abnormality.
