Embryology: tetralogy of Fallot: practice question

A Anatomy question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Anatomy · Embryology: tetralogy of Fallot

Sample item

A cyanotic infant has right ventricular outflow obstruction, a ventricular septal defect, an overriding aorta and right ventricular hypertrophy. What is the primary embryological defect?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

B. Anterior displacement of the infundibular (conal) septum

Tetralogy of Fallot results from anterior and cephalad deviation of the infundibular septum, which narrows the right ventricular outflow tract and causes the VSD and overriding aorta. Right ventricular hypertrophy follows from the obstruction.

Option by option

  • A. Persistence of the right umbilical vein

    The right umbilical vein normally regresses and is unrelated to the cardiac malformations.

  • B. Anterior displacement of the infundibular (conal) septum (correct)

    Correct. The anteriorly displaced conal septum produces all four features.

  • C. Failure of the foramen ovale to close

    A patent foramen ovale causes an interatrial communication and not outflow obstruction.

  • D. Failure of septum primum to grow

    Septum primum failure causes an atrial septal defect.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Anatomy question

What is the answer to this Anatomy question?

The best answer is B, Anterior displacement of the infundibular (conal) septum. Tetralogy of Fallot results from anterior and cephalad deviation of the infundibular septum, which narrows the right ventricular outflow tract and causes the VSD and overriding aorta.

Why is "Persistence of the right umbilical vein" not the answer?

The right umbilical vein normally regresses and is unrelated to the cardiac malformations.

Why is "Failure of the foramen ovale to close" not the answer?

A patent foramen ovale causes an interatrial communication and not outflow obstruction.

Why is "Failure of septum primum to grow" not the answer?

Septum primum failure causes an atrial septal defect.

What concept does this question test?

It tests Embryology: tetralogy of Fallot in Anatomy. Right ventricular hypertrophy follows from the obstruction.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Embryology: tetralogy of Fallot?

Learn every nerve by its route, its muscles and what a lesion looks like at the bedside. That one habit answers a large share of questions. Then use the flashcards and the other Anatomy questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.